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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of presentation

The accompanying unaudited condensed financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, the Company must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the interim periods ended September 30, 2015 and 2014 are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The condensed interim financial statements should be read in conjunction with the audited financial statements and notes as of and for the year ended December 31, 2014.

Initial Public Offering

In May 2015, the Company closed an initial public offering ("IPO") of its common stock, which resulted in the sale of 6,670,000 shares of its common stock at a public offering price of $12.00 per share, including 870,000 shares of common stock upon the exercise by the underwriters of their option to purchase additional shares at the public offering price. The Company received proceeds from the IPO of approximately $72,029, after deducting underwriting discounts, commissions and expenses payable by the Company.

In connection with preparing for the IPO, the Company's Board of Directors and shareholders approved a one-for-6.9 reverse stock split of the Company's common stock. The reverse stock split became effective in April 2015. All share and per share amounts in the condensed interim financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. In connection with the closing of the IPO, all of the Company's outstanding convertible preferred stock automatically converted to common stock in May 2015, resulting in an additional 12,591,456 shares of common stock of the Company becoming outstanding. The significant increase in common stock outstanding in May 2015 is expected to impact the year-over-year comparability of the Company's net loss per share calculations in future periods.

Subsequent Events

The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Through November 12, 2015, the Company has concluded that no subsequent events have occurred that require disclosure, except as described in Note 9.

Critical Accounting Policies

Earnings (Loss) per Common Share

Earnings (loss) per common share is calculated using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for the holders of the Company's common shares and participating securities. All series of preferred stock contain participation rights in any dividend paid by the Company and are deemed to be participating securities. Earnings available to common shareholders and participating convertible redeemable preferred shares is allocated first to the preferred stock based upon the distribution criteria in the Company's Articles of Incorporation then the remainder to the common shareholders. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods that have a net loss.

Diluted earnings per share is computed using the more dilutive of (a) the two-class method, or (b) the if-converted method. The Company allocates earnings first to preferred shareholders based on dividend rights and then to common and preferred shareholders based on ownership interests. The weighted-average number of common shares included in the computation of diluted earnings (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, convertible redeemable preferred stock and the potential issuance of stock upon the conversion of the Company's convertible notes. Common stock equivalent shares are excluded from the computation of diluted earnings (loss) per share if their effect is antidilutive.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB"), issued Accounting Standards Update ("ASU"), No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in Accounting Standards Codification ("ASC"), Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. On August 12, 2015, the FASB issued ASU No. 2015-14, which defers the effective date of ASU No. 2014-09 by one year to December 15, 2017 for annual reporting periods beginning after that date, including interim periods within those periods. The FASB also approved permitting early adoption of the standard, but not before the original effective date of December 15, 2016. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its financial statements.

In July 2015, the FASB issued ASU No. 2015-11, which amends existing guidance for measurement of inventory. Current inventory guidance requires an entity to measure inventory at the lower of cost or market. Market could be replacement cost, net realizable value, or net realizable value less an approximately normal profit margin. The amendments do not apply to inventory that is measured using last-in, first-out (LIFO) or the retail inventory method. The amendments apply to all other inventory, which includes inventory that is measured using first-in, first-out or average cost. An entity should measure all inventory to which the amendments apply at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. Subsequent measurement is unchanged for inventory measured using LIFO or the retail inventory method. The amendments in the ASU No. 2015-11 more closely align the measurement of inventory pursuant to GAAP with the measurement of inventory pursuant to International Financial Reporting Standards. The amendments are effective for fiscal years beginning after December 15, 2016, and interim periods within fiscal years beginning after December 15, 2017. The amendments should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on its condensed financial statements.

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates

The preparation of the Company's financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company's financial statements and accompanying notes. The most significant estimates in the Company's financial statements relate to the valuation of equity awards, fair value estimates of warrants, estimated useful lives of fixed assets, asset retirement obligations and accruals related to clinical trials. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. The Company's actual results may differ from these estimates under different assumptions or conditions.

Unaudited Pro Forma Net Loss per Share Information

Unaudited pro forma net loss per share applicable to common shareholders is computed using the weighted-average number of common shares outstanding after giving effect to the conversion of all the outstanding convertible redeemable preferred stock into shares of common stock as if such conversion had occurred at the beginning of the period presented, or the date of original issuance, if later, and excludes the gain on extinguishment of preferred stock and the accretion of dividends.

Fair Value Measurements

Disclosures of fair value information about financial instruments are required, whether or not recognized in the balance sheet, for financial instruments with respect to which it is practicable to estimate that value. The carrying amounts reported in the Company's financial statements for cash and cash equivalents, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts.

Fair Value Measurements and Disclosures describes the fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, as follows:

Level 1 Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. The Company's Level 1 assets and liabilities consist of money market investments.

Level 2 Quoted prices for similar assets, or inputs that are observable, either directly or indirectly, for substantially the full term through corroboration with observable market data. Level 2 includes investments valued at quoted prices adjusted for legal or contractual restrictions specific to the security. The Company does not have Level 2 assets or liabilities.

Level 3 Pricing inputs are unobservable for the assets or liabilities, that is, inputs that reflect the reporting entity's own assumptions about the assumptions market participants would use in pricing the assets. Level 3 includes private investments that are supported by little or no market activity. The Company does not have Level 3 assets or liabilities.

Transfers are calculated on values as of the transfer date. There were no transfers between Levels 1, 2 and 3 during the years ended December 31, 2013 and 2014.

Concentration of Credit Risk

Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the financial institutions in which those deposits are held. The Company has no financial instruments with off-balance sheet risk of loss.

Cash and Cash Equivalents

Cash and cash equivalents include cash in readily available checking and savings accounts and money market funds. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents.

The Company's cash equivalents, which consist of money market funds, are measured at fair value on a recurring basis. As of December 31, 2013 and 2014, the carrying amount of cash and cash equivalents was $7,551 and $1,634, respectively, which approximates fair value and was determined based upon Level 1 inputs. Money market funds are valued using quoted market prices with no valuation adjustments applied. Accordingly, these securities are categorized as Level 1.

Property and Equipment

Property and equipment are recorded at historical cost. Maintenance and repair costs are expensed as incurred. Costs which materially improve or extend the lives of existing assets are capitalized. The Company provides for depreciation and amortization using the straight-line method over the estimated useful lives of the assets, which are as follows:

Asset Category		Estimated Useful Life

Machinery and equipment		5 years
Computers and office equipment		5 years
Furniture and fixtures		7 years
Leasehold improvements		5 years

Upon retirement or sale, the cost of assets disposed and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recorded in the statements of operations.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. When impairment indicators exist, the Company's management evaluates long-lived assets for potential impairment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. While the Company's current and historical operating losses and negative cash flows are indicators of impairment, management believes that future cash flows to be received support the carrying value of its long-lived assets and, accordingly, has not recognized any impairment losses since inception.

Impairment losses, if any, are recognized in earnings. An impairment loss would be recognized in an amount equal to the excess of the carrying amount over the undiscounted expected future cash flows.

Initial Public Offering Costs

The Company defers direct incremental costs attributable to the initial public offering ("IPO") of its common stock. These costs represent legal, accounting and other direct costs related to the Company's efforts to raise capital through a public sale of its common stock. Future costs will be deferred until the completion of the IPO, at which time they will be reclassified to additional paid-in capital as a reduction of the IPO proceeds. If the Company terminates its plan for an IPO or delays such plan for more than 90 days, any costs deferred will be expensed immediately. As of December 31, 2014, IPO costs were $233 and are included in prepaid expenses and other assets in the balance sheet.

Restricted Cash

Restricted cash represents cash held in a depository account at a financial institution to collateralize a conditional stand-by letter of credit related to the Company's Canton, Massachusetts facility lease agreement. Restricted cash is reported as non-current unless the restrictions are expected to be released in the next twelve months.

Deferred Rent

Deferred rent consists of the difference between cash payments and the recognition of rent expense on a straight-line basis for the facilities the Company occupies. The Company's lease for its facility provides for fixed increases in minimum annual rental payments and for additional rent in the form of maintenance and operating costs during the lease term. The total amount of rental payments due over the lease term is being charged to rent expense ratably over the life of the lease.

Convertible Redeemable Preferred Stock

The Company classifies convertible redeemable preferred stock that is redeemable outside of the Company's control outside of permanent equity. The Company recorded such redeemable preferred stock at fair value upon issuance, net of any issuance costs or discounts, and the carrying value is being increased by periodic accretion to its redemption value at each balance sheet date as if the redeemable preferred stock was redeemable at that date. In the absence of retained earnings these accretion charges are recorded against additional paid-in capital, if any, and then to accumulated deficit.

Research and Development Costs

Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company's research and development activities including salaries and employee related costs, costs associated with market research and design, costs associated with conducting preclinical, clinical and regulatory activities including fees paid to third-party professional consultants and service providers, costs incurred under clinical trial agreements, costs for laboratory supplies and laboratory equipment, costs to acquire, develop and manufacture preclinical study and clinical trial materials, facilities, depreciation and other expenses including allocated expenses for rent and maintenance of facilities. Government grants are recognized as a reduction of the qualifying cost being reimbursed.

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expense as incurred since the recoverability of such expenditures is uncertain.

Stock-Based Compensation

The Company accounts for grants of stock options and restricted stock to employees based on their grant date fair value and recognizes compensation expense over their vesting period. The Company estimates the fair value of stock options as of the date of grant using the Black-Scholes option pricing model and restricted stock based on the fair value of the underlying common stock as determined by management or the value of the services provided, whichever is more readily determinable.

Stock-based compensation expense represents the cost of the grant date fair value of employee stock option grants recognized over the requisite service period of the awards (usually the vesting period) on a straight-line basis, net of estimated forfeitures. The expense is adjusted for actual forfeitures at year end. Stock-based compensation expense recognized in the financial statements is based on awards that are ultimately expected to vest.

For stock option grants with performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable or the performance condition has been achieved. For stock option grants with both performance-based milestones and market conditions, expense is recorded over the derived service period after the point when the achievement of the performance-based milestone is probable or the performance condition has been achieved.

The Company accounts for stock options and restricted stock awards to non-employees using the fair value approach. Stock options and restricted stock awards to non-employees are subject to periodic revaluation over their vesting terms. There were no non-employee grants in 2013 and 2014.

Income Taxes

The Company accounts for income taxes under the liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the years in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future, in excess of its net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more likely than not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company will recognize interest and penalties related to uncertain tax positions within income tax expense. Any accrued interest and penalties will be included within the related tax liability. As of December 31, 2013 and 2014, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company's statements of operations.

Net loss per Common Share

Basic net loss per common share is calculated by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, stock options, warrants, redeemable convertible preferred stock and unvested restricted stock are considered potentially dilutive securities. Because the Company has reported a net loss for the twelve months ended December 31, 2013 and 2014, diluted net loss per common share is the same as basic net loss per common share for those periods.

Diluted earnings per share is computed using the more dilutive of (i) the two-class method, or (ii) the if-converted method. The Company allocates earnings first to preferred shareholders based on dividend rights and then to common and preferred shareholders based on ownership interests. The weighted-average number of common shares included in the computation of diluted earnings (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, convertible redeemable preferred stock and the potential issuance of stock upon the conversion of the Company's convertible notes. Common stock equivalent shares are excluded from the computation of diluted earnings (loss) per share if their effect is antidilutive.

Recently Issued Accounting Pronouncements

In July 2013, the Financial Accounting Standards Board ("FASB") issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exist. ASU 2013-11 amends the presentation requirements of ASC 740 and requires an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if the entity does not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented as a liability and not combined with deferred tax assets. This ASU is effective for annual periods, and interim periods within those years, beginning after December 15, 2013, which is fiscal 2014 for the Company. The amendments are to be applied to all unrecognized tax benefits that exist as of the effective date and may be applied retrospectively to each prior reporting period presented. The adoption of ASU 2013-11 did not have a material impact on the Company's financial position or results of operations.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. This ASU is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. This ASU is effective for annual reporting periods beginning after December 15, 2016 and early adoption is not permitted. Accordingly, the Company will adopt this ASU on January 1, 2017. Management does not believe the adoption of this ASU will have a material impact on the Company's financial condition, results of operations or cash flows.

In June 2014, the FASB issued ASU No. 2014-12, Compensation — Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. ASU 2014-12 applies to all reporting entities that grant their employees share-based payments in which the terms of the award provide that a performance target that affects vesting could be achieved after the requisite service period. That is the case when an employee is eligible to retire or otherwise terminate employment before the end of the period in which a performance target (for example, an initial public offering or a profitability target) could be achieved and still be eligible to vest in the award if and when the performance target is achieved. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2015 and interim periods within those annual periods. The Company plans to implement this standard in the first quarter of fiscal year 2016 and is currently evaluating the potential impact of this new guidance on its financial statements.

In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern. ASU 2014-15 requires management to evaluate, at each annual or interim reporting period, whether there are conditions or events that exist that raise substantial doubt about an entity's ability to continue as a going concern within one year after the date the financial statements are issued and provide related disclosures. ASU 2014-15 is effective for annual periods ending after December 15, 2016 and earlier application is permitted. The adoption of ASU 2014-15 is not expected to have a material effect on the Company's financial statements or disclosures.

In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815) — Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share is More Akin to Debt or to Equity. This ASU was issued to clarify how current U.S. generally accepted accounting principles should be interpreted in evaluating the economic characteristics and risk of a host contract in a hybrid financial instrument that is issued in the form of a share. In addition, this ASU was issued to clarify that in evaluating the nature of a host contract, an entity should assess the substance of the relevant terms and features (that is, the relative strength of the debt-like or equity-like terms and features given the facts and circumstances) when considering how to weight those terms and features. The effects of initially adopting this ASU should be applied on a modified retrospective basis to existing hybrid financial instruments issued in a form of a share as of the beginning of the fiscal year for which the amendments are effective. Retrospective application is permitted to all relevant prior periods. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption in an interim period is permitted. The Company is currently evaluating the impact of the adoption of this ASU on its financial statements.

NET LOSS PER COMMON SHARE

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

NET LOSS PER COMMON SHARE

3. NET LOSS PER COMMON SHARE

	Nine months ended September 30,

	2014			2015
Net loss	$	(14,448	)	$	(17,730	)
Extinguishment of preferred stock — see note 7		—			31,806
Accretion of prior preferred stock — see note 7		(2,469	)		(23,327	)
Accretion and dividends of Series D preferred stock		—			(1,245	)

Loss attributable to common shareholders — basic and diluted	$	(16,917	)	$	(10,496	)



Weighted-average number of common shares used in net loss per share — basic and diluted		926,597			11,179,756



Net loss per share — basic and diluted	$	(18.26	)	$	(0.94	)

The following potentially dilutive securities, which represent all outstanding potentially dilutive securities, were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect (in common stock equivalent shares):

	Nine months ended September 30,

	2014		2015
Outstanding stock options		311,365		1,356,246
Warrants		18,810		2,445
Redeemable convertible preferred stock		6,552,820		—
Unvested restricted stock		28,536		153,589

3. NET LOSS PER COMMON SHARE

Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period. Stock options, warrants, convertible preferred stock and unvested restricted stock are considered to be potentially dilutive securities and are only included in the calculation of diluted net loss per share when their effect is dilutive. For the twelve months ended December 31, 2013 and December 31, 2014, these securities were anti-dilutive due to the net losses in those periods and, therefore, the number of shares used to compute basic and diluted earnings per share are the same for of those periods.

