X0206 3 2013-09-18 0 0001280600 ACCELERON PHARMA INC XLRN 0001131095 AGTC ADVISORS FUND LP C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001399779 Applied Genomic Technology Capital Fund LP C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001419730 AGTC Partners, L.P. C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001222012 AFEYAN NOUBAR C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001400241 NewcoGen Group, Inc. C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001400240 Flagship Ventures Management, Inc. C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 0 0 1 0 0001255927 KANIA EDWIN M JR C/O FLAGSHIP VENTURES 1 MEMORIAL DRIVE CAMBRIDGE MA 02142 1 0 0 0 Common Stock 4867 D Series A Convertible Preferred Stock Common Stock 1376249 D Series B Convertible Preferred Stock Common Stock 507666 D Series C Convertible Preferred Stock Common Stock 293144 D Series D Convertible Preferred Stock Common Stock 39175 D Series F Convertible Preferred Stock Common Stock 60245 D 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. 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). 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. 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). 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. These shares are held directly by Noubar B. Afeyan Ph.D. /s/ Noubar B. Afeyan, Managing Partner 2013-09-18 /s/ Noubar B. Afeyan, Managing Partner 2013-09-18 /s/ Noubar B. Afeyan, Managing Partner 2013-09-18 /s/ Noubar B. Afeyan 2013-09-18 /s/ Noubar B. Afeyan, Director 2013-09-18 /s/ Noubar B. Afeyan, Director 2013-09-18 /s/ Edwin M. Kania, Jr. 2013-09-18