[Form 4] Day One Biopharmaceuticals, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Lauren Merendino, Chief Commercial Officer of Day One Biopharmaceuticals, Inc. (DAWN), reported receipt and partial sale of company shares tied to vested restricted stock units (RSUs). On 08/15/2025 she was treated as acquiring multiple blocks of common stock through vesting of RSUs (3,162; 3,687; 3,687 shares) and the related derivative entries show those RSUs underlie the same share amounts. Following these transactions her reported beneficial ownership figures adjusted across several lines, and on 08/18/2025 she sold 3,766 shares in a block trade at a weighted average price of $6.7671 to cover taxes on RSU settlement.

The filing notes the RSUs represent one share each upon settlement for no consideration, vesting schedules (initial 1/4 on 08/15/2024 with remaining quarterly vesting, and separate 1/16 quarterly vesting for another award) and that RSU sales were solely to cover tax liabilities. The form was filed by one reporting person via attorney-in-fact.

Positive

• Transparent disclosure of RSU vesting schedules, share counts, and purpose of sale (tax withholding).
• Sells only to cover tax liability rather than broader liquidation of holdings, per the filer.

Negative

• None.

Insights

Securities/Equity Compensation Analyst

TL;DR Officer vested RSUs and sold shares to cover taxes; routine equity-compensation activity with no new cash purchases or unusual dilution.

The report documents standard settlement of RSUs and a follow-on sale of 3,766 shares at a weighted average of $6.7671 for tax withholding. Vesting schedules are disclosed and RSUs are exercisable into common stock for no consideration. Transactions were block trades executed across a price range and the filer used an attorney-in-fact to submit the Form 4.

Corporate Governance Specialist

TL;DR Disclosure aligns with Section 16 reporting obligations; activity appears administrative rather than material to operations.

The Form 4 provides required detail: role of reporting person (Chief Commercial Officer), exact RSU vesting mechanics, number of shares acquired via RSU settlement, and a tax-cover sale. No evidence in this filing of changes in control, new equity grants beyond the described vesting, or related-party transactions that would raise additional governance concerns.

SEC 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

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

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^*

Merendino Lauren

(Last) (First) (Middle)

1800 SIERRA POINT PARKWAY, SUITE 200

(Street)

BRISBANE CA 94005

(City) (State) (Zip)

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

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2025

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

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

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

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/15/2025		M		3,162	A	(1)	38,323	D
Common Stock	08/15/2025		M		3,687	A	(1)	42,010	D
Common Stock	08/15/2025		M		3,687	A	(1)	45,697	D
Common Stock	08/18/2025		S(2)		3,766	D	$6.7671(3)	41,931	D

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			3,162	(4)	(5)	Common Stock	3,162	$0	25,302	D
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			3,687	(6)	(5)	Common Stock	3,687	$0	33,191	D
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			3,687	(6)	(5)	Common Stock	3,687	$0	47,939	D

Explanation of Responses:

1. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock upon settlement for no consideration.

2. The sale of shares is for the sole purpose of covering the Reporting Person's tax liability with respect to the settlement of RSUs.

3. The price reported in Column 4 is a weighted average price. These shares were sold as part of block trades for multiple security holders of the Issuer at prices ranging from $6.65 to $6.87, inclusive. The Reporting Person undertakes to provide to the Issuer, any securityholder 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 herein with regard to the block trade.

4. The RSUs vested as to 1/4th of the total award on August 15, 2024, and the remaining 3/4 of the award vests in 12 substantially equal quarterly installments thereafter on November 15, February 15, May 15 and August 15, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

5. RSUs do not expire; they either vest or are canceled prior to the vesting date.

6. The RSUs vest as to 1/16th of the total award in quarterly installments on February 15, May 15, August 15 and November 15, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

	/s/ Charles N. York II, as Attorney-in-Fact	08/19/2025
	** 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.

FAQ

Who filed the Form 4 for DAWN and what is their role?

The Form 4 was filed for Lauren Merendino, who is identified as the company's Chief Commercial Officer.

What transactions were reported on the Form 4 for DAWN?

The filing reports settlement/vestings of RSUs on 08/15/2025 converting into common stock (3,162; 3,687; 3,687 shares) and a sale of 3,766 shares on 08/18/2025.

At what price were the shares sold and why were they sold?

The shares sold on 08/18/2025 were part of block trades at a weighted average price of $6.7671 to cover the reporting person's tax liability on RSU settlement.

What do the RSUs represent and when do they vest?

Each RSU represents a contingent right to one share of common stock for no consideration; one award vested 1/4 on 08/15/2024 with the remainder vesting quarterly, and another vests in 1/16th quarterly installments as described.

Was this Form 4 filed individually or jointly?

The form was filed by one reporting person and signed by an attorney-in-fact on behalf of the reporting person.