The following table presents the computations of basic and dilutive net loss per share:

	Years Ended December 31,

	2013			2014
Net loss	$	(16,197	)	$	(17,917	)
Performance Adjustment of Series A		12,239			—
Accruals of dividends and accretion to redemption value of preferred stock		(2,925	)		(3,300	)

Loss attributable to common shareholders — basic and diluted	$	(6,883	)	$	(21,217	)



Weighted-average shares used in computing basic and diluted net loss per common share		1,697,044			933,997



Basic and diluted net loss per common share	$	(4.06	)	$	(22.72	)

The following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported (in common stock equivalent shares):

	Years Ended December 31,

	2013		2014
Stock Options		229,791		281,029
Warrants		4,170		18,809
Redeemable convertible preferred stock		6,552,820		6,552,820
Unvested restricted stock		55,298		15,387

PREPAID EXPENSES AND OTHER CURRENT ASSETS

12 Months Ended

Dec. 31, 2014

PREPAID EXPENSES AND OTHER CURRENT ASSETS

PREPAID EXPENSES AND OTHER CURRENT ASSETS

4. PREPAID EXPENSES AND OTHER CURRENT ASSETS

Prepaid expenses and other current assets consisted of the following:

	As of December 31,

	2013		2014
Other current assets	$	—	$	253
Initial public offering costs		—		233
Employee advances		21		33
Prepaid expenses		33		8
Prepaid development costs		656		—

Prepaid expenses and other current assets	$	710	$	527

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2014

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT

5. PROPERTY AND EQUIPMENT

Property and equipment consisted of the following:

	As of December 31,

	2013			2014
Machinery and equipment	$	741		$	741
Computers and office equipment		26			26
Furniture and fixtures		36			44
Leasehold improvements		606			606

Total property and equipment		1,409			1,417
Less: accumulated deprecation		(716	)		(903	)

Property and equipment, net	$	693		$	514

Depreciation expense related to property and equipment amounted to $169 and $187 for the years ended December 31, 2013 and 2014, respectively.

ACCRUED EXPENSES

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

COMMITMENTS AND CONTINGENCIES

ACCRUED EXPENSES

5. ACCRUED EXPENSES

Accrued expenses consisted of the following:

	December 31, 2014		September 30, 2015

Accrued compensation	$	635	$	1,169
Accrued development costs		970		597
Accrued marketing		—		685
Accrued audit and legal		249		109
Accrued interest		71		31
Accrued other		31		90

Total accrued expenses	$	1,956	$	2,681

6. ACCRUED EXPENSES

Accrued expenses consisted of the following:

	As of December 31,

	2013		2014
Accrued development costs	$	520	$	970
Accrued compensation		449		635
Accrued audit and legal		12		249
Accrued interest		—		71
Accrued other		32		31

Total accrued expenses	$	1,013	$	1,956

COMMITMENTS AND CONTINGENCIES

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

COMMITMENTS AND CONTINGENCIES.

9. COMMITMENTS AND CONTINGENCIES

The Company's NDA filing for Xtampza is a 505(b)(2) application, which allows the Company to reference data from an approved drug listed in the FDA's Approved Drug Products with Therapeutic Equivalence Evaluations (commonly known as the "Orange Book"), in this case OxyContin OP. In connection with the 505(b)(2) process, the Company certified to the FDA and notified Purdue Pharma, L.P. ("Purdue"), as the holder of the NDA and any other Orange Book-listed patent owners, that the Company does not infringe any of the patents listed for OxyContin OP in the Orange Book. Under the Hatch-Waxman Act of 1984 (the "Hatch-Waxman Act"), Purdue can elect to sue the Company for infringement, and if they do, receive a stay of up to 30 months before the FDA can issue a final approval for Xtampza, unless the stay is earlier terminated. On March 24, 2015, Purdue sued the Company in the District of Delaware asserting infringement of four patents. On March 26, 2015, Purdue filed a second suit against the Company in the District of Massachusetts asserting infringement of the same four patents. On July 23, 2015, Purdue voluntarily dismissed the Massachusetts suit. On August 6, 2015, the Delaware court dismissed the suit in Delaware and issued a memorandum opinion finding the Delaware court lacks personal jurisdiction over the Company Following the dismissal in Delaware, on August 6, 2015, the Company filed a complaint in the Southern District of New York asserting an action to obtain patent certainty, and requesting that the New York court find that Xtampza will not infringe any valid patent claim of the patents asserted by Purdue in the Delaware action. Also on August 6, 2015, Purdue sued the Company in the District of Massachusetts asserting the same claims as the prior suit. On August 7, 2015, Purdue filed a motion in the Delaware court requesting reconsideration of the August 6, 2015 order that dismissed the case. In the motion requesting reconsideration, Purdue asked that the Delaware court find that it does have personal jurisdiction over the Company and then transfer the case to the District of Massachusetts. On October 7, 2015, the Delaware court transferred the case to the District of Massachusetts. On November 9, 2015, the Company filed a motion for summary judgment, for which it requested expedited hearing in Massachusetts. At this time the Company is unable to provide meaningful quantification of how this litigation may impact its future financial condition, results of operations, or cash flows.

In March 2015, the Company amended its lease to include an additional 9,660 square feet of space for a total of 19,335 square feet. In addition, the lease term was extended and now terminates on the date that is 5 years following August 2015 which is the date that the landlord delivered the expansion space with certain improvements substantially completed. At the Company's election, the lease term may be extended for an additional 5-year term.

7. COMMITMENTS AND CONTINGENCIES

Legal Proceedings

From time to time the Company may face legal claims or actions in the normal course of business. The Company is not currently a party to any litigation and, accordingly, does not have any amounts recorded for any litigation related matters.

Operating Leases

The Company leases its office and research facility under a non-cancellable operating lease, which expires in December 2017. Terms of the agreement provide for an initial two-month rent-free period and future rent escalation, and provide that in addition to minimum lease rental payments, the Company is responsible for a pro-rata share of operating expenses and taxes. Aggregate minimum annual lease commitments of the Company under its non-cancellable operating lease as of December 31, 2014 are as follows:

Year Ending December 31,

2015	$	106
2016		111
2017		116

Total minimum lease payments	$	333

Rent expense under the operating lease agreement amounted to approximately $69 for the years ended December 31, 2013 and 2014, respectively. In addition, the Company maintained a stand-by letter of credit in connection with the Canton facility lease of $80 at December 31, 2013 and December 31, 2014. This amount is classified as restricted cash in the balance sheets.

As an inducement to enter into its Canton facility lease, the lessor agreed to provide the Company with an improvement allowance of up to $174 towards leasehold improvements. In addition the lessor provided the Company with a reimbursable allowance of $164 which is to be amortized and repaid by the Company at an 8% interest rate over the initial term of 36 months. Amounts provided by the lessor related to tenant improvements are considered inducements to enter into the lease. The Company has recorded these costs in the balance sheet as leasehold improvements, with the corresponding liabilities as deferred lease incentive and lease note payable. These liabilities are amortized on a straight-line basis over the term of the lease.

DEBT

12 Months Ended

Dec. 31, 2014

DEBT

DEBT

8. DEBT

On August 28, 2012, the Company entered into a loan agreement ("Original Term Loan") with Silicon Valley Bank ("SVB") to borrow up to a maximum amount of $1,000. In August 2012, October 2012 and February 2013, the Company borrowed $250, $250 and $500, respectively. The Original Term Loan bore interest at a rate per annum of 2.25% above the prime rate fixed at the time of advance of the Original Term Loan (5.50%). The Original Term Loan provided for interest-only payments for the first 12 months based on the date of each borrowing, and, thereafter, 36 monthly payments of principal and interest. In connection with the Original Term Loan, the Company granted SVB a warrant to purchase 23,810 shares of common stock at an exercise price of $0.07 per share (See Note 9).

In January 2014, the Original Term Loan was amended ("Amendment No. 1") to provide for the following; borrowings of up to $6,000, repayment in full of the Original Term Loan balance outstanding, and an adjustment of the variable interest rate from 2.25% above the prime rate to 1.75% above the prime rate. In February 2014, the Company borrowed $2,000. The proceeds from the initial borrowing were used to pay down the Original Term Loan balance outstanding resulting in the Company receiving $1,056. Borrowings under Amendment No. 1 bore interest at a rate of 5.0%. Amendment No. 1 provided for interest-only payments for the first 12 months based on the date of each borrowing, and thereafter, 36 monthly payments of principal and interest. In connection with Amendment No. 1, the Company granted to SVB a warrant to purchase 14,430 shares of common stock with an exercise price of $0.05 per share (See Note 9).

In August 2014 the Original Term Loan was further amended ("Amendment No. 2") to provide for total borrowings of up to $8,000. In August 2014 and September 2014 the Company drew down $3,000 and $3,000, respectively. Pursuant to Amendment No. 2, interest-only payments are to be made for the first 12 months based on the date of each borrowing; thereafter, 36 monthly payments of principal and interest are to be made. Borrowings under Amendment 2 bear interest at the rate of 5.0%. The warrant agreement contains a performance clause that the Company met, resulting in additional financing extended and issuance of a warrant to purchase 86,580 additional shares of common stock with an exercise price of $0.05 per share (See Note 9).

In September 2014, the Original Term Loan was further amended ("Amendment No. 3") to extend the loan draw period through the earlier to occur of September 30, 2014 and an Event of Default.

The Company capitalized deferred financing costs of approximately $38 in entering into the Original Term Loan, of which approximately $16 was repaid at the time of Amendment No. 1 with the remaining approximately $22 being amortized to interest expense over the term of the debt. The balance of deferred financing costs was approximately $15 and $7 at December 31, 2013 and December 31, 2014 respectively. The total outstanding amount of the loans was $958 and $8,000 at December 31, 2013 and December 31, 2014 respectively. Interest expense on these notes payable totaled $62 and $208 or the years ended December 31, 2013 and December 31, 2014.

In November and December of 2014 the Company entered into a Note Purchase Agreement (the "Bridge Notes") allowing for the issuance of $5,000 of convertible promissory notes to a group of investors (the "Holders") bearing interest at a rate per annum of 6.0%. The Holders are related parties of the Company. All notes become due and payable at the earlier to occur of a qualified financing, a deemed liquidation event and November 2015.

As of December 31, 2014, future payments under the Company's debt agreements are as follows:


2015	$	6,194
2016		2,667
2017		2,667
2018		1,479

Balance as of December 31, 2014	$	13,007

WARRANTS	12 Months Ended
WARRANTS	Dec. 31, 2014
WARRANTS
WARRANTS	9. WARRANTS In November 2010, the Company issued to Comerica Bank a warrant to purchase 33,746 shares of a series of then outstanding preferred stock with an exercise price of $1.778 per share through October 28, 2017. In February 2012, all outstanding shares of Preferred Stock were converted to shares of Series A Preferred Stock. As such the warrant was amended to be exercisable into 33,746 shares of Series A Preferred Stock. In December 2013, a Performance Adjustment (See Note 10) occurred, pursuant to which the Series A Preferred Stock and common stock were subject to modification such that every two shares of issued and outstanding Series A Preferred Stock and common stock became one share of each class respectively, resulting in the warrant being adjusted to represent the right to purchase 16,873 shares of Series A Preferred Stock. The shares of Series A Preferred Stock have certain mandatorily redeemable features resulting in the warrant being recorded as a liability and re-measured at each period at fair value. The fair value of the warrant was de minimis at December 31, 2013 and December 31, 2014. In connection with the issuance of the Original Term Loan (See Note 8), in August 2012, the Company issued to SVB a warrant to purchase 3,450 shares of common stock with an exercise price of $0.48 per share through August 27, 2022. This Performance Adjustment resulted in the number of common shares issuable upon exercise of the warrant being adjusted to 1,725. In connection with the execution of Amendment No. 1 to the Original Term Loan in January 2014, the Company issued an additional warrant to the lending financial institution. In January 2014, the Company issued a warrant to purchase 2,091 shares of common stock with an exercise price of $0.35 per share through January 31, 2024. The warrant agreement provides for additional warrant shares to be issued and immediately exercisable upon additional borrowings by the Company. Additional borrowings are contingent upon meeting certain performance measures for the Company's lead product candidate. The Company met the performance measures and in August 2014 additional financing was extended. Based on the terms of the warrant agreement an additional 12,548 shares were granted. The fair value of these warrants was de minimis at December 31, 2013 and December 31, 2014.

EQUITY

12 Months Ended

Dec. 31, 2014

EQUITY

EQUITY

10. EQUITY

As of December 31, 2013, the authorized capital stock of the Company included 72,000,000 shares of common stock, par value $0.001 per share, 962,960 of which were issued and outstanding. As of December 31, 2013, 54,481,000 shares of preferred stock were authorized, designated as Series A, Series B and Series C Preferred Stock of which 9,232,334, 27,324,237 and 8,658,008 were issued and outstanding, respectively.

As of December 31, 2014, the authorized capital stock of the Company included 72,000,000 shares of common stock, par value $0.001 per share, 1,006,219 of which were issued and outstanding. As of December 31, 2014, 54,481,000 shares of preferred stock were authorized, designated as Series A, Series B and Series C Preferred Stock of which 9,232,334, 27,324,237 and 8,658,008 were issued and outstanding, respectively.

Common Stock

General

The voting, dividend and liquidation rights of the holders of shares of common stock are subject to and qualified by the rights, powers and preferences of the holders of shares of preferred stock. Common stock has the characteristics described herein.

Voting

The holders of shares of common stock are entitled to one vote for each share of common stock held, may act by written consent in lieu of shareholder's meetings in accordance with the Company's articles of incorporation, and shall be entitled to notice of shareholder's meetings.

Dividends

The Company shall not declare, pay or set aside any dividends on shares of common stock (other than dividends on shares of common stock payable in shares of common stock) unless in addition to obtaining any consents required by law and/or the Company's articles of incorporation, the holders of Series A, Series B and Series C Preferred Stock then outstanding receive a dividend payment as specified in the Company's articles of incorporation.

Liquidation

After payment of all preferential amounts required to be paid to the holders of shares of Preferred Stock, the remaining assets of the Company available for distribution to the shareholders shall be distributed among the holders of shares of Preferred Stock and common stock pro rata based on the number of shares held by each such holder, treating for this purpose all such securities as if they had been converted to common stock pursuant to the terms of the Company's articles of incorporation immediately prior to such dissolution, liquidation or winding up or deemed liquidation event of the Company.

Reserved for future issuance

The Company has reserved for future issuance the following number of shares of common stock:

		As of December 31, 2014

Conversion of Series A Preferred			18,498,419
Conversion of Series B Preferred			27,324,237
Conversion of Series C Preferred			8,658,344
Options to purchase common stock			3,412,685

Total			57,893,685

Convertible Redeemable Preferred Stock

Series A, B and Series C Redeemable Convertible Preferred Stock

In February 2012, the Company exchanged all previously outstanding preferred stock into 18,464,674 shares of Series A Preferred Stock ("Series A"), par value $0.001. On the same date, the Company issued 27,324,237 shares of Series B Preferred Stock ("Series B"), par value $0.001 for $0.84 per share, which resulted in gross proceeds of $20,050. Closing costs associated with the issuance of the Series B amounted to $147. These costs were recorded as a reduction of the carrying amount of the Series B and are being accreted to the carrying value of the applicable preferred stock. During 2013, the Company issued 8,658,008 shares of Series C Preferred Stock ("Series C") in exchange for $12,000 in a series of tranches. Costs incurred in connection with the issuance of Series C amounted to $45 and have been recorded as a reduction to the carrying amount of Series C and were accreted to the carrying value of the applicable preferred stock. In accordance with the terms of the Series C Preferred Stock Purchase Agreement, the Company authorized the sale and issuance of up to 8,658,008 shares of Series C for total gross proceeds of $12,000. Closing costs associated with the issuance of Series C amounted to $45. The Series C financing was structured to close in two tranches. The Company determined the right of the investors to purchase shares of Series C in a future tranche met the definition of a freestanding financial instrument and was recognized as a liability at fair value. The Company adjusted the carrying value of the tranche obligations to its estimated fair value at each reporting date and upon closing of the second tranche in December 2013. Increases or decreases in the fair value of the tranche obligations were recorded as other expense, net, in the statements of operations.

The first tranche closed in August and September 2013 and resulted in the issuance of 2,886,004 shares of Series C for gross cash proceeds of $4,000. Upon the first tranche closing, the Company recognized a liability of $266 for the fair value of the future tranche obligations. The fair value of the freestanding instrument tranche obligations was determined using Black-Scholes option-pricing models on the date of the issuance using the following assumptions: fair value of Series C of $1.30, expected life of 0.35 to 0.43 years and expected volatility of 53% to 60%.

