South San Francisco-based Assembly Biosciences (Nasdaq: ASMB) closed a public offering of common stock and pre-funded warrants, raising approximately USD 115 million in gross proceeds to fund clinical development of its antiviral and liver disease pipeline. The capital raise follows Gilead Sciences' December 2025 decision to exercise its option to exclusively license Assembly Bio's herpesvirus programs, with Assembly aiming to fund independent development of its remaining wholly owned assets.
The offering comprised 3,924,624 shares of common stock priced at USD 26.50 per share, including 566,040 shares issued upon full exercise of the underwriters' overallotment option. In addition, an unnamed existing investor purchased pre-funded warrants to acquire up to 415,000 shares at USD 26.499 per warrant — representing the per-share offering price less the USD 0.001 exercise price — in lieu of common stock. The identity of the existing investor was not disclosed, and the press release does not confirm whether the participant holds insider status. Guggenheim Securities and UBS Investment Bank acted as joint book-running managers, with Mizuho serving as an additional book-running manager and H.C. Wainwright & Co. acting as lead manager. The offering closed May 26, 2026, subject to customary closing conditions.
Company overview and pipeline
Assembly Bio is a South San Francisco-based biotechnology company focused on small-molecule therapeutics for viral and liver diseases, with a pipeline spanning hepatitis delta virus (HDV), herpesvirus, hepatitis B virus (HBV), and cholestatic liver diseases. The company operates under a 12-year research and development collaboration with Gilead Sciences established in October 2023, under which Gilead paid USD 100 million upfront and received options to exclusively license Assembly Bio programs.
The lead wholly owned asset following the Gilead HSV license exercise is ABI-6250, an NTCP (sodium taurocholate co-transporting polypeptide) entry inhibitor in development for HDV and being explored in cholestatic liver diseases including primary biliary cholangitis and primary sclerosing cholangitis. ABI-6250 completed a Phase I safety, tolerability, and pharmacokinetics study in healthy participants (NCT06740474), with topline data from that study planned for presentation at EASL 2026. The company has indicated it anticipates initiating a Phase II trial in HDV in Q4 2026, representing the next near-term clinical milestone for the program.