X0306 4 2021-06-22 0 0001662244 Cyteir Therapeutics, Inc. CYT 0001291804 George Jean 128 SPRING ST, BUILDING A, SUITE 510 LEXINGTON MA 02421 1 0 0 0 Common Stock 2021-06-22 4 C 0 2444268 A 2444268 I See Footnote Series B Convertible Preferred Stock 2021-06-22 4 C 0 7500000 D Common Stock 2200187 0 I See Footnote Series C Convertible Preferred Stock 2021-06-22 4 C 0 832026 D Common Stock 244081 0 I See Footnote Each share of Series B Convertible Preferred Stock and Series C Convertible Preferred Stock converted into shares of Common Stock at a ratio of 3.4088:1 upon completion of the Issuer's initial public offering. The shares have no expiration date. Shares held by Lightstone Ventures II, L.P. and Lightstone Ventures II (A), L.P. LSV Associates II, LLC is the general partner of Lightstone Ventures II, L.P. and Lightstone Ventures II (A), L.P. The Reporting Person is a managing director of LSV Associates II, LLC. The Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of her pecuniary interest therein. /s/ Andrew Gengos, Attorney-in-Fact 2021-06-24