FMR LLC boosts disclosure to 5.6% ownership in Day One Biopharmaceuticals (DAWN)

Rhea-AI Filing Summary

FMR LLC has filed an amended Schedule 13G reporting beneficial ownership of 5,717,007.68 shares of Day One Biopharmaceuticals Inc. common stock, representing 5.6% of the outstanding class as of 12/31/2025. FMR LLC reports sole voting power over 5,702,209.00 shares and sole dispositive power over 5,717,007.68 shares, with no shared voting or dispositive power. Abigail P. Johnson is also listed as a reporting person, with sole dispositive power over 5,717,007.68 shares and no voting power. The securities are stated to be held in the ordinary course of business and not for the purpose of changing or influencing control of the issuer.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 5)

DAY ONE BIOPHARMACEUTICALS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

23954D109

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 23954D109

1

Names of Reporting Persons

FMR LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 5,702,209.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 5,717,007.68
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,717,007.68

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.6 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No. 23954D109

1

Names of Reporting Persons

Abigail P. Johnson

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 5,717,007.68
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,717,007.68

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.6 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: DAY ONE BIOPHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: 2000 SIERRA POINT PARKWAY,SUITE 501,Brisbane,CA,USA,94005
Item 2.
(a)	Name of person filing: FMR LLC
(b)	Address or principal business office or, if none, residence: 245 Summer Street, Boston, Massachusetts 02210
(c)	Citizenship: Not applicable
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 23954D109
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 5717007.68
(b)	Percent of class: 5.6 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Please see the responses to Items 5 and 6 on the cover page.
	(ii) Shared power to vote or to direct the vote: 0.00
	(iii) Sole power to dispose or to direct the disposition of: 5717007.68
	(iv) Shared power to dispose or to direct the disposition of: 0.00
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. One or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the COMMON STOCK of DAY ONE BIOPHARMACEUTICALS INC. No one other person's interest in the COMMON STOCK of DAY ONE BIOPHARMACEUTICALS INC is more than five percent of the total outstanding COMMON STOCK.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See attached Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

FMR LLC

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 3, 2023, by and on behalf of FMR LLC and its direct and indirect subsidiaries*
Date:	02/04/2026

Abigail P. Johnson

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 26, 2023, by and on behalf of Abigail P. Johnson**
Date:	02/04/2026

Comments accompanying signature: * This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 10, 2023, accession number: 0000315066-23-000003. ** This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 31, 2023, accession number: 0000315066-23-000038.

Exhibit Information

Please see Exhibit 99 for 13d-1(k) (1) agreement.

FAQ

What ownership stake does FMR LLC report in Day One Biopharmaceuticals (DAWN)?

FMR LLC reports beneficial ownership of 5,717,007.68 shares of Day One Biopharmaceuticals common stock, representing 5.6% of the class as of December 31, 2025. This stake gives FMR LLC significant institutional exposure to the company’s equity.

How much voting power does FMR LLC have in Day One Biopharmaceuticals (DAWN)?

FMR LLC reports sole voting power over 5,702,209.00 shares and no shared voting power in Day One Biopharmaceuticals. This figure indicates the number of shares for which FMR LLC can directly vote or direct the voting, reflecting its governance influence.

What role does Abigail P. Johnson have in the DAWN shareholding reported here?

Abigail P. Johnson is listed as a separate reporting person with sole dispositive power over 5,717,007.68 shares and no voting power. This reflects her control relationship with FMR LLC rather than direct trading activity, as described in the Schedule 13G/A filing.

Is FMR LLC’s ownership in Day One Biopharmaceuticals intended to influence control?

The filing states the securities were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control of Day One Biopharmaceuticals. It also notes they are not held in connection with any control-related transaction.

Who else may benefit from FMR LLC’s DAWN shareholdings?

The filing notes that one or more other persons have the right to receive dividends or proceeds from the sale of the Day One Biopharmaceuticals shares. However, no single such person has an interest in more than 5% of the total outstanding common stock.

What type of Schedule 13G filing did FMR LLC submit for DAWN?

FMR LLC submitted an Amendment No. 5 to Schedule 13G regarding Day One Biopharmaceuticals common stock. This amendment updates previously reported beneficial ownership information as of December 31, 2025, consistent with institutional investor reporting obligations under SEC rules.