[Form 4] LB PHARMACEUTICALS INC Insider Trading Activity

Rhea-AI Filing Summary

Vida Ventures reporting persons recorded multiple transactions in LB Pharmaceuticals, Inc. (LBRX) on 09/12/2025. Series C preferred shares held by Vida entities converted into common stock immediately prior to the issuer's IPO under a conversion mechanism tied to the IPO price. Vida Ventures III, L.P. reported 547,648 common shares beneficially owned following conversion; Vida Ventures III-A, L.P. reported 1,262 common shares; Vida Ventures Management Co. LLC reported 1,434 common shares.

Additionally, purchases at $15.00 per share were reported: Vida Ventures III, L.P. acquired 332,566 common shares and Vida Ventures III-A, L.P. acquired 767 common shares, bringing Vida Ventures III total to 880,214 and Vida Ventures III-A to 2,029 beneficially owned shares as shown on the form.

Positive

• Significant insider accumulation: Vida Ventures III increased its beneficial common ownership to 880,214 shares following conversion and purchases.
• Transparent conversion disclosure: Footnotes explicitly state Series C preferred converted automatically into common stock prior to the IPO.
• Purchases at disclosed price: Open-market purchases documented at $15.00 per share for reported acquisitions.

Negative

• None.

Insights

Securities Analyst

TL;DR: Insider-held preferred converted to common and material purchases at $15 increased Vida Ventures’ post-IPO common holdings.

The Form 4 shows conversion of Series C preferred into common immediately prior to the IPO and subsequent open-market purchases at a stated price of $15. The largest movement is Vida Ventures III’s conversion and purchase activity resulting in 880,214 common shares beneficially owned. This is a significant insider accumulation event in absolute terms for a single reporting entity and may indicate continued support from cornerstone investors. All holdings are reported as indirect via partnership and management entities with customary disclaimers of beneficial ownership by investment committee members.

Corporate Governance Expert

TL;DR: Transactions are documented and disclosed through appropriate indirect ownership structures; conversion mechanics are explicit.

The filing clearly attributes ownership to Vida Ventures GP III, L.L.C. as general partner of Vida Ventures III and Vida Ventures III-A, and to Vida Ventures Management Co. LLC. Footnotes explain automatic conversion of Series C preferred at IPO pricing and the roles of the investment committee members, including disclaimers of beneficial ownership except for pecuniary interests. Signatures and dates are present, indicating proper execution. The structure and disclosures align with Section 16 reporting norms for related-party and fund-held securities.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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X

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Vida Ventures GP III, L.L.C.

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
LB PHARMACEUTICALS INC [ LBRX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/12/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/12/2025		C(1)		547,648	A	(1)	547,648	I	By Vida Ventures III, L.P.(2)(3)
Common Stock	09/12/2025		C(1)		1,262	A	(1)	1,262	I	By Vida Ventures III-A, L.P.(4)
Common Stock	09/12/2025		P		332,566	A	$15	880,214	I	By Vida Ventures III, L.P.(2)(3)
Common Stock	09/12/2025		P		767	A	$15	2,029	I	By Vida Ventures III-A, L.P.(4)
Common Stock								1,434	I	By Vida Ventures Management Co. LLC(5)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series C Preferred Stock	(1)	09/12/2025		C			13,302,666	(1)	(1)	Common Stock	547,648	$0	0	I	By Vida Ventures III, L.P.(2)(3)
Series C Preferred Stock	(1)	09/12/2025		C			30,667	(1)	(1)	Common Stock	1,262	$0	0	I	By Vida Ventures III-A, L.P.(4)

1. Name and Address of Reporting Person^*

Vida Ventures GP III, L.L.C.

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Vida Ventures III, L.P.

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Vida Ventures III-A, L.P.

