X0508 4 2024-01-11 0 0001840233 Xilio Therapeutics, Inc. XLO 0001708269 Atlas Venture Fund XI, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0001780068 Atlas Venture Associates XI, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0001780067 Atlas Venture Associates XI, LLC 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0001759241 Atlas Venture Opportunity Fund I, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0001780065 Atlas Venture Associates Opportunity I, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0001780066 Atlas Venture Associates Opportunity I, LLC 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE MA 02139 0 0 1 0 0 Common Stock 2024-01-11 4 S 0 1566 0.87 D 2021836 D Common Stock 2024-01-11 4 S 0 569 0.87 D 735373 I See footnote Common Stock 2024-01-12 4 S 0 1540 0.83 D 2020296 D Common Stock 2024-01-12 4 S 0 560 0.83 D 734813 I See footnote The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.85 to $0.9499 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas Venture Fund XI"). The general partner of Atlas Venture Fund XI is Atlas Venture Associates XI, L.P. ("AVA XI LP"). Atlas Venture Associates XI, LLC ("AVA XI LLC") is the general partner of AVA XI LP. Each of AVA XI LP and AVA XI LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Fund XI, except to the extent of its pecuniary interest therein, if any. The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("Atlas Venture Opportunity Fund I"). The general partner of Atlas Venture Opportunity Fund I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. Each of AVAO I LP and AVAO I LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Opportunity Fund I, except to the extent of its pecuniary interest therein, if any. Atlas Venture Fund XI, L.P. By: Atlas Venture Associates XI, L.P., Its: General Partner By: Atlas Venture Associates XI, LLC, Its General Partner, By: /s/ Ommer Chohan 2024-01-16 /s/ Atlas Venture Associates XI, LP, By: Atlas Venture Associates XI, LLC, it's general partner, By: Ommer Chohan, Chief Financial Officer, /s/ Ommer Chohan 2024-01-16 /s/ Atlas Venture Associates XI, LLC, By: Ommer Chohan, Chief Financial Officer, /s/ Ommer Chohan 2024-01-16 /s/ Atlas Venture Opportunity Fund I, L.P., By: Atlas Venture Associates Opportunity I, L.P., its general partner, By: Atlas Venture Associates Opportunity I, LLC, its general partner, By: Ommer Chohan, Chief Financial Officer, /s/ Ommer Chohan 2024-01-16 /s/ Atlas Venture Associates Opportunity I, L.P., By: Atlas Venture Associates Opportunity I, LLC, its general partner, By: Ommer Chohan, Chief Financial Officer, /s/ Ommer Chohan 2024-01-16 /s/ Atlas Venture Associates Opportunity I, LLC, By: Ommer Chohan, Chief Financial Officer, /s/ Ommer Chohan 2024-01-16