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

Rhea-AI Filing Summary

Charles N. York II, COO and CFO of Day One Biopharmaceuticals, Inc. (DAWN), reported settlement and sales related to Restricted Stock Units (RSUs). On 08/15/2025 Mr. York was deemed to have acquired RSUs totaling 16,875 units in four separate grants (1,375; 2,250; 6,625; 6,625). These RSUs convert one-for-one into common shares upon settlement for no consideration and vest in quarterly 1/16th installments on Feb 15, May 15, Aug 15 and Nov 15, subject to continued service. Following those acquisitions his reported beneficial ownership increased through successive totals shown up to 282,106 shares.

On 08/18/2025 Mr. York sold 4,106 shares at a weighted average price of $6.7671 as part of block trades executed at prices ranging from $6.65 to $6.87; the sale was made solely to cover tax withholding for the RSU settlements. The filing is signed and dated 08/19/2025 and discloses no other transactions or amendments.

Positive

• Transparent disclosure of RSU awards, vesting schedule, and purpose of share sale (tax withholding).
• Detailed price range for the block trades ($6.65 to $6.87) and weighted average sale price ($6.7671) provided.

Negative

• No breakdown of the number of shares sold at each separate price within the reported range is provided in the filing.
• Form 4 does not state whether additional planned disposals or Rule 10b5-1 plans exist beyond the tax-cover sale.

Insights

Securities Analyst

TL;DR: CFO acquired sizeable RSU awards and sold a small block of shares to cover taxes; beneficial ownership remains materially large.

The report documents customary equity compensation activity by a senior executive: multiple RSU grants settled or recognized on 08/15/2025 increasing reported beneficial ownership to a sequence culminating at 282,106 shares. A subsequent sale of 4,106 shares on 08/18/2025 at a weighted average $6.7671 was explicitly for tax withholding. These patterns align with standard post-vesting tax-cover sells rather than strategic disposition; however, the filing does not disclose the exact split of shares sold at each price within the stated $6.65–$6.87 range without further detail.

Corporate Governance Expert

TL;DR: Disclosure is routine and addresses tax-related sales; vesting schedule and non-expiration of RSUs are clearly stated.

The filing clearly explains RSU mechanics: each RSU converts to one share upon settlement for no consideration, vests in quarterly 1/16th installments, and does not expire. The reporting person certified the sale's purpose as tax withholding, satisfying standard Section 16 transparency. No indications of unusual related-party transactions, amended filings, or contractual sale plans are included in the form.

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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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)
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		1,375	A	(1)	266,606	D
Common Stock	08/15/2025		M		2,250	A	(1)	268,856	D
Common Stock	08/15/2025		M		6,625	A	(1)	275,481	D
Common Stock	08/15/2025		M		6,625	A	(1)	282,106	D
Common Stock	08/18/2025		S(2)		4,106	D	$6.7671(3)	278,000	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			1,375	(4)	(5)	Common Stock	1,375	$0	1,375	D
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			2,250	(4)	(5)	Common Stock	2,250	$0	11,250	D
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			6,625	(4)	(5)	Common Stock	6,625	$0	59,625	D
Restricted Stock Unit (RSU)	(1)	08/15/2025		M			6,625	(4)	(5)	Common Stock	6,625	$0	86,125	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 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.

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

	/s/ Charles N. York II	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

What RSU activity did DAWN COO/CFO Charles York report on Form 4?

He reported deemed acquisitions on 08/15/2025 of RSUs totaling 16,875 units in four grants that convert one-for-one into common shares upon settlement.

Why were 4,106 DAWN shares sold by Charles York on 08/18/2025?

The filing states the sale was executed solely to cover the Reporting Person's tax liability related to the RSU settlements.

At what price were the DAWN shares sold in the reported transaction?

The shares were sold as block trades at prices ranging from $6.65 to $6.87 with a weighted average price of $6.7671.

How do the RSUs vest according to the Form 4 for DAWN?

RSUs vest in quarterly installments equal to 1/16th of the total award on Feb 15, May 15, Aug 15 and Nov 15, subject to continued service.

How many DAWN shares did Charles York beneficially own after the reported transactions?

The filing shows successive beneficial ownership totals reaching as high as 282,106 shares following the reported RSU acquisitions.