# EDGAR Filing Document

**Accession Number:** 0001845337
**File Stem:** 0001193125-26-095176
**Filing Date:** 2026-3
**Character Count:** 68282
**Document Hash:** cc8a67fff1e3d8309ab716436570a920
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-095176.hdr.sgml**: 20260306

**ACCESSION NUMBER**: 0001193125-26-095176

**CONFORMED SUBMISSION TYPE**: SC14D9C

**PUBLIC DOCUMENT COUNT**: 8

**FILED AS OF DATE**: 20260306

**DATE AS OF CHANGE**: 20260306

**SUBJECT COMPANY**: 

**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

**FILING VALUES:**
- **FORM TYPE:** SC14D9C
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-92582
- **FILM NUMBER:** 26728629

**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
**FILED BY**: 

**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

**FILING VALUES:**
- **FORM TYPE:** SC14D9C

**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** 

**SCHEDULE 14D-9** 

**(Rule 14d-101)** 

**Solicitation/Recommendation Statement** 

**under Section 14(d)(4) of the Securities Exchange Act of 1934** 

## Day One Biopharmaceuticals, Inc.
**(Name of Subject Company)** 

**(Name of Person(s) Filing Statement)** 

**Common Stock, par value $0.001 per share** 

**(Title of Class of Securities)** 

**23954D 109** 

**(CUSIP Number of Class of Securities)** 

**Jeremy Bender** 

**Chief Executive Officer and President** 

**Day One Biopharmaceuticals, Inc.** 

**1800 Sierra Point Parkway, Suite 200** 

**Brisbane, CA 94005** 

**Telephone: (650)-484-0899**

**(Name, address and telephone number of person authorized to receive notice and communications** 

**on behalf of the persons filing statement)** 

***With copies to:***

---

| | |
|:---|:---|
| **Effie Toshav, Esq.**<br> **Douglas N. Cogen, Esq.**<br> **Robert A Freedman, Esq.**<br> **Julia Forbess, Esq.**<br> **Fenwick & West LLP**<br> **555 California Street, 12th Floor**<br> **San Francisco, CA 94104**<br> **(415) 875-2300** | **Charles N. York II**<br> **Chief Operating Officer and Chief Financial Officer**<br> **Day One Biopharmaceuticals, Inc.**<br> **1800 Sierra Point Parkway, Suite 200**<br> **Brisbane, CA 94005**<br> **(650)-484-0899** |

---

☒ Check the box if the filing relates solely to preliminary communications made before the commencement of a
tender offer.

------

This Schedule 14D-9 filing consists of the following communications related to the proposed acquisition of Day One Biopharmaceuticals, Inc., a Delaware corporation (the "Company" or "Day One"), by Servier S.A.S., a French société par actions simplifiée ("Servier"), Servier Pharmaceuticals LLC, a Delaware limited liability company and an indirect wholly owned subsidiary of Servier ("Parent"), and Servier Detroit Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub" and together with Servier and Parent, the "Servier Parties"), pursuant to the terms of the Agreement and Plan of Merger dated March 6, 2026, by and among the Company, Servier, Parent and Merger Sub (the "Merger Agreement"):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• [Joint Press Release, dated March 6, 2026 (Exhibit 99.1).](d321704dex991.htm)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• [Employee FAQ sent to the Company's employees, dated March 6, 2026 (Exhibit 99.2).](d321704dex992.htm)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• [Email sent to the Company's stakeholders, dated March 6, 2026 (Exhibit 99.3).](d321704dex993.htm)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• [Email sent to the Company's employees, dated March 6, 2026 (Exhibit 99.4).](d321704dex994.htm)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• [Company social media post, dated March 6, 2026 (Exhibit 99.5).](d321704dex995.htm)

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by the Servier Parties. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and the Servier Parties to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by the Servier Parties' proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and the Servier Parties are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and the Servier Parties undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

------

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that the Servier Parties will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that the Servier Parties intend to file with the SEC. At the time the offer is commenced, the Servier Parties will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com, or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the Solicitation/Recommendation Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.