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Belldegrun Arie

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Vida Ventures Management Co. LLC

(Last) (First) (Middle)

10100 SANTA MONICA BOULEVARD

SUITE 1500

(Street)

LOS ANGELES CA 90067

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Each share of Series C Preferred Stock has no expiration date and converted automatically into Common Stock immediately prior to the Issuer's initial public offering at a conversion ratio based upon the initial price per share to the public in the Issuer's initial public offering.

2. These shares are held directly by Vida Ventures III, L.P. ("Vida III"). Vida Ventures GP III, L.L.C. ("Vida III GP") is the general partner of Vida III and may be deemed to have voting, investment, and dispositive power with respect to these securities. Arie Belldegrun, Helen Kim and Rajul Jain, are the members of the investment committee of Vida III GP (each, an "Investment Committee Member" and such committee, the "Investment Committee").

3. (Continued from Footnote 2) The Investment Committee and each of the Investment Committee Members may be deemed to share voting, investment and dispositive power with respect to these securities. Vida III GP, the Investment Committee and each of the Investment Committee Members disclaims beneficial ownership of the securities held of record by Vida III, and this report shall not be deemed an admission that they are the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein, if any.

4. These shares are held directly by Vida Ventures III-A, L.P. ("Vida III-A"). Vida III GP is the general partner of Vida III-A and may be deemed to have voting, investment, and dispositive power with respect to these securities. The Investment Committee and each of the Investment Committee Members may be deemed to share voting, investment and dispositive power with respect to these securities. Vida III GP, the Investment Committee and each of the Investment Committee Members disclaims beneficial ownership of the securities held of record by Vida III-A, and this report shall not be deemed an admission that they are the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein, if any.

5. These shares are held directly by Vida Ventures Management Co., LLC ("Vida Management"). Each Investment Committee Member (as defined below) disclaims beneficial ownership of the securities held of record by Vida Management, and this report shall not be deemed an admission that they are the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest therein, if any.

	VIDA VENTURES GP III, L.L.C., By: /s/ Jean-Philippe Kouakou-Zebouah, its Managing Member	09/16/2025
	VIDA VENTURES III, L.P., By: Vida Ventures GP III, L.L.C., its general partner, By: /s/ Jean-Philippe Kouakou-Zebouah, its Managing Member	09/16/2025
	VIDA VENTURES III-A, L.P., By: Vida Ventures GP III, L.L.C., its general partner, By: /s/ Jean-Philippe Kouakou-Zebouah, its Managing Member	09/16/2025
	VIDA VENTURES MANAGEMENT CO., LLC, By: /s/ Jean-Philippe Kouakou-Zebouah, its Managing Member	09/16/2025
	ARIE BELLDEGRUN By: /s/ Jean-Philippe Kouakou-Zebouah, his attorney-in-fact	09/16/2025
	HELEN KIM By: /s/ Jean-Philippe Kouakou-Zebouah, her attorney-in-fact	09/16/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What transactions did Vida Ventures report on the LBRX Form 4?

The filing reports Series C preferred stock conversions into common stock and purchases of common stock on 09/12/2025, including 332,566 shares purchased by Vida Ventures III at $15.00 per share.

How many common shares does Vida Ventures III beneficially own after the reported transactions?

Vida Ventures III, L.P. is reported to beneficially own 880,214 common shares following the conversion and purchases.

Did any other Vida entities report holdings or purchases?

Yes. Vida Ventures III-A, L.P. reported 2,029 common shares beneficially owned after a conversion and a 767-share purchase at $15.00. Vida Ventures Management Co. LLC reported 1,434 common shares.

What is the nature of the conversion of Series C preferred stock?

Footnote 1 states each share of Series C Preferred Stock converted automatically into Common Stock immediately prior to the issuer's IPO at a conversion ratio based on the IPO price per share.

Are individuals named as having voting or dispositive power over these securities?

Footnotes indicate Vida Ventures GP III, L.L.C. is general partner of the funds and the Investment Committee members (Arie Belldegrun, Helen Kim, Rajul Jain) may be deemed to share voting, investment and dispositive power, although they disclaim beneficial ownership except for any pecuniary interest.