X0206 3 2013-09-18 0 0001280600 ACCELERON PHARMA INC XLRN 0001294514 Advanced Technology Ventures VI, L.P. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001294525 Advanced Technology Ventures VII(B), L.P. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001294527 Advanced Technology Ventures VII(C), L.P. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001138942 ADVANCED TECHNOLOGY VENTURES VII LP C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001294971 ATV Alliance 2003, L.P. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001317310 ATV Associates VI, L.L.C. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001317308 ATV Associates VII, L.L.C. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 0001294521 ATV Entrepreneurs VI, L.P. C/O ADVANCED TECHNOLOGY VENTURES 500 BOYLSTON STREET SUITE 1380 BOSTON MA 02116 0 0 1 0 Common Stock 9732 D Series A Convertible Preferred Stock Common Stock 1376248 D Series B Convertible Preferred Stock Common Stock 507664 D Series C Convertible Preferred Stock Common Stock 293142 D Series D Convertible Preferred Stock Common Stock 39172 D Series E Convertible Preferred Stock Common Stock 223806 D Series F Convertible Preferred Stock Common Stock 64019 D Warrants to Purchase Common Stock 5.88 Common Stock 148309 D 7,831 shares of common stock, 119,322 warrants to purchase common stock, 1,103,378 shares of Series A Convertible Preferred Stock, 408,439 shares of Series B Convertible Preferred Stock, 235,847 shares of Series C Convertible Preferred Stock, 31,518 shares of Series D Convertible Preferred Stock, 111,722 shares of Series E Convertible Preferred Stock and 51,507 shares of Series F Convertible Preferred Stock of the registrant are owned directly by Advanced Technology Ventures VII, L.P. (ATV VII). ATV Associates VII, L.L.C. (ATV A VII) is the general partner of ATV VII and exercises voting and dispositive authority over the shares held by ATV VII. Jean George (George) is a managing director of ATV A VII and exercises voting and dispositive decisions of ATV A VII collectively with each of four other managing directors. ATV A VII and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. 314 shares of common stock, 4,788 warrants to purchase common stock, 44,278 shares of Series A Convertible Preferred Stock, 16,390 shares of Series B Convertible Preferred Stock, 9,464 shares of Series C Convertible Preferred Stock, 1,264 shares of Series D Convertible Preferred Stock, 4,483 shares of Series E Convertible Preferred Stock and 2,067 shares of Series F Convertible Preferred Stock of the registrant are owned directly by Advanced Technology Ventures VII (B), L.P. (ATV VII B). ATV A VII is the general partner of ATV VII B and exercises voting and dispositive authority over the shares held by ATV VII B. ATV A VII and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. 151 shares of common stock, 2,301 warrants to purchase common stock, 21,283 shares of Series A Convertible Preferred Stock, 7,878 shares of Series B Convertible Preferred Stock, 4,549 shares of Series C Convertible Preferred Stock, 607 shares of Series D Convertible Preferred Stock, 2,155 shares of Series E Convertible Preferred Stock and 993 shares of Series F Convertible Preferred Stock of the registrant are owned directly by Advanced Technology Ventures VII (C), L.P. (ATV VII C). ATV A VII is the general partner of ATV VII C and exercises voting and authority decisions over the shares held by ATV VII C. ATV A VII and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. 46 shares of common stock, 711 warrants to purchase common stock, 6,575 shares of Series A Convertible Preferred Stock, 2,434 shares of Series B Convertible Preferred Stock, 1,405 shares of Series C Convertible Preferred Stock, 187 shares of Series D Convertible Preferred Stock, 665 shares of Series E Convertible Preferred Stock and 307 shares of Series F Convertible Preferred Stock of the registrant are owned directly by ATV Entrepreneurs VII, L.P. (ATV VII E). ATV A VII is the general partner of ATV VII E and exercises voting and dispositive authority over the shares held by ATV VII E. ATV A VII and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. 1,307 shares of common stock, 19,916 warrants to purchase common stock, 184,810 shares of Series A Convertible Preferred Stock, 68,172 shares of Series B Convertible Preferred Stock, 39,365 shares of Series C Convertible Preferred Stock, 5,260 shares of Series D Convertible Preferred Stock, 18,647 shares of Series E Convertible Preferred Stock and 8,597 shares of Series F Convertible Preferred Stock of the registrant are owned directly by Advanced Technology Ventures VI, L.P. (ATV VI). ATV Associates VI, L.L.C. (ATV A VI) is the general partner of ATV VI and exercises voting and dispositive authority over the shares held by ATV VI. ATV A VI and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. 83 shares of common stock, 1,271 warrants to purchase common stock, 11,796 shares of Series A Convertible Preferred Stock, 4,351 shares of Series B Convertible Preferred Stock, 2,512 shares of Series C Convertible Preferred Stock, 336 shares of Series D Convertible Preferred Stock, 1,190 shares of Series E Convertible Preferred Stock and 548 shares of Series F Convertible Preferred Stock of the registrant are owned directly by ATV Entrepreneurs VI, L.P. (ATV VI E). ATV A VI is the general partner of ATV VI E and exercises voting and dispositive decisions over the shares held by ATV VI E. ATV A VI and each of the managing directors disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. The Series A Convertible Preferred Stock, Series B Convertible Preferred Stock, Series C Convertible Preferred Stock, Series D Convertible Preferred Stock, Series E Convertible Preferred Stock and Series F Convertible Preferred Stock are each convertible into Common Stock at any time at the holders election and upon the consummation of a qualified public offering of the registrant. There is no expiration date for any series of convertible preferred stock. 4,128 shares of Series A Convertible Preferred Stock of the registrant are owned directly by ATV Alliance 2003, L.P. (ATV 2003). ATV Alliance Associates, L.L.C. (ATV Alliance LLC) is the general partner of ATV 2003 and exercises voting and dispositive authority over the shares held by ATV 2003. Voting and dispositive decisions of ATV Alliance LLC are made by Ms. George. ATV Alliance LLC and George disclaim beneficial ownership of these securities and this report shall not be deemed an admission that they are the beneficial owners of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein. The warrants to purchase Common Stock are exercisable at any time at the holders election, and have an expiration date on the ten year anniversary of the warrant issue date. Exhibit List Exhibit 24 Power of Attorney /s/ Douglas Pagan, attorney-in-fact for ATV Associates VII, L.L.C. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for Advanced Technology Ventures VI, L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for Advanced Technology Ventures VII (B), L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for Advanced Technology Ventures VII (C), L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for Advanced Technology Ventures VII, L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for ATV Alliance 2003, L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for ATV Entrepreneurs VI, L.P. 2013-09-18 /s/ Douglas Pagan, attorney-in-fact for ATV Associates VI, L.P. 2013-09-18