## Exhibit 99.1

**Exhibit 99.1** 

---

| | |
|:---|:---|
| ![LOGO](g55904g0306121431906.jpg) | ![LOGO](g55904g0306121440152.jpg) |

---

**Servier and Day One Biopharmaceuticals announce acquisition to expand Servier's rare oncology portfolio** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• **Acquisition positions Servier as a leader in pediatric low-grade glioma and expands its pipeline with programs targeting adult and pediatric cancers with high unmet needs** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• **Transaction represents total equity value of approximately $2.5 billion** 

**Suresnes, France and Brisbane, California, March 6, 2026 –** Servier, an independent international pharmaceutical group governed by a foundation, and Day One Biopharmaceuticals, Inc. (Nasdaq: DAWN) ("Day One"), a biopharmaceutical company dedicated to developing and commercializing targeted therapies for people of all ages with life-threatening diseases, today announced that they have entered into a definitive agreement for Servier to acquire Day One for $21.50 per share in cash, representing a total equity value of approximately $2.5 billion. The transaction remains subject to customary closing conditions and is expected to close in the second quarter of 2026.

This acquisition will reinforce Servier's position in oncology targeted therapies in line with its 2030 ambition to develop innovative treatments for patients with high unmet medical needs. It strengthens Servier's portfolio and expands its oncology pipeline with programs ranging from early stage to phase 3. The combination of Day One's scientific expertise with Servier's established global capabilities advances a shared commitment to delivering innovative solutions for patients worldwide.

"This acquisition of Day One Biopharmaceuticals marks another decisive step in strengthening Servier's position in rare oncology," **said Olivier Laureau, President of Servier**. "It reflects our long-term commitment to investing in science that can make a meaningful difference for patients. This announcement is fully aligned with our 2030 ambition, and we believe that combining our expertise will accelerate innovation for people living with a rare cancer."

"Servier's successful track record in rare cancers and its commitment to advancing targeted therapies makes it the ideal home for our portfolio as part of Day One's mission to bring medicines to patients of all ages with life threatening diseases" **said Jeremy Bender, Ph.D., chief executive officer of Day One**. "Joining Servier represents a unique opportunity to extend the reach of our science and our lead program in pediatric low-grade glioma. Importantly, Servier's dedication to the rare disease community preserves the patient-first mindset that has defined our company since the beginning and has driven our deep commitment to the communities we serve."

------

---

| | |
|:---|:---|
| ![LOGO](g55904g0306121431906.jpg) | ![LOGO](g55904g0306121440152.jpg) |

---

**Transaction terms** 

Under the terms of the merger agreement, Servier will commence a cash tender offer to acquire all of the issued and outstanding shares of Day One's common stock for $21.50 per share in cash, representing a total equity value of approximately of $2.5 billion. The offer price represents a premium of approximately 68% over the closing price of Day One on March 5, 2026, and a premium of approximately 86% over the one-month volume weighted average price (VWAP) of Day One as of March 5, 2026.

Servier expects to fund the transaction through existing cash and investments.

The consummation of the tender offer is subject to certain customary closing conditions, including the tender by Day One shareholders of at least a majority of the issued and outstanding shares of Day One common stock and the receipt of U.S. antitrust clearance. Upon the successful completion of the tender offer, Servier will acquire any shares not acquired in the tender through a second-step merger for the same consideration per share paid in the tender offer. Day One's Board of Directors recommends that Day One shareholders tender their shares in the tender offer.

**Advisors** 

Goldman Sachs Bank Europe SE is serving as exclusive financial advisor to Servier<sup>,</sup> and Baker McKenzie is serving as legal counsel. Centerview Partners LLC is serving as the exclusive financial advisor to Day One, with Fenwick & West LLP serving as legal counsel.

**Contacts** 

**Servier Group** 

Laura Visserias

<u>laura.visserias.part@servier.com</u>

**Servier Pharmaceuticals (U.S.)** 

Paulina Bucko

<u>Paulina.bucko@servier.com</u> 

**Day One Biopharmaceuticals Media** 

<u>media@dayonebio.com</u> 

**Day One Biopharmaceuticals Investors** 

LifeSci Advisors, PJ Kelleher

<u>pkelleher@lifesciadvisors.com</u> 

**About Servier** 

Servier is an independent international pharmaceutical group governed by a foundation. With its governance model, the Group is committed to therapeutic progress to serve patients and integrates the patient voice at every stage of the medicine life cycle.

