SEC FORM 4

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last)

(First)

(Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK

10022

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
ACCELERON PHARMA INC [ XLRN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

Director		10% Owner
Officer (give title below)	X	Other (specify below)
		Former 10% Owner

3. Date of Earliest Transaction (Month/Day/Year)
09/24/2013

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	09/24/2013		C		1,127,346	A	⁽¹⁾	1,133,171	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		422,101	A	⁽¹⁾	424,282	I	See footnote⁽⁹⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		175,419	A	⁽²⁾	1,308,590	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		65,680	A	⁽²⁾	489,962	I	See footnote⁽⁹⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		23,442	A	⁽³⁾	1,332,032	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		8,777	A	⁽³⁾	498,739	I	See footnote⁽⁹⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		133,930	A	⁽⁴⁾	1,465,962	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		50,145	A	⁽⁴⁾	548,884	I	See footnote⁽⁹⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		35,873	A	⁽⁵⁾	1,501,835	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		13,431	A	⁽⁵⁾	562,315	I	See footnote⁽⁹⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		38,924	A	⁽⁶⁾	1,540,759	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Common Stock	09/24/2013		C		14,574	A	⁽⁶⁾	576,889	I	See footnote⁽⁹⁾⁽¹⁰⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Series B Convertible Preferred Stock	⁽¹⁾	09/24/2013		C			1,127,346	⁽¹⁾	⁽¹⁾	Common Stock	1,127,346	⁽¹⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series B Convertible Preferred Stock	⁽¹⁾	09/24/2013		C			422,101	⁽¹⁾	⁽¹⁾	Common Stock	422,101	⁽¹⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾
Series C Convertible Preferred	⁽²⁾	09/24/2013		C			175,419	⁽²⁾	⁽²⁾	Common Stock	175,419	⁽²⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series C Convertible Preferred Stock	⁽²⁾	09/24/2013		C			65,680	⁽²⁾	⁽²⁾	Common Stock	65,680	⁽²⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾
Series D Convertible Preferred	⁽³⁾	09/24/2013		C			23,442	⁽³⁾	⁽³⁾	Common Stock	23,442	⁽³⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series D Convertible Preferred Stock⁽³⁾	⁽³⁾	09/24/2013		C			8,777	⁽³⁾	⁽³⁾	Common Stock	8,777	⁽³⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾
Series E Convertible Preferred	⁽⁴⁾	09/24/2013		C			83,097	⁽⁴⁾	⁽⁴⁾	Common Stock	133,930	⁽⁴⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series E Convertible Preferred Stock	⁽⁴⁾	09/24/2013		C			31,113	⁽⁴⁾	⁽⁴⁾	Common Stock	50,145	⁽⁴⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾
Series E Convertible Preferred	⁽⁵⁾	09/24/2013		C			22,612	⁽⁵⁾	⁽⁵⁾	Common Stock	35,873	⁽⁵⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series E Convertible Preferred	⁽⁵⁾	09/24/2013		C			8,466	⁽⁵⁾	⁽⁵⁾	Common Stock	13,431	⁽⁵⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾
Series F Convertible Preferred	⁽⁶⁾	09/24/2013		C			38,924	⁽⁶⁾	⁽⁶⁾	Common Stock	38,924	⁽⁶⁾	0	I	See footnote⁽⁷⁾⁽⁸⁾⁽¹⁰⁾
Series F Convertible Preferred	⁽⁶⁾	09/24/2013		C			14,574	⁽⁶⁾	⁽⁶⁾	Common Stock	14,574	⁽⁶⁾	0	I	See footnote⁽⁹⁾⁽¹⁰⁾

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last)

(First)

(Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK

10022

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

Director		10% Owner
Officer (give title below)	X	Other (specify below)
		Former 10% Owner

1. Name and Address of Reporting Person^*

ORBIMED CAPITAL GP II LLC

(Last)

(First)

(Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK\

10022

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

Director		10% Owner
Officer (give title below)	X	Other (specify below)
		Former 10% Owner

1. Name and Address of Reporting Person^*

ISALY SAMUEL D

(Last)

(First)

(Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK

10022

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

Director		10% Owner
Officer (give title below)	X	Other (specify below)
		Former 10% Owner

Explanation of Responses:

1. Represents shares of Common Stock acquired upon the automatic conversion of Series B convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series B convertible preferred stock did not have an expiration date. The Series B convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1:1, for no additional consideration.

2. Represents shares of Common Stock acquired upon the automatic conversion of Series C convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series C convertible preferred stock did not have an expiration date. The Series C convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1:1, for no additional consideration.

3. Represents shares of Common Stock acquired upon the automatic conversion of Series D convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series D convertible preferred stock did not have an expiration date. The Series D convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1:1, for no additional consideration.

4. Represents shares of Common Stock acquired upon the automatic conversion of Series E convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series E convertible preferred stock did not have an expiration date. The Series E convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1.61 shares of Common Stock for every 1 share of Series E convertible preferred stock, for no additional consideration.

5. Represents shares of Common Stock acquired upon the automatic conversion of Series E convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series E convertible preferred stock did not have an expiration date. The Series E convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1.59 shares of Common Stock for every 1 share of Series E convertible preferred stock, for no additional consideration.

6. Represents shares of Common Stock acquired upon the automatic conversion of Series F convertible preferred stock upon the closing of the Issuer's initial public offering of Common Stock. The Series F convertible preferred stock did not have an expiration date. The Series F convertible preferred stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering of Common Stock, at a conversion ratio of 1:1, for no additional consideration.

7. These securities are directly owned by OrbiMed Private Investments II, LP ("OPI II") and may be deemed to be indirectly beneficially owned by OrbiMed Capital GP II LLC ("GP II"), OrbiMed Advisors LLC ("Advisors") and Samuel D. Isaly ("Isaly"). GP II is the sole general partner of OPI II. Advisors, a registered adviser under the Investment Advisers Act of 1940, as amended, is the sole managing member of GP II. By virtue of such relationships, GP II and Advisors may be deemed to have voting and investment power over the securities held by OPI II noted above. Accordingly, GP II and Advisors may be deemed to have beneficial ownership of such securities.

8. Isaly, a natural person, may also be deemed to have voting and investment power over the securities held by OPI II noted above in his capacity as the managing member of, and owner of a controlling interest in, Advisors. Accordingly, Isaly may be deemed to have beneficial ownership of such securities.

9. These securities are directly owned by OrbiMed Private Investments II (QP), LP ("OPI II QP") and may be deemed to be indirectly beneficially owned by GP II, Advisors and Isaly. GP II is the sole general partner of OPI II QP. Advisors is the sole managing member of GP II. Isaly is the managing member of, and owner of a controlling interest in, Advisors. By virtue of such relationships, GP II, Advisors and Isaly may be deemed to have voting and investment power over the securities held by OPI II QP noted above. Accordingly, GP II, Advisors and Isaly may be deemed to have beneficial ownership of such securities.

10. This report on Form 4 is jointly filed by GP II, Advisors and Isaly. GP II, Advisors and Isaly designated a representative, Carl L. Gordon ("Gordon"), a member of Advisors, to serve on the Issuer's board of directors. On September 18, 2013 and in connection with the Issuer's initial public offering, Gordon resigned from the Issuer's board of directors. Each of GP II, Advisors, Isaly and Gordon disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its or his pecuniary interest therein, if any. This report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 of the Exchange Act or for any other purpose.

Remarks:

	/s/ Samuel D. Isaly	09/26/2013
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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