JATT III gets RA Capital 5.1% passive stake

RA Capital entities and two managers report beneficial ownership of 5.1% of JATT III Acquisition Corp’s ordinary shares on a Schedule 13G.

Rhea-AI Filing Summary

JATT III Acquisition Corp (JTTT) is the subject of a Schedule 13G reporting that RA Capital Healthcare Fund, L.P. directly holds 450,000 ordinary shares, with RA Capital Management, L.P., Peter Kolchinsky, and Rajeev Shah reported as additional filing persons. These shares represent 5.1% of the ordinary shares outstanding, based on 8,859,000 ordinary shares outstanding as of August 27, 2026. The reporting persons have shared voting and shared dispositive power over 450,000 shares and report their holdings on a beneficial ownership basis under Section 13(d), while including customary disclaimers of beneficial ownership outside that context.

Key Figures

Ordinary shares beneficially owned: 450,000 shares Percent of class beneficially owned: 5.1% Ordinary shares outstanding: 8,859,000 shares +3 more

6 metrics

Ordinary shares beneficially owned 450,000 shares Ordinary shares of JATT III Acquisition Corp reported by each reporting person

Percent of class beneficially owned 5.1% Ownership percentage of JATT III Acquisition Corp ordinary shares

Ordinary shares outstanding 8,859,000 shares Shares outstanding as of August 27, 2026, per final prospectus

Sole voting power 0 shares Shares over which each reporting person has sole voting power

Shared voting power 450,000 shares Shares over which the reporting persons have shared voting power

Shared dispositive power 450,000 shares Shares over which the reporting persons have shared dispositive power

Key Terms

beneficial owner, Section 13(d), Sole Voting Power, Shared Dispositive Power, +2 more

6 terms

beneficial owner financial

"may be deemed a beneficial owner, for purposes of Section 13(d)"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

Section 13(d) regulatory

"for purposes of Section 13(d) of the Act, of any securities"

A Section 13(d) filing is a public disclosure required under U.S. securities law when a person or group acquires more than 5% of a company’s registered equity and may influence control. The filer must report who owns the shares, how they were acquired, and any plans or intentions for the company, so the market and other shareholders can see if a large buyer is attempting a takeover or other strategic move. Think of it like a formal announcement that someone has crossed a threshold and is showing their hand.

Sole Voting Power financial

"5 | Sole Voting Power 0.00 6 | Shared Voting Power 450,000.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

Shared Dispositive Power financial

"8 | Shared Dispositive Power 450,000.00 9 450,000.00"

investment adviser financial

"RA Capital serves as investment adviser for the Fund"

An investment adviser is a person or firm that professionally manages money and gives recommendations about buying, selling, or holding investments. Like a financial coach or guide, they have a legal duty to act in a client's best financial interest, so their advice, fees and potential conflicts can directly affect returns and risk — making their role important for investors who want informed, accountable help with portfolios.

Schedule 13G regulatory

"filed with the (the "SEC") on August 26, 2026"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

FAQ

What ownership stake in JATT III Acquisition Corp (JTTT) is reported on this Schedule 13G?

The filing reports beneficial ownership of 450,000 ordinary shares of JATT III Acquisition Corp, representing 5.1% of the outstanding ordinary shares based on 8,859,000 shares outstanding as of August 27, 2026.

Who are the reporting persons on the JTTT Schedule 13G?

The reporting persons are RA Capital Management, L.P., RA Capital Healthcare Fund, L.P., Peter Kolchinsky, and Rajeev Shah. Together they are referred to as the “Reporting Persons,” and they file with customary disclaimers regarding group status and beneficial ownership.

How many JTTT shares does the RA Capital Healthcare Fund directly hold?

The RA Capital Healthcare Fund, L.P. directly holds 450,000 ordinary shares of JATT III Acquisition Corp. Voting and investment authority over these securities has been delegated to RA Capital Management, L.P. under the arrangements described in the filing.

