[SCHEDULE 13G] LB PHARMACEUTICALS INC SEC Filing

Rhea-AI Filing Summary

Commodore Capital entities and two individuals report beneficial ownership of 1,225,000 shares of LB Pharmaceuticals Inc. common stock, representing 5.5% of the outstanding shares based on 22,442,989 shares reported as issued and outstanding. The filing states the Firm (Commodore Capital LP) acts as investment manager to Commodore Capital Master LP and that the Firm's managing partners, Michael Kramarz and Robert Egen Atkinson, exercise investment discretion with respect to these securities. The ownership is reported as shared voting and dispositive power for each filer. A joint filing agreement is attached.

Positive

• Clear disclosure of a material >5% stake (1,225,000 shares, 5.5%), meeting regulatory transparency requirements
• Identification of reporting relationships (investment manager, master fund, and managing partners) and allocation of voting/dispositive power
• Joint Filing Agreement included, formalizing the coordinated disclosure among filers

Negative

• None.

Insights

Institutional Ownership Analyst

TL;DR: Commodore/related filers disclose a passive stake of 5.5% (1,225,000 shares) in LBRX, with shared voting and disposition authority.

The Schedule 13G indicates a non-control, passive reporting position by an investment manager and affiliated master fund plus two managing partners. The filing attributes shared voting and dispositive power to each filer rather than sole control, consistent with passive investment reporting standards. For investors, a >5% passive stake can increase monitoring of corporate actions and may lead to engagement but does not, by itself, indicate an intent to change control.

Corporate Governance Specialist

TL;DR: Filing documents material share ownership above the 5% disclosure threshold and clarifies reporting relationships and investment discretion.

The document clearly identifies the reporting entities, their relationships (manager to master fund), and the managers who exercise investment discretion. It classifies the position as shared voting/dispositive power and includes a joint filing agreement. From a governance perspective, the disclosure enhances transparency around potential concentrated ownership but does not assert activist intent or control arrangements.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

LB PHARMACEUTICALS INC

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

50180M108

(CUSIP Number)

09/11/2025

(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. 50180M108

1

Names of Reporting Persons

Commodore Capital 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 0.00
6	Shared Voting Power 1,225,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,225,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,225,000.00

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)

5.5 %

12

Type of Reporting Person (See Instructions)

PN, IA

SCHEDULE 13G

CUSIP No. 50180M108

1

Names of Reporting Persons

Commodore Capital Master 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

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,225,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,225,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,225,000.00

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)

5.5 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 50180M108

1

Names of Reporting Persons

Robert Egen Atkinson

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 1,225,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,225,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,225,000.00

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)

5.5 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP No. 50180M108

1

Names of Reporting Persons

Michael Kramarz

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 1,225,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,225,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,225,000.00

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)

5.5 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: LB PHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: One Pennsylvania Plaza, Suite 1025, New York, NEW YORK, 10119.
Item 2.
(a)	Name of person filing: Commodore Capital LP Commodore Capital Master LP Robert Egen Atkinson Michael Kramarz Each a "Filer."
(b)	Address or principal business office or, if none, residence: The address for Commodore Capital LP, Robert Egen Atkinson, and Michael Kramarz is 444 Madison Avenue, Floor 35, New York, NY 10022. The address for Commodore Capital Master LP is c/o Maples Corporate Services Limited, Ugland House, South Church Street, PO Box 309, Grand Cayman KY1-1104, Cayman Islands.
(c)	Citizenship: See Item 4 of the cover page for each Filer.
(d)	Title of class of securities: Common Stock, $0.0001 par value per share
(e)	CUSIP No.: 50180M108
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: See Item 9 of the cover page for each Filer. This report on Schedule 13G is being filed by Commodore Capital LP (the "Firm"), Commodore Capital Master LP ("Commodore Master"), Michael Kramarz, and Robert Egen Atkinson. The Firm is the investment manager to Commodore Master. As of September 11, 2025, the Firm may be deemed to beneficially own an aggregate of 1,225,000 shares of Common Stock, $0.0001 par value per share (the "Common Stock"), of LB Pharmaceuticals Inc (the "Issuer"). The Firm, as the investment manager to Commodore Master, may be deemed to beneficially own these securities. Michael Kramarz and Robert Egen Atkinson are the managing partners of the Firm and exercise investment discretion with respect to these securities. Ownership percentages are based on 22,442,989 shares of Common Stock reported as issued and outstanding as of September 10, 2025 in the Issuer's Rule 424(b)(4) Prospectus filed with the Securities and Exchange Commission on September 12, 2025.
(b)	Percent of class: See Item 11 of the cover page for each Filer.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See Item 5 of the cover page for each Filer.
	(ii) Shared power to vote or to direct the vote: See Item 6 of the cover page for each Filer.
	(iii) Sole power to dispose or to direct the disposition of: See Item 7 of the cover page for each Filer.
	(iv) Shared power to dispose or to direct the disposition of: See Item 8 of the cover page for each Filer.
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 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.

Commodore Capital LP

Signature:	Michael Kramarz
Name/Title:	Managing Partner
Date:	09/18/2025

Commodore Capital Master LP

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	09/18/2025

Robert Egen Atkinson

Signature:	Robert Egen Atkinson
Name/Title:	Authorized Sigantory
Date:	09/18/2025

Michael Kramarz

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	09/18/2025

Exhibit Information

Exhibit 1: Joint Filing Agreement

FAQ

Who reported ownership of LBRX in this Schedule 13G?

Commodore Capital LP, Commodore Capital Master LP, and individuals Michael Kramarz and Robert Egen Atkinson are the filers.

How many LB Pharmaceuticals (LBRX) shares are reported and what percentage of the class do they represent?

The filers report beneficial ownership of 1,225,000 shares, representing 5.5% of the reported outstanding shares (22,442,989).

Do the filers claim sole voting or dispositive power over the reported LBRX shares?

No. The filing reports 0 sole voting and dispositive power and 1,225,000 shared voting and shared dispositive power for each filer.

Does this Schedule 13G indicate an intent to change control of LB Pharmaceuticals?

The filers certify the securities were not acquired with the purpose of changing or influencing control; the position is reported as a passive stake.

What relationship exists between Commodore Capital LP and Commodore Capital Master LP?

The filing states the Firm (Commodore Capital LP) is the investment manager to Commodore Capital Master LP and may be deemed to beneficially own the reported securities.