X0306 4 2017-11-20 1 0001501697 Arsanis, Inc. ASNS 0001691436 Section 32 Fund 1, LP 2071 SAN ELIJO AVENUE CARDIFF-BY-THE-SEA CA 92007 0 0 1 0 0001691437 Section 32 GP 1, LLC 2071 SAN ELIJO AVENUE CARDIFF-BY-THE-SEA CA 92007 0 0 1 0 0001722210 Maris William J 2071 SAN ELIJO AVENUE CARDIFF-BY-THE-SEA CA 92007 0 0 1 0 Common Stock 2017-11-20 4 C 0 451362 A 451362 D Series D Convertible Preferred Stock 2017-11-20 4 C 0 1540500 0.00 D Common Stock 451362 0 D The Series D Convertible Preferred Stock converted into Common Stock on a 0.29300-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series D Convertible Preferred Stock was convertible at any time at the holder's election and automatically upon the closing at the Issuer's initial public offering. The shares had no expiration date. The reported securities are held of record by Section 32 Fund 1, LP ("Fund 1"). Section 32 GP 1, LLC (the "GP"), the general partner of Fund 1, and William J. Maris, the managing member of the GP, may be deemed to share voting and dispositive power over the shares held by Fund 1. Such persons and entities disclaim beneficial ownership of shares held by Fund 1 except to the extent of any pecuniary interest therein. /s/ Mike Gray, attorney-in-fact on behalf of Section 32 Fund 1, LP 2015-11-20 /s/ Mike Gray, attorney-in-fact on behalf of Section 32 GP 1, LLC 2015-11-20 /s/ Mike Gray, attorney-in-fact on behalf of William J. Maris 2015-11-20