X0306 4 2020-11-03 0 0001604477 SQZ Biotechnologies Co SQZ 0001438226 SCHULMAN AMY W C/O SQZ BIOTECHNOLOGIES COMPANY 200 ARSENAL YARDS BLVD, SUITE 210 WATERTOWN MA 02472 1 0 1 0 Common Stock 2020-11-03 4 C 0 22204 A 190684 D Common Stock 2020-11-03 4 C 0 161994 A 161994 I See footnotes Common Stock 2020-11-03 4 C 0 2315652 A 2315652 I See footnotes Common Stock 2020-11-03 4 C 0 275860 A 275860 I See footnote Common Stock 2020-11-03 4 P 0 16346 16.00 A 178340 I See footnotes Common Stock 2020-11-03 4 P 0 233654 16.00 A 2549306 I See footnotes Series A Convertible Preferred Stock 2020-11-03 4 C 0 28863 D Common Stock 30392 0 I See footnotes Series A Convertible Preferred Stock 2020-11-03 4 C 0 412608 D Common Stock 434476 0 I See footnotes Series B Convertible Preferred Stock 2020-11-03 4 C 0 56462 D Common Stock 59454 0 I See footnotes Series B Convertible Preferred Stock 2020-11-03 4 C 0 807096 D Common Stock 849872 0 I See footnotes Series C Convertible Preferred Stock 2020-11-03 4 C 0 44120 D Common Stock 46458 0 I See footnotes Series C Convertible Preferred Stock 2020-11-03 4 C 0 630672 D Common Stock 664097 0 I See footnotes Series C Convertible Preferred Stock 2020-11-03 4 C 0 168698 D Common Stock 177638 0 I See footnote Series C Convertible Preferred Stock 2020-11-03 4 C 0 21087 D Common Stock 22204 0 D Series D Convertible Preferred Stock 2020-11-03 4 C 0 24396 D Common Stock 25690 0 I See footnotes Series D Convertible Preferred Stock 2020-11-03 4 C 0 348725 D Common Stock 367207 0 I See footnotes Series D Convertible Preferred Stock 2020-11-03 4 C 0 93279 D Common Stock 98222 0 I See footnote Each share of preferred stock automatically converted on a 1.053 for one basis into common stock upon the closing of the Issuer's initial public offering. The shares have no expiration date. These shares are held of record by Polaris Entrepreneurs' Fund VII, L.P. ("EF VII"). Polaris Management Co. VII, L.L.C. ("PMC VII") is the general partner of EF VII. David Barrett, Brian Chee, Amir Nashat and Bryce Youngren (the "Managing Members") are the managing members of PMC VII. The Reporting Person, a member of the Issuer's board of directors, holds an interest in PMC VII. Each of the Managing Members and the Reporting Person, in their respective capacities with respect to PMC VII, may be deemed to have shared investment, voting and dispositive power over these shares. Each of PMC VII, the Managing Members and the Reporting Person disclaim beneficial ownership of these shares and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein. These shares are held of record by Polaris Partners VII, L.P. ("PP VII"). PMC VII is the general partner of PP VII. The Managing Members are the managing members of PMC VII. The Reporting Person, a member of the Issuer's board of directors, holds an interest in PMC VII. These shares are held of record by LS Polaris Innovation Fund, L.P. ("LSPIF"). LS Polaris Innovation Fund GP, L.L.C. ("LSPIF GP") is the general partner of LSPIF. The Reporting Person is the sole managing member of LSPIF GP. Each of LSPIF GP and the Reporting Person may be deemed to have sole investment, voting and dispositive power over these shares. LSPIF GP and the Reporting Person disclaim beneficial ownership of the shares held by LSPIF and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein. /s/ Lawrence Knopf, Attorney-in-Fact for Amy W. Schulman 2020-11-03