The liability related to the tranche obligations was remeasured at fair value up to the date of the closing of the second tranche in December 2013. Upon the closing of the second tranche, the Company derecognized the tranche obligation, which resulted in a net increase in the proceeds allocated to the Series C shares of $345. The fair value of the freestanding instrument tranche obligations was determined using Black-Scholes option-pricing models on the date of the issuance using the following assumptions: fair value of Series C of $1.27, expected life of 0.16 years and expected volatility of 52%.

The valuation of the tranche obligation liability was determined to be a Level 3 valuation based upon the use of unobservable inputs. A roll-forward of the recurring fair value measurements of the tranche liability categorized with Level 3 inputs are as follows:


Balance — December 31, 2012	$	—
Tranche liability upon issuance		266
Change in fair value		79
Tranche liability upon close of tranche		(345	)

Balance — December 31, 2013	$	—

The closing of the second tranche of Series C in December 2013 triggered the Performance Adjustment (described below) of the outstanding shares of Series A and common stock to which the Series A and common stock were subject to modification in which every two shares of issued and outstanding Series A and common shares became one share of each class respectively. In connection with the Performance Adjustment, the Company adjusted the carrying value of the outstanding shares of Series A to its redemption amount by recording a decrease of $12,239.

As of December 31, 2014, the holders of Series A, Series B and Series C Preferred Stock had rights, preferences, privileges and restrictions as follows:

Voting

The holders of shares of Preferred Stock are entitled to the number of votes equal to the number of whole shares of common stock into which the shares of the applicable series of Preferred Stock held by such holder are convertible as of the record date. Except as provided by law or otherwise, the holders of shares of Preferred Stock vote together with the holders of shares of common stock as a single class. The holders of record of Series A exclusively and as a separate class are entitled to elect two directors of the Company. The holders of record of Series B and Series C exclusively and as a separate class are entitled to elect one director, respectively, of the Company. The Company cannot amend, alter or repeal the preferences, special rights or other powers of the Series A, Series B or Series C without the written consent or affirmative vote of not less than 66% of the then outstanding shares of the respective class.

Dividends

From and after the issuance of any shares of Series A, Series B and Series C cumulative non-compounding stock, dividends will accrue at a rate of 4.5%, 8.0% and 8.0% per annum respectively per share. In the event a dividend is declared on common stock, Series A, Series B and Series C will receive a dividend equal to the equivalent number of common shares multiplied by the dividend payable on each class of stock. The Company has recorded cumulative accrued dividends for Series A, Series B and Series C of $2,371, $5,307 and $1,114, respectively, as of December 31, 2013 and 2014.

Conversion

Each share of Series A, Series B and Series C is convertible at the option of the holder at any time into such number of fully paid and nonassessable shares of common stock as is determined by dividing the original issue price of each Series by its conversion price of $8.46, $5.80 and $9.59 per share, respectively.

Conversion is mandatory for all Series upon an IPO with gross proceeds in excess of $50,000 and a price per share of at least $20.70.

Special Mandatory Conversion

Any holder of at least 1,000,000 shares of Preferred Stock who does not participate in a Qualified Financing by purchasing such holder's applicable portion of the shares of each Preferred Stock, within the time period specified by the Company, are automatically converted into shares of Common Stock at the applicable Conversion Price to that series of Preferred Stock concurrently with the Qualified Financing. A Qualified Financing is a financing or series of financings after the issuance date of the Series C involving the sale of additional shares of common stock (including pursuant to the conversion of debt) with gross proceeds of more than $1,000.

Liquidation Rights

In the event of any voluntary or involuntary liquidation, dissolution or winding-up of the affairs of the Company or a Deemed Liquidation Event, the holders of Series B are entitled to be paid out an amount per share equal to two times the Series B original issue price of $5.80 plus unpaid accrued dividends. The holders of Series A and Series C are entitled to be paid out an amount per share equal to one times the original issue price of $8.46 and $9.59, respectively, plus any unpaid accrued dividends. After the payment of all preferential amounts required to be paid to the holders of the Preferred Stock, all the remaining assets of the Company shall be distributed among the holders of the common and Preferred Stock pro rata based on the number of shares held.

Participation

In the event of liquidation, payment to the holders of Series C shall precede payment to the holders of Series B, which shall precede payment to the holders of Series A. Holders of Series C shall be paid at their Original Issuance Price plus any unpaid accrued dividends. In the event that the amount to be distributed to the shareholders is in excess of the Series A, Series B and Series C liquidation preferences, the preferred holders shall participate on an as-converted basis with the common stock holders in the distribution of the remaining assets.

Redemption

The Company shall require a redemption of Series A, Series B and Series C in the event of a deemed liquidation event, including (i) merger or consolidation, (ii) sale or transfer of substantially all of the Company's assets or (iii) sale or exchange or transfer by the Company's shareholders of a majority of the voting power of the Company unless the requisite holders (as defined in the Company's articles of incorporation) elect otherwise.

There is an optional redemption feature on or after August 27, 2019 for all series of Preferred Stock, upon a vote of at least 60% of the holders of the Preferred Stock voting as a single class. The payment is equal to the original issuance price for Series A and Series C and two (2) times the original issuance price for Series B, plus unpaid accrued dividends on the date of the redemption. Optional redemption shall be paid in three installments.

Protective Provision

At any time when there are shares of Series B and Series C outstanding the Company will not engage in certain activities (including enter into a liquidating event) without written consent of a majority of the Series B and Series C holders.

Performance Adjustment

The Company's articles of incorporation provided that if the Company raised additional capital in excess of $4,000 after the initial closing of the Series C financing, that such additional financing would trigger a one-time modification of the Series A and common stock shares (the "Performance Adjustment"), such that every two shares of issued and outstanding Series A and common stock became one share of each class, respectively. The Performance Adjustment occurred in December 2013.

STOCK BASED COMPENSATION

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

STOCK BASED COMPENSATION

8. STOCK-BASED COMPENSATION

In July 2014, the Company adopted the 2014 Stock Incentive Plan (the "Plan"), under which 525,700 shares of common stock are authorized for issuance to employees, officers, directors, consultants and advisors of the Company. In connection with the Company's reincorporation into Virginia in July 2014, each outstanding option to purchase shares of common stock under the Company's 2012 Stock Incentive Plan and 2002 Stock Plan, was automatically terminated and replaced with an option to purchase shares of common stock under the Plan having the same vesting terms and exercise price as the option that was replaced. The Plan provides for granting of both Internal Revenue Service qualified incentive stock options ("ISOs") and non-qualified options ("NQs"), restricted stock awards ("RSAs") and restricted stock units ("RSUs"). Stock options generally vest over a four year period of service; however, certain options contain performance conditions. The options generally have a ten year contractual life and, upon termination, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately.

In April 2015, the Plan was amended to increase the maximum number of shares of common stock that may be issued to 2,700,000 shares. In addition, an "evergreen provision" was added to the Plan that allows for an annual increase in the number of shares of common stock available for issuance under the Plan. The annual increase will be added on the first day of each fiscal year beginning with the fiscal year ending December 31, 2016, and on each anniversary thereof until the expiration of the Plan equal to 4% of the outstanding shares of our common stock on December 31st of the immediately preceding fiscal year (or such lesser number of shares of common stock as determined by the board of directors).

Restricted common stock

A summary of the Company's restricted stock activity for the nine months ended September 30, 2015 and related information is as follows:

			Weighted average purchase price per share

Unvested at December 31, 2014	15,387		$	0.69
Granted	194,694			5.73
Vested	(128,955	)		5.13

Unvested at September 30, 2015⁽¹⁾	81,126		$	5.73

(1): Excludes 72,463 shares of unvested restricted stock remaining from the early exercise of stock options as of September 30, 2015.

Stock options

A summary of the Company's stock option activity and related information follows:

			Weighted- average exercise price per share			Aggregate Intrinsic Value

Outstanding at December 31, 2014	281,029		$	0.69
Granted	1,197,452			10.47
Exercised	(121,729	)		3.89
Cancelled	(506	)		2.06

Outstanding at September 30, 2015	1,356,246		$	9.04	9.2	$	17,722



Exercisable at September 30, 2015	208,438		$	2.65	7.9	$	4,056



Vested and expected to vest at September 30, 2015	1,341,543		$	9.13	9.2	$	18,595

The fair value of each stock option is estimated on the grant date using the Black-Scholes option-pricing model using the following assumptions:

	Nine months ended September 30,

	2014			2015
Risk-free interest rate		1.8	%		1.7	%
Dividend yield		—			—
Volatility		77	%		77	%
Expected term (years)		6.25			6.21

11. STOCK-BASED COMPENSATION

Restricted Stock Awards and Stock Options

In July 2014, the Company adopted the 2014 Stock Incentive Plan (the "Plan"), under which 525,700 shares of common stock are authorized for issuance to employees, officers, directors, consultants and advisors of the Company. As of December 31, 2014, 281,029 of the shares of common stock authorized for issuance pursuant to the Plan were outstanding. In connection with the Company's reincorporation into Virginia in July 2014, each outstanding option to purchase shares of common stock under the 2012 Stock Incentive Plan and 2002 Stock Plan, was automatically terminated and replaced with an option to purchase shares of common stock under the Plan having the same vesting terms and exercise price as the option that was replaced. The Plan provides for granting of both Internal Revenue Service qualified incentive stock options ("ISOs") and non-qualified options ("NQs"), restricted stock awards ("RSAs") and restricted stock units ("RSUs"). Stock options generally vest over a four year period of service; however, certain options contain performance conditions. The options generally have a ten year contractual life and, upon termination, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately.

In determining the exercise prices for options granted, the board of directors considered the fair value of the common stock as of the measurement date. The fair value of the common stock was determined by the board of directors based on a variety of factors, including valuations prepared by third parties, Company's financial position, the status of development efforts within the Company, the composition and ability of the current scientific and management teams, the current climate in the marketplace, the illiquid nature of the Company's common stock, arm's length sales of the Company's preferred stock, the effect of the rights and preferences of the preferred shareholders, and the prospects of a liquidity event, among others.

In connection with the Performance Adjustment which occurred on December 4, 2013 (See Note 10) the Company adjusted previously granted and then outstanding options such that for each option exercised, the option holder would receive one share of common stock for every two shares of common stock underlying the grant.

Stock option activity under the Plan is summarized as follows:

			Weighted- Average Exercise Price			Aggregate Intrinsic Value

Outstanding at December 31, 2012	323,488		$	1.73	6.94	$	8
Granted	146,730			0.48
Exercised	(1,077	)		0.62
Cancelled	(9,559	)		2.76
Modification	(229,791	)		1.17

Outstanding at December 31, 2013	229,791			1.17	7.02		117
Granted	89,641			0.28
Exercised	(32,390	)		2.21			—
Cancelled	(6,013	)		4.42

Outstanding at December 31, 2014	281,029		$	0.69	7.49	$	1,505



Vested and expected to vest at December 31, 2014	247,139		$	0.83	4.31	$	1,293
Exercisable at December 31, 2014	121,304		$	1.38	4.31	$	570

As of December 31, 2013 and 2014, the unrecognized compensation cost related to outstanding options was $40 and $215, respectively, and is expected to be recognized as expense over approximately 1.1 years and 1.0 years, respectively.

As of December 31, 2014, the weighted average fair value of vested options was $1.93.

Additional information about the Company's stock option activity is as follows:

	As of December 31,

	2013		2014
Weighted-average grant date fair value per share of employee option grants	$	0.28	$	0.76

Restricted stock awards under the Plan are summarized as follows:

			Weighted-Average Grant Date Fair Value

Unvested at December 31, 2012	203,342		$	0.62
Vesting of restricted stock	(89,308	)		0.55
Performance Adjustment	(58,736	)		0.62

Unvested at December 31, 2013	55,298			0.69
Grant of restricted stock	10,869			1.24
Vesting of restricted stock	(50,780	)		0.62

Unvested at December 31, 2014	15,387		$	0.69

As of December 31, 2013 and 2014, the unrecognized compensation cost related to restricted stock awards was $73 and $26, respectively, and is expected to be recognized as expense over approximately 1.2 years and 0.2 years, respectively.

Stock-Based Compensation Expense

The Company granted stock options to employees for the years ended December 31, 2013 and 2014. The Company estimates the fair value of stock options as of the date of grant using the Black-Scholes option pricing model and restricted stock based on the fair value of the award. Stock options and restricted stock issued to non-board member, non-employees are accounted for using the fair value approach and are subject to periodic revaluation over their vesting terms.

Stock-based compensation for all stock options and restricted stock awards are reported within:

	Years Ended December 31,

	2013		2014
Research and development	$	24	$	12
General and administrative		38		10

Total stock-based compensation expense	$	62	$	22

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:

	Years Ended December 31,

	2013	2014
Risk-free interest rate	1.09% – 1.22%		1.80	%
Expected volatility	87.8%		77.1	%
Expected term (in years)	6.25		6.25
Expected dividend yield	0.0%		0.0	%

Risk-free Interest Rate. The risk-free interest rate assumption is based on observed interest rates appropriate for the expected term of the stock option grants.

Expected Volatility. Due to the Company's limited operating history and lack of company-specific historical or implied volatility, the expected volatility assumption is based on historical volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the biotechnology and medical device industries.

Expected Term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historical exercise behavior, through December 31, 2014 it determined the expected life assumption using the simplified method, which is an average of the contractual term of the option and its vesting period. In 2013, some of the stock option grants were in-the-money, based on the retrospective fair value determinations, so the Company determined the expected life using a risk-adjusted method, which adjusts the average of the contractual term of the option and its vesting period for risk, thereby reducing the expected life.

Expected Dividend Yield. The expected dividend yield assumption is based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends.

INCOME TAXES

12 Months Ended

Dec. 31, 2014

INCOME TAXES

INCOME TAXES

12. INCOME TAXES

For the years ended December 31, 2014 and 2013, the Company did not record a current or deferred income tax expense or (benefit) due to current and historical losses incurred by the Company. The Company's losses before income taxes consist solely of domestic losses.

A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows:

	As of December 31,

	2013			2014
Federal income tax (benefit) at statutory rate		34.00	%		34.00	%
(Increase) decrease income tax (benefit) resulting from:
Expiration of state net operating losses		(12.11	)		0.00
Permanent items		(0.01	)		(0.17	)
Research and experimental credits		4.19			3.74
Change in valuation allowance		(26.07	)		(37.57	)

Income tax expense (benefit)		0.00	%		0.00	%

Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the Company's deferred tax assets and liabilities are comprised of the following:

	As of December 31,

	2013			2014
Deferred tax assets:
Net operating loss carryforwards	$	21,392		$	28,419
Depreciation and amortization		—			36
Research Credits		2,400			3,070

Deferred tax assets before valuation allowance		23,792			31,525
Valuation allowance		(23,788	)		(31,525	)

		4			—
Deferred tax liabilities:
Depreciation and amortization		(4	)		—

		(4	)		—

Net deferred tax assets	$	—		$	—

The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. As of December 31, 2014 and 2013, based on the Company's history of operating losses, the Company has concluded that it is not more likely than not that the benefit of its deferred tax assets will be realized. Accordingly, the Company has provided a full valuation allowance for deferred tax assets as of December 31, 2014 and 2013. The valuation allowance increased $7,737 during the year ended December 31, 2014, due primarily to net operating losses generated. The valuation allowance increased by $5,081 during the year ended December 31, 2013, due primarily to net operating losses generated.

As of December 31, 2014 and 2013, the Company had U.S. federal net operating loss carryforwards of $78,276 and $60,380, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2034. As of December 31, 2014 and 2013, the Company also had U.S. state net operating loss carryforwards of $34,184 and $16,354, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2034.

Utilization of the NOL and research and development credit carryforwards may be subject to a substantial annual limitation due to ownership change limitations that have occurred or that could occur in the future, as required by Section 382 and Section 383 of the Internal Revenue Code of 1986, as amended (the "Code"), as well as similar state and foreign provisions. These ownership changes may limit the amount of net operating loss and research and development credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. In general, an "ownership change" as defined by Section 382 of the Code results from a transaction or series of transactions over a three-year period resulting in an ownership change of more than 50 percentage points of the outstanding stock of a company by certain shareholders. The Company has not completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since its formation. The Company has not recorded net operating losses that, as a result of these restrictions, will expire unused.

