UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

x

Rule 13d-1(b)

o

Rule 13d-1(c)

o

Rule 13d-1(d)

CUSIP No. 19459J104

1.

Names of Reporting Persons.
I.R.S. Identification Nos. of Above persons (entities only).

Sectoral Asset Management Inc.

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

3.

SEC Use Only

4.

Citizenship or Place of Organization :
Canada

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
1,120,251

6.

Shared Voting Power
-0-

7.

Sole Dispositive Power
2,104,756

8.

Shared Dispositive Power
-0-

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
2,104,756

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions).  o

11.

Percent of Class Represented by Amount in Row (9)
7.4%

12.

Type of Reporting Person (See Instructions)
IA

CUSIP No. 19459J104

1.

Names of Reporting Persons.
I.R.S. Identification Nos. of Above persons (entities only).

Jérôme G. Pfund

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

3.

SEC Use Only

4.

Citizenship or Place of Organization :
Swiss

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
1,120,251

6.

Shared Voting Power
-0-

7.

Sole Dispositive Power
2,104,756

8.

Shared Dispositive Power
-0-

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
2,104,756

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions).  o

11.

Percent of Class Represented by Amount in Row (9)
7.4%

12.

Type of Reporting Person (See Instructions)
IN

CUSIP No. 19459J104

1.

Names of Reporting Persons.
I.R.S. Identification Nos. of Above persons (entities only).

Michael L. Sjöström

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

3.

SEC Use Only

4.

Citizenship or Place of Organization :
Swiss

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
1,120,251

6.

Shared Voting Power
-0-

7.

Sole Dispositive Power
2,104,756

8.

Shared Dispositive Power
-0-

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
2,104,756

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions).  o

11.

Percent of Class Represented by Amount in Row (9)
7.4%

12.

Type of Reporting Person (See Instructions)
IN

CUSIP No. 19459J104

Item 1.

(a)

Name of Issuer:
Collegium Pharmaceutical Inc.

(b)

Address of Issuer’s Principal Executive Offices:
800-780 Dedham Street, Canton, MA 02021, United States

Item 2.

(a)

Name of Person(s) Filing:
Sectoral Asset Management Inc.

Jérôme G. Pfund

Michael L. Sjöström

(b)

Address of Principal Business Office or, if none, Residence:
The principal business address of each person filing is:

1610-1010 Sherbrooke St. West Montreal PQ H3A 2R7 Canada

(c)

Citizenship:
Sectoral Asset Management Inc. is a Canadian corporation

Jérôme G. Pfund is a Swiss citizen

Michael L. Sjöström is a Swiss citizen

(d)

Title of Class of Securities:
Common Stock

(e)

CUSIP Number:
19459J104

Item 3.

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

o

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

o

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

(e)

x

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

x

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

o

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J);

(k)

o

Group, in accordance with § 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with

§ 240.13d-1(b)(1)(ii)(J), please specify the type of institution:____________________________

CUSIP No. 19459J104

Ownership.

Sectoral Asset Management Inc, in its capacity as an investment adviser, has the sole right to dispose of or vote the number of shares of common stock of the Issuer set forth in this filing.  Jérôme G. Pfund and Michael L. Sjöström, together, hold majority of shares of Sectoral Asset Management Inc.  Sectoral Asset Management, Inc. and Messrs. Pfund and Sjöström disclaim beneficial ownership of the Issuer’s common stock held by Sectoral Asset Management Inc.

(a)

Amount beneficially owned:   

Sectoral Asset Management Inc.: 2,104,756 shares

Jérôme G. Pfund:  2,104,756 shares

Michael L. Sjöström:  2,104,756 shares

(b)

Percent of class:   

Sectoral Asset Management Inc.:  7.4%

Jérôme G. Pfund:  7.4%

Michael L. Sjöström:  7.4%

(c)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote:   

Sectoral Asset Management Inc.:  1,120,251 shares

Jérôme G. Pfund:  1,120,251 shares

Michael L. Sjöström:  1,120,251 shares

(ii)

Shared power to vote or to direct the vote:    

Sectoral Asset Management Inc.: -0- shares

Jérôme G. Pfund:  -0- shares

Michael L. Sjöström:  -0- shares

(iii)

Sole power to dispose or to direct the disposition of:   

Sectoral Asset Management Inc.:  2,104,756 shares

Jérôme G. Pfund:  2,104,756 shares

Michael L. Sjöström:  2,104,756 shares

(iv)

Shared power to dispose or to direct the disposition of:   

Not applicable.

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following   o

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Various persons, as investment advisory clients of Sectoral Asset Management, Inc., have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the common stock of the Issuer.  To the knowledge of Sectoral Asset Management, Inc., no one such person’s interest in the common stock of the Issuer is more than five percent of the total outstanding common stock of the Issuer.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

Not applicable.

Item 8.

Identification and Classification of Members of the Group.

Not applicable.

Item 9.

Notice of Dissolution of Group.

Not applicable.

CUSIP No. 19459J104

Item 10.

Certification.

By signing below the undersigned each certifies that, to the best knowledge and belief of the undersigned, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Dated: February 2, 2017

SECTORAL ASSET MANAGEMENT INC.

/s/Jérôme G. Pfund

By:  Jérôme G. Pfund

Its:   CEO

Dated: February 2, 2017

/s/Jérôme G. Pfund

Jérôme G. Pfund

Dated: February 2, 2017

/s/Michael L. Sjöström

Michael L. Sjöström

CUSIP No. 19459J104

SECTORAL ASSET MANAGEMENT INC.

/s/Jérôme G. Pfund

By:  Jérôme G. Pfund

Its:   CEO

/s/Jérôme G. Pfund

Jérôme G. Pfund

/s/Michael L. Sjöström

Michael L. Sjöström