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 QC, 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:____________________________

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.: 1,426,862 shares
Jérôme G. Pfund:  1,426,862 shares
Michael L. Sjöström:  1,426,862 shares

(b)

Percent of class:   

Sectoral Asset Management Inc.:  4.4%
Jérôme G. Pfund:  4.4%
Michael L. Sjöström:  4.4%

(c)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote:   

Sectoral Asset Management Inc.:  919,394 shares
Jérôme G. Pfund:  919,394 shares
Michael L. Sjöström:  919,394 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.:  1,426,862 shares
Jérôme G. Pfund:  1,426,862 shares
Michael L. Sjöström:  1,426,862 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 x

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.

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.