X0306 4 2018-07-02 0 0001693415 Translate Bio, Inc. TBIO 0001030575 FORMELA JEAN FRANCOIS C/O TRANSLATE BIO, INC. 29 HARTWELL AVENUE LEXINGTON MA 02421 1 0 0 0 Common Stock 2018-07-02 4 C 0 3832010 A 3922010 I By Atlas Venture Fund VIII, L.P. Series A Preferred Stock 2018-07-02 4 C 0 12925244 0.00 D Common Stock 2326567 0 I By Atlas Venture Fund VIII, L.P. Series B Preferred Stock 2018-07-02 4 C 0 5838230 0.00 D Common Stock 1050891 0 I By Atlas Venture Fund VIII, L.P. Series C Preferred Stock 2018-07-02 4 C 0 2525253 0.00 D Common Stock 454550 0 I By Atlas Venture Fund VIII, L.P. The Series A, Series B and Series C Preferred Stock converted into Common Stock on a 5.5555-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date. These shares are held directly by Atlas Venture Fund VIII, L.P. ("Atlas Venture Fund VIII"). The sole general partner of Atlas Venture Fund VIII is Atlas Venture Associates VIII, L.P. ("AVA VIII LP"). Atlas Venture Associates VIII, Inc. ("AVA VIII INC") is the sole general partner of AVA VIII LP. Dr. Formela is a director of AVA VIII INC and disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Fund VIII, except to the extent of his pecuniary interest therein, if any. This report shall not be deemed to be an admission that Dr. Formela is the beneficial owner of such securities for purposes of Section 16 or for any other purpose. /s/ Frank Castellucci, as attorney-in-fact for Jean-Francois Formela 2018-07-03