Company: LBRX
Filing Date: 2025-09-08
Form Type: S-1/A
Source: 0001193125-25-197877
Chunk: 2

Company: LB PHARMACEUTICALS INC
Filing Date: 2025-09-08
Form: S-1/A
Chunk 2
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 common stock. The initial public offering price is expected to be between $14.00 and $16.00 per share. Prior to this offering, there has been no public market for our common stock. We have applied to list our common stock on the Nasdaq Global Market, or Nasdaq, under the symbol “LBRX.” We believe that upon the completion of this offering, we will meet the standards for listing on Nasdaq, and the completion of this offering is contingent upon such listing. We are an “emerging growth company” and a “smaller reporting company” under applicable Securities and Exchange Commission rules and have elected to comply with certain reduced public company reporting requirements for this prospectus and future filings. Investing in our common stock involves a high degree of risk. See the section titled “ Risk Factors” beginning on page 13 to read about factors you should consider before buying shares of our common stock. Neither the Securities and Exchange Commission nor any other state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

|                                  |     | Per Share |     | Total |
|:---------------------------------|:----|:----------|:----|:------|
| Initial public offering price    |     | $         |     | $     |
| Underwriting discounts and       
 commissions(1)                   |     | $         |     | $     |
| Proceeds, before expenses, to us |     | $         |     | $     |

| (1) | See the section titled “Underwriting” for additional information regarding compensation payable to 
 the underwriters.                                                                                  |

We have granted the underwriters an option for a period of 30 days to purchase up to 2,500,000 additional shares of common stock from us at the initial public offering price, less the underwriting discounts and commissions. The underwriters expect to deliver the shares of common stock to purchasers on , 2025 through the book-entry facilities of The Depository Trust Company.

| Leerink Partners |     | Piper Sandler |     | Stifel |

Prospectus Dated , 2025

TABLE OF CONTENTS

| Prospectus Summary                                                      |     |   1 |
| The Offering                                                            |     |   8 |
| Summary Financial Information                                           |     |  11 |
| Risk Factors                                                            |     |  13 |
| Special Note Regarding Forward-Looking Statements                       |     |  83