Cabaletta Bio: T. Rowe Price reports 8% ownership

Cabaletta Bio, Inc. (CABA) is the issuer named in an amended ownership report from T. Rowe Price Investment Management, Inc., which reports beneficial ownership of 17,250,098 common shares, or 8.0%, as of September 30, 2026.

Available on EDGAR 11/06/2026 - 10:59 AM EST Accepted by SEC EDGAR 11/06/2026 - 10:58 AM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Cabaletta Bio, Inc. (CABA) is the issuer named in an amended ownership report from T. Rowe Price Investment Management, Inc., which reports beneficial ownership of 17,250,098 common shares, or 8.0%, as of September 30, 2026. The manager reports sole voting power over 17,186,616 shares and sole dispositive power over 17,250,098 shares; shared voting and dispositive power are each reported as zero. T. Rowe Price Investment Management states that the report is not an admission that it is the beneficial owner and expressly denies beneficial ownership.

Key Figures

Beneficial ownership reported: 17,250,098 shares Class ownership reported: 8.0% Sole voting power: 17,186,616 shares +3 more

6 metrics

Beneficial ownership reported 17,250,098 shares As of September 30, 2026

Class ownership reported 8.0% As of September 30, 2026

Sole voting power 17,186,616 shares As of September 30, 2026

Shared voting power 0 shares As of September 30, 2026

Sole dispositive power 17,250,098 shares As of September 30, 2026

Shared dispositive power 0 shares As of September 30, 2026

Key Terms

beneficial ownership, Sole Voting Power, Sole Dispositive Power

3 terms

beneficial ownership regulatory

"Amount beneficially owned"

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.

Sole Voting Power regulatory

"Sole Voting Power 17,186,616.00"

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.

Sole Dispositive Power regulatory

"Sole Dispositive Power 17,250,098.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

FAQ

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

How many CABA shares does T. Rowe Price Investment Management report?

It reports beneficial ownership of 17,250,098 common shares, or 8.0%, as of September 30, 2026. The manager also expressly denies that it is the beneficial owner.

How much voting power does T. Rowe Price Investment Management report over CABA shares?

It reports sole voting power over 17,186,616 shares and sole dispositive power over 17,250,098 shares. Shared voting power and shared dispositive power are each reported as zero.

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

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 5)

CABALETTA BIO INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

12674W109

(CUSIP Number)

09/30/2026

(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): 12674W109

1

Names of Reporting Persons

T. Rowe Price Investment Management, Inc.

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

MARYLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 17,186,616.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 17,250,098.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

17,250,098.00

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)

8.0 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: CABALETTA BIO INC
(b)	Address of issuer's principal executive offices: 2929 ARCH STREET, SUITE 600, PHILADELPHIA, PA, 19104
Item 2.
(a)	Name of person filing: T. Rowe Price Investment Management, Inc.
(b)	Address or principal business office or, if none, residence: 1307 Point Street, Baltimore, MD 21231
(c)	Citizenship: Maryland
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 12674W109
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: 17250098
(b)	Percent of class: 8.0 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 17186616
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 17250098
	(iv) Shared power to dispose or to direct the disposition of: 0
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 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. T. Rowe Price Investment Management, Inc. hereby declares and affirms that the filing of Schedule 13G shall not be construed as an admission that Price Investment Management is the beneficial owner of the securities referred to, which beneficial ownership is expressly denied.

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.

T. Rowe Price Investment Management, Inc.

Signature:	Ellen York
Name/Title:	Vice President
Date:	11/06/2026