RSU vesting drives insider trades at Day One (NASDAQ: DAWN)

Rhea-AI Filing Summary

Day One Biopharmaceuticals’ Chief Commercial Officer Lauren Merendino reported several equity transactions. On February 17, 2026, she sold 5,814 shares of common stock in an open-market sale at a weighted average price of $11.6009 per share, solely to cover tax liabilities from RSU settlements.

On February 15, 2026, multiple Restricted Stock Units converted into common stock at no cost, increasing her direct holdings. Footnotes state each RSU converts into one common share, does not expire, and vests in scheduled quarterly installments contingent on continued service.

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

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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^*

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)
02/15/2026

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	02/15/2026		M		3,162	A	(1)	53,971	D
Common Stock	02/15/2026		M		3,688	A	(1)	57,659	D
Common Stock	02/15/2026		M		3,687	A	(1)	61,346	D
Common Stock	02/15/2026		M		4,625	A	(1)	65,971	D
Common Stock	02/17/2026		S(2)		5,814	D	$11.6009(3)	60,157	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)	02/15/2026		M			3,162	(4)	(5)	Common Stock	3,162	$0	18,978	D
Restricted Stock Unit (RSU)	(1)	02/15/2026		M			3,688	(6)	(5)	Common Stock	3,688	$0	25,816	D
Restricted Stock Unit (RSU)	(1)	02/15/2026		M			3,687	(6)	(5)	Common Stock	3,687	$0	40,565	D
Restricted Stock Units (RSU)	(1)	02/15/2026		M			4,625	(6)	(5)	Common Stock	4,625	$0	69,375	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 $11.195 to $11.8508, 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	02/18/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transactions did DAWN’s Chief Commercial Officer report?

Lauren Merendino reported an open-market sale of 5,814 shares of Day One Biopharmaceuticals common stock at a weighted average price of $11.6009 per share, along with multiple RSU conversions into common stock at no cost following scheduled vesting on February 15, 2026.

Why did Lauren Merendino sell Day One Biopharmaceuticals (DAWN) shares?

The filing states the 5,814-share sale was executed solely to cover Lauren Merendino’s tax liability arising from the settlement of Restricted Stock Units. This indicates the transaction was tax-related rather than a discretionary portfolio sale, according to the explicit explanatory footnote in the document.

What RSU terms apply to DAWN’s Chief Commercial Officer’s awards?

Each Restricted Stock Unit represents a contingent right to receive one share of Day One Biopharmaceuticals common stock for no consideration. Footnotes explain RSUs either vest or are canceled and follow quarterly vesting schedules tied to continued service on specific dates such as February 15 and August 15.

How do the RSUs for DAWN’s Lauren Merendino vest over time?

One RSU grant vested 1/4 of the award on August 15, 2024, with the remaining 3/4 vesting in 12 equal quarterly installments on November 15, February 15, May 15, and August 15. Another grant vests 1/16 in quarterly installments on those same dates.

What price range applied to the DAWN insider’s share sale?

The reported weighted average sale price was $11.6009 per share. A footnote explains the shares were sold in block trades for multiple security holders at prices ranging from $11.195 to $11.8508, and detailed price breakdowns are available upon request from the reporting person.

Did the DAWN insider pay cash to exercise RSUs into common stock?

The RSU conversions into common stock occurred at a reported price of $0.0000 per share. Footnotes clarify each RSU converts into one common share for no consideration, meaning the insider did not pay cash to receive those shares upon vesting and settlement.