DAWN COO and CFO reports RSU settlement and tax-related share sale

Rhea-AI Filing Summary

Day One Biopharmaceuticals, Inc. insider and COO and CFO Charles N. York II reported the settlement of restricted stock units (RSUs) and a related sale of common stock. On 11/15/2025, multiple RSU awards were exercised, delivering blocks of 1,375, 2,250 and 6,625 shares of common stock in several transactions. Following these issuances, he held up to 298,777 shares of common stock before a subsequent sale.

On 11/17/2025, he sold 4,062 shares of common stock at a weighted average price of $8.9147 per share, with actual prices ranging from $8.545 to $9.305. The sale is stated to be solely to cover his tax liability arising from the RSU settlements. After the transactions, he directly owned 294,715 shares of common stock and held 79,500 RSUs, each representing a right to receive one share of common stock upon vesting.

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^*

York Charles N II

(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)
	COO and CFO

3. Date of Earliest Transaction (Month/Day/Year)
11/15/2025

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	11/15/2025		M		1,375	A	(1)	283,277(2)	D
Common Stock	11/15/2025		M		2,250	A	(1)	285,527	D
Common Stock	11/15/2025		M		6,625	A	(1)	292,152	D
Common Stock	11/15/2025		M		6,625	A	(1)	298,777	D
Common Stock	11/17/2025		S(3)		4,062	D	$8.9147(4)	294,715	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)	11/15/2025		M			1,375	(5)	(6)	Common Stock	1,375	$0	0	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			2,250	(5)	(6)	Common Stock	2,250	$0	9,000	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			6,625	(5)	(6)	Common Stock	6,625	$0	53,000	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			6,625	(5)	(6)	Common Stock	6,625	$0	79,500	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. Includes 3,902 shares of Common Stock acquired by the Reporting Person between May 12, 2023 and November 14, 2025 pursuant to the Issuer's employee stock purchase plan.

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

4. 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 $8.545 to $9.305, 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.

5. The RSUs will 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.

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

	/s/ Charles N. York II	11/18/2025
	** 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.
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FAQ

What insider transaction did DAWN report in this Form 4?

The filing reports that Charles N. York II, COO and CFO of Day One Biopharmaceuticals, settled several restricted stock unit (RSU) awards into common stock and then sold a portion of the resulting shares.

How many DAWN shares did the insider sell and at what price?

On 11/17/2025, the insider sold 4,062 shares of Day One Biopharmaceuticals common stock at a weighted average price of $8.9147 per share, with individual sale prices ranging from $8.545 to $9.305.

Why were the DAWN shares sold by the reporting person?

The filing states that the 4,062 shares were sold solely to cover the reporting person's tax liability arising from the settlement of RSUs.

How many DAWN shares does the insider own after these transactions?

After the reported transactions, the insider directly owned 294,715 shares of Day One Biopharmaceuticals common stock.

How many RSUs related to DAWN stock does the reporting person still hold?

Following the RSU settlements reported, the insider beneficially owned 79,500 restricted stock units, each representing a contingent right to receive one share of Day One Biopharmaceuticals common stock upon settlement.

What are the vesting terms for the DAWN RSUs held by the insider?

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 continued service with the company on each vesting date.

Do the DAWN RSUs held by the insider expire?

The filing explains that RSUs do not expire; they either vest or are canceled prior to the vesting date.