X0306 4 2013-05-14 0 0001463729 Receptos, Inc. RCPT 0001508052 Flagship Ventures Fund 2007, L.P. ONE MEMORIAL DRIVE, 7TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 0001508053 Flagship Ventures 2007 General Partner LLC ONE MEMORIAL DRIVE, 7TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 0001255927 KANIA EDWIN M JR ONE MEMORIAL DRIVE, 7TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 0001222012 AFEYAN NOUBAR ONE MEMORIAL DRIVE, 7TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2013-05-14 4 C 0 1152039 5.25 A 1266324 D Common Stock 2013-05-14 4 C 0 550873 7.73 A 1817197 D Common Stock 2013-05-14 4 P 0 107142 14.00 A 1924339 D Series A Preferred Stock 5.25 2013-05-14 4 C 0 8640289 0 D Common Stock 1152039 0 D Series B Preferred Stock 7.73 2013-05-14 4 C 0 4131552 0 D Common Stock 550873 0 D The Series A preferred stock and Series B preferred stock converted upon the closing of the Issuer's initial public offering at a conversion ratio of 1 share of common stock for every 7.5 shares of Series A preferred stock and Series B preferred stock, for no additional consideration. Beneficial ownership consists of: (i) 221,427 shares of common stock held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund"); and (ii) an aggregate of 1,702,912 shares of common stock issued upon conversion of shares of Series A preferred stock and Series B preferred stock held by Flagship Fund. The general partner of Flagship Fund is Flagship Ventures 2007 General Partner LLC ("Flagship GP"), and the managing members of Flagship GP are Noubar B. Afeyan and Edwin M. Kania, Jr. The General Partner and Messrs. Afeyan and Kania have voting and investment control over the shares held by Flagship Fund and may be deemed to be the beneficial owners of such shares and each of them disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein. FLAGSHIP VENTURES FUND 2007, L.P. By: /s/ Noubar B. Afeyan 2013-05-14 FLAGSHIP VENTURES 2007 GENERAL PARTNER LLC By: /s/ Noubar B. Afeyan 2013-05-14 /s/ Edwin M. Kania, Jr. 2013-05-14 /s/ Noubar B. Afeyan 2013-05-14