The Company files income tax returns in the United States and Massachusetts. The federal and Massachusetts income tax returns are generally subject to tax examinations for the tax years ended December 31, 2011 through December 31, 2013. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period.

EMPLOYEE BENEFITS	12 Months Ended
EMPLOYEE BENEFITS	Dec. 31, 2014
EMPLOYEE BENEFITS
EMPLOYEE BENEFITS	13. EMPLOYEE BENEFITS The Company has a retirement savings plan, which is qualified under section 401(k) of the Code, for its employees. The plan allows eligible employees to defer, at the employee's discretion, pretax compensation up to the Internal Revenue Service annual limits. Employees become eligible to participate after completing 3 months of service. The Company is not required to contribute to this plan. Total expense for contributions made by the Company was $31 for the year ended December 31, 2013 and $35 for the year ended December 31, 2014.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2014
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	14. SUBSEQUENT EVENTS The Company has completed an evaluation of all subsequent events through April 27, 2015, the date these financial statements are available to be issued. The Company has concluded that no subsequent event has occurred that requires disclosure, except as noted below: (a) In March 2015, the Company sold 41,666,667 shares of Series D convertible preferred stock for aggregate consideration of $50,000, comprised of $45,000 in cash and conversion of $5,000 in convertible notes with related parties. The convertible notes converted into 4,166,667 shares of Series D convertible preferred stock. The accrued interest on the convertible notes was waived. In this financing, the mandatory conversion for all series of preferred stock was modified so as to occur upon an initial public offering with gross proceeds in excess of $50,000. (b) On March 24, 2015, Purdue sued the Company in the District of Delaware asserting infringement of four patents. On March 26, 2015, Purdue filed a second suit against the Company in the District of Massachusetts asserting infringement of the same four patents. (c) In March 2015, the Company granted a total of 638,095 stock options under the Plan to employees. The stock options were granted at fair market value on the date of grant, vest over approximately four years and expire ten years from the date of grant. (d) In March 2015, the Plan was amended to increase the maximum number authorized for issuance pursuant to the Plan to 1,087,005 shares. (e) In March 2015, the Company amended its lease to include an additional 9,660 square feet of space for a total of 19,335 square feet. In addition, the lease term was extended and now terminates on the date that is 5 years following the date, which has not yet been determined, on which the landlord delivers the expansion space with certain improvements substantially completed. At the Company's election, the lease term may be extended for an additional 5-year term. (f) In April 2015, the Company granted 194,694 shares of restricted stock to an employee. Pursuant to the grant, 97,347 shares vested upon grant, while the remaining 97,347 shares of restricted stock vest in monthly installments over a three-year period commencing as of the date of grant. (g) In April 2015, the Company's board of directors and shareholders approved a one-for-6.9 reverse split of the Company's common stock. All common stock share and per share amounts in the financial statements have been retroactively adjusted for all periods presented to give effect to the reverse split of our common stock, including reclassifying an amount equal to the reduction in par value to additional paid-in capital.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Unaudited Pro Forma Balance Sheet and Net Loss per Share Information

Use of Estimates

Use of Estimates

Unaudited Pro Forma Net Loss per Share Information

Fair Value Measurements

Fair Value Measurements

Transfers are calculated on values as of the transfer date. There were no transfers between Levels 1, 2 and 3 during the years ended December 31, 2013 and 2014.

Concentration of Credit Risk

Concentration of Credit Risk

Cash and Cash Equivalents

Cash and Cash Equivalents

Property and Equipment

Property and Equipment

Asset Category		Estimated Useful Life

Machinery and equipment		5 years
Computers and office equipment		5 years
Furniture and fixtures		7 years
Leasehold improvements		5 years

Upon retirement or sale, the cost of assets disposed and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recorded in the statements of operations.

Impairment of Long Lived Assets

Impairment of Long-Lived Assets

Impairment losses, if any, are recognized in earnings. An impairment loss would be recognized in an amount equal to the excess of the carrying amount over the undiscounted expected future cash flows.

Initial Public Offering Costs

Initial Public Offering

Initial Public Offering Costs

Restricted Cash

Restricted Cash

Deferred Rent

Deferred Rent

Convertible Redeemable Preferred Stock

Convertible Redeemable Preferred Stock

Research and Development Costs

Research and Development Costs

Patent Costs

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expense as incurred since the recoverability of such expenditures is uncertain.

Stock-Based Compensation

Stock-Based Compensation

Income Taxes

Income Taxes

Net loss per Common Share

Earnings (Loss) per Common Share

Net loss per Common Share

Recently Issued Accounting Pronouncements

Recent Accounting Pronouncements

Recently Issued Accounting Pronouncements

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2014

Schedule of estimated useful lives of property and equipment

Asset Category		Estimated Useful Life

Machinery and equipment		5 years
Computers and office equipment		5 years
Furniture and fixtures		7 years
Leasehold improvements		5 years

NET LOSS PER COMMON SHARE (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Schedule of computations of basic and diluted net loss per share

	Nine months ended September 30,

	2014			2015
Net loss	$	(14,448	)	$	(17,730	)
Extinguishment of preferred stock — see note 7		—			31,806
Accretion of prior preferred stock — see note 7		(2,469	)		(23,327	)
Accretion and dividends of Series D preferred stock		—			(1,245	)

Loss attributable to common shareholders — basic and diluted	$	(16,917	)	$	(10,496	)



Weighted-average number of common shares used in net loss per share — basic and diluted		926,597			11,179,756



Net loss per share — basic and diluted	$	(18.26	)	$	(0.94	)

	Years Ended December 31,

	2013			2014
Net loss	$	(16,197	)	$	(17,917	)
Performance Adjustment of Series A		12,239			—
Accruals of dividends and accretion to redemption value of preferred stock		(2,925	)		(3,300	)

Loss attributable to common shareholders — basic and diluted	$	(6,883	)	$	(21,217	)



Weighted-average shares used in computing basic and diluted net loss per common share		1,697,044			933,997



Basic and diluted net loss per common share	$	(4.06	)	$	(22.72	)

Schedule of potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding

	Nine months ended September 30,

	2014		2015
Outstanding stock options		311,365		1,356,246
Warrants		18,810		2,445
Redeemable convertible preferred stock		6,552,820		—
Unvested restricted stock		28,536		153,589

	Years Ended December 31,

	2013		2014
Stock Options		229,791		281,029
Warrants		4,170		18,809
Redeemable convertible preferred stock		6,552,820		6,552,820
Unvested restricted stock		55,298		15,387

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)

12 Months Ended

Dec. 31, 2014

PREPAID EXPENSES AND OTHER CURRENT ASSETS

Schedule of components of prepaid expenses and other current assets

	As of December 31,

	2013		2014
Other current assets	$	—	$	253
Initial public offering costs		—		233
Employee advances		21		33
Prepaid expenses		33		8
Prepaid development costs		656		—

Prepaid expenses and other current assets	$	710	$	527

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2014

PROPERTY AND EQUIPMENT

Schedule of components of property and equipment

	As of December 31,

	2013			2014
Machinery and equipment	$	741		$	741
Computers and office equipment		26			26
Furniture and fixtures		36			44
Leasehold improvements		606			606

Total property and equipment		1,409			1,417
Less: accumulated deprecation		(716	)		(903	)

Property and equipment, net	$	693		$	514

ACCRUED EXPENSES (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Schedule of components of accrued expenses

	December 31, 2014		September 30, 2015

Accrued compensation	$	635	$	1,169
Accrued development costs		970		597
Accrued marketing		—		685
Accrued audit and legal		249		109
Accrued interest		71		31
Accrued other		31		90

Total accrued expenses	$	1,956	$	2,681

	As of December 31,

	2013		2014
Accrued development costs	$	520	$	970
Accrued compensation		449		635
Accrued audit and legal		12		249
Accrued interest		—		71
Accrued other		32		31

Total accrued expenses	$	1,013	$	1,956

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2014

COMMITMENTS AND CONTINGENCIES.

Schedule of aggregate minimum annual lease commitments under non-cancellable operating lease

Aggregate minimum annual lease commitments of the Company under its non-cancellable operating lease as of December 31, 2014 are as follows:

Year Ending December 31,

2015	$	106
2016		111
2017		116

Total minimum lease payments	$	333

DEBT (Tables)

12 Months Ended

Dec. 31, 2014

DEBT

Schedule of future payments under debt agreements

As of December 31, 2014, future payments under the Company's debt agreements are as follows:


2015	$	6,194
2016		2,667
2017		2,667
2018		1,479

Balance as of December 31, 2014	$	13,007

EQUITY (Tables)

12 Months Ended

Dec. 31, 2014

EQUITY

Schedule of shares of common stock reserved for future issuance

		As of December 31, 2014

Conversion of Series A Preferred			18,498,419
Conversion of Series B Preferred			27,324,237
Conversion of Series C Preferred			8,658,344
Options to purchase common stock			3,412,685

Total			57,893,685

Schedule of roll-forward of recurring fair value measurements of tranche liability categorized with Level 3 inputs


Balance — December 31, 2012	$	—
Tranche liability upon issuance		266
Change in fair value		79
Tranche liability upon close of tranche		(345	)

Balance — December 31, 2013	$	—

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Summary of stock option activity

			Weighted- average exercise price per share			Aggregate Intrinsic Value

Outstanding at December 31, 2014	281,029		$	0.69
Granted	1,197,452			10.47
Exercised	(121,729	)		3.89
Cancelled	(506	)		2.06

Outstanding at September 30, 2015	1,356,246		$	9.04	9.2	$	17,722



Exercisable at September 30, 2015	208,438		$	2.65	7.9	$	4,056



Vested and expected to vest at September 30, 2015	1,341,543		$	9.13	9.2	$	18,595

			Weighted- Average Exercise Price			Aggregate Intrinsic Value

Outstanding at December 31, 2012	323,488		$	1.73	6.94	$	8
Granted	146,730			0.48
Exercised	(1,077	)		0.62
Cancelled	(9,559	)		2.76
Modification	(229,791	)		1.17

Outstanding at December 31, 2013	229,791			1.17	7.02		117
Granted	89,641			0.28
Exercised	(32,390	)		2.21			—
Cancelled	(6,013	)		4.42

Outstanding at December 31, 2014	281,029		$	0.69	7.49	$	1,505



Vested and expected to vest at December 31, 2014	247,139		$	0.83	4.31	$	1,293
Exercisable at December 31, 2014	121,304		$	1.38	4.31	$	570

Schedule of additional information about stock option activity

	As of December 31,

	2013		2014
Weighted-average grant date fair value per share of employee option grants	$	0.28	$	0.76

Summary of restricted stock awards

			Weighted average purchase price per share

Unvested at December 31, 2014	15,387		$	0.69
Granted	194,694			5.73
Vested	(128,955	)		5.13

Unvested at September 30, 2015⁽¹⁾	81,126		$	5.73

(1): Excludes 72,463 shares of unvested restricted stock remaining from the early exercise of stock options as of September 30, 2015.

			Weighted-Average Grant Date Fair Value

Unvested at December 31, 2012	203,342		$	0.62
Vesting of restricted stock	(89,308	)		0.55
Performance Adjustment	(58,736	)		0.62

Unvested at December 31, 2013	55,298			0.69
Grant of restricted stock	10,869			1.24
Vesting of restricted stock	(50,780	)		0.62

Unvested at December 31, 2014	15,387		$	0.69

Schedule of stock-based compensation for all stock options and restricted stock awards

	Years Ended December 31,

	2013		2014
Research and development	$	24	$	12
General and administrative		38		10

Total stock-based compensation expense	$	62	$	22

Schedule of weighted-average assumptions used in Black-Scholes option-pricing model

	Nine months ended September 30,

	2014			2015
Risk-free interest rate		1.8	%		1.7	%
Dividend yield		—			—
Volatility		77	%		77	%
Expected term (years)		6.25			6.21

	Years Ended December 31,

	2013	2014
Risk-free interest rate	1.09% – 1.22%		1.80	%
Expected volatility	87.8%		77.1	%
Expected term (in years)	6.25		6.25
Expected dividend yield	0.0%		0.0	%

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2014

INCOME TAXES

Schedule of reconciliation of income tax expense (benefit) at statutory federal income tax rate to income taxes

	As of December 31,

	2013			2014
Federal income tax (benefit) at statutory rate		34.00	%		34.00	%
(Increase) decrease income tax (benefit) resulting from:
Expiration of state net operating losses		(12.11	)		0.00
Permanent items		(0.01	)		(0.17	)
Research and experimental credits		4.19			3.74
Change in valuation allowance		(26.07	)		(37.57	)

Income tax expense (benefit)		0.00	%		0.00	%

Schedule of significant components of deferred tax assets and liabilities

	As of December 31,

	2013			2014
Deferred tax assets:
Net operating loss carryforwards	$	21,392		$	28,419
Depreciation and amortization		—			36
Research Credits		2,400			3,070

Deferred tax assets before valuation allowance		23,792			31,525
Valuation allowance		(23,788	)		(31,525	)

		4			—
Deferred tax liabilities:
Depreciation and amortization		(4	)		—

		(4	)		—

Net deferred tax assets	$	—		$	—

NATURE OF BUSINESS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Deficit accumulated
Deficit accumulated	$ 119,483	$ 101,753	$ 80,536

NATURE OF BUSINESS (Details 2) - USD ($) $ in Thousands		1 Months Ended	9 Months Ended
NATURE OF BUSINESS (Details 2) - USD ($) $ in Thousands	Mar. 06, 2015	Mar. 31, 2015	Sep. 30, 2015
Preferred stock
Principal amount converted			$ 5,000
6.0% Convertible promissory notes
Preferred stock
Principal amount converted		$ 5,000
Series D convertible redeemable preferred stock
Preferred stock
Cash consideration from issuance of preferred stock		$ 45,000
Subsequent events \| Private Placement \| Investors \| Series D convertible redeemable preferred stock
Preferred stock
Aggregate consideration	$ 50,000
Cash consideration from issuance of preferred stock	45,000
Subsequent events \| Conversion of convertible notes into convertible preferred stock \| Investors \| 6.0% Convertible promissory notes
Preferred stock
Principal amount converted	$ 5,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair value measurements
Asset transfers out of Level 1 into Level 2	$ 0	$ 0
Asset transfers out of Level 2 into Level 1	0	0
Asset transfers into (out of) Level 3	0	$ 0
Financial instruments with off balance sheet risk of loss, assets	0
Financial instruments with off balance sheet risk of loss, liabilities	$ 0

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Carrying amount
Cash and Cash Equivalents
Cash and cash equivalents	$ 1,634	$ 7,551

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3)	Dec. 31, 2014
Machinery and equipment
Property and Equipment
Estimate Useful Life	5 years
Computers and office equipment
Property and Equipment
Estimate Useful Life	5 years
Furniture and fixtures
Property and Equipment
Estimate Useful Life	7 years
Leasehold improvements
Property and Equipment
Estimate Useful Life	5 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4) $ in Thousands	Dec. 31, 2014 USD ($)
Sale of stock
Deferred IPO costs	$ 233
Prepaid expenses and other current assets
Sale of stock
Deferred IPO costs	$ 233

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 5) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation
Options granted (in shares)	1,197,452
Restricted stock granted (in shares)	194,694
Non-employee stock options
Stock-based compensation
Options granted (in shares)		0	0
Restricted stock
Stock-based compensation
Restricted stock granted (in shares)		10,869
Restricted stock \| Non-employee
Stock-based compensation
Restricted stock granted (in shares)		0	0

NET LOSS PER COMMON SHARE (Details) - $ / shares	9 Months Ended		12 Months Ended
NET LOSS PER COMMON SHARE (Details) - $ / shares	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
NET LOSS PER COMMON SHARE
Basic and diluted net loss per common share (in dollars per share)	$ (0.94)	$ (18.26)	$ (18.26)	$ (4.06)

