FMR LLC holds 23,639.69 shares in Day One Biopharmaceuticals (NASDAQ: DAWN) amendment

Rhea-AI Filing Summary

Day One Biopharmaceuticals Inc. Schedule 13G/A reports that FMR LLC (with Abigail P. Johnson listed) beneficially owns 23,639.69 shares of common stock, representing 0.0% of the class as reported. The filing is an amendment and is signed under powers of attorney dated in 2023.

Key Figures

Beneficial ownership: 23,639.69 shares Percent of class: 0.0% CUSIP: 23954D109 +2 more

5 metrics

Beneficial ownership 23,639.69 shares Amount beneficially owned reported on Schedule 13G/A

Percent of class 0.0% Percent of class reported for 23,639.69 shares

CUSIP 23954D109 Identifier for Day One Biopharmaceuticals common stock on the cover

Reporting date 03/31/2026 Date shown near the cover/page header

Signature date 04/06/2026 Date signatures for the amendment were provided

Key Terms

Schedule 13G/A, Beneficially owned, Power of Attorney

3 terms

Schedule 13G/A regulatory

"Item 1. | (a) | Name of issuer: DAY ONE BIOPHARMACEUTICALS INC"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 23639.69"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Power of Attorney legal

"Signed: | Signature: | Stephanie J. Brown ... Power of Attorney effective as of January 3, 2023"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/07/2026 - 01:22 PM Learn about SEC filing dates

FAQ

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

FMR LLC beneficially owns 23,639.69 shares of Day One Biopharmaceuticals common stock, reported as 0.0% of the class. The Schedule 13G/A lists sole dispositive power for that amount and shows voting/dispositive breakdowns on the cover data.

Who else is named in the DAWN Schedule 13G/A amendment?

Abigail P. Johnson is named alongside FMR LLC; the filing shows her with 23,639.69 shares of dispositive power. Signatures were provided under powers of attorney on behalf of both FMR LLC and Abigail P. Johnson dated in 2023.

Does the filing indicate any person holds more than 5% of DAWN stock?

No other person’s interest exceeds 5% according to the filing. The Schedule 13G/A states that no one other person's interest in the common stock is more than five percent of total outstanding common stock.

When was the Schedule 13G/A for DAWN signed and amended?

Signatures are dated April 6, 2026 on this amendment. The cover shows a reporting date of 03/31/2026 and references powers of attorney effective in January 2023 incorporated by reference in the exhibit information.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 6)

DAY ONE BIOPHARMACEUTICALS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

23954D109

(CUSIP Number)

03/31/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 4,883.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 23,639.69
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

23,639.69

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)

0.0 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP Number(s): 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 23,639.69
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

23,639.69

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)

0.0 %

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: 1800 SIERRA POINT PARKWAY,SUITE 200,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.:
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: 23639.69
(b)	Percent of class: 0.0 %
(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: 23639.69
	(iv) Shared power to dispose or to direct the disposition of: 0.00
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
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:	04/06/2026

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:	04/06/2026

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.