[SCHEDULE 13G] Cabaletta Bio, Inc. SEC Filing

Rhea-AI Filing Summary

Alyeska entities and Anand Parekh report shared beneficial ownership of 8,904,367 shares of Cabaletta Bio common stock, representing 9.9% of the outstanding class. The reported position reflects 4,800,000 directly held shares plus warrants exercisable only to the extent permitted under their terms so that post-exercise ownership does not exceed 9.9% of the company's outstanding common stock. The filing notes the warrant cap limits actual exercisable shares to 4,104,367 under the agreement and that the percentage calculation uses the issuer's prospectus share count of 89,943,101. The reporting parties filed a joint statement and certify the holdings are in the ordinary course of business.

Positive

• Material passive stake of 8,904,367 shares (9.9%) signals significant investor interest without asserting control
• Warrants include an exercise cap that limits post-exercise ownership to 9.9%, reducing immediate dilution or control shifts
• Joint filing clarifies coordination and assigns responsibility for timely amendments among reporting parties

Negative

• No sole voting or dispositive power reported, indicating the holders do not unilaterally control voting outcomes
• Position is just below common thresholds (9.9%), which may limit certain regulatory or shareholder-triggered actions compared with a 10%+ stake

Insights

Financial Analyst

TL;DR: A 9.9% position with capped warrants is material but non-controlling; monitor potential future exercises and disclosures.

The combined position of 8,904,367 shares equals 9.9% of the outstanding class as reported, which is a size that can attract investor attention while remaining below common 10% thresholds that often trigger additional regulatory or strategic scrutiny. The structure—4.8 million shares plus warrants limited by a 9.9% cap—means actual dilution or additional voting exposure is contractually constrained. From a capital-market perspective, this is a meaningful passive stake rather than an asserted control position, based on the certification that holdings are in the ordinary course of business.

Corporate Governance Expert

TL;DR: Reporting indicates coordinated ownership but no sole voting or dispositive power; governance impact appears limited today.

The filing shows zero sole voting or dispositive power and 100% of the reported authority is shared among the reporting persons, which signals joint control over voting decisions of the disclosed stake. The warrant terms that cap exercise to maintain a 9.9% post-exercise stake reduce the likelihood of an abrupt change in control from these parties alone. The joint filing and certification language are standard; however, investors should expect future amendments if the parties seek to change the extent of their position or coordination.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

CABALETTA BIO, INC.

(Name of Issuer)

Common Stock, par value $0.00001 per share

(Title of Class of Securities)

12674W109

(CUSIP Number)

06/30/2025

(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)

SCHEDULE 13G

CUSIP No. 12674W109

1

Names of Reporting Persons

Alyeska Investment Group, 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 8,904,367.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,904,367.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,904,367.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No. 12674W109

1

Names of Reporting Persons

Alyeska Fund GP, LLC

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 8,904,367.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,904,367.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,904,367.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 12674W109

1

Names of Reporting Persons

Anand Parekh

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 8,904,367.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,904,367.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,904,367.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

IN

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: (i) Alyeska Investment Group, L.P. (ii) Alyeska Fund GP, LLC (iii) Anand Parekh
(b)	Address or principal business office or, if none, residence: (i) 77 West Wacker Drive, 7th Floor, Chicago, IL 60601 (ii) 77 West Wacker Drive, 7th Floor, Chicago, IL 60601 (iii) 77 West Wacker Drive, 7th Floor, Chicago, IL 60601
(c)	Citizenship: (i) Alyeska Investment Group, L.P. - Delaware (ii) Alyeska Fund GP, LLC - Delaware (iii) Anand Parekh - United States of America
(d)	Title of class of securities: Common Stock, par value $0.00001 per share
(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: 8,904,367
(b)	Percent of class: 9.9%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 8,904,367
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 8,904,367
Item 5.	Ownership of 5 Percent or Less of a Class.
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.

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.

Alyeska Investment Group, L.P.

Signature:	Jason Bragg
Name/Title:	Jason Bragg | Chief Financial Officer
Date:	08/14/2025

Alyeska Fund GP, LLC

Signature:	Jason Bragg
Name/Title:	Jason Bragg | Chief Financial Officer
Date:	08/14/2025

Anand Parekh

Signature:	Anand Parekh
Name/Title:	Anand Parekh | Self
Date:	08/14/2025

Exhibit Information

Item 4. Ownership: The reporting persons are the beneficial owners of 4,800,000 shares of Common Stock and held warrants to purchase 4,500,000 shares of the Issuer's Common Stock (the "Warrants"). However, per their terms, the Warrants can only be exercised into such number of shares that would constitute 9.9% of the total number of Common Stock of the Issuer outstanding immediately after giving effect to the issuance of Common Stock upon exercise of this Warrant by the Holder. Accordingly, as of June 30, 2025 the reporting persons may only exercise up to 4,104,367 Ordinary Shares under the Warrant Agreement, and as such, is reporting beneficial ownership of only such number of shares. The percentage calculation assumes that there are currently 89,943,101 outstanding Common Stock of the Issuer, based on the Issuer's Prospectus filed with the Securities and Exchange Commission on June 12, 2025. JOINT FILING STATEMENT PURSUANT TO RULE 13d-1(k) The undersigned acknowledge and agree that the foregoing statement on SCHEDULE 13G, is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on SCHEDULE 13G, shall be filed on behalf of each of the undersigned without the necessity of filing additional joint acquisition statements. The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.

FAQ

How many Cabaletta Bio (CABA) shares do the reporting persons beneficially own?

The reporting persons beneficially own 8,904,367 shares, which the filing states represents 9.9% of Cabaletta Bio's outstanding common stock.

What is the composition of the reported position for CABA?

The position comprises 4,800,000 directly held shares plus warrants to purchase up to 4,500,000 shares, though warrant exercise is contractually limited so only 4,104,367 additional shares are currently exercisable under the cap.

Do the reporting parties have sole voting or dispositive power over the CABA shares?

No. The filing reports 0 sole voting power and 0 sole dispositive power; all reported voting and dispositive power (8,904,367) is shared.

Does the filing indicate the reporting persons seek to influence control of Cabaletta Bio?

The filing includes a certification that the securities are held in the ordinary course of business and were not acquired to change or influence control, per the stated certification language.

What share count was used to calculate the 9.9% ownership reported?

The percentage calculation is based on the issuer's prospectus share count of 89,943,101 outstanding common shares, as referenced in the filing.