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

Rhea-AI Filing Summary

Day One Biopharmaceuticals (DAWN) filed a Form 4 showing an option repricing for its COO and CFO. On November 6, 2025, multiple stock option grants held by the reporting person were repriced to an exercise price of $8.99 if lower than the original price, following a Board approval on October 7, 2025.

The filing lists prior grants adjusted from higher strikes, including 497,667 underlying shares previously at $16 (fully vested), 151,000 at $14.26, 116,000 at $23.41, 162,000 at $14.44, and 162,000 at $11.87. The revised entries show corresponding grants at $8.99 with the same underlying share counts. Vesting terms remain unchanged, such as 2.0833% monthly with full vest by January 18, 2026, and multiple 1/48th monthly schedules starting on specified dates.

To exercise at the new price, continued service is required through the “Retention Period,” which runs from the effective date until the earlier of 12 months or a Corporate Transaction, with an exception for death or Disability under the plan.

Insights

Equity compensation analyst

Administrative repricing to $8.99 with service-based conditions; neutral impact.

The filing details a Board-approved option repricing effective November 6, 2025, resetting multiple grants to an exercise price of $8.99 when above that level. The underlying share counts for each grant are unchanged, and vesting schedules remain intact per each grant’s original terms.

Exercisability at the new price requires the reporting person to remain in service through the Retention Period, defined to end on the earlier of 12 months after the effective date or a Corporate Transaction, with an exception for death or Disability. These transactions are cited as exempt under Rule 16b‑6(d) and Rule 16b‑3.

Because no issuance or cash proceeds are described here, the near‑term impact hinges on continued service and future exercise decisions. Subsequent company filings may detail any further administrative or compensation updates.

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

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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)
11/06/2025

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)	$16	11/06/2025		D(1)(2)			497,667	(3)	05/25/2031	Common Stock	497,667	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		497,667		(3)	05/25/2031	Common Stock	497,667	$0	497,667	D
Stock Option (right to buy Common Stock)	$14.26	11/06/2025		D(1)(2)			151,000	(4)	01/17/2032	Common Stock	151,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		151,000		(4)	01/17/2032	Common Stock	151,000	$0	151,000	D
Stock Option (right to buy Common Stock)	$23.41	11/06/2025		D(1)(2)			116,000	(5)	01/16/2033	Common Stock	116,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		116,000		(5)	01/16/2033	Common Stock	116,000	$0	116,000	D
Stock Option (right to buy Common Stock)	$14.44	11/06/2025		D(1)(2)			162,000	(6)	01/04/2034	Common Stock	162,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		162,000		(6)	01/04/2034	Common Stock	162,000	$0	162,000	D
Stock Option (right to buy Common Stock)	$11.87	11/06/2025		D(1)(2)			162,000	(7)	01/14/2035	Common Stock	162,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		162,000		(7)	01/14/2035	Common Stock	162,000	$0	162,000	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 options are fully vested.

4. The option vests as to 2.0833% of the total shares monthly, with 100% of the total shares vested on January 18, 2026, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

5. The option vests as to 1/48th of the total shares monthly, commencing February 17, 2023, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

6. The option vests as to 1/48th of the total shares monthly, commencing February 5, 2024, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

7. The option vests as to 1/48th of the total shares monthly, commencing February 15, 2025, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

	/s/ Charles N. York II	11/07/2025
	** Signature of Reporting Person	Date
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FAQ

What did Day One Biopharmaceuticals (DAWN) disclose in this Form 4?

An option repricing effective November 6, 2025, resetting certain grants to an exercise price of $8.99 if above that level.

Which executive is covered and what is their role at DAWN?

The reporting person is the company’s COO and CFO, who signed the filing.

How many shares were in the largest affected option grant?

A grant covering 497,667 underlying shares previously carried a $16 exercise price and is fully vested.

Do vesting terms change due to the repricing?

No. The filing states all other terms remain unchanged, including existing vesting schedules.

What conditions apply to exercise at the new $8.99 price?

The executive must remain in service through the Retention Period, ending on the earlier of 12 months from the effective date or a Corporate Transaction.

Are there exceptions to the Retention Period requirement?

Yes. The filing notes an exception if service ends due to death or Disability under the plan definitions.