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

Rhea-AI Filing Summary

Day One Biopharmaceuticals (DAWN) reported a director’s Form 4 reflecting an option repricing effective November 6, 2025. Existing stock options were reset to a new exercise price of $8.99, the Nasdaq closing price on the effective date.

The filing shows dispositions of options previously priced at $13.81 (66,660 shares; expiring 01/16/2034) and $13.87 (32,335 shares; expiring 05/22/2034), and corresponding acquisitions of options for the same share amounts at $8.99 with the same expiration dates. One grant vests 1/36 monthly beginning February 17, 2024; the other is fully vested. Exercising at the new price requires continued service through a defined Retention Period, and the transactions were noted as exempt under Rule 16b-6(d) and Rule 16b-3.

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^*

Grossman William

(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)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
11/06/2025

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

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
Stock Option (right to buy Common Stock)	$13.81	11/06/2025		D(1)(2)			66,660	(3)	01/16/2034	Common Stock	66,660	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		66,660		(3)	01/16/2034	Common Stock	66,660	$0	66,660	D
Stock Option (right to buy Common Stock)	$13.87	11/06/2025		D(1)(2)			32,335	(4)	05/22/2034	Common Stock	32,335	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		32,335		(4)	05/22/2034	Common Stock	32,335	$0	32,335	D

Explanation of Responses:

1. On October 7, 2025, the Issuer's Board of Directors approved an option repricing (the "Repricing") whereby the Reporting Person's options were repriced on November 6, 2025 (the "Effective Date") with a new exercise price of $8.99 (if lower than the original exercise price), the closing price on Nasdaq as of the Effective Date. In order to exercise the repriced options at the new exercise price, the Reporting Person is required to remain in service with the Issuer through the Retention Period; provided that the additional premium payment will not be required if the Reporting Person's service to the Issuer is terminated by reason of death or Disability (as defined in the Company's 2021 Equity Incentive Plan ("the Plan")).

2. (Continued from Footnote 1) The "Retention Period" commenced on the Effective Date and ends upon the earliest of (i) the 12-month anniversary of the Effective Date and (ii) a Corporate Transaction (as defined in the Plan). All of the other terms of the options remain unchanged. Such transactions were exempt pursuant to Rule 16b-6(d) and Rule 16b-3 of the Exchange Act, as applicable.

3. The option vests as to 1/36th of the total shares on each monthly anniversary, beginning on February 17, 2024, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

4. The options are fully vested.

	/s/ Charles N. York II, as Attorney-in-Fact	11/07/2025
	** 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 did Day One Biopharmaceuticals (DAWN) disclose in this Form 4?

A director’s stock options were repriced to an exercise price of $8.99 effective November 6, 2025.

Which option grants were affected for DAWN?

Grants for 66,660 shares (exp. 01/16/2034) and 32,335 shares (exp. 05/22/2034) were repriced.

What were the prior exercise prices before repricing?

The prior exercise prices were $13.81 (66,660-share grant) and $13.87 (32,335-share grant).

How do the vesting terms look after the change?

One grant vests 1/36 monthly beginning February 17, 2024; the other is fully vested.

Is there a service requirement tied to the new exercise price?

Yes. Exercising at $8.99 requires service through the defined Retention Period as described.

Were these transactions exempt under SEC rules?

Yes. The filing cites exemptions under Rule 16b-6(d) and Rule 16b-3.