SEC FORM 3

SEC Form 3

FORM 3

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

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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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1. Name and Address of Reporting Person^*

AGTC ADVISORS FUND LP

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
09/18/2013

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

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

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

5. 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 Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	4,867	D⁽⁶⁾

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Series A Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	1,376,249	⁽¹⁾	D⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
Series B Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	507,666	⁽¹⁾	D⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
Series C Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	293,144	⁽¹⁾	D⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
Series D Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	39,175	⁽¹⁾	D⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
Series F Convertible Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	60,245	⁽¹⁾	D⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾

1. Name and Address of Reporting Person^*

AGTC ADVISORS FUND LP

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Applied Genomic Technology Capital Fund LP

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

AGTC Partners, L.P.

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

AFEYAN NOUBAR

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

NewcoGen Group, Inc.

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Flagship Ventures Management, Inc.

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

KANIA EDWIN M JR

(Last)

(First)

(Middle)

C/O FLAGSHIP VENTURES

1 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02142

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

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

Explanation of Responses:

1. The Series A Convertible Preferred Stock, Series B Convertible Preferred Stock, Series C Convertible Preferred Stock, Series D Convertible Preferred Stock and Series F Convertible Preferred Stock are each convertible into Common Stock on a 1 for 1 basis at any time at the holder's election and upon the consummation of a qualified public offering of the issuer. There is no expiration date for any series of convertible preferred stock.

2. 1,297,803 shares of Series A Convertible Preferred Stock, 478,729 shares of Series B Convertible Preferred Stock, 276,435 shares of Series C Convertible Preferred Stock, 36,942 shares of Series D Convertible Preferred Stock, and 56,811 shares of Series F Convertible Preferred Stock of the issuer are owned directly by Applied Genomic Technology Capital Fund, L.P. (AGTC Fund).

3. NewcoGen Group, Inc. (NewcoGen Inc.) is the general partner of AGTC Partners, L.P., which is the general partner of AGTC Fund. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. Noubar B. Afeyan Ph.D. and Edwin M. Kania, Jr. are the directors of Flagship Venture Management, Inc. and may be deemed to have beneficial ownership with respect to all shares held by AGTC Fund. Each of Mr. Kania and Dr. Afeyan disclaim beneficial ownership over such shares held by AGTC Fund except to the extent of their pecuniary interest therein. Mr. Kania holds 4,867 shares of the issuers common stock directly. Mr. Kanias beneficial ownership of such shares is reflected on a separate Form 3 that is being filed concurrently herewith.

4. 78,446 shares of Series A Convertible Preferred Stock, 28,937 shares of Series B Convertible Preferred Stock, 16,709 shares of Series C Convertible Preferred Stock, 2,233 shares of Series D Convertible Preferred Stock, and 3,434 shares of Series F Convertible Preferred Stock of the issuer are owned directly by AGTC Advisors Fund, L.P. (AGTC).

5. NewcoGen Inc., is the general partner of AGTC Partners, L.P., which is the general partner of AGTC. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. Noubar B. Afeyan Ph.D. and Edwin M. Kania, Jr. are the directors of Flagship Venture Management, Inc. and may be deemed to have beneficial ownership with respect to all shares held by AGTC. Each of Mr. Kania and Dr. Afeyan disclaim beneficial ownership over such shares held by AGTC except to the extent of their pecuniary interest therein. Mr. Kania holds 4,867 shares of the issuers common stock directly. Mr. Kania's beneficial ownership of such shares is reflected on a separate Form 3 that is being filed concurrently herewith.

6. These shares are held directly by Noubar B. Afeyan Ph.D.

	/s/ Noubar B. Afeyan, Managing Partner	09/18/2013
	/s/ Noubar B. Afeyan, Managing Partner	09/18/2013
	/s/ Noubar B. Afeyan, Managing Partner	09/18/2013
	/s/ Noubar B. Afeyan	09/18/2013
	/s/ Noubar B. Afeyan, Director	09/18/2013
	/s/ Noubar B. Afeyan, Director	09/18/2013
	/s/ Edwin M. Kania, Jr.	09/18/2013
	** 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 5 (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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