X0202
SCHEDULE 13G/A
0001104659-24-119006
0001708269
XXXXXXXX
LIVE
4
COMMON STOCK, $0.0001 PAR VALUE
03/31/2026
0001845337 Day One Biopharmaceuticals, Inc.
23954D109
1800 Sierra Point Parkway, Suite 200
BRISBANE
CA
94005
Rule 13d-1(c)
Atlas Venture Fund XI, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates XI, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates XI, LLC
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
OO
Atlas Venture Opportunity Fund I, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates Opportunity I, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates Opportunity I, LLC
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
OO
Atlas Venture Opportunity Fund II, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates Opportunity II, L.P.
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
PN
Atlas Venture Associates Opportunity II, LLC
b
DE
0.00
0.00
0.00
0.00
0.00
0.0
OO
Day One Biopharmaceuticals, Inc.
1800 Sierra Point Parkway, Suite 200, BRISBANE, CA, 94005.
This Schedule 13G is filed by (i) Atlas Venture Fund XI, L.P., a Delaware limited partnership ("Atlas XI"), (ii) Atlas Venture Associates XI, L.P., a Delaware limited partnership ("AVA XI LP"), (iii) Atlas Venture Associates XI, LLC, a Delaware limited liability company ("AVA XI LLC" and together with Atlas XI and AVA XI LP, the "Fund XI Reporting Persons"), (iv) Atlas Venture Opportunity Fund I, L.P., a Delaware limited partnership ("AVO I"), (v) Atlas Venture Associates Opportunity I, L.P., a Delaware limited partnership ("AVAO LP"), (vi) Atlas Venture Associates Opportunity I, LLC, a Delaware limited liability company ("AVAO LLC" and together with AVO I and AVAO LP, the "Opportunity Fund Reporting Persons"), (vii) Atlas Venture Opportunity Fund II, L.P., a Delaware limited partnership ("AVO II"), (viii) Atlas Venture Associates Opportunity II, L.P., a Delaware limited partnership ("AVAO II LP") and (ix) Atlas Venture Associates Opportunity II, LLC, a Delaware limited liability company ("AVAO II LLC" and together with AVO II and AVAO II LP, the "Opportunity Fund II Reporting Persons" and together with the Fund XI Reporting Persons and Opportunity Fund Reporting Persons, the "Reporting Persons"). 300 Technology Square, 8th Floor
Cambridge, Massachusetts 02139 Each of Atlas XI, AVA XI LP, AVO I, AVAO LP, AVO II and AVAO II LP is a Delaware limited partnership.
Each of AVA XI LLC, AVAO LLC and AVAO II LLC is a Delaware limited liability company.
Y
0 0
0
0
0
0
N
Y
Y
Y
Y
Y
N
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
JOINT FILING AGREEMENT
Atlas Venture Fund XI, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates XI, L.P., its GP, By: Atlas Venture Associates XI, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates XI, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates XI, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates XI, LLC
/s/ Ommer Chohan
Ommer Chohan, CFO
05/14/2026
Atlas Venture Opportunity Fund I, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates Opportunity I, L.P., its GP, By: Atlas Venture Associates Opportunity I, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates Opportunity I, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates Opportunity I, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates Opportunity I, LLC
/s/ Ommer Chohan
Ommer Chohan, CFO
05/14/2026
Atlas Venture Opportunity Fund II, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates Opportunity II, L.P., its GP, By: Atlas Venture Associates Opportunity II, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates Opportunity II, L.P.
/s/ Ommer Chohan
By: Atlas Venture Associates Opportunity II, LLC, its GP, By: Ommer Chohan, CFO
05/14/2026
Atlas Venture Associates Opportunity II, LLC
/s/ Ommer Chohan
Ommer Chohan, CFO
05/14/2026