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

Rhea-AI Filing Summary

Day One Biopharmaceuticals (DAWN) filed a Form 4 reporting an option repricing for its Chief Commercial Officer. On November 6, 2025, certain stock options were repriced to a new exercise price of $8.99, equal to the Nasdaq closing price on the effective date.

The transactions replaced prior exercise prices for options covering 330,200 shares (originally $12.54, expiring 06/11/2033), 90,000 shares (originally $14.44, expiring 01/04/2034), and 90,000 shares (originally $11.87, expiring 01/14/2035). All other terms remain unchanged. To exercise at $8.99, the reporting person must remain in service through the Retention Period, which ends on the earliest of the 12‑month anniversary of the effective date or a Corporate Transaction; the additional premium is waived upon death or disability.

Vesting continues as previously set: 25% on June 12, 2024 with monthly vesting thereafter through June 12, 2027 for the 330,200‑share grant; and 1/48th monthly starting February 5, 2024 and February 15, 2025 for the two 90,000‑share grants. The issuer states these transactions are exempt under Rule 16b‑6(d) and Rule 16b‑3.

Insights

Equity Compensation Analyst

Administrative repricing to $8.99; terms otherwise unchanged.

The filing lists a repricing of previously granted stock options for the CCO to an exercise price of $8.99 as of November 6, 2025. Three grants are affected, covering 330,200, 90,000, and 90,000 underlying common shares, originally priced at $12.54, $14.44, and $11.87, respectively.

Vesting schedules remain intact: one grant vested 25% on June 12, 2024 with monthly vesting to June 12, 2027, and two grants vest 1/48th monthly beginning February 5, 2024 and February 15, 2025. Expiration dates of 06/11/2033, 01/04/2034, and 01/14/2035 are unchanged.

The Retention Period runs until the earlier of the 12‑month anniversary of the effective date or a Corporate Transaction. The transactions are noted as exempt under Rule 16b‑6(d) and Rule 16b‑3. Overall, this is a routine administrative adjustment; actual impact depends on future service and exercise decisions.

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
Estimated average burden
hours per response:			0.5

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^*

Merendino Lauren

(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)
	Chief Commercial Officer

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)	$12.54	11/06/2025		D(1)(2)			330,200	(3)	06/11/2033	Common Stock	330,200	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		330,200		(3)	06/11/2033	Common Stock	330,200	$0	330,200	D
Stock Option (right to buy Common Stock)	$14.44	11/06/2025		D(1)(2)			90,000	(4)	01/04/2034	Common Stock	90,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		90,000		(4)	01/04/2034	Common Stock	90,000	$0	90,000	D
Stock Option (right to buy Common Stock)	$11.87	11/06/2025		D(1)(2)			90,000	(5)	01/14/2035	Common Stock	90,000	$0	0	D
Stock Option (right to buy Common Stock)	$8.99	11/06/2025		A(1)(2)		90,000		(5)	01/14/2035	Common Stock	90,000	$0	90,000	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 option vests as to 25% of the total shares on June 12, 2024 and then 2.0833% of the total shares vest monthly thereafter, with 100% of the total shares vested on June 12, 2027, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

4. 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.

5. 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, 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.
* 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 did Day One Biopharmaceuticals (DAWN) disclose in this Form 4?

An option repricing for the Chief Commercial Officer to an exercise price of $8.99 effective November 6, 2025.

Which option grants were repriced and what were their original exercise prices?

Grants for 330,200 shares at $12.54, 90,000 shares at $14.44, and 90,000 shares at $11.87 were repriced to $8.99.

Do the option expiration dates change after the DAWN repricing?

No. Expiration dates remain 06/11/2033, 01/04/2034, and 01/14/2035.

What is the Retention Period associated with the repriced options?

It ends on the earlier of the 12‑month anniversary of the effective date or a Corporate Transaction.

What are the vesting schedules for the repriced DAWN option grants?

One grant vested 25% on June 12, 2024 with monthly vesting to June 12, 2027; two grants vest 1/48th monthly from Feb 5, 2024 and Feb 15, 2025.

Are these transactions exempt under SEC rules?

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