Adage Capital Discloses 6.29% Stake in Centessa (8.4M Shares)

Adage Capital Management, together with principals Robert Atchinson and Phillip Gross, reports beneficial ownership of 8,403,000 ordinary shares of Centessa Pharmaceuticals, representing 6.29% of the outstanding class based on 133,618,774 shares.

Rhea-AI Filing Summary

Adage Capital Management, together with principals Robert Atchinson and Phillip Gross, reports beneficial ownership of 8,403,000 ordinary shares of Centessa Pharmaceuticals, representing 6.29% of the outstanding class based on 133,618,774 shares. The shares are ordinary shares underlying ADSs traded under ticker CNTA. The filing shows no sole voting or dispositive power — all voting and dispositive rights are reported as shared — and includes a certification that the securities are held in the ordinary course of business and not for the purpose of changing control. The statement contains ownership details and reporting person roles but does not disclose any transaction terms or plans.

Positive

• Adage Capital and named principals beneficially own 8,403,000 shares, representing a material 6.29% stake in Centessa.
• The filing includes a certification that the holdings were acquired and are held in the ordinary course of business and not to change control.

Negative

• No sole voting or dispositive power is reported; all 8,403,000 shares are disclosed as subject to shared voting and dispositive authority.

Insights

Financial Analyst

TL;DR Institutional stake of 6.29% is materially sized but reported with shared control and no stated intent to change control.

Adage Capital and the named principals report beneficial ownership of 8,403,000 shares, equal to 6.29% of the class, calculated on an outstanding base of 133,618,774 shares. For investors, a >5% disclosure is material because it signals a meaningful economic position, but the filing also makes clear that voting and dispositive powers are shared and the holders certify the position is not intended to effect control. Absent additional transactions or statements of intent, this remains a disclosure of ownership rather than an activist or control move.

Corporate Governance Expert

TL;DR The filing documents a sizeable passive stake with shared voting/dispositive power and an explicit certification against control-seeking.

The Schedule 13G/A identifies Adage Capital Management as the reporting entity and names Robert Atchinson and Phillip Gross as related reporting persons with managerial roles in the reporting structure. All 8,403,000 shares are reported with shared voting and dispositive authority, and the signatory certification states the securities are held in the ordinary course and not to influence control. From a governance perspective, the filing increases transparency about substantial ownership while signaling an absence of immediate governance actions or control initiatives.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many Centessa (CNTA) shares does Adage Capital report owning?

The filing reports 8,403,000 ordinary shares beneficially owned by Adage Capital and the named reporting persons.

What percentage of CNTA does the reported stake represent?

The reported position represents 6.29% of the outstanding ordinary shares, based on 133,618,774 shares outstanding.

Does Adage Capital claim voting or dispositive control over the CNTA shares?

No. The filing shows 0 sole voting power and 0 sole dispositive power, with 8,403,000 shares reported as shared voting and dispositive power.

Are the Centessa shares held to seek control according to the filing?

The certification in the filing states the securities are held in the ordinary course of business and not for the purpose of changing or influencing control of the issuer.

Under what structure are the shares held by the reporting persons?

The statement indicates the position is held by Adage Capital Management as investment manager with related reporting persons described in management roles; specific ownership is reported on behalf of the investment entities named in the filing.

Are the reported shares ordinary shares or ADSs for CNTA?

The filing clarifies the reported holdings are ordinary shares underlying American Depositary Shares (ADSs) that trade under ticker CNTA.

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

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Accepted by SEC EDGAR 08/12/2025 - 09:01 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Centessa Pharmaceuticals plc

(Name of Issuer)

Ordinary shares, nominal value 0.002 GBP per share

(Title of Class of Securities)

152309100

(CUSIP Number)

06/30/2025

(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. 152309100

1

Names of Reporting Persons

Adage Capital Management, L.P.

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 0.00
6	Shared Voting Power 8,403,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,403,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,403,000.00

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)

6.29 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP No. 152309100

1

Names of Reporting Persons

Robert Atchinson

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 8,403,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,403,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,403,000.00

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)

6.29 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP No. 152309100

1

Names of Reporting Persons

Phillip Gross

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 8,403,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,403,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,403,000.00

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)

6.29 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Centessa Pharmaceuticals plc
(b)	Address of issuer's principal executive offices: 3rd Floor, 1 Ashley Road, Altrincham, Cheshire WA14 2DT, United Kingdom
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Adage Capital Management, L.P., a Delaware limited partnership ("ACM"), as the investment manager of Adage Capital Partners, L.P., a Delaware limited partnership ("ACP"), with respect to the American Depositary Shares, each representing one ordinary share, nominal value euro 0.002 per share ("Ordinary Shares") of Centessa Pharmaceuticals PLC, a limited liability company incorporated under the laws of England and Wales (the "Company") underlying the ADSs (as defined below) directly held by ACP; (ii) Robert Atchinson ("Mr. Atchinson"), as (1) managing member of Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), managing member of Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), general partner of ACP and (2) managing member of Adage Capital Partners LLC, a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Ordinary Shares underlying the ADSs directly held by ACP; and (iii) Phillip Gross ("Mr. Gross"), as (1) managing member of ACA, managing member of ACPGP and (2) managing member of ACPLLC, general partner of ACM, with respect to the Ordinary Shares underlying the ADSs directly held by ACP. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein. There is no CUSIP number assigned to the Ordinary Shares. The CUSIP number 152309100 has been assigned to the American Depositary Shares ("ADSs") of the Company, which are quoted on Nasdaq under the symbol "CNTA." Each ADS represents one Ordinary Share.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116.
(c)	Citizenship: ACM is a limited partnership organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States.
(d)	Title of class of securities: Ordinary shares, nominal value 0.002 GBP per share
(e)	CUSIP No.: 152309100
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: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 133,618,774 Ordinary Shares outstanding as of May 1, 2025 as reported in the Company's Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2025, filed with the Securities and Exchange Commission on May 14, 2025.
(b)	Percent of class: 6.29%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
Item 5.	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. See Item 2(a).
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
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.

Adage Capital Management, L.P.

Signature:	/s/ Robert Atchinson
Name/Title:	By: Adage Capital Partners LLC, its General Partner, By: Robert Atchinson, its Managing Member
Date:	08/12/2025

Robert Atchinson

Signature:	/s/ Robert Atchinson
Name/Title:	Robert Atchinson, individually
Date:	08/12/2025

Phillip Gross

Signature:	/s/ Phillip Gross
Name/Title:	Phillip Gross, individually
Date:	08/12/2025