Adage Capital discloses 7.75% KPET Ultra Paceline (KPET) ownership in 13G

Rhea-AI Filing Summary

Adage Capital Management, L.P. and related principals reported a significant ownership stake in KPET Ultra Paceline Corporation. Through Adage Capital Partners, L.P., the group beneficially owns 1,800,000 Class A Ordinary Shares, par value $0.0001 per share, representing 7.75% of this class. This percentage is based on 23,235,000 Class A Ordinary Shares outstanding as of May 13, 2026, as reported by the company. The shares are held with shared voting and shared dispositive power and no sole voting or dispositive power for any reporting person. Adage Capital Management, L.P., and its managing members Robert Atchinson and Phillip Gross report this position in their capacities as investment manager and controlling persons of related entities.

Key Figures

Beneficially owned shares: 1,800,000 Class A Ordinary Shares Ownership percentage: 7.75% Shares outstanding: 23,235,000 Class A Ordinary Shares +4 more

7 metrics

Beneficially owned shares 1,800,000 Class A Ordinary Shares Shares of KPET beneficially owned by the reporting persons

Ownership percentage 7.75% Portion of KPET Class A Ordinary Shares beneficially owned

Shares outstanding 23,235,000 Class A Ordinary Shares KPET Class A Ordinary Shares outstanding as of May 13, 2026

Sole voting power 0 shares Sole voting power reported by each reporting person

Shared voting power 1,800,000 shares Shared voting power over KPET Class A Ordinary Shares

Par value $0.0001 per share Par value of KPET Class A Ordinary Shares

CUSIP G53157106 CUSIP for KPET Class A Ordinary Shares

Key Terms

beneficial ownership, shared voting power, shared dispositive power, Investment Company Act of 1940, +1 more

5 terms

beneficial ownership financial

"The percentage set forth in this is calculated based upon an aggregate of 23,235,000 shares"

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.

shared voting power financial

"6 | Shared Voting Power 1,800,000.00 7 | Sole Dispositive Power 0.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"8 | Shared Dispositive Power 1,800,000.00 9 1,800,000.00"

Investment Company Act of 1940 regulatory

"A listing of the shareholders of an investment company registered under the Investment Company Act of 1940"

A U.S. federal law that sets the rulebook for pooled investment vehicles such as mutual funds, exchange-traded funds and similar money managers, requiring them to register with regulators, disclose holdings and fees, limit conflicts of interest, and follow governance standards. It matters to investors because these protections and transparency rules act like a referee and scoreboard, helping people compare funds, trust that managers follow fair practices, and spot hidden costs or risks.

Class A Ordinary Shares financial

"Title of class of securities: Class A Ordinary Shares, par value $0.0001 per share"

Class A ordinary shares are a type of ownership stake in a company that typically grants voting rights to shareholders, allowing them to have a say in important company decisions. They often come with priority in receiving dividends or profits, making them attractive to investors seeking influence and potential income. These shares help distinguish different levels of ownership and rights within a company's stock structure.

FAQ

How much of KPET does Adage Capital Management own according to this Schedule 13G?

Adage Capital Management and related reporting persons beneficially own 1,800,000 Class A Ordinary Shares of KPET, representing 7.75% of the Class A Ordinary Shares based on 23,235,000 shares outstanding as of May 13, 2026.

Who are the reporting persons on the KPET (KPET) Schedule 13G filing?

The reporting persons are Adage Capital Management, L.P., and individuals Robert Atchinson and Phillip Gross, who are managing members of entities that control the investment manager to Adage Capital Partners, L.P., which directly holds the KPET shares.

What type of KPET securities are reported in this Schedule 13G for KPET?

The filing covers Class A Ordinary Shares of KPET Ultra Paceline Corporation, each with a par value of $0.0001 per share, identified by CUSIP G53157106.

What voting and dispositive powers over KPET shares are reported in this KPET Schedule 13G?

Each reporting person reports 0 shares with sole voting or dispositive power and 1,800,000 shares with shared voting and shared dispositive power, reflecting coordinated control over the KPET stake through related entities.

On what share count is the 7.75% ownership in KPET (KPET) based?

The 7.75% ownership of KPET is calculated using 23,235,000 Class A Ordinary Shares outstanding as of May 13, 2026, as reported in KPET’s Quarterly Report for the quarter ended March 31, 2026.

Where are the KPET reporting persons based in the KPET Schedule 13G?

The business address for all reporting persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116, while KPET Ultra Paceline Corporation’s principal executive offices are located in Sioux Falls, South Dakota.

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Available on EDGAR 08/12/2026 - 12:04 PM Accepted by SEC EDGAR 08/12/2026 - 12:03 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

KPET Ultra Paceline Corporation

(Name of Issuer)

Class A Ordinary Shares, par value $0.0001 per share

(Title of Class of Securities)

G53157106

(CUSIP Number)

06/30/2026

(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): G53157106

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 1,800,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,800,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,800,000.00

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)

7.75 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): G53157106

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 1,800,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,800,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,800,000.00

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)

7.75 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): G53157106

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 1,800,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,800,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,800,000.00

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)

7.75 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: KPET Ultra Paceline Corporation
(b)	Address of issuer's principal executive offices: 5109 S. Broadband Lane, Sioux Falls, SD 57108
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 Class A ordinary shares, par value $0.0001 per share ("Class A Ordinary Shares") of KPET Ultra Paceline Corporation, a Cayman Islands exempted company (the "Company") 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, L.L.C., a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Class A Ordinary Shares 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 Class A Ordinary Shares 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.
(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: Class A Ordinary Shares, par value $0.0001 per share
(e)	CUSIP Number(s): G53157106
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 23,235,000 shares of Class A Ordinary Shares outstanding as of May 13, 2026, as reported in the Company's Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2026, filed with the Securities and Exchange Commission on May 13, 2026.
(b)	Percent of class: 7.75%
(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, L.L.C., its General Partner, By: Robert Atchinson, its Managing Member
Date:	08/12/2026

Robert Atchinson

Signature:	/s/ Robert Atchinson
Name/Title:	Robert Atchinson, individually
Date:	08/12/2026

Phillip Gross

Signature:	/s/ Phillip Gross
Name/Title:	Phillip Gross, individually
Date:	08/12/2026

Exhibit Information

Exhibit 99.1: Joint Filing Agreement