Electra Therapeutics, Inc.（ETRA）IPO 进程与发行信息

424B4 1 d61940d424b4.htm 424B4 424B4 Table of Contents Filed pursuant to Rule 424(b)(4) Registration Nos. 333-298617 and 333-298997 PROSPECTUS 23,333,334 Shares Electra Therapeutics, Inc. Common stock We are offering 23,333,334 shares of our common stock. This is our initial public offering, and prior to this offering, there has been no public market for our common stock. The initial public offering price is $15.00 per share of our common stock. Our common stock has been approved for listing on the Nasdaq Global Select Market (Nasdaq) under the symbol “ETRA.” We are an “emerging growth company” and a “smaller reporting company” as defined under the U.S. federal securities laws and, as such, may elect to comply with certain reduced public company reporting requirements in future reports after the closing of this offering. See the section titled “Prospectus Summary—Implications of Being an Emerging Growth Company and a Smaller Reporting Company.” Investing in our common stock involves a high degree of risk. See the section titled “ Risk Factors ” beginning on page 12 of this prospectus to read about factors you should consider before buying shares of our common stock. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense. PER SHARE TOTAL Initial public offering price $ 15.00 $ 350,000,010 Underwriting discounts and commissions (1) $ 1.05 $ 24,500,001 Proceeds to Electra Therapeutics, Inc., before expenses $ 13.95 $ 325,500,009 (1) See the section titled “Underwriting” for additional information regarding underwriting compensation. Delivery of the shares of common stock is expected to be made on or about September 21, 2026. We have granted the underwriters an option for a period of 30 days from the date of this prospectus to purchase up to an additional 3,500,000 shares of our common stock. If the underwriters exercise the option in full, the total underwriting discounts and commissions payable by us will be $28,175,001, and the total proceeds to us, before expenses, will be $374,325,009. Jefferies TD Cowen Evercore ISI Cantor Prospectus dated September 17, 2026 Table of Contents TABLE OF CONTENTS PAGE PROSPECTUS SUMMARY 1 RISK FACTORS 12 SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS 79 MARKET, INDUSTRY, AND OTHER DATA 81 DIVIDEND POLICY 82 USE OF PROCEEDS 83 CAPITALIZATION 84 DILUTION 86 MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS 88 BUSINESS 105 MANAGEMENT 151 EXECUTIVE AND DIRECTOR COMPENSATION 159 CERTAIN RELATIONSHIPS AND RELATED PERSON TRANSACTIONS 177 PRINCIPAL STOCKHOLDERS 182 DESCRIPTION OF CAPITAL STOCK 185 SHARES ELIGIBLE FOR FUTURE SALE 190 MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES TO NON-U.S. HOLDERS OF OUR COMMON STOCK 193 UNDERWRITING 197 LEGAL MATTERS 206 EXPERTS 207 WHERE YOU CAN FIND MORE INFORMATION 208 INDEX TO FINANCIAL STATEMENTS F-1 Neither we nor the underwriters have authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus, any amendment or supplement to this prospectus or in any free writing prospectus we may authorize to be delivered or made available to you. Neither we nor the underwriters take responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We and the underwriters are offering to sell, and seeking offers to buy, shares of our common i Table of Contents stock only in jurisdictions where offers and sales are permitted. The information contained in this prospectus is accurate only as of the date on the front cover of this prospectus, or other earlier date stated in this prospectus, regardless of the time of delivery of this prospectus or any sale of shares of our common stock. Our business, financial condition, results of operations, and prospects may have changed since that date. For investors outside of the United States : Neither we nor the underwriters have done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of our common stock and the distribution of this prospectus outside the United States. ii Table of Contents PROSPECTUS SUMMARY This summary highlights selected information included elsewhere in this prospectus. This summary does not contain all of the information you should consider before investing in our common stock. You should read this entire prospectus carefully, including the sections titled “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and “Special Note Regarding Forward-Looking Statements,” and our financial statements and the related notes included elsewhere in this prospectus, before making an investment decision. Unless the context otherwise requires, all references in this prospectus to “Electra Therapeutics,” “Electra,” “Registrant,” “we,” “us,” “our,” and “Company” refer to Electra Therapeutics, Inc. Overview We are a late clinical-stage biopharmaceutical company focused on pioneering a new class of precision medicines for the treatment of immune-mediated diseases and cancer. Our novel approach targets signal regulatory proteins (SIRP), a family of cell surface receptors whose expression is restricted to specific immune cell populations, and increases upon activation to enable selective depletion of disease-driving cells while preserving normal immune function. By replacing broad immunosuppression with selective elimination of principal cells that drive disease, we believe our approach can do for immune-mediated diseases what precision oncology has done for cancer, transforming the treatment paradigm for patients. To our knowledge, we are the first company to advance this SIRP-targeted precision immune cell depletion approach into clinical development and demonstrate proof-of-concept in humans. Our lead product candidate is ipsoprubart, a novel pan-SIRP monoclonal antibody designed to selectively deplete pathological myeloid cells and T cells via binding to SIRP a /ß1/ g , which is currently in a global registrational program for patients with secondary hemophagocytic lymphohistiocytosis (sHLH). In our Phase 1b trial, ipsoprubart was generally well tolerated and demonstrated a 100% 8-week overall survival (OS) rate and 100% overall response rate (ORR) in 12 frontline patients with malignancy-associated HLH (mHLH), the largest subset of sHLH and the population associated with the poorest outcomes. Of the 12 mHLH frontline patients, 10 achieved a partial response (PR) and two achieved a modified complete response (mCR). We are conducting SURPASS, our global Phase 2/3 registrational trial in newly diagnosed, treatment-naïve sHLH patients, as well as COMPASS, our natural history study designed to provide an external control comparator for SURPASS. We expect to complete enrollment in our registrational program in the second half of 2027. Ipsoprubart has received Breakthrough Therapy designation (BTD) from the U.S. Food and Drug Administration (FDA) and PRIority MEdicine (PRIME) designation from the European Medicines Agency (EMA), each granted for the treatment of sHLH broadly. In addition, eight evaluable sHLH patients with underlying T or B cell lymphomas treated with ipsoprubart across our Phase 1b trial and Expanded Access Program who had tumor response measurements within weeks of treatment ipsoprubart demonstrated a 100% objective tumor response rate, with seven out of eight patients achieving a complete response (CR). We are conducting a Phase 1 clinical trial evaluating ipsoprubart as a monotherapy in patients with relapsed/refractory T cell and natural killer (NK) cell malignancies, with initial data expected in the second half of 2027. We are also advancing ELA822, a novel SIRP g -specific monoclonal antibody designed to selectively deplete activated T cells, with potential applications across chronic T cell-mediated immune and inflammatory diseases. In August 2026, we obtained regulatory clearance and initiated a Phase 1 clinical trial of ELA822 in healthy volunteers (HV) in Europe, with data expected in the first half of 2027, followed by initiation of a Phase 1/2 clinical trial in patients with T cell-mediated immune disorders, which is expected in the middle of 2027, subject to regulatory approval. We have generated a proprietary library of SIRP-targeted antibodies with distinct profiles, developed over years of dedicated discovery and engineering. This platform provides substantial flexibility to align antibody design w