NET LOSS PER COMMON SHARE (Details 2) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Net loss per common share
Net loss	$ (17,730)	$ (14,448)	$ (14,448)	$ (16,197)
Accruals of dividends and accretion to redemption value of preferred stock			(3,300)	(2,925)
Loss attributable to common stockholders - basic and diluted	$ (10,496)	$ (16,917)	$ (21,217)	$ (6,883)
Weighted-average shares used in computing basic and diluted net loss per common share (in shares)	11,179,756	926,597	926,597	1,697,044
Basic and diluted net loss per common share (in dollars per share)	$ (0.94)	$ (18.26)	$ (18.26)	$ (4.06)
Series A convertible redeemable preferred stock
Net loss per common share
Performance Adjustment				$ 12,239
Pro Forma
Net loss per common share
Weighted-average shares used in computing basic and diluted net loss per common share (in shares)			7,471,303
Basic and diluted net loss per common share (in dollars per share)			$ (2.84)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

NET LOSS PER COMMON SHARE (Details 3) - shares	9 Months Ended		12 Months Ended
NET LOSS PER COMMON SHARE (Details 3) - shares	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Stock options
Anti-dilutive securities
Potentially dilutive securities outstanding excluded from the computations of diluted weighted-average shares outstanding (in shares)	1,356,246	311,365	281,029	229,791
Warrants
Anti-dilutive securities
Potentially dilutive securities outstanding excluded from the computations of diluted weighted-average shares outstanding (in shares)	2,445	18,810	18,809	4,170
Redeemable Convertible Preferred Stock
Anti-dilutive securities
Potentially dilutive securities outstanding excluded from the computations of diluted weighted-average shares outstanding (in shares)		6,552,820	6,552,820	6,552,820
Restricted stock
Anti-dilutive securities
Potentially dilutive securities outstanding excluded from the computations of diluted weighted-average shares outstanding (in shares)	153,589	28,536	15,387	55,298

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
PREPAID EXPENSES AND OTHER CURRENT ASSETS
Other current assets		$ 253
Initial public offering costs		233
Employee advances		33	$ 21
Prepaid expenses		8	33
Prepaid development costs			656
Total prepaid expenses and other current assets	$ 866	$ 527	$ 710

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Property and Equipment
Total property and equipment		$ 1,417	$ 1,409
Less: accumulated deprecation		(903)	(716)
Property and equipment, net	$ 627	514	693
Machinery and equipment
Property and Equipment
Total property and equipment		741	741
Computers and office equipment
Property and Equipment
Total property and equipment		26	26
Furniture and fixtures
Property and Equipment
Total property and equipment		44	36
Leasehold improvements
Property and Equipment
Total property and equipment		$ 606	$ 606

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
ACCRUED EXPENSES
Accrued development costs	$ 597	$ 970	$ 520
Accrued compensation	1,169	635	449
Accrued audit and legal	109	249	12
Accrued interest	31	71
Accrued other	90	31	32
Total accrued expenses	$ 2,681	$ 1,956	$ 1,013

COMMITMENTS AND CONTINGENCIES (Details)	9 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details)	Sep. 30, 2015	Dec. 31, 2014
Hatch-Waxman Act of 1984 election to sue for patent infringement \| Maximum
Contingencies
Stay period before FDA can issue a final approval if patent litigation is elected	30 months	30 months

COMMITMENTS AND CONTINGENCIES (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Lease
Rent-free term	2 months
Aggregate minimum annual lease commitments under non cancellable operating lease
2015	$ 106
2016	111
2017	116
Total minimum lease payments	333
Rent expense under operating lease agreement
Rent expense	69	$ 69
Guarantees
Restricted cash	80	80	$ 97
Maximum
Lease inducements
Leasehold improvement allowance	174
Canton facility lease reimbursable allowance
Lease inducements
Reimbursable improvement allowance	$ 164
Interest rate (as a percent)	8.00%
Term	36 months
Stand-by letter of credit
Guarantees
Restricted cash	$ 80	$ 80

DEBT (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended							12 Months Ended
	Aug. 28, 2012	Sep. 30, 2014	Aug. 31, 2014	Feb. 28, 2014	Jan. 31, 2014	Feb. 28, 2013	Oct. 31, 2012	Aug. 31, 2012	Dec. 31, 2014	Dec. 31, 2013
Loan and Security Agreements
Maximum borrowing capacity	$ 1,000
Proceeds from notes payable, net of original note payoff									$ 7,056	$ 500
Common stock warrant, Silicon Valley Bank, Original Term Loan
Loan and Security Agreements
Common stock that may be purchased upon exercise of warrant (in shares)	23,810
Exercise price of warrant (in dollars per share)	$ 0.07
Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 1
Loan and Security Agreements
Common stock that may be purchased upon exercise of warrant (in shares)				14,430
Exercise price of warrant (in dollars per share)				$ 0.05
Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 2
Loan and Security Agreements
Common stock that may be purchased upon exercise of warrant (in shares)			86,580
Exercise price of warrant (in dollars per share)			$ 0.05
Term loan \| Silicon Valley Bank loan agreement
Loan and Security Agreements
Maximum borrowing capacity	$ 1,000
Amount borrowed						$ 500	$ 250	$ 250
Initial period of interest only payments	12 months
Subsequent period of principal and interest payments	36 months
Deferred financing costs	$ 38				$ 22
Financing costs repaid					16
Deferred financing costs, net									7	15
Outstanding amount of loans									8,000	958
Interest expense on notes payable									$ 208	$ 62
Term loan \| Silicon Valley Bank loan agreement \| Prime
Loan and Security Agreements
Variable interest rate margin (as a percent)									2.25%	2.25%
Interest rate (as a percent)	5.50%
Term loan \| Silicon Valley Bank loan agreement, Amendment No. 1
Loan and Security Agreements
Maximum borrowing capacity					$ 6,000
Amount borrowed				$ 2,000
Proceeds from notes payable, net of original note payoff				$ 1,056
Initial period of interest only payments				12 months
Subsequent period of principal and interest payments				36 months
Term loan \| Silicon Valley Bank loan agreement, Amendment No. 1 \| Prime
Loan and Security Agreements
Variable rate basis					1.75%
Interest rate (as a percent)				5.00%
Term loan \| Silicon Valley Bank loan agreement Amendment No. 2
Loan and Security Agreements
Maximum borrowing capacity			$ 8,000
Amount borrowed		$ 3,000	$ 3,000
Initial period of interest only payments			12 months
Subsequent period of principal and interest payments			36 months
Term loan \| Silicon Valley Bank loan agreement Amendment No. 2 \| Prime
Loan and Security Agreements
Interest rate (as a percent)			5.00%

DEBT (Details 2) - Bridge Notes Purchase Agreement - Investors - 6.0% Convertible promissory notes $ in Thousands	2 Months Ended
	Dec. 31, 2014 USD ($)
Related party transactions
Amount issued	$ 5,000
Stated interest rate	6.00%

DEBT (Details 3) $ in Thousands	Dec. 31, 2014 USD ($)
Future payments under debt agreements
2015	$ 6,194
2016	2,667
2017	2,667
2018	1,479
Total	$ 13,007

WARRANTS (Details)	1 Months Ended
WARRANTS (Details)	Apr. 30, 2015	Dec. 31, 2013 shares	Aug. 31, 2014 $ / shares shares	Feb. 28, 2014 $ / shares shares	Jan. 31, 2014 $ / shares shares	Aug. 28, 2012 $ / shares shares	Feb. 29, 2012 shares	Nov. 30, 2010 $ / shares shares
Performance adjustment ratio	0.144927536
Common stock
Performance adjustment ratio		0.5
Series A convertible redeemable preferred stock
Performance adjustment ratio		0.5
Preferred stock warrant issued November 2010
Stock that may be purchased upon exercise of warrant (in shares)								33,746
Exercise price of warrant (in dollars per share) \| $ / shares								$ 1.778
Series A preferred stock warrant
Stock that may be purchased upon exercise of warrant (in shares)		16,873
Common stock warrant, Silicon Valley Bank, Original Term Loan
Stock that may be purchased upon exercise of warrant (in shares)						23,810
Exercise price of warrant (in dollars per share) \| $ / shares						$ 0.07
Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 1
Stock that may be purchased upon exercise of warrant (in shares)				14,430
Exercise price of warrant (in dollars per share) \| $ / shares				$ 0.05
Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 2
Stock that may be purchased upon exercise of warrant (in shares)			86,580
Exercise price of warrant (in dollars per share) \| $ / shares			$ 0.05
Conversion of preferred stock warrant into Series A Preferred Stock warrant \| Series A preferred stock warrant
Stock that may be purchased upon exercise of warrant (in shares)							33,746
Pro Forma \| Common stock warrant, Silicon Valley Bank, Original Term Loan
Stock that may be purchased upon exercise of warrant (in shares)		1,725				3,450
Exercise price of warrant (in dollars per share) \| $ / shares						$ 0.48
Pro Forma \| Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 1
Stock that may be purchased upon exercise of warrant (in shares)					2,091
Exercise price of warrant (in dollars per share) \| $ / shares					$ 0.35
Pro Forma \| Common stock warrant, Silicon Valley Bank, Term Loan, Amendment No. 2
Stock that may be purchased upon exercise of warrant (in shares)			12,548

EQUITY (Details)	12 Months Ended
EQUITY (Details)	Dec. 31, 2014 Vote $ / shares shares	Sep. 30, 2015 $ / shares shares	Dec. 31, 2013 $ / shares shares	Dec. 31, 2012 shares
Equity
Authorized common stock (in shares)	72,000,000	100,000,000	72,000,000
Par value of common stock (in dollars per share) \| $ / shares	$ 0.001	$ 0.001	$ 0.001
Common stock issued (in shares)	1,006,219	20,687,829	962,960
Common stock outstanding (in shares)	1,006,219	1,006,219	962,960
Authorized preferred stock (in shares)	54,481,000		54,481,000
Number of votes each share of common stock held is entitled \| Vote	1
Common stock reserved for future issuance (in shares)	57,893,685
Stock options
Equity
Common stock reserved for future issuance (in shares)	3,412,685
Series A convertible redeemable preferred stock
Equity
Authorized preferred stock (in shares)	18,498,419	0	18,498,419
Preferred stock issued (in shares)	9,232,334	0	9,232,334	18,464,674
Preferred stock outstanding (in shares)	9,232,334	0	9,232,334
Series A convertible redeemable preferred stock \| Conversion of convertible redeemable preferred stock into common stock
Equity
Common stock reserved for future issuance (in shares)	18,498,419
Series B convertible redeemable preferred stock
Equity
Authorized preferred stock (in shares)	27,324,237	0	27,324,237
Preferred stock issued (in shares)	27,324,237	0	27,324,237	27,324,237
Preferred stock outstanding (in shares)	27,324,237	0	27,324,237
Series B convertible redeemable preferred stock \| Conversion of convertible redeemable preferred stock into common stock
Equity
Common stock reserved for future issuance (in shares)	27,324,237
Series C convertible redeemable preferred stock
Equity
Authorized preferred stock (in shares)	8,658,344	0	8,658,344
Preferred stock issued (in shares)	8,658,008	0	8,658,008
Preferred stock outstanding (in shares)	8,658,008	0	8,658,008
Series C convertible redeemable preferred stock \| Conversion of convertible redeemable preferred stock into common stock
Equity
Common stock reserved for future issuance (in shares)	8,658,344

EQUITY (Details 2) $ / shares in Units, $ in Thousands	1 Months Ended			2 Months Ended	12 Months Ended
EQUITY (Details 2) $ / shares in Units, $ in Thousands	Apr. 30, 2015	Dec. 31, 2013 USD ($) $ / shares	Feb. 29, 2012 USD ($) $ / shares shares	Sep. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) tranche $ / shares shares	Sep. 30, 2015 $ / shares	Dec. 31, 2014 $ / shares
Performance Adjustment
Performance adjustment ratio	0.144927536
Common stock
Performance Adjustment
Performance adjustment ratio		0.5
Series A convertible redeemable preferred stock
Preferred stock
Convertible redeemable preferred stock, par value (in dollars per share) \| $ / shares		$ 0.001	$ 0.001		$ 0.001	$ 0.001	$ 0.001
Performance Adjustment
Performance adjustment ratio		0.5
Performance Adjustment		$ 12,239			$ 12,239
Series B convertible redeemable preferred stock
Preferred stock
Convertible redeemable preferred stock, par value (in dollars per share) \| $ / shares		$ 0.001	$ 0.001		$ 0.001	0.001	0.001
Series C convertible redeemable preferred stock
Preferred stock
Issuance of stock (in shares) \| shares					8,658,008
Convertible redeemable preferred stock, par value (in dollars per share) \| $ / shares		0.001			$ 0.001	$ 0.001	$ 0.001
Series B Preferred Stock financing February 2012 \| Series B convertible redeemable preferred stock
Preferred stock
Issuance of stock (in shares) \| shares			27,324,237
Issue price (in dollars per share) \| $ / shares			$ 0.84
Gross proceeds			$ 20,050
Closing costs			$ 147
Series C Preferred Stock financing 2013 \| Series C convertible redeemable preferred stock
Preferred stock
Issuance of stock (in shares) \| shares					8,658,008
Gross proceeds					$ 12,000
Closing costs					$ 45
Number of tranches into which financing was structured \| tranche					2
Series C Preferred Stock financing 2013 \| Series C convertible redeemable preferred stock \| Maximum
Preferred stock
Shares authorized for sale and issuance (in shares) \| shares					8,658,008
Amount authorized for sale and issuance					$ 12,000
Series C Preferred Stock financing 2013 \| Series C convertible redeemable preferred stock \| Stock purchase right
Preferred stock
Stock purchase right liability				$ 266
Series C Preferred Stock financing 2013, first tranche \| Series C convertible redeemable preferred stock
Preferred stock
Issuance of stock (in shares) \| shares				2,886,004
Gross proceeds				$ 4,000
Series C Preferred Stock financing 2013, second tranche \| Series C convertible redeemable preferred stock \| Stock purchase right
Fair value assumptions
Fair value of stock (in dollars per share) \| $ / shares		$ 1.27		$ 1.30	$ 1.27
Expected life		1 month 28 days
Volatility (as a percent)		52.00%
Roll forward of the recurring fair value measurements of the tranche liability categorized with Level 3 inputs
Tranche liability upon issuance		$ 266
Change in fair value		79
Tranche liability upon close of tranche		$ (345)
Series C Preferred Stock financing 2013, second tranche \| Series C convertible redeemable preferred stock \| Stock purchase right \| Minimum
Fair value assumptions
Expected life				4 months 6 days
Volatility (as a percent)				53.00%
Series C Preferred Stock financing 2013, second tranche \| Series C convertible redeemable preferred stock \| Stock purchase right \| Maximum
Fair value assumptions
Expected life				5 months 5 days
Volatility (as a percent)				60.00%
Conversion of preferred stock into Series A Preferred Stock \| Series A convertible redeemable preferred stock
Preferred stock
Number of shares issued in exchange for previously outstanding stock (in shares) \| shares			18,464,674

