LB Pharmaceuticals Inc美股招股说明书(2026-06-10版)

PROSPECTUS SUPPLEMENT(To the Prospectus Dated April14, 2026) This prospectus supplement updates, amends and supplements the prospectus dated April14, 2026 (the “Prospectus”), which forms a part of ourRegistration Statement on Form S-1 (Registration No.333-294900). Capitalized terms used in this prospectus supplement and not otherwise definedherein have the meanings specified in the prospectus. This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with the information contained inour Current Report on Form 8-K, filed with the Securities and Exchange Commission on June10, 2026, which is set forth below. This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus,which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in thisprospectus supplement updates or supersedes the information contained in the Prospectus. Please keep this prospectus supplement with your Prospectusfor future reference. Our common stock is listed on The Nasdaq Global Market under the symbol “LBRX.” On June9, 2026, the last reported sale price of our common stockwas $29.27 per share. Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertaintiesdescribed in the section titled “Risk Factors” beginning on page 8 of the Prospectus, and under similar headings in anyamendments or supplements to the Prospectus. Neither the Securities and Exchange Commission nor any other state securities commission has approved or disapproved of these securities orpassed upon the accuracy or adequacy of the Prospectus or this prospectus supplement. Any representation to the contrary is a criminaloffense. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM 8-K CURRENT REPORTPursuant to Section 13 or 15(d)of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2026 LB Pharmaceuticals Inc (Exact name of registrant as specified in its charter) 001-42831(CommissionFile Number) 10119(Zip Code) Not applicable(Former name or former address, if changed since last report.) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowing provisions: ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of thischapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). 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 anynew or revised financial accounting standards provided pursuant to Section13(a) of the Exchange Act.☐ Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; CompensatoryArrangement of Certain Officers. On June16, 2026, Anna Eramo, M.D., for personal reasons will transition to a role of advisor to LB Pharmaceuticals Inc(the “Company”). OnJune8, 2026, she resigned from her position as Chief Medical Officer of the Company effective June15, 2026 (the “Separation Date”). She willcontinue to provide consulting services in a full-time capacity to the Company through September15, 2026. Dr.Eramo’s departure is not related to theCompany’s clinical program operations or practices, and the Company does not expect her departure to have a material impact on the Company’sclinical development activities or previously disclosed clinical milestones. A search is underway for her replacement, and the Company hasexperiencedclinical development and operations teams who will continue to oversee the execution of the ongoing clinical trials. In connection with her resignation, Dr.Eramo’s has entered into a separation and consulting agreement with the Company, dated as of June8,2026 (the “Separation Agreement”). Pursuant to the Separation Agreement, Dr.Eramo will provide consulting services to the Company for the three-month period following the Separation Date until September15, 2026 (the “Consulting Period”). Pursuant to the Separation Agreement, if Dr.Eramoremains engaged as a consultant and complies with her obligations to the Company through the end of the Consulting Period, she will be entitled to(a)her current base salary on a monthly basis until June15, 2027, (b) 100% of