Atlas Venture Fund XI, L.P. - 26 May 2021 Form 3 Insider Report for Day One Biopharmaceuticals, Inc. (DAWN)

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
holding	DAWN	Series A Preferred Stock							26 May 2021	Common Stock	7,761,380		Direct	F1, F2
holding	DAWN	Series B Preferred Stock							26 May 2021	Common Stock	741,396		Direct	F3, F4

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Id	Content
F1	Each share of Series A Preferred Stock is automatically convertible into one share of Common Stock at the close of the Issuer's offering and has no expiration date.
F2	The shares are held directly by Atlas Venture Fund XI, L.P. ("Fund XI"). The general partner of 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 Fund XI, except to the extent of its pecuniary interest therein, if any.
F3	Each share of Series B Preferred Stock is automatically convertible into one share of Common Stock at the close of the Issuer's offering and has no expiration date.
F4	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.