Cabaletta Bio (CABA) SC 13G/A Cabaletta Bio / Boxer Capital ownership change

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

Cabaletta Bio, Inc.

(Name of Issuer)

Class A Common Stock, par value $0.00001

(Title of Class of Securities)

12674W109

(CUSIP Number)

December 31, 2021

(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)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 12674W109

1	Name of reporting persons.   Boxer Capital, 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-
	6	Shared voting power.   540,000
	7	Sole dispositive power.   -0-
	8	Shared dispositive power.   540,000

9	Aggregate amount beneficially owned by each reporting person.   540,000
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).   1.9%*
12	Type of reporting person   OO

* Based on 28,331,638 shares of common stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (“SEC”) on November 1, 2021.

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CUSIP No. 12674W109

1	Name of reporting persons.   Boxer Asset 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.   Bahamas

NUMBER OF SHARES   BENEFICIALLY   OWNED BY EACH REPORTING PERSON WITH:	5	Sole voting power.   -0-
	6	Shared voting power.   540,000
	7	Sole dispositive power.   -0-
	8	Shared dispositive power.   540,000

9	Aggregate amount beneficially owned by each reporting person.   540,000
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).   1.9%*
12	Type of reporting person   CO

* Based on 28,331,638 shares of common stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the SEC on November 1, 2021.

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CUSIP No. 12674W109

1	Name of reporting persons.   Joe Lewis
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 Kingdom

NUMBER OF SHARES   BENEFICIALLY   OWNED BY EACH REPORTING PERSON WITH:	5	Sole voting power.   -0-
	6	Shared voting power.   540,000
	7	Sole dispositive power.   -0-
	8	Shared dispositive power.   540,000

9	Aggregate amount beneficially owned by each reporting person.   540,000
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).   1.9%*
12	Type of reporting person   IN

* Based on 28,331,638 shares of common stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the SEC on November 1, 2021.

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CUSIP No. 12674W109

1	Name of reporting persons.   MVA Investors, 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-
	6	Shared voting power.   32,497
	7	Sole dispositive power.   -0-
	8	Shared dispositive power.   32,497

9	Aggregate amount beneficially owned by each reporting person.   32,497
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).   0.1%*
12	Type of reporting person   OO

* Based on 28,331,638 shares of common stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the SEC on November 1, 2021.

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CUSIP No. 12674W109

1	Name of reporting persons.   Aaron I. Davis
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-
	6	Shared voting power.   32,497
	7	Sole dispositive power.   -0-
	8	Shared dispositive power.   32,497

9	Aggregate amount beneficially owned by each reporting person.   32,497
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).   0.1%*
12	Type of reporting person   IN

* Based on 28,331,638 shares of common stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the SEC on November 1, 2021.

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This Amendment No. 3 (“Amendment No. 3”) amends and supplements the statement on Schedule 13G initially filed on November 7, 2019 (the “Original Filing”) by Boxer Capital, LLC (“Boxer Capital”), Boxer Asset Management Inc. (“Boxer Management”), MVA Investors, LLC (“MVA Investors”) and Joe Lewis, as amended by Amendment No. 1 filed on February 14, 2020 by Boxer Capital, Boxer Management, MVA Investors, Joe Lewis and Aaron Davis (collectively, the “Reporting Persons”) and Amendment No. 2 filed on February 16, 2021 by the Reporting Persons. The Original Filing remains in effect except to the extent that it is amended, restated or superseded by information contained in this Amendment No. 3. Capitalized terms used and not defined in this Amendment No. 3 have the meanings set forth in the Original Filing, as amended.

Item 4. Ownership.

(a) Amount beneficially owned:

Boxer Capital, Boxer Management and Joe Lewis beneficially own 540,000 shares of Common Stock. MVA Investors and Aaron Davis beneficially own 32,497 shares of Common Stock. The Reporting Persons beneficially own, in the aggregate, 572,497 shares of Common Stock.

(b) Percent of class:

The number of shares of Common Stock beneficially owned by Boxer Capital, Boxer Management and Joe Lewis represent 1.9% of the Issuer’s outstanding Common Stock. The number of shares of Common Stock beneficially owned by MVA Investors and Aaron Davis represent 0.1% of the Issuer’s outstanding Common Stock. The number of shares of Common Stock beneficially owned by the Reporting Persons represent, in the aggregate, 2.0% of the Issuer’s outstanding Common Stock. All percentages are based on 28,331,638 shares of Common Stock outstanding as of October 29, 2021, as set forth in the Issuer’s Quarterly Report on Form 10-Q filed with the SEC on November 1, 2021.

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote:

None of the Reporting Persons has sole power to vote or to direct the vote of any shares of Common Stock.

(ii) Shared power to vote or to direct the vote:

Boxer Capital, Boxer Asset Management and Joe Lewis have shared power to vote or to direct the vote of the 540,000 shares of Common Stock they beneficially own. MVA Investors and Aaron Davis have shared power to vote or to direct the vote of the 32,497 shares of Common Stock they beneficially own.

(iii) Sole power to dispose or to direct the disposition of:

None of the Reporting Persons has sole power to dispose or to direct the disposition of any shares of Common Stock.

(iv) Shared power to dispose or to direct the disposition of:

Boxer Capital, Boxer Asset Management and Joe Lewis have shared power to dispose or to direct the disposition of the 540,000 shares of Common Stock they beneficially own. MVA Investors and Aaron Davis have the sole power to dispose or to direct the disposition of the 32,497 shares of Common Stock they beneficially own.

Item 5. Ownership of Five Percent or Less of a Class.

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With respect to each Reporting Person:

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following ☒.

Item 10. Certification.

(c) 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.

Exhibits

1 Joint Filing Agreement, dated February 14, 2020, among the Reporting Persons, incorporated herein by reference to Exhibit 1 to the Schedule 13G filed by the Reporting Persons on February 14, 2020.

Page 8 of 9

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.

February 14, 2022

BOXER CAPITAL, LLC
By:	/s/ Aaron I. Davis
Name:	Aaron I. Davis
Title:	Chief Executive Officer
BOXER ASSET MANAGEMENT INC.
By:	/s/ Jason Callender
Name:	Jason Callender
Title:	Director
JOSEPH C. LEWIS
/s/ Joseph C. Lewis
Joseph C. Lewis, Individually
MVA INVESTORS, LLC
By:	/s/ Aaron I. Davis
Name:	Aaron I. Davis
Title:	Authorized Signatory
AARON I. DAVIS
/s/ Aaron I. Davis
Aaron I. Davis, Individually