X0306 4 2020-07-17 0 0001807901 Pandion Therapeutics, Inc. PAND 0001598542 Carroll Jill C/O S.R. ONE, LIMITED 161 WASHINGTON STREET, SUITE 500 CONSHOHOCKEN PA 19428 1 0 1 0 Common Stock 2020-07-21 4 C 0 1538724 A 1538724 I See Footnote Common Stock 2020-07-21 4 C 0 348469 A 1887193 I See Footnote Common Stock 2020-07-21 4 P 0 361111 18.00 A 2248304 I See Footnote Series A Preferred Stock 2020-07-21 4 C 0 7846554 D Common Stock 1538724 0 I See Footnote Series B Preferred Stock 2020-07-21 4 C 0 1776980 D Common Stock 348469 0 I See Footnote Stock Option (right to buy) 18.00 2020-07-17 4 A 0 13997 0.00 A 2030-07-16 Common Stock 13997 13997 I See Footnote The Series A Preferred Stock were convertible at a conversion rate equal to one share of Common Stock per 5.0994 shares of Series A Preferred Stock at any time at the option of the holder and were automatically converted upon the closing of the Issuer's initial public offering. The shares had no expiration date. The shares reported herein are held of record by S.R. One, Limited, an indirect, wholly-owned subsidiary of GlaxoSmithKline plc (the "Reporting Person"). The Series B Preferred Stock were convertible at a conversion rate equal to one share of Common Stock per 5.0994 shares of Series B Preferred Stock at any time at the option of the holder and were automatically converted upon the closing of the Issuer's initial public offering. The shares had no expiration date. S.R. One, Limited purchased 361,111 shares of Common Stock of Pandion Therapeutics, Inc. (the "Issuer") in connection with the Issuer's public offering. The stock option was granted to Jill A. Carroll as director's compensation with the shares vesting with respect to 2.7778% of the shares at the end of each successive one month period following the grant date until the third anniversary of the grant date, subject to Ms. Carroll's continued service on each applicable veting date. As Principal at S.R. One, Limited and an employee of GlaxoSmithKline LLC, an indirect, wholly-owned subsidiary of GlaxoSmithKline plc., Ms. Carroll disclaims beneficial ownership of all the shares held by S.R. One, Limited and this report shall not be deemed an admission of beneficial ownership of such shares for the purposes of Section 16 or for any other purpose except to the extent of her pecuniary interest therein. /s/ Edward Freedman, as attorney-in-fact for Jill A. Carroll 2020-07-21