As a leading global player in cardiology and venous diseases, Servier aims to become a leading innovator in oncology and neurology. The Group intends to offer targeted therapeutic solutions, particularly in rare cancers and neurological diseases, and invests nearly 20% of its brand-name sales in R&D.

------

---

| | |
|:---|:---|
| ![LOGO](g55904g0306121431906.jpg) | ![LOGO](g55904g0306121440152.jpg) |

---

Headquartered in France, Servier relies on its more than 20,000 employees and a solid geographic presence with medicines distributed in more than 130 countries. In the 2024/25 financial year, the Group achieved revenues of €6.9 billion.

More information on the Group website: <u>servier.com</u>

Follow us on social media: <u>LinkedIn</u>, <u>Facebook</u>, <u>X</u>, <u>Instagram</u>

**About Day One Biopharmaceuticals** 

Day One Biopharmaceuticals is a commercial-stage biopharmaceutical company that believes when it comes to pediatric cancer, we can do better. The Company was founded to address a critical unmet need: the dire lack of therapeutic development in pediatric cancer. Inspired by "The Day One Talk" that physicians have with patients and their families about an initial cancer diagnosis and treatment plan, Day One aims to re-envision cancer drug development and redefine what's possible for all people living with cancer—regardless of age—starting from Day One.

Day One partners with leading clinical oncologists, families, and scientists to identify, acquire, and develop important targeted cancer treatments.

Day One is based in Brisbane, California. For more information, please visit <u>www.dayonebio.com</u> or find the Company on <u>LinkedIn</u> or <u>X</u>.

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by Servier. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and Servier to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by Servier's proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to, future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are

------

---

| | |
|:---|:---|
| ![LOGO](g55904g0306121431906.jpg) | ![LOGO](g55904g0306121440152.jpg) |

---

satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and Servier are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and Servier undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Servier and the Purchaser will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that Servier and the Purchaser intend to file with the SEC. At the time the offer is commenced, Servier and the Purchaser will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com , or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the Solicitation/Recommendation Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.

## Exhibit 99.2

**Exhibit 99.2** 

Employee FAQ

**ABOUT THE AGREEMENT** 

**Key Points:** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Servier and Day One announced an agreement for the acquisition of Day One by Servier for $21.50 per share, or
approximately $2.5 billion.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The acquisition represents an opportunity to expand the reach of Day One's innovation and community impact,
and strengthens Servier's growing offerings in rare cancers, expanding its portfolio and pipeline with programs that address significant unmet needs.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The transaction remains subject to customary closing conditions and is expected to close in the second quarter of
2026. **1.** **Why are we being acquired? Why is Servier the right company to acquire us?** 

The acquisition represents an opportunity to expand the reach of Day One's innovation and community impact, and strengthens Servier's growing offerings in rare cancers, expanding its portfolio and pipeline with programs that address significant unmet needs.

**2.** **When will the tender offer and acquisition be completed?** 

We currently anticipate that the tender offer and acquisition will be completed in the second quarter of 2026. The acquisition is subject to customary closing conditions, including receipt of U.S. antitrust regulatory clearances and the tender of a majority of the outstanding shares of Day One's common stock.

**3.** **Will Servier retain our product and pipeline? What about our facilities?** 

Servier has expressed their commitment to supporting the portfolio and pipeline we've built. While no specific decisions have been made on facilities, more information will be shared during the integration process.

**4.** **Can we discuss the acquisition externally or post on social media?** 

You may acknowledge the acquisition externally since it has been publicly announced, but you should not post any information on your social media channels, chat rooms or engage in other public discussion forums about the acquisition. Please do not reach out, respond to or communicate with any Servier employees unless directed to do so by senior management, as this effort remains under review by regulatory authorities and there are restrictions on integration planning efforts.

------

**ABOUT THE PROCESS** 

**5.** **What should we expect to occur prior to the close of the acquisition? What about immediately after the close?** 

Both companies will operate independently until the acquisition is closed.

Servier will use this upcoming period of time before closing to meet our team, to learn more about the organization and to develop plans on how best to combine our two organizations. Once the transaction is closed and the integration plans are developed, Servier will be able to communicate and start to implement the plans.

We are sensitive to the feeling of uncertainty during this time, and rest assured that both companies are committed to treating everyone fairly, honestly, and with respect and transparency throughout this process.

