CUSIP No. 12674W109
1
|
NAMES OF REPORTING PERSONS
Baker Bros. Advisors 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
1,344,000
|
6
|
SHARED VOTING POWER
-0-
|
7
|
SOLE DISPOSITIVE POWER
1,344,000
|
8
|
SHARED DISPOSITIVE POWER
-0-
|
9
|
AGGREGATE AMOUNT BENEFICIALLY
OWNED BY EACH REPORTING PERSON
1,344,000
|
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
5.2% (1)
|
12
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TYPE OF REPORTING PERSON (See
Instructions)
IA, PN
|
| (1) | Based on 25,728,310 shares of Common Stock (“Common Stock”) of Cabaletta Bio, Inc. (the “Issuer”) outstanding
as of December 12, 2022, as reported in the Issuer’s Prospectus filed with the Securities and Exchange Commission (“SEC”)
on December 8, 2022. |
CUSIP No. 12674W109
1
|
NAMES OF REPORTING PERSONS
Baker Bros. Advisors (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
1,344,000
|
6
|
SHARED VOTING POWER
-0-
|
7
|
SOLE DISPOSITIVE POWER
1,344,000
|
8
|
SHARED DISPOSITIVE POWER
-0-
|
9
|
AGGREGATE AMOUNT BENEFICIALLY
OWNED BY EACH REPORTING PERSON
1,344,000
|
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
5.2% (1)
|
12
|
TYPE
OF REPORTING PERSON (See Instructions)
HC, OO
|
| (1) | Based on 25,728,310 shares of Common Stock of the Issuer outstanding as of December 12, 2022, as reported in the Issuer’s Prospectus
filed with the SEC on December 8, 2022. |
CUSIP No. 12674W109
1
|
NAMES OF REPORTING PERSONS
Felix J. Baker
|
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
1,344,000
|
6
|
SHARED VOTING POWER
-0-
|
7
|
SOLE DISPOSITIVE POWER
1,344,000
|
8
|
SHARED DISPOSITIVE POWER
-0-
|
9
|
AGGREGATE AMOUNT BENEFICIALLY
OWNED BY EACH REPORTING PERSON
1,344,000
|
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
5.2% (1)
|
12
|
TYPE
OF REPORTING PERSON (See Instructions)
IN, HC
|
| (1) | Based on 25,728,310 shares of Common Stock of the Issuer outstanding as of December 12, 2022, as reported in the Issuer’s Prospectus
filed with the SEC on December 8, 2022. |
CUSIP No. 12674W109
1
|
NAMES OF REPORTING PERSONS
Julian C. Baker
|
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
1,344,000
|
6
|
SHARED VOTING POWER
-0-
|
7
|
SOLE DISPOSITIVE POWER
1,344,000
|
8
|
SHARED DISPOSITIVE POWER
-0-
|
9
|
AGGREGATE AMOUNT BENEFICIALLY
OWNED BY EACH REPORTING PERSON
1,344,000
|
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
5.2% (1)
|
12
|
TYPE
OF REPORTING PERSON (See Instructions)
IN, HC
|
| (1) | Based on 25,728,310 shares of Common Stock of the Issuer outstanding as of December 12, 2022, as reported in the Issuer’s Prospectus
filed with the SEC on December 8, 2022. |
Schedule 13G
Cabaletta Bio, Inc. (the
“Issuer”)
| Item 1(b) | Address of Issuer’s Principal Executive Offices: |
2929
Arch Street, Ste. 600
Philadelphia,
PA 19104
| Item 2(a) | Name of Person Filing: |
This Schedule 13G is being filed jointly by Baker Bros. Advisors
LP (the “Adviser”), Baker Bros. Advisors (GP) LLC (the “Adviser GP”), Felix J. Baker and Julian C. Baker (collectively,
the “Reporting Persons”).
| Item 2(b) | Address of Principal Business Office or, if None, Residence: |
The business address of each of the Reporting
Persons is:
c/o Baker Bros. Advisors LP
860 Washington Street, 3rd
Floor
New York, NY 10014
(212) 339-5690
The Adviser is a limited partnership organized under the laws
of the State of Delaware. The Adviser GP is a limited liability company organized under the laws of the State of Delaware. The citizenship
of each of Julian C. Baker and Felix J. Baker is the United States of America.
| Item 2(d) | Title of Class of Securities: |
Common Stock, par value $0.00001 per
share (“Common Stock”).