What percentage of JTTT’s class do the reported holdings represent?

The reported 450,000 ordinary shares represent 5.1% of JATT III Acquisition Corp’s ordinary shares. This percentage is calculated using 8,859,000 ordinary shares outstanding as of August 27, 2026, as stated in the company’s final prospectus.

What voting and dispositive powers over JTTT shares are reported by RA Capital and related persons?

The reporting persons state 0 shares with sole voting or dispositive power and 450,000 shares with shared voting and shared dispositive power over JATT III Acquisition Corp’s ordinary shares, as reflected in the cover page ownership fields.

How is beneficial ownership over JTTT shares structured among the RA Capital entities and individuals?

The Fund directly holds the 450,000 shares. RA Capital Management, L.P. serves as investment adviser and may be deemed a beneficial owner. As managers of RA Capital, Peter Kolchinsky and Rajeev Shah may also be deemed beneficial owners, while all include disclaimers of beneficial ownership outside Section 13(d).

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

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Available on EDGAR 09/03/2026 - 05:38 PM Accepted by SEC EDGAR 09/03/2026 - 05:11 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

JATT III Acquisition Corp

(Name of Issuer)

Ordinary Shares, par value $0.0001 per share

(Title of Class of Securities)

G5080G109

(CUSIP Number)

08/27/2026

(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): G5080G109

1

Names of Reporting Persons

RA 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 450,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 450,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

450,000.00

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)

5.1 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): G5080G109

1

Names of Reporting Persons

Peter Kolchinsky

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 450,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 450,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

450,000.00

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)

5.1 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): G5080G109

1

Names of Reporting Persons

Rajeev Shah

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 450,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 450,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

450,000.00

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)

5.1 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): G5080G109

1

Names of Reporting Persons

RA Capital Healthcare Fund, 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 450,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 450,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

450,000.00

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)

5.1 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: JATT III Acquisition Corp
(b)	Address of issuer's principal executive offices: 153 Central Avenue, C/O 56, Westfield, NJ, 07091.
Item 2.
(a)	Name of person filing: The names of the persons filing this report (collectively, the "Reporting Persons") are: RA Capital Management, L.P. ("RA Capital") Peter Kolchinsky ("Dr. Kolchinsky") Rajeev Shah ("Mr. Shah") RA Capital Healthcare Fund, L.P. (the "Fund") The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G.
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of the Reporting Persons is: c/o RA Capital Management, L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116
(c)	Citizenship: RA Capital and the Fund are Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.
(d)	Title of class of securities: Ordinary Shares, par value $0.0001 per share
(e)	CUSIP Number(s): G5080G109
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: Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of ordinary shares of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The Fund directly holds 450,000 ordinary shares of the Issuer. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund's portfolio, including the ordinary shares of the Issuer reported herein. Because the Fund has divested voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days' notice, the Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13G shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.
(b)	Percent of class: Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentages of ordinary shares of the Issuer beneficially owned by such Reporting Person and is incorporated herein by reference. Such percentage is based upon 8,859,000 ordinary shares outstanding as of August 27, 2026, as reported in the Issuer's final prospectus dated August 25, 2026 filed with the Securities and Exchange Commission (the "SEC") on August 26, 2026.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person 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.
	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.

RA Capital Management, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By Peter Kolchinsky, Authorized Signatory
Date:	09/03/2026

Peter Kolchinsky

Signature:	/s/ Peter Kolchinsky
Name/Title:	Peter Kolchinsky
Date:	09/03/2026

Rajeev Shah

Signature:	/s/ Rajeev Shah
Name/Title:	Rajeev Shah
Date:	09/03/2026

RA Capital Healthcare Fund, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By RA Capital Healthcare Fund GP, LLC, its General Partner, By Peter Kolchinsky, Manager
Date:	09/03/2026

Exhibit Information

Exhibit 99.1 Joint Filing Agreement