Access Industries group tenders Day One (DAWN) 12.9M-share stake at $21.50

Rhea-AI Filing Summary

AI Day1 LLC and its affiliates updated their ownership filing on Day One Biopharmaceuticals after tendering their entire stake into a cash buyout offer. On April 9, 2026, AI Day1 tendered 12,929,322 shares of Common Stock to Servier Detroit Inc.’s tender offer at $21.50 per share in cash.

The reporting group’s stake represented 12.52% of Day One’s Common Stock, based on 103,297,691 shares outstanding as of February 19, 2026. AI Day1 also directly holds warrants to purchase 827,586 additional shares, which may be deemed beneficially owned indirectly by Access Industries Holdings LLC, Access Industries Management, LLC and Len Blavatnik, although each of them disclaims beneficial ownership.

Insights

Equity ownership & M&A specialist

Large 12.5% shareholder tenders entire DAWN stake into $21.50 cash offer.

The filing shows AI Day1 LLC, part of the Access Industries group, tendered 12,929,322 Day One Biopharmaceuticals shares into Servier Detroit Inc.’s cash tender offer at $21.50 per share on April 9, 2026. This reflects acceptance of the proposed change in control terms.

The position equated to 12.52% of Day One’s outstanding common stock, based on 103,297,691 shares as of February 19, 2026, making this a sizable block. AI Day1 also directly holds warrants for 827,586 shares, which are attributed up the ownership chain but expressly disclaimed by those indirect holders.

Because the cash consideration and share counts are fixed in the offer documents, the economic effect for this holder is clear, though the broader impact for remaining investors depends on how many other shareholders tender under the same $21.50 terms.

Key Figures

Shares tendered: 12,929,322 shares Tender offer price: $21.50 per share Ownership percentage: 12.52% +2 more

5 metrics

Shares tendered 12,929,322 shares Common Stock tendered by AI Day1 on April 9, 2026

Tender offer price $21.50 per share Cash consideration in Servier Detroit Inc. tender offer

Ownership percentage 12.52% Portion of Day One Common Stock attributed to reporting persons

Shares outstanding baseline 103,297,691 shares Day One Common Stock outstanding as of February 19, 2026

Warrants held 827,586 warrants Warrants to purchase Common Stock directly owned by AI Day1

Key Terms

tender offer, Schedule 13D, beneficial ownership, sole Voting Power, +2 more

6 terms

tender offer financial

"tender offer by Servier Detroit Inc. to purchase all of the issued and outstanding shares"

A tender offer is a proposal made by a person or company to buy shares from existing shareholders at a set price, usually higher than the current market value, within a specific time frame. It matters to investors because it can lead to a change in ownership or control of a company, and shareholders must decide whether to sell their shares at the offered price.

Schedule 13D regulatory

"This Amendment No. 5 to is being filed by AI Day1 LLC ... together, the "Schedule""

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

beneficial ownership financial

"disclaims beneficial ownership of these securities"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

sole Voting Power financial

"Number of Shares Beneficially Owned by Each Reporting Person With: | 7 | Sole Voting Power 12,929,322.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

dispositive power financial

"sole or shared power to dispose of or to direct the disposition of"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

warrants financial

"12,929,322 shares of Common Stock and Warrants to purchase 827,586 shares of Common Stock are owned directly by AI Day1"

Warrants are special documents that give you the right to buy a company's stock at a set price before a certain date. They are often used as a way for companies to attract investors or raise money, and their value can increase if the company's stock price goes up.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 5)

Day One Biopharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

23954D109

(CUSIP Number)

Alejandro Moreno
c/o Access Industries, Inc., 40 West 57th Street, 28th Floor
New York, NY, 10019
(212) 247-6400

Langhorne S. Perrow
c/o Access Industries, Inc., 40 West 57th Street, 28th Floor
New York, NY, 10019
(212) 247-6400

Nicholas P. Pellicani
Debevoise & Plimpton LLP, The Northcliffe, 28 Tudor St.
London, X0, EC4Y 0AY
44 20 7786 9000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

04/09/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 23954D109

1

Name of reporting person

AI Day1 LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 12,929,322.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 12,929,322.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

12,929,322.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.52 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) All percentages of ownership of Common Stock by the Reporting Persons presented in this Statement are based on 103,297,691 shares of Common Stock outstanding as of February 19, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission (the "SEC") on February 24, 2026.