**6.** **How will the company be integrated into Servier? How will this transaction impact Day One employees?** 

The integration planning is in process, and more information will follow. That said, we will work with Servier to ensure our employees are treated fairly in this transition. For now, we need to remain focused on our day-to-day work, keeping in mind the same scientific rigor and patient focus that has driven everything we have done to date.

**7.** **When will we receive more information on timelines and integration plans?** 

We will work with the Servier team to plan more detailed communications over the coming weeks, with more specifics following the closing.

**8.** **What should we advise customers about purchase agreements / plans during the transition?** 

No changes should be made to current initiatives. We will continue to operate independently until the acquisition is closed.

**ABOUT STAFF IMPACT** 

**9.** **What is expected of employees between now and when the transaction is closed?** 

We will continue to operate independently until we receive approval and the acquisition is closed. We know this is a time of uncertainty, but we ask that you stay focused and continue doing the great job that has created our success to date. The vast majority of our work – including supplying our medicine to patients, patient support programs, clinical trial operations, engaging with regulatory agencies and health care providers – will continue as they normally would. Patients are counting on us.

Outside of approved integration planning work streams, please do not reach out, respond to or communicate with any Servier employees as this transaction remains under review by regulatory authorities.

------

**10.** **Are there any immediate impacts to my current reporting structure / leadership?** 

No. Both companies will operate independently until we receive approval and the acquisition is closed.

**11.** **Will I keep my job?** 

It's premature at this point to be able to answer this question. For now, all Day One employees are expected to continue in their roles through closing, to ensure we continue business as usual. Post close, and as part of the integration activities, Servier will assess the combined infrastructure and align resources to support their growth aspirations. Servier will communicate organizational alignment decisions and individual impacts for each Day One employee. Both companies are aligned in our intent to treat everyone fairly, honestly, and with respect and transparency throughout this process.

**12.** **Will Servier offer severance for employees who are affected by the transition?** 

At this time, no decisions have been made around changes to the organizational structure. Following the closing, should your position be eliminated by Servier during calendar year 2026, you would be eligible for certain change in control benefits and a prorated bonus from Jan 1, 2026 through your final date of employment with Servier.

**13.** **How will benefits change after the acquisition has been completed?** 

Between now and close, nothing changes. You will remain on Day One benefits. No specific details are available yet about benefits, however, Servier will make these determinations. The company offers competitive and comparable benefit packages.

**14.** **What happens to stock options, restricted stock units (RSUs) or other shares employees were granted as part of their equity compensation?** 

All outstanding options and RSUs will be accelerated and become fully vested at the closing of the transaction and holders will be cashed out at closing, provided that the strike price of the options is lower than the transaction price. This means that, shortly following the closing of the transaction, option holders will receive in cash the purchase price of $21.50 per share less the stock option exercise price per share, tax withholdings, and required deductions for each share subject to the stock option. Stock options that were re-priced will reflect the new, lower exercise price (and the retention period that was applied in connection with the repricing will be satisfied upon the closing). Employees will not be required to exercise their stock options.

At the same time, holders of RSUs or outstanding shares will receive in cash the purchase price of $21.50 per share less tax withholdings and required deductions for each RSU held. More specifics on this process will be provided in the coming weeks.

**15.** **What happens to the ESPP?** 

The current ESPP offering period will continue as offered until either the scheduled end of the current ESPP offering period or close of this transaction, whichever comes first. If the current ESPP offering period ends prior to the closing, then there will not be another ESPP offering period under our ESPP.

------

**16.** **If I see an open role at Servier that is of interest, can I apply for it?** 

Both companies will operate independently until the acquisition is completed. Post-integration opportunities will be shared by Servier.

**17.** **Will there be a hiring freeze between now and close?** 

No. We will continue our usual practice of carefully evaluating and approving open positions.

**18.** **When can you share more information about the transaction?** 

Servier will initiate the tender offer process with a public filing of a tender offer document, and Day One will make its own public filing at the same time. Please review these documents for additional information about the transaction and the background on the transaction when they become available.

**19.** **What about the current Day One leadership?** 

Nothing changes prior to close. Day One leadership will continue to focus on pursuing our strategic plan. Day One and Servier are two independent companies until the transaction has obtained regulatory approvals and has closed. Any consideration of organizational changes related to the transaction will wait until regulatory approvals have been obtained and will be announced post close.

**20.** **Whom do I contact with additional questions?** 

Prior to closing of the transaction, please submit any questions regarding the acquisition to the AskIntegrationTeam@DayOne.com.

\# \# \#

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by Servier. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and Servier to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by Servier's proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to, future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

------

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and Servier are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and Servier undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Servier and the Purchaser will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that Servier and the Purchaser intend to file with the SEC. At the time the offer is commenced, Servier and the Purchaser will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com , or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the Solicitation/Recommendation

------

Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.

## Exhibit 99.3

**Exhibit 99.3** 

Dear Day One [Customer/Vendor/Supplier/Partner/Collaborator],

This morning we announced that we have entered into a definitive agreement to be acquired by Servier, an international pharmaceutical group with a growing oncology portfolio. You can read the announcement here. [link]

Servier is enthusiastic about the planned acquisition, and looks forward to integrating OJEMDA<sup>®</sup> and our pipeline as it continues to grow its portfolio. Servier has made incredible strides in cancer innovation and shares our aspirations to address real unmet needs by integrating the patient voice at every stage of the medicine life cycle.

There are no changes at this time in terms of your points of contact or contracts. Please continue your usual processes with us until you receive further notice. The acquisition is subject to customary closing conditions and approvals. Until closing, Day One and Servier will continue to operate independently.

We are committed to ensuring a smooth transition. Over the coming weeks, you will receive additional information on changes in process.

Thank you for your continued support and partnership.

Sincerely,

[INSERT]

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by Servier. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and Servier to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by Servier's proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to, future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

------

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and Servier are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and Servier undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Servier and the Purchaser will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that Servier and the Purchaser intend to file with the SEC. At the time the offer is commenced, Servier and the Purchaser will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com , or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the Solicitation/Recommendation Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by

------

reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.

## Exhibit 99.4

**Exhibit 99.4** 

Dear colleagues,

This morning, we announced that we have entered into a definitive agreement to be acquired by Servier, an international pharmaceutical group with a growing oncology portfolio. You can read the announcement here [link]. We believe that joining forces with Servier will allow us to further our mission to deliver life-changing medicines for people of all ages, and begins a new chapter in the Day One journey.

While I understand this announcement will come as a surprise, I am genuinely enthusiastic about joining our incredible team with the growing global presence of Servier. Servier has made incredible strides in cancer innovation and shares our aspirations to address real unmet needs by integrating the patient voice at every stage of the medicine life cycle. Servier's team is truly excited about the planned acquisition and looks forward to incorporating OJEMDA<sup>®</sup> and our growing pipeline into its growth plans.

To our entire team, I am deeply grateful for your contributions, commitment and partnership throughout the Day One journey. I am so proud of the company we've built together, the programs we've advanced, and most importantly, the difference we've made for individuals and families affected by pLGG. We should all celebrate how far we've come, and look forward to the opportunity to reach many more communities as part of Servier's growing global footprint.

So, what does this mean for all of us today? The acquisition is subject to U.S antitrust regulatory approvals and other closing conditions, so there is no change right now. We will continue to operate independently until the regulatory approval process is complete. Please continue to focus on what's most important – delivering on the needs of the communities we serve. The vast majority of our work – including supplying OJEMDA to patients, patient support programs, clinical trial operations, advancing our pipeline and engaging with regulatory agencies and health care providers – will continue as normal.

Shortly, you'll receive an invitation for a brief All Hands meeting today at 8 am PT to discuss this announcement and answer your questions to the extent possible today. For those who are local, I'll be in the office all day and you are welcome to join in person.

I recognize that this type of change brings uncertainty and we are committed to keeping you updated as we navigate this process. For now, my ask is that you focus on execution through the values and culture we've worked so hard to establish together. I look forward to connecting with all of you shortly.

Sincerely,

Jeremy

------

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by Servier. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and Servier to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by Servier's proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to, future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and Servier are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and Servier undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

------

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Servier and the Purchaser will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that Servier and the Purchaser intend to file with the SEC. At the time the offer is commenced, Servier and the Purchaser will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com , or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the Solicitation/Recommendation Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.

