Commodore discloses 6.4% stake in JATT II

JATT II Acquisition Corp. ownership disclosure: Commodore Capital LP, Commodore Capital Master LP, and managing partners report beneficial ownership of 500,000 ordinary shares of JATT II Acquisition Corp. as of April 17, 2026.

Rhea-AI Filing Summary

JATT II Acquisition Corp. ownership disclosure: Commodore Capital LP, Commodore Capital Master LP, and managing partners report beneficial ownership of 500,000 ordinary shares of JATT II Acquisition Corp. as of April 17, 2026. The filing states this represents 6.4% of the class based on 7,800,000 shares outstanding as of April 2, 2026, and attributes shared voting and dispositive power over the 500,000 shares to the named filers.

Insights

Institutional Ownership Analyst

Commodore reports a 6.4% beneficial stake via shared power over 500,000 shares.

Commodore Capital LP and Commodore Capital Master LP, with managing partners Michael Kramarz and Robert Egen Atkinson, are disclosed as having shared voting and dispositive authority over 500,000 ordinary shares of JATT II Acquisition Corp.

Ownership percentage is calculated using 7,800,000 shares reported as outstanding in a Rule 424(b)(4) Prospectus Supplement dated April 2, 2026. Subsequent filings may update position size or percentage.

Corporate Governance Specialist

Filing shows joint reporting and centralized investment discretion at the firm level.

The Firm is identified as investment manager to Commodore Master; the managing partners exercise investment discretion and the filing is a joint filing under Schedule 13G. Shared powers indicate the position is reported at the entity/fund and manager level rather than individual sole control.

Watch for any amended Schedule 13D/G filings if trading becomes active or control intentions change.

Key Figures

Position size: 500,000 shares Percent of class: 6.4% Shares outstanding: 7,800,000 shares

3 metrics

Position size 500,000 shares Beneficial ownership reported as of April 17, 2026

Percent of class 6.4% Calculated using 7,800,000 shares outstanding as of April 2, 2026

Shares outstanding 7,800,000 shares Reported in Rule 424(b)(4) Prospectus Supplement, April 2, 2026

Key Terms

beneficially own, shared dispositive power, Rule 424(b)(4) Prospectus Supplement

3 terms

beneficially own regulatory

"the Firm may be deemed to beneficially own an aggregate of 500,000 ordinary shares"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

shared dispositive power regulatory

"Shared Dispositive Power 500,000.00"

Rule 424(b)(4) Prospectus Supplement regulatory

"reported as issued and outstanding on April 2, 2026, in the Issuer's Rule 424(b)(4) Prospectus Supplement"

FAQ

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

What stake does Commodore Capital report in JATT II (JATT)?

Commodore reports beneficial ownership of 500,000 ordinary shares, representing 6.4% of the class based on 7,800,000 shares outstanding as of April 2, 2026. The position is reported as shared voting and dispositive power.

Who are the filers on the Schedule 13G for JATT?

Commodore Capital LP, Commodore Capital Master LP, and managing partners Michael Kramarz and Robert Egen Atkinson are listed as joint filers reporting the 500,000-share position on April 17, 2026.

How was the 6.4% ownership percentage calculated?

The filing uses 7,800,000 shares outstanding reported in a Rule 424(b)(4) Prospectus Supplement dated April 2, 2026, as the denominator to compute the 6.4% ownership percentage for 500,000 shares.

Does the filing show sole control of the shares?

No. The Schedule 13G discloses shared voting and shared dispositive power over the 500,000 shares rather than sole voting or sole dispositive authority by any single filer.

What addresses are listed for the filers in the Schedule 13G?

Commodore Capital LP and the two managing partners list 444 Madison Avenue, Floor 35, New York, NY 10022. Commodore Capital Master LP lists a Cayman Islands address at Ugland House, Grand Cayman.

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

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Accepted by SEC EDGAR 04/24/2026 - 04:48 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

JATT II Acquisition Corp.

(Name of Issuer)

ordinary shares, par value $0.0001 per share

(Title of Class of Securities)

G50765109

(CUSIP Number)

04/17/2026

(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): G50765109

1

Names of Reporting Persons

Commodore Capital LP

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 500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

500,000.00

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)

6.4 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): G50765109

1

Names of Reporting Persons

Commodore Capital Master LP

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

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

500,000.00

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)

6.4 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP Number(s): G50765109

1

Names of Reporting Persons

Robert Egen Atkinson

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 500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

500,000.00

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)

6.4 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): G50765109

1

Names of Reporting Persons

Michael Kramarz

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 500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

500,000.00

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)

6.4 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: JATT II Acquisition Corp.
(b)	Address of issuer's principal executive offices: 153 Central Avenue, C/O 56, Westfield, NEW JERSEY, 07091.
Item 2.
(a)	Name of person filing: Commodore Capital LP Commodore Capital Master LP Robert Egen Atkinson Michael Kramarz Each a "Filer."
(b)	Address or principal business office or, if none, residence: The address for Commodore Capital LP, Robert Egen Atkinson, and Michael Kramarz is 444 Madison Avenue, Floor 35, New York, NY 10022. The address for Commodore Capital Master LP is c/o Maples Corporate Services Limited, Ugland House, South Church Street, PO Box 309, Grand Cayman KY1-1104, Cayman Islands.
(c)	Citizenship: See Item 4 of the cover page for each Filer.
(d)	Title of class of securities: ordinary shares, par value $0.0001 per share
(e)	CUSIP Number(s): G50765109
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: See Item 9 of the cover page for each Filer. This report on Schedule 13G is being filed by Commodore Capital LP (the "Firm"), Commodore Capital Master LP ("Commodore Master"), Michael Kramarz, and Robert Egen Atkinson. The Firm is the investment manager to Commodore Master. As of April 17, 2026, the Firm may be deemed to beneficially own an aggregate of 500,000 ordinary shares, par value $0.0001 per share (the "Ordinary Shares") of JATT II Acquisition Corp. (the "Issuer"). The Firm, as the investment manager to Commodore Master, may be deemed to beneficially own these securities. Michael Kramarz and Robert Egen Atkinson are the managing partners of the Firm and exercise investment discretion with respect to these securities. Ownership percentages are based on 7,800,000 shares of Ordinary Shares reported as issued and outstanding on April 2, 2026, in the Issuer's Rule 424(b)(4) Prospectus Supplement filed with the Securities and Exchange Commission on April 17, 2026.
(b)	Percent of class: See Item 11 of the cover page for each Filer.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See Item 5 of the cover page for each Filer.
	(ii) Shared power to vote or to direct the vote: See Item 6 of the cover page for each Filer.
	(iii) Sole power to dispose or to direct the disposition of: See Item 7 of the cover page for each Filer.
	(iv) Shared power to dispose or to direct the disposition of: See Item 8 of the cover page for each Filer.
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.
	Not Applicable
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 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.

Commodore Capital LP

Signature:	Michael Kramarz
Name/Title:	Managing Partner
Date:	04/24/2026

Commodore Capital Master LP

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	04/24/2026

Robert Egen Atkinson

Signature:	Robert Egen Atkinson
Name/Title:	Authorized Signatory
Date:	04/24/2026

Michael Kramarz

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	04/24/2026

Exhibit Information

Exhibit 1: Joint Filing Agreement