Company: LBRX
Filing Date: 2025-08-22
Form Type: S-1
Source: 0001193125-25-186467
Chunk: 1

Company: LB PHARMACEUTICALS INC
Filing Date: 2025-08-22
Form: S-1
Chunk 1
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 offering. ☐ If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, a 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 Act. ☐ The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission acting pursuant to said section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is declared effective. This preliminary prospectus is not an offer to sell nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. Subject to Completion. Dated , 2025 Shares Common Stock This is the initial public offering of LB Pharmaceuticals Inc. We are offering shares of our common stock. The initial public offering price is expected to be between $ and $ per share. Prior to this offering