Lauren Merendino - Nov 6, 2025 Form 4 Insider Report for Day One Biopharmaceuticals, Inc. (DAWN)

Signature
/s/ Charles N. York II, as Attorney-in-Fact
Stock symbol
DAWN
Transactions as of
Nov 6, 2025
Transactions value $
$0
Form type
4
Date filed
11/7/2025, 05:58 PM
Previous filing
Aug 19, 2025
Next filing
Nov 18, 2025

Reporting Owners (1)

Name Relationship Address Signature Signature date CIK
Merendino Lauren Chief Commercial Officer 1800 SIERRA POINT PARKWAY, SUITE 200, BRISBANE /s/ Charles N. York II, as Attorney-in-Fact 2025-11-07 0001855298

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Underlying Class Amount Exercise Price Ownership Footnotes
transaction DAWN Stock Option (right to buy Common Stock) Disposed to Issuer $0 -330K -100% $0.00 0 Nov 6, 2025 Common Stock 330K $12.54 Direct F1, F2, F3
transaction DAWN Stock Option (right to buy Common Stock) Award $0 +330K $0.00 330K Nov 6, 2025 Common Stock 330K $8.99 Direct F1, F2, F3
transaction DAWN Stock Option (right to buy Common Stock) Disposed to Issuer $0 -90K -100% $0.00 0 Nov 6, 2025 Common Stock 90K $14.44 Direct F1, F2, F4
transaction DAWN Stock Option (right to buy Common Stock) Award $0 +90K $0.00 90K Nov 6, 2025 Common Stock 90K $8.99 Direct F1, F2, F4
transaction DAWN Stock Option (right to buy Common Stock) Disposed to Issuer $0 -90K -100% $0.00 0 Nov 6, 2025 Common Stock 90K $11.87 Direct F1, F2, F5
transaction DAWN Stock Option (right to buy Common Stock) Award $0 +90K $0.00 90K Nov 6, 2025 Common Stock 90K $8.99 Direct F1, F2, F5
* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id Content
F1 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")).
F2 (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.
F3 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.
F4 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.
F5 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.