Michael Vasconcelles - 23 Apr 2026 Form 4 Insider Report for Day One Biopharmaceuticals, Inc. (DAWN)

Reporting relationship: Head of Research and Dev.
Issuer ticker: DAWN
Reported as of: 23 Apr 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 23 Apr 2026, 16:39:50 UTC
Prior SEC filing: 18 Feb 2026
Next SEC filing: 04 Jun 2026
Source filing: View source filing
Reporting owner signature: /s/ Charles N. York II, as Attorney-in-Fact

Key filing fact

Michael Vasconcelles filed Form 4 for Day One Biopharmaceuticals, Inc. (DAWN) on 23 Apr 2026.

Key facts

This page summarizes Michael Vasconcelles's Form 4 filing for Day One Biopharmaceuticals, Inc. (DAWN).
5 reported transactions and 4 derivative rows are listed below.
Accepted by SEC: 23 Apr 2026, 16:39.

Change

Previous filing in this sequence was filed on 18 Feb 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001734755 Primary reporting owner

VASCONCELLES MICHAEL

Relationship: Head of Research and Dev.
Address: 1800 SIERRA POINT PARKWAY, SUITE 200, BRISBANE
Signature: /s/ Charles N. York II, as Attorney-in-Fact
Signature date: 23 Apr 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

DAWN transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -4,397
Change %: -100%
Price
Shares after: 0
Date: 23 Apr 2026
Ownership: Direct
Footnotes: F1, F2

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

DAWN transaction Derivative

Stock Option (right to buy Common Stock)

Disposed to Issuer

Transaction value
Shares: -346,000
Change %: -100%
Price
Shares after: 0
Date: 23 Apr 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 346,000
Exercise price: $6.64
Footnotes: F3, F4

DAWN transaction Derivative

Stock Option (right to buy Common Stock)

Disposed to Issuer

Transaction value
Shares: -171,000
Change %: -100%
Price
Shares after: 0
Date: 23 Apr 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 171,000
Exercise price: $11.16
Footnotes: F4, F5

DAWN transaction Derivative

Restricted Stock Unit (RSU)

Disposed to Issuer

Transaction value
Shares: -226,000
Change %: -100%
Price
Shares after: 0
Date: 23 Apr 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 226,000
Exercise price
Footnotes: F4, F6, F7, F8

DAWN transaction Derivative

Restricted Stock Unit (RSU)

Disposed to Issuer

Transaction value
Shares: -106,875
Change %: -100%
Price
Shares after: 0
Date: 23 Apr 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 106,875
Exercise price
Footnotes: F4, F6, F8, F9

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Section 16 status

Michael Vasconcelles is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may still apply in specific circumstances.

Explanation of responses 9 footnotes

Footnote F1

On March 6, 2026, Servier Pharmaceuticals LLC, a Delaware limited liability company ("Parent"), Servier Detroit Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"), Day One Biopharmaceuticals, Inc., a Delaware corporation (the "Company"), and Servier S.A.S., a French societe par actions simplifiee, solely as a guarantor, entered into an Agreement and Plan of Merger (the "Merger Agreement"). Pursuant to the Merger Agreement, the Merger Sub merged with and into the Company (such merger and the other transactions contemplated by the Merger Agreement, the "Merger") with the Company surviving the Merger as a wholly owned subsidiary of the Parent.

Footnote F2

Upon the closing of the Merger on April 23, 2026, each issued and outstanding share of the Company's Common Stock, par value $0.0001 per share, was either (x) purchased for $21.50 per share (the "Offer Price"), net to the seller in cash, without interest, and subject to applicable withholding taxes, on the terms and conditions set forth in the Merger Agreement, or (y) automatically converted into the right to receive the Offer Price (the "Merger Consideration"), net to the seller in cash, without interest, and subject to applicable withholding taxes, on the terms and conditions set forth in the Merger Agreement.

Footnote F3

The option vests as to 1/4th of the total grant on June 16, 2026, and 1/48th of the total grant will vest on each monthly anniversary thereafter, subject to the Reporting Person's provision of service to the Issuer on each option vesting date.

Footnote F4

Immediately prior to the effective time of the Merger, all outstanding unvested stock options and unvested restricted stock units became fully vested. At the effective time of the Merger, each stock option and restricted stock unit was canceled and converted into the right to receive an amount in cash equal to the Merger Consideration (or, in the case of stock options, the difference between the Merger Consideration and the applicable per share exercise price), less any applicable withholding taxes.

Footnote F5

The option vests as to 1/48th of the total shares monthly, commencing February 28, 2026, subject to the Reporting Person's provision of service to the Issuer on each vesting date.

Footnote F6

Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock upon settlement for no consideration.

Footnote F7

The RSUs vest as to 25% of the total award on August 15, 2026, and 1/12th of the remaining RSUs vest in quarterly installments thereafter on November 15, February 15, May 15 and August 15, subject to the Reporting Person's provision of service to the Issuer on each RSU vesting date.

Footnote F8

RSUs do not expire; they either vest or are canceled prior to the RSU vesting date.

Footnote F9

The RSUs 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.