Centessa Pharmaceuticals plc Schedule 13G/A Amendment discloses that Adage Capital and related reporting persons beneficially own 8,925,010 ordinary shares, representing 5.77% of the class. The percentage is calculated using 154,568,531 ordinary shares outstanding as of March 17, 2026.
The statement clarifies reporting relationships among Adage Capital Management, L.P., Adage Capital Partners entities, Robert Atchinson and Phillip Gross and is signed on May 13, 2026.
Positive
None.
Negative
None.
Insights
Adage reports a passive >5% stake in Centessa.
Adage Capital's filing shows 8,925,010 shares beneficially owned, equal to 5.77% of the 154,568,531 ordinary shares outstanding as of March 17, 2026. The position meets the Schedule 13G threshold for disclosure.
Timing and voting/dispositive powers are disclosed as shared holdings; further activity will appear in subsequent filings if the ownership or intent changes.
Filing clarifies control pathways and signature attribution.
The amendment maps ownership through Adage entities and names Robert Atchinson and Phillip Gross as managing members involved in reporting. The cover rows show shared voting and dispositive power of 8,925,010 shares.
Signatures dated May 13, 2026 complete the amendment; any shifts in voting intent or greater-than-5% accumulation would require updated disclosures.
Key Figures
Shares beneficially owned:8,925,010 sharesPercent of class:5.77%Shares outstanding:154,568,531 shares
3 metrics
Shares beneficially owned8,925,010 sharesreported by Adage as beneficially owned
Percent of class5.77%percentage of class based on outstanding shares as of <date>March 17, 2026</date>
Shares outstanding154,568,531 sharesordinary shares outstanding as of <date>March 17, 2026</date> (source: company's Form 10-K)
Key Terms
Schedule 13G/A, American Depositary Shares (ADSs), Beneficially owned
3 terms
Schedule 13G/Aregulatory
"This statement is filed by: (i) Adage Capital Management, L.P."
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.
American Depositary Shares (ADSs)market
"Each ADS represents one Ordinary Share"
A U.S.-listed certificate that stands for a specific number of shares in a non‑U.S. company held by a U.S. bank, making the foreign stock tradable on American exchanges in dollars. Think of it like a local voucher that represents ownership of an overseas product — it lets U.S. investors buy and sell foreign companies without handling foreign currency or foreign brokerage accounts, but it can affect dividends, voting rights, fees, liquidity and exposure to currency and regulatory differences.
Beneficially ownedregulatory
"Amount beneficially owned: The information required by Item 4(a)"
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.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 3)
Centessa Pharmaceuticals plc
(Name of Issuer)
Ordinary shares, nominal value 0.002 GBP per share
(Title of Class of Securities)
152309100
(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):
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
8,925,010.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,925,010.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,925,010.00
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)
5.77 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
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
8,925,010.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,925,010.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,925,010.00
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)
5.77 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
CUSIP Number(s):
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
8,925,010.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,925,010.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,925,010.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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 0.002 GBP 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 154,568,531 Ordinary Shares outstanding as of March 17, 2026 as reported in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the Securities and Exchange Commission on March 31, 2026.
(b)
Percent of class:
5.77%
(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.
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.
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
What stake does Adage Capital report in Centessa (CNTA)?
Adage Capital and related reporting persons report beneficial ownership of 8,925,010 ordinary shares, equal to 5.77% of the class based on 154,568,531 shares outstanding as of March 17, 2026.
How was the 5.77% ownership percentage calculated for CNTA?
The percentage uses an outstanding share base of 154,568,531 ordinary shares as of March 17, 2026, as stated in the company's Form 10-K, with Adage's beneficial holding of 8,925,010 shares as reported in the amendment.
Who are the named reporting persons in the Schedule 13G/A for CNTA?
The filing names Adage Capital Management, L.P., Adage-related entities and individuals Robert Atchinson and Phillip Gross as reporting persons, with roles described as managing members and general partner representatives.
When was the Schedule 13G/A amendment for CNTA signed?
The amendment (Amendment No. 3) bears signatures dated May 13, 2026, reflecting the reporting persons' attestation to the disclosed beneficial ownership and related cover-page entries.
Does the filing indicate sole voting or dispositive power for Adage?
The cover-page rows show 0 sole voting and dispositive power and 8,925,010 shared voting and dispositive power, indicating shared control over the disclosed shares among the reporting persons.