SCHEDULE 13D

CUSIP Number(s): 23954D109

1

Name of reporting person

Access Industries Holdings LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 12,929,322.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 12,929,322.00

11

Aggregate amount beneficially owned by each reporting person

12,929,322.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.52 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) All percentages of ownership of Common Stock by the Reporting Persons presented in this Statement are based on 103,297,691 shares of Common Stock outstanding as of February 19, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 24, 2026.

SCHEDULE 13D

CUSIP Number(s): 23954D109

1

Name of reporting person

Access Industries Management, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 12,929,322.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 12,929,322.00

11

Aggregate amount beneficially owned by each reporting person

12,929,322.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.52 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) All percentages of ownership of Common Stock by the Reporting Persons presented in this Statement are based on 103,297,691 shares of Common Stock outstanding as of February 19, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 24, 2026.

SCHEDULE 13D

CUSIP Number(s): 23954D109

1

Name of reporting person

Len Blavatnik

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 12,929,322.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 12,929,322.00

11

Aggregate amount beneficially owned by each reporting person

12,929,322.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.52 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

(1) All percentages of ownership of Common Stock by the Reporting Persons presented in this Statement are based on 103,297,691 shares of Common Stock outstanding as of February 19, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 24, 2026.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.0001 per share
(b)	Name of Issuer: Day One Biopharmaceuticals, Inc.
(c)	Address of Issuer's Principal Executive Offices: 1800 Sierra Point Parkway, Suite 200, Brisbane, CALIFORNIA , 94005.
Item 1 Comment: This Amendment No. 5 to Schedule 13D is being filed by AI Day1 LLC ("AI Day1"), Access Industries Holdings LLC ("AIH"), Access Industries Management, LLC ("AIM") and Len Blavatnik (collectively, the "Reporting Persons", and each, a "Reporting Person"), in respect of the common stock, par value $0.0001 per share (the "Common Stock"), of Day One Biopharmaceuticals, Inc. (the "Issuer"). The Schedule 13D filed with the Securities and Exchange Commission ("SEC") on June 9, 2021, as amended and supplemented by Amendment No. 1 to the Schedule 13D filed by the Reporting Persons with the SEC on June 21, 2022, Amendment No. 2 to the Schedule 13D filed by the Reporting Persons with the SEC on June 12, 2023, Amendment No. 3 to the Schedule 13D filed by the Reporting Persons with the SEC on October 20, 2023 and Amendment No. 4 to the Schedule 13D filed by the Reporting Persons with the SEC on August 1, 2024 (together, the "Schedule") is hereby amended and supplemented by the Reporting Persons as set forth below in this Amendment No. 5. This amendment is filed by the Reporting Persons in accordance with Rule 13d-2 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and refers only to information that has materially changed since the filing of the Schedule. The items identified below, or the particular paragraphs of such items which are identified below, are amended as set forth below. Unless otherwise indicated, all capitalized terms used and not defined herein have the respective meanings assigned to them in the Schedule.
Item 4.	Purpose of Transaction
	The disclosure in Item 4 is hereby supplemented by adding the following at the end thereof: On April 9, 2026, AI Day1 tendered all of its shares of Common Stock pursuant to the tender offer by Servier Detroit Inc. to purchase all of the issued and outstanding shares of Common Stock for $21.50 per share in cash, upon the terms and subject to the conditions described in the Offer to Purchase and related Letter of Transmittal filed with the SEC on Schedule TO on March 26, 2026.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5 of the Schedule 13D is hereby amended and restated as follows: The responses of each of the Reporting Persons with respect to Rows 11, 12, and 13 of the cover pages of this Schedule 13D that relate to the aggregate number and percentage of Common Stock (including but not limited to footnotes to such information) are incorporated herein by reference. The responses of each of the Reporting Persons with respect to Rows 7, 8, 9, and 10 of the cover pages of this Schedule 13D that relate to the number of Common Stock as to which each of the persons or entities referenced in Item 2 above has sole or shared power to vote or to direct the vote of and sole or shared power to dispose of or to direct the disposition of (including but not limited to footnotes to such information) are incorporated herein by reference.
(b)	12,929,322 shares of Common Stock and Warrants to purchase 827,586 shares of Common Stock are owned directly by AI Day1 and may be deemed to be beneficially owned by AIH, AIM and Mr. Blavatnik because (i) AIH indirectly controls all of the outstanding voting interests in AI Day1, (ii) AIM controls AIH and (iii) Mr. Blavatnik controls AIM and controls a majority of the outstanding voting interests in AIH. Each of the Reporting Persons (other than AI Day1), and each of their affiliated entities and the officers, partners, members and managers thereof, disclaims beneficial ownership of these securities.
(c)	The following transactions in the Issuer's securities have been effected by Reporting Persons within the 60 days prior to this filing: The information set forth in Item 3 of this Schedule 13D is incorporated by reference herein.
(d)	Not applicable.
(e)	Not applicable.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

AI Day1 LLC

Signature:	/s/ Alejandro Moreno
Name/Title:	By: Access Industries Management, LLC, its Manager; its Executive Vice President/Alejandro Moreno
Date:	04/13/2026

Access Industries Holdings LLC

Signature:	/s/ Alejandro Moreno
Name/Title:	By: Access Industries Management, LLC, its Manager; its Executive Vice President/Alejandro Moreno
Date:	04/13/2026

Access Industries Management, LLC

Signature:	/s/ Alejandro Moreno
Name/Title:	By: Executive Vice President/Alejandro Moreno
Date:	04/13/2026

Len Blavatnik

Signature:	*
Name/Title:	Len Blavatnik
Date:	04/13/2026

Comments accompanying signature:

* The undersigned, by signing his name hereto, executes this Amendment No. 5 to Schedule 13D pursuant to the Limited Power of Attorney executed on behalf of Mr. Blavatnik and filed herewith. By: /s/ Alejandro Moreno Name: Alejandro Moreno Attorney-in-Fact

FAQ

What did AI Day1 LLC disclose in the latest Schedule 13D/A for DAWN?

AI Day1 LLC disclosed that on April 9, 2026, it tendered all 12,929,322 shares of Day One Biopharmaceuticals common stock it held into Servier Detroit Inc.’s cash tender offer at $21.50 per share, updating its previously filed beneficial ownership report.

How large was Access Industries’ reported stake in Day One Biopharmaceuticals (DAWN)?

The reporting group stated beneficial ownership of 12,929,322 shares of Day One Biopharmaceuticals common stock. This represented 12.52% of the company’s outstanding common stock, based on 103,297,691 shares outstanding as of February 19, 2026, from the issuer’s Form 10-K.

At what price were AI Day1 LLC’s DAWN shares tendered in the Servier offer?

AI Day1 LLC tendered its Day One Biopharmaceuticals common shares at a cash price of $21.50 per share. The tender was made into Servier Detroit Inc.’s offer to purchase all issued and outstanding shares, as described in an Offer to Purchase filed on Schedule TO.

Who are the reporting persons in the Day One Biopharmaceuticals (DAWN) Schedule 13D/A?

The reporting persons are AI Day1 LLC, Access Industries Holdings LLC, Access Industries Management, LLC, and Len Blavatnik. AI Day1 directly holds the Day One securities, while the other reporting persons may be deemed indirect beneficial owners through their control relationships but disclaim beneficial ownership.

What warrants related to Day One Biopharmaceuticals (DAWN) are mentioned in the filing?

The filing notes that AI Day1 LLC directly owns warrants to purchase 827,586 shares of Day One Biopharmaceuticals common stock. These warrants are described as securities that may be deemed beneficially owned by Access Industries Holdings LLC, Access Industries Management, LLC and Len Blavatnik through their control of AI Day1.

How was the 12.52% ownership in DAWN calculated in the Schedule 13D/A?

The 12.52% figure was calculated using 103,297,691 shares of Day One Biopharmaceuticals common stock outstanding as of February 19, 2026. That outstanding share count was taken from the company’s Annual Report on Form 10-K for the year ended December 31, 2025, filed on February 24, 2026.