X0306 4 2020-07-21 0 0001807901 Pandion Therapeutics, Inc. PAND 0001818137 Polaris Partners GP VIII, L.L.C. ONE MARINA PARK DRIVE, 10TH FLOOR BOSTON MA 02210 0 0 1 0 0001693818 Polaris Entrepreneurs' Fund VIII, L.P. ONE MARINA PARK DRIVE, 10TH FLOOR BOSTON 02210 0 0 1 0 0001679211 Polaris Partners VIII, L.P. ONE MARINA PARK DRIVE, 10TH FLOOR BOSTON MA 02210 0 0 1 0 Common Stock 2020-07-21 4 C 0 2783892 A 2783892 I See footnote Common Stock 2020-07-21 4 C 0 272046 A 3055938 I See footnote Common Stock 2020-07-21 4 C 0 99637 A 99637 I See footnote Common Stock 2020-07-21 4 C 0 9736 A 109373 I See footnote Common Stock 2020-07-21 4 P 0 34863 18.00 A 3090801 I See footnote Common Stock 2020-07-21 4 P 0 1248 18.00 A 110621 I See footnote Series A Preferred Stock 2020-07-21 4 C 0 14196152 0.00 D Common Stock 2783892 0 I See footnote Series A Preferred Stock 2020-07-21 4 C 0 508090 0.00 D Common Stock 99637 0 I See footnote Series B Preferred Stock 2020-07-21 4 C 0 1387268 0.00 D Common Stock 272046 0 I See footnote Series B Preferred Stock 2020-07-21 4 C 0 49652 0.00 D Common Stock 9736 0 I See footnote The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 5.0994-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The shares had no expiration date. The reportable securities are owned directly by Polaris Partners VIII, L.P. ("PP VIII"). Polaris Partners GP VIII, L.L.C. ("PPGP VIII") is the general partner of PP VIII. Each of David Barrett, Brian Chee, Amir Nashat and Bryce Youngren are the managing members of PPGP VIII (collectively, the "Managing Members"). Each of the Managing Members may be deemed to have shared voting and dispositive power over the shares held by PP VIII. Each of PPGP VIII and the Managing Members disclaims beneficial ownership of these securities 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. The reportable securities are owned directly by Polaris Entrepreneurs' Fund VIII, L.P. ("PEF VIII"). PPGP VIII is the general partner of PEF VIII. Each of the Managing Members may be deemed to have shared voting and dispositive power over the shares held by PEF VIII. Each of PPGP VIII and the Managing Members disclaims beneficial ownership of these securities 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/ Lauren Crockett, as attorney-in-fact for Polaris Partners VIII, L.P. 2020-07-21 /s/ Lauren Crockett, as attorney-in-fact for Polaris Entrepreneurs' Fund VIII L.P. 2020-07-21 /s/ Lauren Crockett, as attorney-in-fact for Polaris Partners GP VIII, L.L.C. 2020-07-21