X0306 4 2016-06-27 1 0001453687 SELECTA BIOSCIENCES INC SELB 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 0001222012 AFEYAN NOUBAR ONE MEMORIAL DRIVE, 7TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2016-06-27 4 C 0 318752 A 349867 I See Footnote Common Stock 2016-06-27 4 C 0 631458 A 981325 I See Footnote Common Stock 2016-06-27 4 C 0 235042 A 1216367 I See Footnote Common Stock 2016-06-27 4 C 0 241718 A 1458085 I See Footnote Common Stock 2016-06-27 4 C 0 193777 A 1651862 I See Footnote Series A Convertible Preferred Stock 2016-06-27 4 C 0 318752 0 D Common Stock 318752 0 I See Footnote Series B Convertible Preferred Stock 2016-06-27 4 C 0 631458 0 D Common Stock 631458 0 I See Footnote Series C Convertible Preferred Stock 2016-06-27 4 C 0 235042 0 D Common Stock 235042 0 I See Footnote Series D Convertible Preferred Stock 2016-06-27 4 C 0 241718 0 D Common Stock 241718 0 I See Footnote Series E Convertible Preferred Stock 2016-06-27 4 C 0 125008 0 D Common Stock 193777 0 I See Footnote Held by Flagship Ventures Fund 2007, L.P. ("Flagship 2007"). Flagship Ventures 2007 General Partner LLC ("Flagship 2007 LLC") is the general partner of Flagship 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship 2007 LLC. Flagship 2007 LLC and each of these individuals may be deemed to share voting and investment power with respect to all shares held by Flagship 2007. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein. The preferred stock is convertible at any time, at the holder's election and has no expiration date. The preferred stock automatically converted into common stock on a 1-for-1 basis upon the closing of the Issuer's initial public offering. The Series E Convertible Preferred Stock is convertible at any time, at the holder's election and has no expiration date. The Series E Convertible Preferred Stock automatically converted into common stock on an approximately 1-for-1.550115 basis upon the closing of the Issuer's initial public offering. FLAGSHIP VENTURES FUND 2007, L.P. By: Flagship Ventures 2007 General Partner LLC By: /s/ Noubar B. Afeyan, Ph.D., Manager 2016-06-29 FLAGSHIP VENTURES 2007 GENERAL PARTNER LLC By: /s/ Noubar B. Afeyan, Ph.D., Manager 2016-06-29 s/ Noubar B. Afeyan, Ph.D. 2016-06-29