Gilead exercises option to license Assembly helicase-primase inhibitor programs

Gilead (GILD) and Assembly Biosciences (ASMB), announced Gilead has exercised its combined option to exclusively license Assembly Bio’s herpes simplex virus helicase-primase inhibitor programs, including long-acting investigational candidates ABI-1179 and ABI-5366 for recurrent genital herpes. These represent the first programs Gilead will advance under the ongoing Assembly Bio R&D collaboration. ABI-1179 and ABI-5366 are novel long-acting inhibitors of viral helicase-primase, an enzyme essential for herpes virus replication with the potential to improve chronic suppressive therapy for recurrent genital herpes. Positive interim Phase 1b data for ABI-5366 and ABI-1179 demonstrated strong antiviral activity and improvements in clinical outcomes, including significant reduction in virus-positive lesions. Both compounds also exhibit pharmacokinetic and safety profiles supportive of once-weekly oral dosing. Under the terms of the 2023 collaboration agreement between Gilead and Assembly Bio, Assembly Bio will receive a $35M payment for Gilead’s exercise of the combined HSV program option, which comprises both ABI-5366 and ABI-1179. The $35M payment reflects a $45M option fee, net of $10M accelerated funding Assembly Bio received under a December 2024 amendment, which was creditable against future payments. Gilead will receive an exclusive license to ABI-5366 and ABI-1179 and will have the sole right and responsibility for further clinical development and commercialization of these programs. Assembly Bio remains eligible for up to $330M in regulatory and commercial milestones, as well as tiered royalties on net sales. Assembly Bio will also have the right to opt in to share 40% of all costs and profits in the United States in lieu of receiving milestones and royalties for that program in the United States after receipt of development plans and budgets from Gilead next year.