Gilead Sciences has exercised its option to acquire exclusive rights to Assembly Biosciences’ helicase‑primase inhibitor programs for recurrent genital herpes, including the long‑acting candidates ABI‑1179 and ABI‑5366. The deal provides Assembly with a $35 million upfront payment—$45 million net of a $10 million accelerated‑funding credit received in December 2024—while Gilead gains worldwide rights to develop, test, and commercialize the programs. Assembly is eligible for up to $330 million in regulatory and commercial milestones and tiered royalties on net sales.
The transaction builds on a 12‑year partnership that began in October 2023, when Gilead paid $100 million upfront for opt‑in rights to Assembly’s pipeline and invested $15.2 million in equity. The 2025 option exercise is the first time Gilead will take full control of a program that was originally contributed by Gilead to Assembly, marking a significant shift from a collaborative model to a proprietary development strategy.
For Gilead, the deal represents a deliberate pivot into a new antiviral indication that has seen no new approvals in 25 years. The recurrent genital herpes market, with more than four million patients in the U.S. and Europe, offers a sizable unmet need and the potential for a first‑in‑class once‑weekly oral therapy. By leveraging its antiviral expertise and global commercial platform, Gilead aims to accelerate the development of ABI‑1179 and ABI‑5366 and capture a share of a market that has been largely stagnant.
Assembly Biosciences benefits from the upfront cash infusion and the prospect of milestone payments that can fund further development and offset past clinical setbacks. The company’s long‑acting candidates have shown strong antiviral activity in Phase 1b trials, with reductions in virus‑positive lesions and favorable pharmacokinetics that support once‑weekly dosing. The partnership provides Assembly with the resources and expertise needed to bring these programs to market.
Senior Vice President of Clinical Development, Virology, Jared Baeten, said the collaboration “has been highly fruitful” and that Gilead’s expertise will help advance the herpes program. Assembly CEO Jason Okazaki added that the option exercise “validates the strength of our pipeline” and that Gilead’s track record in antiviral development will accelerate progress toward a new treatment for patients.
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