SEC FORM 4

SEC FORM 4SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Grossman William

(Last)

(First)

(Middle)

1800 SIERRA POINT PARKWAY, SUITE 200

(Street)

BRISBANE

CALIFORNIA

94005

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Day One Biopharmaceuticals, Inc. [ DAWN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/23/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (right to buy Common Stock)	$8.99	04/23/2026		D			66,660	⁽¹⁾	01/16/2034	Common Stock	66,660	⁽²⁾⁽³⁾⁽⁴⁾	0	D
Stock Option (right to buy Common Stock)	$8.99	04/23/2026		D			32,335	⁽⁵⁾	05/22/2034	Common Stock	32,335	⁽²⁾⁽³⁾⁽⁴⁾	0	D
Stock Option (right to buy Common Stock)	$7.01	04/23/2026		D			22,500	⁽⁶⁾	06/01/2035	Common Stock	22,500	⁽²⁾⁽³⁾⁽⁴⁾	0	D
Restricted Stock Unit (RSU)	⁽⁷⁾	04/23/2026		D			15,000	⁽⁸⁾	⁽⁹⁾	Common Stock	15,000	⁽²⁾⁽³⁾⁽⁴⁾	0	D

Explanation of Responses:

1. The option vests as to 1/36th of the total shares on each monthly anniversary, beginning on February 17, 2024, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

2. On March 6, 2026, Servier Pharmaceuticals LLC, a Delaware limited liability company ("Parent"), Servier Detroit Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"), Day One Biopharmaceuticals, Inc., a Delaware corporation (the "Company"), and Servier S.A.S., a French societe par actions simplifiee, solely as a guarantor, entered into an Agreement and Plan of Merger (the "Merger Agreement"). Pursuant to the Merger Agreement, the Merger Sub merged with and into the Company (such merger and the other transactions contemplated by the Merger Agreement, the "Merger") with the Company surviving the Merger as a wholly owned subsidiary of the Parent.

3. Upon the closing of the Merger on April 23, 2026, each issued and outstanding share of the Company's Common Stock, par value $0.0001 per share, was either (x) purchased for $21.50 per share (the "Offer Price"), net to the seller in cash, without interest, and subject to applicable withholding taxes, on the terms and conditions set forth in the Merger Agreement, or (y) automatically converted into the right to receive the Offer Price (the "Merger Consideration"), net to the seller in cash, without interest, and subject to applicable withholding taxes, on the terms and conditions set forth in the Merger Agreement.

4. Immediately prior to the effective time of the Merger, all outstanding unvested stock options and unvested restricted stock units became fully vested. At the effective time of the Merger, each stock option and restricted stock unit was canceled and converted into the right to receive an amount in cash equal to the Merger Consideration (or, in the case of stock options, the difference between the Merger Consideration and the applicable per share exercise price), less any applicable withholding taxes.

5. The options are fully vested.

6. The option vests as to 1/12th of the total grant on each monthly anniversary, beginning on July 2, 2025, subject to the Reporting Person's provision of service to the Issuer on each option vesting date.

7. Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock upon settlement for no consideration.

8. The RSUs will vest as to 100% of the award on the earlier of (i) June 2, 2026 and (ii) the date of the Issuer's 2026 annual meeting of stockholders (in each case, the "RSU Vesting Date"), subject to the Reporting Person's provision of services to the Issuer on each RSU Vesting Date. Shares of the Issuer's Common Stock will be delivered to the Reporting Person following vesting.

9. RSUs do not expire; they either vest or are canceled prior to the RSU Vesting Date.

	/s/ Charles N. York II, as Attorney-in-Fact	04/23/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

SEC Form 4 filed by Director Grossman William to satisfy withholding tax