Company: LBRX
Filing Date: 2025-09-11
Form Type: S-8
Source: 0001193125-25-200401
Chunk: 0

Company: LB PHARMACEUTICALS INC
Filing Date: 2025-09-11
Form: S-8
Chunk 0
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As filed with the Securities and Exchange Commission on September 10, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 LB Pharmaceuticals Inc (Exact name of registrant as specified in its charter)

| Delaware                                 |     |         81-1854347 |
| (State or other jurisdiction of          
 incorporation or organization)           |     |   -I.R.S. Employer 
 Identification No. |
| One Pennsylvania Plaza, Suite 1025       
 New York, NY                             |     |              10119 |
| (Address of Principal Executive Offices) |     |          -Zip Code |

LB Pharmaceuticals Inc 2017 Stock Incentive Plan LB Pharmaceuticals Inc 2018 Stock Incentive Plan LB Pharmaceuticals Inc 2023 Stock Incentive Plan LB Pharmaceuticals Inc 2025 Equity Incentive Plan LB Pharmaceuticals Inc 2025 Employee Stock Purchase Plan (Full titles of the plans) Heather Turner Chief Executive Officer LB Pharmaceuticals Inc One Pennsylvania Plaza, Suite 1025 New York, NY 10119 Tel: (212) 605-0300 (Name, address, including zip code, and telephone number, including area code, of agent for service) Copies to: Divakar Gupta Brandon Fenn Marc Recht Minkyu Park Cooley LLP 55 Hudson Yards New York, NY 10001 Tel: (212) 479-6000 Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large Accelerated filer |     | ☐ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☒ |     | Smaller reporting company |     | ☒ |
|                         |     |   |     | Emerging growth company   |     | ☒ |

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities