Charles N. York II - 15 Feb 2026 Form 4 Insider Report for Day One Biopharmaceuticals, Inc. (DAWN)

Role
COO and CFO
Signature
/s/ Charles N. York II
Issuer symbol
DAWN
Transactions as of
15 Feb 2026
Net transactions value
-$70,359
Form type
4
Filing time
18 Feb 2026, 17:16:10 UTC
Previous filing
30 Jan 2026
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 18 Feb 2026 0001655962

Transactions Table

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Ownership Footnotes
transaction DAWN Common Stock Options Exercise +2,250 +0.76% 296,965 15 Feb 2026 Direct F1
transaction DAWN Common Stock Options Exercise +6,625 +2.2% 303,590 15 Feb 2026 Direct F1
transaction DAWN Common Stock Options Exercise +6,625 +2.2% 310,215 15 Feb 2026 Direct F1
transaction DAWN Common Stock Options Exercise +7,875 +2.5% 318,090 15 Feb 2026 Direct F1
transaction DAWN Common Stock Sale $70,359 -6,065 -1.9% $11.60 312,025 17 Feb 2026 Direct F2, F3

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 -2,250 -25% $0.000000 6,750 15 Feb 2026 Common Stock 2,250 Direct F1, F4, F5
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -6,625 -12% $0.000000 46,375 15 Feb 2026 Common Stock 6,625 Direct F1, F4, F5
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -6,625 -8.3% $0.000000 72,875 15 Feb 2026 Common Stock 6,625 Direct F1, F4, F5
transaction DAWN Restricted Stock Unit (RSU) Options Exercise $0 -7,875 -6.2% $0.000000 118,125 15 Feb 2026 Common Stock 7,875 Direct F1, F4, F5
* 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 The sale of shares is for the sole purpose of covering the Reporting Person's tax liability with respect to the settlement of RSUs.
F3 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 $11.195 to $11.8508, 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.
F4 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.
F5 RSUs do not expire; they either vest or are canceled prior to the vesting date.