Charles N. York II - Nov 15, 2025 Form 4 Insider Report for Day One Biopharmaceuticals, Inc. (DAWN)

Role
COO and CFO
Signature
/s/ Charles N. York II
Stock symbol
DAWN
Transactions as of
Nov 15, 2025
Transactions value $
-$36,212
Form type
4
Date filed
11/18/2025, 07:02 PM
Previous filing
Nov 7, 2025
SEC
View on sec.gov

Reporting Owners (1)

Name Relationship Address Signature Signature date CIK
York Charles N II COO and CFO 1800 SIERRA POINT PARKWAY, SUITE 200, BRISBANE /s/ Charles N. York II 2025-11-18 0001655962

Transactions Table

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Ownership Footnotes
transaction DAWN Common Stock Options Exercise +1.38K +0.49% 283K Nov 15, 2025 Direct F1, F2
transaction DAWN Common Stock Options Exercise +2.25K +0.79% 286K Nov 15, 2025 Direct F1
transaction DAWN Common Stock Options Exercise +6.63K +2.32% 292K Nov 15, 2025 Direct F1
transaction DAWN Common Stock Options Exercise +6.63K +2.27% 299K Nov 15, 2025 Direct F1
transaction DAWN Common Stock Sale -$36.2K -4.06K -1.36% $8.91 295K Nov 17, 2025 Direct F3, F4

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 Restricted Stock Unit (RSU) Options Exercise $0 -1.38K -100% $0.00 0 Nov 15, 2025 Common Stock 1.38K Direct F1, F5, F6
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -2.25K -20% $0.00 9K Nov 15, 2025 Common Stock 2.25K Direct F1, F5, F6
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -6.63K -11.11% $0.00 53K Nov 15, 2025 Common Stock 6.63K Direct F1, F5, F6
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -6.63K -7.69% $0.00 79.5K Nov 15, 2025 Common Stock 6.63K Direct F1, F5, F6
* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id Content
F1 Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock upon settlement for no consideration.
F2 Includes 3,902 shares of Common Stock acquired by the Reporting Person between May 12, 2023 and November 14, 2025 pursuant to the Issuer's employee stock purchase plan.
F3 The sale of shares is for the sole purpose of covering the Reporting Person's tax liability with respect to the settlement of RSUs.
F4 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.
F5 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.
F6 RSUs do not expire; they either vest or are canceled prior to the vesting date.