Day One Biopharmaceuticals (DAWN) exec sells shares to cover RSU tax bill

Rhea-AI Filing Summary

Day One Biopharmaceuticals’ Head of Research and Development, Michael Vasconcelles, reported RSU vesting and a related share sale. On February 15, he acquired 7,125 shares of common stock at $0 per share through the settlement of Restricted Stock Units, each RSU converting into one common share.

On February 17, he conducted an open‑market sale of 2,728 common shares at a weighted average price of $11.6009 per share. The company notes that this sale was made solely to cover his tax liability arising from the RSU settlement and that the sale price reflects block trades executed within a range of $11.195 to $11.8508. After these transactions, he continued to hold common shares directly and retained a substantial RSU balance that vests quarterly, subject to 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^*

VASCONCELLES MICHAEL

(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)
	Head of Research and Dev.

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		7,125	A	(1)	7,125	D
Common Stock	02/17/2026		S(2)		2,728	D	$11.6009(3)	4,397	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			7,125	(4)	(5)	Common Stock	7,125	$0	106,875	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 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.

5. RSUs do not expire; they either vest or are canceled prior to the 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.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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FAQ

What insider transactions did DAWN’s Michael Vasconcelles report?

Michael Vasconcelles reported RSU settlement and a related share sale. He acquired 7,125 common shares through RSU conversion on February 15, then sold 2,728 shares on February 17 in open‑market trades, with proceeds used solely to cover tax liabilities.

How many Day One Biopharmaceuticals (DAWN) shares did the insider sell?

He sold 2,728 shares of Day One Biopharmaceuticals common stock. The sale occurred on February 17 as open‑market block trades at a weighted average price of $11.6009 per share, within a disclosed price range between $11.195 and $11.8508.

At what price did the DAWN insider sell his shares?

The shares were sold at a weighted average price of $11.6009 per share. The filing explains these were block trades for multiple holders, executed within a price range from $11.195 to $11.8508, with detailed price breakdowns available upon request.

Why did the DAWN insider sell shares after RSU settlement?

The sale was executed solely to cover the reporting person’s tax liability from RSU settlement. After receiving 7,125 common shares through RSU conversion, he sold 2,728 shares to fund taxes, a common practice following equity compensation vesting events.

How do Michael Vasconcelles’ RSUs at Day One Biopharmaceuticals vest?

His RSUs vest in 1/16th increments of the total award on February 15, May 15, August 15 and November 15. Vesting on each date depends on his continued service with the company, and RSUs either vest or are canceled rather than expiring.

What does each RSU represent in the DAWN insider filing?

Each Restricted Stock Unit represents a contingent right to receive one share of Day One Biopharmaceuticals common stock. Upon settlement, the RSUs convert into common shares for no cash consideration, effectively delivering stock as part of the executive’s compensation package.