EQUITY (Details 3) $ / shares in Units, $ in Thousands	1 Months Ended		2 Months Ended	12 Months Ended
EQUITY (Details 3) $ / shares in Units, $ in Thousands	Apr. 30, 2015	Dec. 31, 2013 USD ($)	Feb. 28, 2015	Dec. 31, 2014 USD ($) director installment $ / shares shares	Dec. 31, 2013 USD ($)
Performance Adjustment
Performance adjustment ratio	0.144927536
Common stock
Performance Adjustment
Performance adjustment ratio		0.5
Redeemable Convertible Preferred Stock
Equity
Optional redemption feature, number of installment payments \| installment				3
Redeemable Convertible Preferred Stock \| Minimum
Equity
Affirmative vote of outstanding shares for optional redemption (as a percent)				60.00%
Redeemable Convertible Preferred Stock \| Mandatory conversion, initial public offering \| Minimum
Equity
Gross proceeds from sale of stock \| $				$ 50,000
Issue price (in dollars per share) \| $ / shares				$ 20.70
Redeemable Convertible Preferred Stock \| Automatic conversion concurrently with Qualified Financing \| Minimum
Equity
Shares owned by a shareholder (in shares) \| shares				1,000,000
Gross proceeds from sale of stock \| $				$ 1,000
Series A convertible redeemable preferred stock
Equity
Number of directors holders of record are entitled to elect \| director				2
Dividend rate (as a percent)			4.50%	4.50%
Cumulative accrued dividends \| $		$ 2,371		$ 2,371	$ 2,371
Conversion price (in dollars per share) \| $ / shares				$ 8.46
Liquidation rights, ratio applied to original issue price				1
Liquidation rights, original issue price (in dollars per share) \| $ / shares				$ 8.46
Performance Adjustment
Performance adjustment ratio		0.5
Performance Adjustment \| $		$ 12,239			12,239
Series A convertible redeemable preferred stock \| Minimum
Equity
Written consent or affirmative vote of outstanding shares to amend, alter or repeal the preferences, special rights or other powers (as a percent)				66.00%
Series B convertible redeemable preferred stock
Equity
Number of directors holders of record are entitled to elect \| director				1
Dividend rate (as a percent)			8.00%	8.00%
Cumulative accrued dividends \| $				$ 5,307
Conversion price (in dollars per share) \| $ / shares				$ 5.80
Liquidation rights, ratio applied to original issue price				2
Liquidation rights, original issue price (in dollars per share) \| $ / shares				$ 5.80
Optional redemption feature, ratio applied to original price				2
Series B convertible redeemable preferred stock \| Minimum
Equity
Written consent or affirmative vote of outstanding shares to amend, alter or repeal the preferences, special rights or other powers (as a percent)				66.00%
Series C convertible redeemable preferred stock
Equity
Number of directors holders of record are entitled to elect \| director				1
Dividend rate (as a percent)			8.00%	8.00%
Cumulative accrued dividends \| $				$ 1,114
Conversion price (in dollars per share) \| $ / shares				$ 9.59
Liquidation rights, ratio applied to original issue price				1
Liquidation rights, original issue price (in dollars per share) \| $ / shares				$ 9.59
Series C convertible redeemable preferred stock \| Minimum
Equity
Written consent or affirmative vote of outstanding shares to amend, alter or repeal the preferences, special rights or other powers (as a percent)				66.00%
Series C convertible redeemable preferred stock \| Series C Preferred Stock financing 2013, second tranche
Performance Adjustment
Threshold of additional capital raised to trigger Performance Adjustment \| $					$ 4,000

STOCK-BASED COMPENSATION (Details)		1 Months Ended	9 Months Ended	12 Months Ended
STOCK-BASED COMPENSATION (Details)	Dec. 04, 2013	Apr. 30, 2015 shares	Sep. 30, 2015 shares	Dec. 31, 2014 shares	Jul. 31, 2014 shares	Dec. 31, 2013 shares	Dec. 31, 2012 shares
Stock-based compensation
Shares of common stock authorized for issuance outstanding (in shares)			1,356,246	281,029
Performance adjustment ratio		0.144927536
Stock options
Stock-based compensation
Shares of common stock authorized for issuance outstanding (in shares)				281,029		229,791	323,488
Vesting period			4 years	4 years
Contractual life			10 years	10 years
Performance adjustment ratio	0.5
Stock options \| Minimum
Stock-based compensation
Period following termination date vested options are exercisable			1 month	1 month
Stock options \| Maximum
Stock-based compensation
Period following termination date vested options are exercisable			3 months	3 months
2014 Stock Incentive Plan
Stock-based compensation
Shares of common stock authorized for issuance (in shares)		2,700,000			525,700
Shares of common stock authorized for issuance outstanding (in shares)				281,029

STOCK-BASED COMPENSATION (Details 2) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock option activity
Outstanding at beginning of year (in shares)	281,029
Granted (in shares)	1,197,452
Exercised (in shares)	(121,729)
Cancelled (in shares)	(506)
Outstanding at end of period (in shares)	1,356,246	281,029
Exercisable at end of period (in shares)	208,438
Vested and expected to vest at end of period (in shares)	1,341,543
Weighted average exercise price per share
Outstanding at beginning of year (in dollars per share)	$ 0.69
Granted (in dollars per share)	10.47
Exercised (in dollars per share)	3.89
Cancelled (in dollars per share)	2.06
Outstanding at end of period (in dollars per share)	9.04	$ 0.69
Exercisable at end of period (in dollars per share)	2.65
Vested and expected to vest at end of period (in dollars per share)	$ 9.13
Stock option activity, additional information
Outstanding at end of period, Weighted-average remaining contractual term	9 years 2 months 12 days
Exercisable at end of period, Weighted-average remaining contractual term	7 years 10 months 24 days
Vested and expected to vest at end of period, weighted-average remaining contractual term	9 years 2 months 12 days
Outstanding at end of period, Aggregate intrinsic value	$ 17,722
Exercisable at end of period, Aggregate intrinsic value	4,056
Vested and expected to vest at end of period, Aggregate intrinsic value	$ 18,595
Stock options
Stock option activity
Outstanding at beginning of year (in shares)	281,029	229,791	323,488
Granted (in shares)		89,641	146,730
Exercised (in shares)		(32,390)	(1,077)
Cancelled (in shares)		(6,013)	(9,559)
Modification (in shares)			(229,791)
Outstanding at end of period (in shares)		281,029	229,791	323,488
Exercisable at end of period (in shares)		121,304
Vested and expected to vest at end of period (in shares)		247,139
Weighted average exercise price per share
Outstanding at beginning of year (in dollars per share)	$ 0.69	$ 1.17	$ 1.73
Granted (in dollars per share)		0.28	0.48
Exercised (in dollars per share)		2.21	0.62
Cancelled (in dollars per share)		4.42	2.76
Modification (in dollars per share)			1.17
Outstanding at end of period (in dollars per share)		0.69	$ 1.17	$ 1.73
Exercisable at end of period (in dollars per share)		1.38
Vested and expected to vest at end of period (in dollars per share)		$ 0.83
Stock option activity, additional information
Outstanding at end of period, Weighted-average remaining contractual term		7 years 5 months 27 days	7 years 7 days	6 years 11 months 9 days
Exercisable at end of period, Weighted-average remaining contractual term		4 years 3 months 22 days
Vested and expected to vest at end of period, weighted-average remaining contractual term		4 years 3 months 22 days
Outstanding at end of period, Aggregate intrinsic value		$ 1,505	$ 117	$ 8
Exercisable at end of period, Aggregate intrinsic value		570
Vested and expected to vest at end of period, Aggregate intrinsic value		1,293
Unrecognized compensation cost related to outstanding options		$ 215	$ 40
Period over which unrecognized compensation cost is expected to be recognized as expense		1 year	1 year 1 month 6 days
Weighted average fair value of vested options (in dollars per share)		$ 1.93
Employee stock options
Stock option activity, additional information
Weighted-average grant date fair value per share of employee option grants (in dollars per share)		$ 0.76	$ 0.28

STOCK-BASED COMPENSATION (Details 3) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted stock awards
Unvested at beginning of year (in shares)	15,387
Granted (in shares)	194,694
Vested (in shares)	(128,955)
Unvested at end of year (in shares)	81,126	15,387
Weighted-Average Grant Date Fair Value
Unvested at beginning of year (in dollars per share)	$ 0.69
Granted (in dollars per share)	5.73
Vested (in dollars per share)	5.13
Unvested at end of year (in dollars per share)	$ 5.73	$ 0.69
Restricted stock
Restricted stock awards
Unvested at beginning of year (in shares)	15,387	55,298	203,342
Granted (in shares)		10,869
Vested (in shares)		(50,780)	(89,308)
Performance Adjustment (in shares)			(58,736)
Unvested at end of year (in shares)		15,387	55,298
Weighted-Average Grant Date Fair Value
Unvested at beginning of year (in dollars per share)	$ 0.69	$ 0.69	$ 0.62
Granted (in dollars per share)		1.24
Vested (in dollars per share)		0.62	0.55
Performance Adjustment (in dollars per share)			0.62
Unvested at end of year (in dollars per share)		$ 0.69	$ 0.69
Unrecognized compensation cost
Unrecognized stock-based compensation expense		$ 26	$ 73
Period over which unrecognized compensation cost is expected to be recognized as expense		2 months 12 days	1 year 2 months 12 days

STOCK-BASED COMPENSATION (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 22	$ 62
Research and development
Stock-Based Compensation Expense
Total stock-based compensation expense	12	24
General and administrative
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 10	$ 38

STOCK-BASED COMPENSATION (Details 5)	9 Months Ended		12 Months Ended
STOCK-BASED COMPENSATION (Details 5)	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants
Risk-free interest rate (as a percent)	1.70%	1.80%	1.80%
Volatility (as a percent)	77.00%	77.00%	77.10%	87.80%
Expected term	6 years 2 months 16 days	6 years 3 months	6 years 3 months	6 years 3 months
Expected dividend yield (as a percent)			0.00%	0.00%
Minimum
Weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants
Risk-free interest rate (as a percent)				1.09%
Maximum
Weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants
Risk-free interest rate (as a percent)				1.22%

INCOME TAXES (Details)	12 Months Ended
INCOME TAXES (Details)	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate to income taxes as reflected in the financial statements
Federal income tax (benefit) at statutory rate (as a percent)	34.00%	34.00%
Expiration of state net operating losses (as a percent)	(0.00%)	(12.11%)
Permanent items (as a percent)	(0.17%)	(0.01%)
Research and experimental credits (as a percent)	3.74%	4.19%
Change in valuation allowance (as a percent)	(37.57%)	(26.07%)
Income tax expense (benefit) (as a percent)	0.00%	0.00%

INCOME TAXES (Details 2) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES (Details 2) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 28,419	$ 21,392
Depreciation and amortization	36
Research Credits	3,070	2,400
Deferred tax assets before valuation allowance	31,525	23,792
Valuation allowance	(31,525)	(23,788)
Deferred tax assets net of valuation allowance		4
Deferred tax liabilities:
Depreciation and amortization		(4)
Total deferred tax liabilities		4
Valuation allowance
Deferred tax asset valuation allowance increase	$ 7,737	$ 5,081

INCOME TAXES (Details 3) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
State
Net operating loss carryforwards
Available net operating loss carryforwards as of the end of the year	$ 34,184	$ 16,354
U.S. federal
Net operating loss carryforwards
Available net operating loss carryforwards as of the end of the year	$ 78,276	$ 60,380

EMPLOYEE BENEFITS (Details) - USD ($) $ in Thousands	12 Months Ended
EMPLOYEE BENEFITS (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
EMPLOYEE BENEFITS
Requisite service period of employees to be eligible to participate in the 401(k) plan	3 months
Total expense for contributions made to 401(k) plan	$ 35	$ 31

SUBSEQUENT EVENTS (Details) $ in Thousands				1 Months Ended			9 Months Ended	12 Months Ended
SUBSEQUENT EVENTS (Details) $ in Thousands	Mar. 26, 2015 patent	Mar. 24, 2015 patent	Mar. 06, 2015 USD ($) shares	Apr. 30, 2015 shares	Mar. 31, 2015 USD ($) ft² shares	Dec. 31, 2013	Sep. 30, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Jul. 31, 2014 shares
SUBSEQUENT EVENTS
Principal amount converted \| $							$ 5,000
Stock-based compensation
Options granted (in shares)							1,197,452
Restricted stock granted (in shares)							194,694
Stockholders' Equity Note [Abstract]
Common stock split ratio				0.144927536
Office and research facility operating lease
Lease
Area of Real Estate Property \| ft²					19,335
Term of lease extension option					5 years
Office and research facility operating lease \| Delivery of expansion space with substantial completion of certain improvements
Lease
Lease term					5 years
Amendment to office and research facility operating lease
Lease
Area of Real Estate Property \| ft²					9,660
2014 Stock Incentive Plan
Stock-based compensation
Maximum number of shares authorized for issuance (in shares)				2,700,000					525,700
Restricted stock
Stock-based compensation
Restricted stock granted (in shares)								10,869
Purdue Pharma, L. P. patent infringement suit, District of Delaware
Contingencies
Number of patents asserted to have been infringed \| patent		4
Purdue Pharma, L. P., patent infringement suit, District of Massachusetts
Contingencies
Number of patents asserted to have been infringed \| patent	4
Redeemable Convertible Preferred Stock \| Mandatory conversion, initial public offering \| Minimum
SUBSEQUENT EVENTS
Gross proceeds from sale of stock \| $								$ 50,000
Series D convertible redeemable preferred stock
SUBSEQUENT EVENTS
Cash consideration from issuance of preferred stock \| $					$ 45,000
6.0% Convertible promissory notes
SUBSEQUENT EVENTS
Principal amount converted \| $					$ 5,000
Common stock
Stockholders' Equity Note [Abstract]
Common stock split ratio						0.5
Subsequent events \| Office and research facility operating lease
Lease
Area of Real Estate Property \| ft²					19,335
Term of lease extension option					5 years
Subsequent events \| Office and research facility operating lease \| Delivery of expansion space with substantial completion of certain improvements
Lease
Lease term					5 years
Subsequent events \| Amendment to office and research facility operating lease
Lease
Area of Real Estate Property \| ft²					9,660
Subsequent events \| 2014 Stock Incentive Plan
Stock-based compensation
Maximum number of shares authorized for issuance (in shares)					1,087,005
Subsequent events \| Employee stock options
Stock-based compensation
Options granted (in shares)					638,095
Vesting period					4 years
Period from grant date to expiration					10 years
Subsequent events \| Restricted stock
Stock-based compensation
Restricted stock granted (in shares)				194,694
Subsequent events \| Restricted stock \| Vested upon grant
Stock-based compensation
Restricted stock granted (in shares)				97,347
Subsequent events \| Restricted stock \| Vesting in monthly installments
Stock-based compensation
Restricted stock granted (in shares)				97,347
Vesting period				3 years
Subsequent events \| Purdue Pharma, L. P. patent infringement suit, District of Delaware
Contingencies
Number of patents asserted to have been infringed \| patent		4
Subsequent events \| Purdue Pharma, L. P., patent infringement suit, District of Massachusetts
Contingencies
Number of patents asserted to have been infringed \| patent	4
Subsequent events \| Private Placement \| Investors \| Series D convertible redeemable preferred stock
SUBSEQUENT EVENTS
Issuance of stock (in shares)			41,666,667
Aggregate consideration \| $			$ 50,000
Cash consideration from issuance of preferred stock \| $			45,000
Subsequent events \| Conversion of convertible notes into convertible preferred stock \| Investors \| 6.0% Convertible promissory notes
SUBSEQUENT EVENTS
Principal amount converted \| $			$ 5,000
Subsequent events \| Conversion of convertible notes into convertible preferred stock \| Investors \| 6.0% Convertible promissory notes \| Series D convertible redeemable preferred stock
SUBSEQUENT EVENTS
Number of shares of stock into which debt was converted (in shares)			4,166,667

BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 105,460	$ 1,634	$ 4,178	$ 7,551	$ 11,936
Refundable PDUFA fee		2,335
Prepaid expenses and other current assets	866	527		710
Total current assets	106,326	4,496		8,261
Property and equipment, net	627	514		693
Restricted cash	97	80		80
Total assets	107,050	5,090		9,034
Current liabilities:
Accounts payable	3,237	2,208		1,217
Accrued expenses	2,681	1,956		1,013
Current portion of deferred rent and lease note payable	15	59		55
Current portion of term loan payable	2,667	1,194		333
Convertible bridge notes with related parties		5,000
Total current liabilities	8,600	10,417		2,618
Lease incentive obligation	76	101		135
Term loan payable, long-term	4,813	6,813		640
Total liabilities	13,489	17,331		3,452
Commitments and contingencies (See Note 9)
Shareholders' equity (deficit):
Common stock	20	1		1
Additional paid-in capital	213,027	12,407		12,313
Accumulated deficit	(119,483)	(101,753)		(80,536)
Treasury stock	(3)	(3)		(3)
Total shareholders' equity (deficit)	93,561	(89,348)		(68,225)	(61,404)
Total liabilities, convertible redeemable preferred stock and shareholders' equity (deficit)	$ 107,050	5,090		9,034
Series A convertible redeemable preferred stock
Convertible redeemable preferred stock
Convertible redeemable preferred stock		12,781		12,277	23,546
Series B convertible redeemable preferred stock
Convertible redeemable preferred stock
Convertible redeemable preferred stock		51,212		49,376	$ 47,540
Series C convertible redeemable preferred stock
Convertible redeemable preferred stock
Convertible redeemable preferred stock		$ 13,114		$ 12,154

BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Convertible redeemable preferred stock, authorized shares		54,481,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	100,000,000	72,000,000
Common stock, issued shares	20,687,829	1,006,219
Common stock, outstanding shares	1,006,219	1,006,219
Series A convertible redeemable preferred stock
Convertible redeemable preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible redeemable preferred stock, authorized shares	0	18,498,419
Convertible redeemable preferred stock, issued shares	0	9,232,334
Convertible redeemable preferred stock, outstanding shares	0	9,232,334
Convertible redeemable preferred stock, liquidation preference	$ 0	$ 12,781
Series B convertible redeemable preferred stock
Convertible redeemable preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible redeemable preferred stock, authorized shares	0	27,324,237
Convertible redeemable preferred stock, issued shares	0	27,324,237
Convertible redeemable preferred stock, outstanding shares	0	27,324,237
Convertible redeemable preferred stock, liquidation preference	$ 0	$ 51,212
Series C convertible redeemable preferred stock
Convertible redeemable preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible redeemable preferred stock, authorized shares	0	8,658,344
Convertible redeemable preferred stock, issued shares	0	8,658,008
Convertible redeemable preferred stock, outstanding shares	0	8,658,008
Convertible redeemable preferred stock, liquidation preference	$ 0	$ 13,114
Series D convertible redeemable preferred stock
Convertible redeemable preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible redeemable preferred stock, authorized shares	0	0
Convertible redeemable preferred stock, issued shares	0	0
Convertible redeemable preferred stock, outstanding shares	0	0
Convertible redeemable preferred stock, liquidation preference	$ 0	$ 0

STATEMENTS OF OPERATIONS - USD ($)	9 Months Ended		12 Months Ended
STATEMENTS OF OPERATIONS - USD ($)	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$ 6,444,000	$ 12,652,000	$ 12,652,000	$ 14,157,000
General and administrative	11,027,000	1,686,000	1,686,000	1,885,000
Total operating expenses	17,471,000		14,338,000	16,042,000
Loss from operations	(17,471,000)	(14,338,000)	(14,338,000)	(16,042,000)
Other expense:
Interest expense, net	350,000	110,000	110,000	76,000
Gain on extinguishment	(91,000)
Total other expense, net	259,000	110,000	110,000	155,000
Net loss	$ (17,730,000)	$ (14,448,000)	$ (14,448,000)	$ (16,197,000)
Net loss per share - basic and diluted (in dollars per share)	$ (0.94)	$ (18.26)	$ (18.26)	$ (4.06)
Weighted-average number of common shares used in net loss per share-basic and diluted (in shares)	11,179,756	926,597	926,597	1,697,044

STATEMENTS OF CASH FLOWS - USD ($)	9 Months Ended
STATEMENTS OF CASH FLOWS - USD ($)	Sep. 30, 2015	Sep. 30, 2014
Operating activities
Net loss	$ (17,730,000)	$ (14,448,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	130,000	141,000
Lease incentive	(25,000)	(25,000)
Stock-based compensation expense	1,217,000	16,000
Non cash interest expense	6,000	6,000
Accrual of back end fees related to note payable		(12,000)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(338,000)	(139,000)
Refundable PDUFA fee	2,335,000
Accounts payable	962,000	1,563,000
Accrued expenses	815,000	2,518,000
Net cash used in operating activities	(12,628,000)	(10,380,000)
Investing activities
Purchases of property and equipment	(175,000)
Net cash used in investing activities	(175,000)
Financing activities
(Repayment of) borrowing from term note	(619,000)	7,044,000
Repayment of lease note payable	(44,000)	(46,000)
Restricted cash	(16,000)
Proceeds from the exercise of stock options	472,000	9,000
Net cash provided by financing activities	116,629,000	7,007,000
Net increase (decrease) in cash and cash equivalents	103,826,000	(3,373,000)
Cash and cash equivalents at beginning of period	1,634,000	7,551,000
Cash and cash equivalents at end of period	105,460,000	4,178,000
Supplemental disclosure of noncash activities
Accruals of dividends and accretion to redemption value	24,572,000	2,469,000
Conversion of bridge note to preferred stock	5,000,000
Cash paid for interest	260,000	46,000
Cash paid for taxes	4,000
Repayment of term note with proceeds of notes payable		$ 944,000
Common stock
Financing activities
Proceeds from issuance of stock, net of issuance costs	72,029,000
Series D convertible redeemable preferred stock
Financing activities
Proceeds from issuance of stock, net of issuance costs	44,807,000
Supplemental disclosure of noncash activities
Accruals of dividends and accretion to redemption value	24,572,000
Conversion of redeemable convertible preferred stock into common stock \| Redeemable Convertible Preferred Stock
Supplemental disclosure of noncash activities
Preferred stock conversion to common stock	$ 120,302,000

STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	9 Months Ended
STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	Sep. 30, 2015 USD ($)
Common stock
Preferred stock
Stock issuance costs	$ 2,408
Series D convertible redeemable preferred stock
Preferred stock
Stock issuance costs	$ 193

Nature of Business	9 Months Ended	12 Months Ended
Nature of Business	Sep. 30, 2015	Dec. 31, 2014
NATURE OF BUSINESS
NATURE OF BUSINESS	1. NATURE OF BUSINESS Collegium Pharmaceutical, Inc. (the "Company") was incorporated in Delaware in April 2002 and then reincorporated in Virginia in July 2014. The Company has its principal operations in Canton, Massachusetts. The Company is a specialty pharmaceutical company developing and planning to commercialize next-generation abuse-deterrent products that incorporate the Company's patented DETERx® platform technology for the treatment of chronic pain and other diseases. The Company's lead product candidate, Xtampza™ ER, or Xtampza, is an abuse-deterrent, extended-release, oral formulation of oxycodone, a widely prescribed opioid medication. Xtampza has received Fast Track status from the U.S. Food and Drug Administration ("FDA"). The Company's new drug application ("NDA") filing for Xtampza was accepted by the FDA on February 10, 2015. On February 25, 2015, the FDA set a Prescription Drug User Fee Act, or PDUFA, goal date of October 12, 2015 for completion of its review of the Xtampza NDA. On November 6, 2015, the FDA granted tentative approval to the Xtampza NDA for the management of pain severe enough to require daily, around-the-clock, long-term opioid treatment and for which alternative treatment options are inadequate. With a tentative approval, the FDA has determined that Xtampza meets the required quality, safety and efficacy standards for approval but that it is subject to an automatic stay of up to 30 months as a result of patent litigation filed by Purdue Pharma, L.P (Purdue) in March 2015. The Company's operations are subject to certain risks and uncertainties. The principal risks include negative outcome of clinical trials, inability or delay in completing clinical trials or obtaining regulatory approvals, changing market conditions for products being developed by the Company, the need to retain key personnel and protect intellectual property, patent infringement litigation and the availability of additional capital financing on terms acceptable to the Company.	1. NATURE OF BUSINESS Organization Collegium Pharmaceutical, Inc. (the "Company") was incorporated in Delaware in April 2002 and then reincorporated in Virginia in July 2014. The Company has its principal operations in Canton, Massachusetts. The Company is a specialty pharmaceutical company developing and planning to commercialize next-generation abuse-deterrent products that incorporate the Company's patented DETERx® platform technology for the treatment of chronic pain and other diseases. The Company's lead product candidate, Xtampza™ ER, or Xtampza, is an abuse-deterrent, extended-release, oral formulation of oxycodone, a widely prescribed opioid medication. Xtampza has received Fast Track status from the U.S. Food and Drug Administration ("FDA"). The Company's new drug application ("NDA") filing for Xtampza was accepted by the FDA on February 10, 2015. The Company's operations are subject to certain risks and uncertainties. The risks include negative outcome of clinical trials, inability or delay in completing clinical trials or obtaining regulatory approvals, changing market conditions for products being developed by the Company, the need to retain key personnel and protect intellectual property, patent infringement litigation and the availability of additional capital financing on terms acceptable to the Company. Basis of Accounting The financial statements include the accounts of the Company and are prepared in conformity with accounting principles generally accepted in the United States of America. Liquidity The Company has experienced net losses and negative cash flows from operating activities since its inception, and as of December 31, 2013 and December 31, 2014, had a deficit accumulated of $80,536 and $101,753, respectively. The Company expects to continue to incur net losses in the foreseeable future. A successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company's cost structure. On March 6, 2015, the Company received aggregate consideration of $50,000 from the issuance of Series D preferred stock, comprised of $45,000 in cash and $5,000 in convertible notes from related parties. The Company expects to continue to incur losses for the foreseeable future. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional cash. Management intends to fund future operations through additional private or public debt or equity offerings, and may seek additional capital through arrangements with strategic partners or from other sources. The Company believes that it will have sufficient cash to fund operations and future growth initiatives through December 31, 2015; however, there can be no assurance that the Company will be successful in achieving its projections, reducing costs, or raising additional funds with terms acceptable to the Company. If the Company is unable to obtain financing or increase profitability, the related lack of liquidity will have a material adverse effect on the Company's operations and future prospects.

Summary of Significant Accounting Policies

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of presentation

Initial Public Offering

Subsequent Events

Critical Accounting Policies

Earnings (Loss) per Common Share

Recent Accounting Pronouncements

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates

Unaudited Pro Forma Net Loss per Share Information

Fair Value Measurements

Transfers are calculated on values as of the transfer date. There were no transfers between Levels 1, 2 and 3 during the years ended December 31, 2013 and 2014.

Concentration of Credit Risk

Cash and Cash Equivalents

Property and Equipment

Asset Category		Estimated Useful Life

Machinery and equipment		5 years
Computers and office equipment		5 years
Furniture and fixtures		7 years
Leasehold improvements		5 years

Upon retirement or sale, the cost of assets disposed and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recorded in the statements of operations.

Impairment of Long-Lived Assets

Impairment losses, if any, are recognized in earnings. An impairment loss would be recognized in an amount equal to the excess of the carrying amount over the undiscounted expected future cash flows.

Initial Public Offering Costs

Restricted Cash

Deferred Rent

Convertible Redeemable Preferred Stock

Research and Development Costs

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expense as incurred since the recoverability of such expenditures is uncertain.

Stock-Based Compensation

Income Taxes

Net loss per Common Share

Recently Issued Accounting Pronouncements

Net Loss per Common Share

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

NET LOSS PER COMMON SHARE

3. NET LOSS PER COMMON SHARE

	Nine months ended September 30,

	2014			2015
Net loss	$	(14,448	)	$	(17,730	)
Extinguishment of preferred stock — see note 7		—			31,806
Accretion of prior preferred stock — see note 7		(2,469	)		(23,327	)
Accretion and dividends of Series D preferred stock		—			(1,245	)

Loss attributable to common shareholders — basic and diluted	$	(16,917	)	$	(10,496	)



Weighted-average number of common shares used in net loss per share — basic and diluted		926,597			11,179,756



Net loss per share — basic and diluted	$	(18.26	)	$	(0.94	)

	Nine months ended September 30,

	2014		2015
Outstanding stock options		311,365		1,356,246
Warrants		18,810		2,445
Redeemable convertible preferred stock		6,552,820		—
Unvested restricted stock		28,536		153,589

3. NET LOSS PER COMMON SHARE

The following table presents the computations of basic and dilutive net loss per share:

	Years Ended December 31,

	2013			2014
Net loss	$	(16,197	)	$	(17,917	)
Performance Adjustment of Series A		12,239			—
Accruals of dividends and accretion to redemption value of preferred stock		(2,925	)		(3,300	)

Loss attributable to common shareholders — basic and diluted	$	(6,883	)	$	(21,217	)



Weighted-average shares used in computing basic and diluted net loss per common share		1,697,044			933,997



Basic and diluted net loss per common share	$	(4.06	)	$	(22.72	)

	Years Ended December 31,

	2013		2014
Stock Options		229,791		281,029
Warrants		4,170		18,809
Redeemable convertible preferred stock		6,552,820		6,552,820
Unvested restricted stock		55,298		15,387

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2015

Fair Value of Financial Instruments

Fair Value of Financial Instruments

4. FAIR VALUE OF FINANCIAL INSTRUMENTS

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy is now established that prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:

Level 1 inputs Quoted prices in active markets for identical assets or liabilities

Level 2 inputs Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly

Level 3 inputs Unobservable inputs that reflect the Company's own assumptions about the assumptions market participants would use in pricing the asset or liability

The following tables present the Company's financial instruments carried at fair value using the lowest level input applicable to each financial instrument at December 31, 2014 and September 30, 2015.

Description	Total		Quoted Prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)

December 31, 2014
Money market funds, included in cash equivalents	$	457	$	457	$	—	$	—
September 30, 2015
Money market funds, included in cash equivalents	$	104,911	$	104,911	$	—	$	—

The Company's cash equivalents are comprised of money market funds that are measured on a recurring basis based on quoted market prices.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Accrued Expenses

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

ACCRUED EXPENSES

5. ACCRUED EXPENSES

Accrued expenses consisted of the following:

	December 31, 2014		September 30, 2015

Accrued compensation	$	635	$	1,169
Accrued development costs		970		597
Accrued marketing		—		685
Accrued audit and legal		249		109
Accrued interest		71		31
Accrued other		31		90

Total accrued expenses	$	1,956	$	2,681

6. ACCRUED EXPENSES

Accrued expenses consisted of the following:

	As of December 31,

	2013		2014
Accrued development costs	$	520	$	970
Accrued compensation		449		635
Accrued audit and legal		12		249
Accrued interest		—		71
Accrued other		32		31

Total accrued expenses	$	1,013	$	1,956

Convertible Bridge Note with Related Party	9 Months Ended
Convertible Bridge Note with Related Party	Sep. 30, 2015
Convertible Bridge Note with Related Party
Convertible Bridge Note with Related Party	6. CONVERTIBLE BRIDGE NOTE WITH RELATED PARTY In November and December 2014, the Company entered into a Note Purchase Agreement (the "Bridge Notes") allowing for the issuance of $5,000 of convertible promissory notes to a group of investors (the "Holders") bearing interest at a rate per annum of 6.0%. The Holders are related parties of the Company. In connection with the Series D convertible preferred stock financing (see note 7), the Bridge Notes converted into Series D convertible preferred stock. Upon the conversion, the Company recognized a gain on extinguishment of $91.

Convertible Preferred Stock	9 Months Ended
Convertible Preferred Stock	Sep. 30, 2015
Convertible Preferred Stock
Convertible Preferred Stock	7. CONVERTIBLE PREFERRED STOCK In March 2015, the Company issued and sold an aggregate of 41,666,667 shares of Series D convertible preferred stock for aggregate consideration of $50,000, comprised of $45,000 in cash and conversion of $5,000 in Bridge Notes. The accrued interest on the convertible notes was waived. Concurrently with the issuance of the Series D Preferred Stock, the Company amended and restated its Articles of Incorporation (the "Amended Articles"). The Company made certain amendments to the terms of the Series A, Series B, and Series C Preferred Stock (together, the "Prior Preferred Stock"). Prior to the adoption of the Amended Articles, the Series A, Series B, and Series C Preferred Stock accrued dividends at a rate of 4.5%, 8.0% and 8.0% per annum, respectively, per share. All accrued and unpaid dividends on the Prior Preferred Stock were automatically cancelled and forfeited and the Prior Preferred Stock no longer accrued dividends. Prior to the cancellation and forfeiture of accrued dividends, the Prior Preferred Stock had accrued dividends of $622 during 2015. The holders of outstanding shares of Prior Preferred Stock were entitled to receive dividends, when, as and if declared by the Board of Directors. The mandatory conversion for all series of Prior Preferred Stock was modified so as to occur upon an initial public offering with gross proceeds in excess of $50,000. The amendments to the Prior Preferred Stock were treated as an extinguishment which resulted in a gain on extinguishment of $31,806. The gain on extinguishment was added to net loss to arrive at income available to common shareholders in the calculation of earnings per share. During the nine months ended September 30, 2015, total accrued dividends and accretion for preferred stock was $24,572. In connection with the closing of the IPO, all of the Company's outstanding convertible preferred stock automatically converted to common stock in May 2015, resulting in an additional 12,591,456 shares of common stock of the Company becoming outstanding.