12674W109
| Item 3 | If this statement is filed pursuant to §§240.13d-1(b) or (c), check whether the person filing is a: |
|
(a) |
¨ |
Broker or dealer registered under Section 15 of the Exchange Act. |
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(b) |
¨ |
Bank as defined in section 3(a)(6) of the Exchange Act. |
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(c) |
¨ |
Insurance company as defined in section 3(a)(19) of the Exchange Act. |
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(d) |
¨ |
Investment company registered under section 8 of the Investment Company Act of 1940. |
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(e) |
x |
An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E). |
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(f) |
¨ |
An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F). |
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(g) |
x |
A parent holding company or control person in accordance with Rule
13d-1(b)(1)(ii)(G). |
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(h) |
¨ |
A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act. |
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(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. |
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(j) |
¨ |
Group, in accordance with Rule 13d-1(b)(1)(ii)(J). |
Items 5 through 9 and 11 of each of the cover pages to this Schedule 13G are incorporated herein by reference. Set forth below is the
aggregate number of shares of Common Stock directly held by each of Baker Brothers Life Sciences, L.P. (“Life Sciences”) and
667, L.P. (“667”, and together with Life Sciences, the “Funds”) which may be deemed to be indirectly beneficially
owned by the Reporting Persons, as well as shares of Common Stock that may be acquired upon conversion of non-voting common stock convertible
at any time on a 1-to-1 basis without consideration into Common Stock (“Non-Voting Common Stock”) and shares of Common Stock
that may be acquired upon exercise of pre-funded warrants to purchase Common Stock at an exercise price of $0.00001 per share with no
expiration date (the “Pre-Funded Warrants”), subject to the limitations on conversion and exercise described below.
The information
set forth below is based on 25,728,310 shares of Common Stock outstanding as of December 12, 2022, as reported in the Issuer’s Prospectus
filed with the Securities and Exchange Commission on December 8, 2022. Such percentage figures are calculated in accordance with Rule 13d-3 under the Securities Exchange Act of 1934, as amended
(the “Exchange Act”).
Holder | |
Number of Shares of
Common Stock we own or have the right
to acquire within 60 days | | |
Percent of Class Outstanding | |
667, L.P. | |
| 102,322 | | |
| 0.4 | % |
Baker Brothers Life Sciences, L.P. | |
| 1,241,678 | | |
| 4.8 | % |
Total | |
| 1,344,000 | | |
| 5.2 | % |
The Non-Voting Common Stock are only convertible to the extent
that after giving effect or immediately prior to such exercise the holders thereof, their affiliates and any person who are members of
a Section 13(d) group with the holders or one of their affiliates would beneficially own in the aggregate, for purposes of Rule 13d-3
under the Exchange Act, no more than 4.99% of the outstanding Common Stock (the “Beneficial Ownership Limitation”). By written
notice to the Issuer, the Funds may from time to time increase or decrease the Beneficial Ownership Limitation applicable to that Fund.
Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer. As a result of this
restriction, the number of shares of Common Stock that may be issued upon conversion of the Non-Voting Common Stock by the above holders
may change depending upon changes in the outstanding Common Stock.
The Pre-Funded Warrants are only exercisable to the extent
that after giving effect or immediately prior to such exercise the holders thereof, their affiliates and any person who are members of
a Section 13(d) group with the holders or one of their affiliates would beneficially own in the aggregate, for purposes of Rule 13d-3
under the Exchange Act, no more than 4.99% of the outstanding Common Stock (“Maximum Percentage”). By written notice to the
Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not
in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer. As
a result of this restriction, the number of shares of Common Stock that may be issued upon exercise of the Pre-Funded Warrants by the
above holders may change depending upon changes in the outstanding Common Stock.
The Adviser GP, Felix J. Baker and Julian C. Baker as managing
members of the Adviser GP, and the Adviser may be deemed to be beneficial owners of securities of the Issuer directly held by the Funds.
The Adviser GP is the sole general partner of the Adviser. Pursuant
to the management agreements, as amended, among the Adviser, Life Sciences and 667 and their respective general partners, the Funds’
respective general partners relinquished to the Adviser all discretion and authority with respect to the investment and voting power of
the securities held by the Funds, and thus the Adviser has complete and unlimited discretion and authority with respect to the Funds’
investments and voting power over investments.
| Item 5 | Ownership of Five Percent or Less of a Class: |
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 five percent of the class of securities, check
the following ¨. N/A
| Item
6 | Ownership of More than Five
Percent on Behalf of Another Person: |
N/A
| Item 7 | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company
or Control Person: |
The information in Item 4 is
incorporated herein by reference.
| Item 8 | Identification and Classification of Members of the Group: |
N/A
| Item 9 | Notice of Dissolution of Group: |
N/A
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.
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, 2023
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BAKER BROS. ADVISORS LP
By: Baker Bros. Advisors (GP) LLC, its general partner |
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By: |
/s/ Scott L. Lessing |
|
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Name: Scott L. Lessing
Title: President |
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BAKER BROS. ADVISORS (GP) LLC |
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By: |
/s/ Scott L. Lessing |
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Name: Scott L. Lessing
Title: President |
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/s/ Julian C. Baker |
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Julian C. Baker |
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/s/ Felix J. Baker |
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Felix J. Baker |