## Exhibit 99.5

**Exhibit 99.5** 

**Social post** 

*Formal announcement:* 

Today we've announced a definitive agreement to be acquired by Servier. Servier shares our deep commitment to advancing innovation in cancer along with our patient-focused methodology to address the most pressing areas of unmet need. Please refer to today's press release for important information about this transaction. [link]

*Jeremy Quote: "Servier's successful track record in rare cancers and its commitment to advancing targeted therapies makes it the ideal home for our portfolio as part of Day One's mission to bring medicines to patients of all ages with life threatening diseases."* 

**Cautionary Notice Regarding Forward-Looking Statements** 

This communication contains forward-looking statements relating to the proposed acquisition of Day One by Servier. These forward-looking statements are not based on historical fact and include statements regarding the ability of Day One and Servier to complete the transactions contemplated by the Merger Agreement, including the parties' ability to satisfy the conditions to the consummation of the tender offer (the "offer") contemplated thereby and the other conditions set forth in the Merger Agreement, statements about the expected timetable for completing the transaction, Day One and Servier's beliefs and expectations and statements about the benefits sought to be achieved by Servier's proposed acquisition of Day One, the potential effects of the acquisition on both Day One and Servier, and the possibility of any termination of the Merger Agreement. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions and include words such as "may," "will," "should," "would," "expect," "plan," "intend," and other similar expressions, among others. These forward-looking statements are based on current assumptions that involve risks, uncertainties, and other factors that may cause actual results, events, or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties, many of which are beyond our control, include, but are not limited to, future events and trends that Day One believes may affect the financial condition, results of operations, business strategy, short-term and long-term business operations and objectives and financial needs of Day One. There can be no guarantee that such expectations and projections will prove accurate in the future.

All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the offer and the subsequent merger; uncertainties as to how many of Day One's stockholders will tender their shares in the offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the merger and the offer contemplated thereby may not be satisfied or

------

waived; the effects of disruption from the transactions contemplated by the Merger Agreement on Day One's business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; and the risk that stockholder litigation in connection with the offer or the merger may result in significant costs of defense, indemnification and liability. Moreover, Day One operates in a very competitive and rapidly changing environment, and new risks emerge from time to time. Although Day One believes that the expectations reflected in such forward-looking statements are reasonable, it cannot guarantee future events, results, actions, levels of activity, performance or achievements, business and market conditions, the timing and results of any developments and whether the conditions to the closing of the proposed acquisition are satisfied on the expected timetable or at all. Other risks that may affect the future results of Day One and Servier are identified in their respective filings with the Securities and Exchange Commission (the "SEC") or other public disclosures. These forward-looking statements speak only as of the date they are made, and Day One and Servier undertake no obligation to update forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

**Additional Information about the Acquisition and Where to Find It** 

The offer referenced in this communication has not yet commenced. This communication is for informational purposes only, is not a recommendation and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Servier and the Purchaser will file with the SEC upon commencement of the offer. A solicitation and offer to buy outstanding shares of Day One will only be made pursuant to the tender offer materials that Servier and the Purchaser intend to file with the SEC. At the time the offer is commenced, Servier and the Purchaser will file with the SEC tender offer materials on Schedule TO, and Day One will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer.

THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES THERETO. INVESTORS AND STOCKHOLDERS OF DAY ONE ARE URGED TO READ THESE DOCUMENTS CAREFULLY WHEN THEY BECOME AVAILABLE (AND EACH AS IT MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME), BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND STOCKHOLDERS OF DAY ONE SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES OF COMMON STOCK IN THE OFFER. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal) will be made available to all stockholders of Day One at no expense to them under the "Investor Resources" section of Day One's website at https://ir.dayonebio.com/ or by email at investors@dayonebio.com , or by directing requests for such materials to the information agent for the offer, which will be named in the tender offer materials, and (once they become available) the tender offer materials as well as the

------

Solicitation/Recommendation Statement will be mailed to the stockholders of Day One free of charge. Copies of the documents filed with the SEC by Day One will be available free of charge on Day One's website, https://ir.dayonebio.com/, or by contacting Day One's investor relations department at investors@dayonebio.com. The information contained in, or that can be accessed through, Day One's website is not a part of or incorporated by reference herein. The tender offer materials (including the Offer to Purchase and the related Letter of Transmittal), as well as the Solicitation/Recommendation Statement, will also be made available for free on the SEC's website at www.sec.gov. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, Day One files annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read any reports, statements, or other information filed by Servier or Day One with the SEC for free on the SEC's website at www.sec.gov.