Stock-based Compensation

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

COMMITMENTS AND CONTINGENCIES

STOCK BASED COMPENSATION

8. STOCK-BASED COMPENSATION

Restricted common stock

A summary of the Company's restricted stock activity for the nine months ended September 30, 2015 and related information is as follows:

			Weighted average purchase price per share

Unvested at December 31, 2014	15,387		$	0.69
Granted	194,694			5.73
Vested	(128,955	)		5.13

Unvested at September 30, 2015⁽¹⁾	81,126		$	5.73

(1): Excludes 72,463 shares of unvested restricted stock remaining from the early exercise of stock options as of September 30, 2015.

Stock options

A summary of the Company's stock option activity and related information follows:

			Weighted- average exercise price per share			Aggregate Intrinsic Value

Outstanding at December 31, 2014	281,029		$	0.69
Granted	1,197,452			10.47
Exercised	(121,729	)		3.89
Cancelled	(506	)		2.06

Outstanding at September 30, 2015	1,356,246		$	9.04	9.2	$	17,722



Exercisable at September 30, 2015	208,438		$	2.65	7.9	$	4,056



Vested and expected to vest at September 30, 2015	1,341,543		$	9.13	9.2	$	18,595

The fair value of each stock option is estimated on the grant date using the Black-Scholes option-pricing model using the following assumptions:

	Nine months ended September 30,

	2014			2015
Risk-free interest rate		1.8	%		1.7	%
Dividend yield		—			—
Volatility		77	%		77	%
Expected term (years)		6.25			6.21

11. STOCK-BASED COMPENSATION

Restricted Stock Awards and Stock Options

In July 2014, the Company adopted the 2014 Stock Incentive Plan (the "Plan"), under which 525,700 shares of common stock are authorized for issuance to employees, officers, directors, consultants and advisors of the Company. As of December 31, 2014, 281,029 of the shares of common stock authorized for issuance pursuant to the Plan were outstanding. In connection with the Company's reincorporation into Virginia in July 2014, each outstanding option to purchase shares of common stock under the 2012 Stock Incentive Plan and 2002 Stock Plan, was automatically terminated and replaced with an option to purchase shares of common stock under the Plan having the same vesting terms and exercise price as the option that was replaced. The Plan provides for granting of both Internal Revenue Service qualified incentive stock options ("ISOs") and non-qualified options ("NQs"), restricted stock awards ("RSAs") and restricted stock units ("RSUs"). Stock options generally vest over a four year period of service; however, certain options contain performance conditions. The options generally have a ten year contractual life and, upon termination, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately.

Stock option activity under the Plan is summarized as follows:

			Weighted- Average Exercise Price			Aggregate Intrinsic Value

Outstanding at December 31, 2012	323,488		$	1.73	6.94	$	8
Granted	146,730			0.48
Exercised	(1,077	)		0.62
Cancelled	(9,559	)		2.76
Modification	(229,791	)		1.17

Outstanding at December 31, 2013	229,791			1.17	7.02		117
Granted	89,641			0.28
Exercised	(32,390	)		2.21			—
Cancelled	(6,013	)		4.42

Outstanding at December 31, 2014	281,029		$	0.69	7.49	$	1,505



Vested and expected to vest at December 31, 2014	247,139		$	0.83	4.31	$	1,293
Exercisable at December 31, 2014	121,304		$	1.38	4.31	$	570

As of December 31, 2014, the weighted average fair value of vested options was $1.93.

Additional information about the Company's stock option activity is as follows:

	As of December 31,

	2013		2014
Weighted-average grant date fair value per share of employee option grants	$	0.28	$	0.76

Restricted stock awards under the Plan are summarized as follows:

			Weighted-Average Grant Date Fair Value

Unvested at December 31, 2012	203,342		$	0.62
Vesting of restricted stock	(89,308	)		0.55
Performance Adjustment	(58,736	)		0.62

Unvested at December 31, 2013	55,298			0.69
Grant of restricted stock	10,869			1.24
Vesting of restricted stock	(50,780	)		0.62

Unvested at December 31, 2014	15,387		$	0.69

Stock-Based Compensation Expense

Stock-based compensation for all stock options and restricted stock awards are reported within:

	Years Ended December 31,

	2013		2014
Research and development	$	24	$	12
General and administrative		38		10

Total stock-based compensation expense	$	62	$	22

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:

	Years Ended December 31,

	2013	2014
Risk-free interest rate	1.09% – 1.22%		1.80	%
Expected volatility	87.8%		77.1	%
Expected term (in years)	6.25		6.25
Expected dividend yield	0.0%		0.0	%

Risk-free Interest Rate. The risk-free interest rate assumption is based on observed interest rates appropriate for the expected term of the stock option grants.

Expected Dividend Yield. The expected dividend yield assumption is based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends.

Commitments and Contingencies

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

COMMITMENTS AND CONTINGENCIES.

9. COMMITMENTS AND CONTINGENCIES

7. COMMITMENTS AND CONTINGENCIES

Legal Proceedings

Operating Leases

Year Ending December 31,

2015	$	106
2016		111
2017		116

Total minimum lease payments	$	333

Summary of Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2015	Dec. 31, 2014
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Basis of presentation	Basis of presentation The accompanying unaudited condensed financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, the Company must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the interim periods ended September 30, 2015 and 2014 are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The condensed interim financial statements should be read in conjunction with the audited financial statements and notes as of and for the year ended December 31, 2014.
Initial Public Offering	Initial Public Offering In May 2015, the Company closed an initial public offering ("IPO") of its common stock, which resulted in the sale of 6,670,000 shares of its common stock at a public offering price of $12.00 per share, including 870,000 shares of common stock upon the exercise by the underwriters of their option to purchase additional shares at the public offering price. The Company received proceeds from the IPO of approximately $72,029, after deducting underwriting discounts, commissions and expenses payable by the Company. In connection with preparing for the IPO, the Company's Board of Directors and shareholders approved a one-for-6.9 reverse stock split of the Company's common stock. The reverse stock split became effective in April 2015. All share and per share amounts in the condensed interim financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. In connection with the closing of the IPO, all of the Company's outstanding convertible preferred stock automatically converted to common stock in May 2015, resulting in an additional 12,591,456 shares of common stock of the Company becoming outstanding. The significant increase in common stock outstanding in May 2015 is expected to impact the year-over-year comparability of the Company's net loss per share calculations in future periods.	Initial Public Offering Costs The Company defers direct incremental costs attributable to the initial public offering ("IPO") of its common stock. These costs represent legal, accounting and other direct costs related to the Company's efforts to raise capital through a public sale of its common stock. Future costs will be deferred until the completion of the IPO, at which time they will be reclassified to additional paid-in capital as a reduction of the IPO proceeds. If the Company terminates its plan for an IPO or delays such plan for more than 90 days, any costs deferred will be expensed immediately. As of December 31, 2014, IPO costs were $233 and are included in prepaid expenses and other assets in the balance sheet.
Subsequent Events	Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Through November 12, 2015, the Company has concluded that no subsequent events have occurred that require disclosure, except as described in Note 9.
Earnings (Loss) per Common Share	Earnings (Loss) per Common Share Earnings (loss) per common share is calculated using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for the holders of the Company's common shares and participating securities. All series of preferred stock contain participation rights in any dividend paid by the Company and are deemed to be participating securities. Earnings available to common shareholders and participating convertible redeemable preferred shares is allocated first to the preferred stock based upon the distribution criteria in the Company's Articles of Incorporation then the remainder to the common shareholders. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods that have a net loss. Diluted earnings per share is computed using the more dilutive of (a) the two-class method, or (b) the if-converted method. The Company allocates earnings first to preferred shareholders based on dividend rights and then to common and preferred shareholders based on ownership interests. The weighted-average number of common shares included in the computation of diluted earnings (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, convertible redeemable preferred stock and the potential issuance of stock upon the conversion of the Company's convertible notes. Common stock equivalent shares are excluded from the computation of diluted earnings (loss) per share if their effect is antidilutive.	Net loss per Common Share Basic net loss per common share is calculated by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, stock options, warrants, redeemable convertible preferred stock and unvested restricted stock are considered potentially dilutive securities. Because the Company has reported a net loss for the twelve months ended December 31, 2013 and 2014, diluted net loss per common share is the same as basic net loss per common share for those periods. Diluted earnings per share is computed using the more dilutive of (i) the two-class method, or (ii) the if-converted method. The Company allocates earnings first to preferred shareholders based on dividend rights and then to common and preferred shareholders based on ownership interests. The weighted-average number of common shares included in the computation of diluted earnings (loss) gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, convertible redeemable preferred stock and the potential issuance of stock upon the conversion of the Company's convertible notes. Common stock equivalent shares are excluded from the computation of diluted earnings (loss) per share if their effect is antidilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB"), issued Accounting Standards Update ("ASU"), No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in Accounting Standards Codification ("ASC"), Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. On August 12, 2015, the FASB issued ASU No. 2015-14, which defers the effective date of ASU No. 2014-09 by one year to December 15, 2017 for annual reporting periods beginning after that date, including interim periods within those periods. The FASB also approved permitting early adoption of the standard, but not before the original effective date of December 15, 2016. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its financial statements. In July 2015, the FASB issued ASU No. 2015-11, which amends existing guidance for measurement of inventory. Current inventory guidance requires an entity to measure inventory at the lower of cost or market. Market could be replacement cost, net realizable value, or net realizable value less an approximately normal profit margin. The amendments do not apply to inventory that is measured using last-in, first-out (LIFO) or the retail inventory method. The amendments apply to all other inventory, which includes inventory that is measured using first-in, first-out or average cost. An entity should measure all inventory to which the amendments apply at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. Subsequent measurement is unchanged for inventory measured using LIFO or the retail inventory method. The amendments in the ASU No. 2015-11 more closely align the measurement of inventory pursuant to GAAP with the measurement of inventory pursuant to International Financial Reporting Standards. The amendments are effective for fiscal years beginning after December 15, 2016, and interim periods within fiscal years beginning after December 15, 2017. The amendments should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on its condensed financial statements.	Recently Issued Accounting Pronouncements In July 2013, the Financial Accounting Standards Board ("FASB") issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exist. ASU 2013-11 amends the presentation requirements of ASC 740 and requires an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if the entity does not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented as a liability and not combined with deferred tax assets. This ASU is effective for annual periods, and interim periods within those years, beginning after December 15, 2013, which is fiscal 2014 for the Company. The amendments are to be applied to all unrecognized tax benefits that exist as of the effective date and may be applied retrospectively to each prior reporting period presented. The adoption of ASU 2013-11 did not have a material impact on the Company's financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. This ASU is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. This ASU is effective for annual reporting periods beginning after December 15, 2016 and early adoption is not permitted. Accordingly, the Company will adopt this ASU on January 1, 2017. Management does not believe the adoption of this ASU will have a material impact on the Company's financial condition, results of operations or cash flows. In June 2014, the FASB issued ASU No. 2014-12, Compensation — Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. ASU 2014-12 applies to all reporting entities that grant their employees share-based payments in which the terms of the award provide that a performance target that affects vesting could be achieved after the requisite service period. That is the case when an employee is eligible to retire or otherwise terminate employment before the end of the period in which a performance target (for example, an initial public offering or a profitability target) could be achieved and still be eligible to vest in the award if and when the performance target is achieved. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2015 and interim periods within those annual periods. The Company plans to implement this standard in the first quarter of fiscal year 2016 and is currently evaluating the potential impact of this new guidance on its financial statements. In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern. ASU 2014-15 requires management to evaluate, at each annual or interim reporting period, whether there are conditions or events that exist that raise substantial doubt about an entity's ability to continue as a going concern within one year after the date the financial statements are issued and provide related disclosures. ASU 2014-15 is effective for annual periods ending after December 15, 2016 and earlier application is permitted. The adoption of ASU 2014-15 is not expected to have a material effect on the Company's financial statements or disclosures. In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815) — Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share is More Akin to Debt or to Equity. This ASU was issued to clarify how current U.S. generally accepted accounting principles should be interpreted in evaluating the economic characteristics and risk of a host contract in a hybrid financial instrument that is issued in the form of a share. In addition, this ASU was issued to clarify that in evaluating the nature of a host contract, an entity should assess the substance of the relevant terms and features (that is, the relative strength of the debt-like or equity-like terms and features given the facts and circumstances) when considering how to weight those terms and features. The effects of initially adopting this ASU should be applied on a modified retrospective basis to existing hybrid financial instruments issued in a form of a share as of the beginning of the fiscal year for which the amendments are effective. Retrospective application is permitted to all relevant prior periods. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption in an interim period is permitted. The Company is currently evaluating the impact of the adoption of this ASU on its financial statements.

Net Loss per Common Share (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Schedule of computations of basic and diluted net loss per share

	Nine months ended September 30,

	2014			2015
Net loss	$	(14,448	)	$	(17,730	)
Extinguishment of preferred stock — see note 7		—			31,806
Accretion of prior preferred stock — see note 7		(2,469	)		(23,327	)
Accretion and dividends of Series D preferred stock		—			(1,245	)

Loss attributable to common shareholders — basic and diluted	$	(16,917	)	$	(10,496	)



Weighted-average number of common shares used in net loss per share — basic and diluted		926,597			11,179,756



Net loss per share — basic and diluted	$	(18.26	)	$	(0.94	)

	Years Ended December 31,

	2013			2014
Net loss	$	(16,197	)	$	(17,917	)
Performance Adjustment of Series A		12,239			—
Accruals of dividends and accretion to redemption value of preferred stock		(2,925	)		(3,300	)

Loss attributable to common shareholders — basic and diluted	$	(6,883	)	$	(21,217	)



Weighted-average shares used in computing basic and diluted net loss per common share		1,697,044			933,997



Basic and diluted net loss per common share	$	(4.06	)	$	(22.72	)

Schedule of potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding

	Nine months ended September 30,

	2014		2015
Outstanding stock options		311,365		1,356,246
Warrants		18,810		2,445
Redeemable convertible preferred stock		6,552,820		—
Unvested restricted stock		28,536		153,589

	Years Ended December 31,

	2013		2014
Stock Options		229,791		281,029
Warrants		4,170		18,809
Redeemable convertible preferred stock		6,552,820		6,552,820
Unvested restricted stock		55,298		15,387

Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value of Financial Instruments

Schedule of financial instruments measured at fair value by level within fair value hierarchy

Description	Total		Quoted Prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)

December 31, 2014
Money market funds, included in cash equivalents	$	457	$	457	$	—	$	—
September 30, 2015
Money market funds, included in cash equivalents	$	104,911	$	104,911	$	—	$	—

Accrued Expenses (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Schedule of components of accrued expenses

	December 31, 2014		September 30, 2015

Accrued compensation	$	635	$	1,169
Accrued development costs		970		597
Accrued marketing		—		685
Accrued audit and legal		249		109
Accrued interest		71		31
Accrued other		31		90

Total accrued expenses	$	1,956	$	2,681

	As of December 31,

	2013		2014
Accrued development costs	$	520	$	970
Accrued compensation		449		635
Accrued audit and legal		12		249
Accrued interest		—		71
Accrued other		32		31

Total accrued expenses	$	1,013	$	1,956

Stock-based Compensation (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014