# EDGAR Filing Document

**Accession Number:** 0001776351
**File Stem:** 0001776351-26-000001
**Filing Date:** 2026-4
**Character Count:** 9533
**Document Hash:** 4ab7d38a029dab009ad118712746b243
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001776351-26-000001.hdr.sgml**: 20260423

**ACCESSION NUMBER**: 0001776351-26-000001

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260423

**FILED AS OF DATE**: 20260423

**DATE AS OF CHANGE**: 20260423

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Josey John A.
- **CENTRAL INDEX KEY:** 0001776351

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-40431
- **FILM NUMBER:** 26889195

**MAIL ADDRESS:**
- **STREET 1:** C/O PELOTON THERAPEUTICS, INC.
- **STREET 2:** 2330 INWOOD ROAD, SUITE 226
- **CITY:** DALLAS
- **STATE:** TX
- **ZIP:** 75235
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Day One Biopharmaceuticals, Inc.
- **CENTRAL INDEX KEY:** 0001845337
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 832415215
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 1800 SIERRA POINT PARKWAY, SUITE 200
- **CITY:** BRISBANE
- **STATE:** CA
- **ZIP:** 94005
- **BUSINESS PHONE:** 650 484-0899

**MAIL ADDRESS:**
- **STREET 1:** 1800 SIERRA POINT PARKWAY, SUITE 200
- **CITY:** BRISBANE
- **STATE:** CA
- **ZIP:** 94005

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Day One Biopharmaceuticals Holding Co LLC
- **DATE OF NAME CHANGE:** 20210209

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[x] 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**<sup>*</sup><br>Josey John A.<br><sub>(Last) (First) (Middle)</sub><br>1800 SIERRA POINT PARKWAY, SUITE 200<br><sub>(Street)</sub><br>BRISBANE, CA 94005<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-04-23 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director [ ] 10% Owner<br>[ ] Officer (give title below) [ ] Other (specify below)<br>_ _ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>Day One Biopharmaceuticals, Inc. [ DAWN ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2026-04-23 |  | D |  | 72292 | D | <sup>(1)(2)</sup> | 0 | D |  |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock Option (right to buy Common Stock) | $8.99 | 2026-04-23 |  | D |  |  | 63000 | <sup>(3)</sup> | 2031-05-25 | Common Stock | 63000 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy Common Stock) | $8.99 | 2026-04-23 |  | D |  |  | 1181 | <sup>(3)</sup> | 2031-05-25 | Common Stock | 1181 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy Common Stock) | $8.99 | 2026-04-23 |  | D |  |  | 28700 | <sup>(3)</sup> | 2032-06-20 | Common Stock | 28700 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy Common Stock) | $8.99 | 2026-04-23 |  | D |  |  | 37500 | <sup>(3)</sup> | 2033-06-21 | Common Stock | 37500 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy Common Stock) | $8.99 | 2026-04-23 |  | D |  |  | 32335 | <sup>(3)</sup> | 2034-05-22 | Common Stock | 32335 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy Common Stock) | $7.01 | 2026-04-23 |  | D |  |  | 22500 | <sup>(5)</sup> | 2035-06-01 | Common Stock | 22500 | <sup>(4)</sup> | 0 | D |  |
| Restricted Stock Unit (RSU) | <sup>(6)</sup> | 2026-04-23 |  | D |  |  | 15000 | <sup>(7)</sup> | <sup>(8)</sup> | Common Stock | 15000 | <sup>(4)</sup> | 0 | D |  |

---

### Footnotes:

(1) 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.

(2) 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.

(3) The options are fully vested.

(4) 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.

(5) The option vests as to 1/12th of the total grant on each monthly anniversary, beginning on July 2, 2025, subject to the Reporting Person's provision of service to the Issuer on each option vesting date.

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

(7) The RSUs will vest as to 100% of the award on the earlier of (i) June 2, 2026 and (ii) the date of the Issuer's 2026 annual meeting of stockholders (in each case, the "RSU Vesting Date"), subject to the Reporting Person's provision of services to the Issuer on each RSU Vesting Date. Shares of the Issuer's Common Stock will be delivered to the Reporting Person following vesting.

(8) RSUs do not expire; they either vest or are canceled prior to the RSU Vesting Date.

**Signature:** /s/ Charles N. York II, as Attorney-in-Fact  
**Date:** 2026-04-23

### Remarks:

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.**