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

Rhea-AI Filing Summary

Day One Biopharmaceuticals (DAWN) reported insider equity activity by its General Counsel & Secretary. On November 15, 2025, several blocks of Restricted Stock Units (RSUs) were settled, delivering 2,963, 1,750, and two blocks of 3,687 shares of common stock, each RSU converting into one share for no cash consideration. The RSUs vest over time based on continued service, with portions vesting on specified quarterly dates.

On November 17, 2025, the insider sold 4,319 shares of common stock at a weighted average price of $8.9147 per share, solely to cover tax liabilities related to the RSU settlements. After these transactions, the insider beneficially owned 62,626 shares of Day One common stock directly.

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^*

Dubow Adam

(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)
	Gen Counsel & Secretary

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		2,963	A	(1)	57,821	D
Common Stock	11/15/2025		M		1,750	A	(1)	59,571	D
Common Stock	11/15/2025		M		3,687	A	(1)	63,258	D
Common Stock	11/15/2025		M		3,687	A	(1)	66,945	D
Common Stock	11/17/2025		S(2)		4,319	D	$8.9147(3)	62,626	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			2,963	(4)	(5)	Common Stock	2,963	$0	11,852	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			1,750	(6)	(5)	Common Stock	1,750	$0	7,000	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			3,687	(6)	(5)	Common Stock	3,687	$0	29,504	D
Restricted Stock Unit (RSU)	(1)	11/15/2025		M			3,687	(6)	(5)	Common Stock	3,687	$0	44,252	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 $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.

4. The RSUs vest as to 25% of the total award on November 15, 2023, and 1/12th of the remaining amount vest in quarterly installments thereafter 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.

6. 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.

	/s/ Charles N. York II, as Attorney-in-Fact	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.
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 insider transaction did Day One Biopharmaceuticals (DAWN) report?

Day One Biopharmaceuticals reported that its General Counsel & Secretary settled multiple blocks of Restricted Stock Units (RSUs) into common stock and then sold 4,319 shares to cover tax liabilities arising from those RSU settlements.

How many Day One (DAWN) shares did the insider sell and at what price?

The insider sold 4,319 shares of Day One common stock on November 17, 2025 at a weighted average price of $8.9147 per share, with individual sale prices ranging from $8.545 to $9.305.

How many Day One (DAWN) shares does the insider own after these transactions?

Following the reported RSU settlements and the sale to cover taxes, the insider directly beneficially owned 62,626 shares of Day One Biopharmaceuticals common stock.

What are RSUs in the context of Day One (DAWN) insider compensation?

Each Restricted Stock Unit (RSU)

What is the vesting schedule for the reported Day One (DAWN) RSUs?

One RSU award vests as to 25% of the total on November 15, 2023, with the remaining amount vesting in equal quarterly installments on February 15, May 15, August 15, and November 15, contingent on continued service. Another RSU grant vests as to 1/16th of the total award on the same quarterly dates, also subject to continued service.

Why did the Day One (DAWN) insider sell shares after RSU settlement?

The filing states that the sale of shares was made solely to cover the tax liability associated with the settlement of RSUs, indicating a tax-withholding transaction rather than a discretionary sale for other purposes.

Do the Day One (DAWN) RSUs expire if they do not vest?

The disclosure notes that RSUs do not expire; they either vest according to the schedule or are canceled prior to the vesting date if vesting conditions, such as continued service, are not satisfied.