Gilead Sciences exercises option to license Assembly Biosciences Helicase-Primase Inhibitor programs for recurrent genital herpes

Genital herpes, caused by HSV, is a chronic infection that leads to painful lesions, psychological and social stigma, and an increased risk of HIV acquisition. Over four million people in the U.S. and major European countries experience recurrent genital herpes, with HSV type 2 (HSV-2) infections typically associated with multiple recurrences each year. No new therapies have been approved for HSV in the U.S. or Europe for more than 25 years.

“At Gilead, we develop novel antiviral therapeutics that aim to deliver meaningful solutions that improve the lives of people affected by serious viral infections. Our research partnership with Assembly Bio has been highly fruitful, and we are excited to continue the clinical development of our herpes simplex virus candidates,“ said Jared Baeten, MD, PhD, Senior Vice President, Clinical Development, Virology Therapeutic Area Head, Gilead Sciences. “Collaborations and partnerships are key in the pursuit of life-changing innovations.”

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.

“We are pleased Gilead has opted in to advance the helicase-primase program for recurrent genital herpes,” said Jason Okazaki, Chief Executive Officer and President of Assembly Bio. “This milestone reflects the strength of our collaboration and the potential of our antiviral pipeline. With Gilead’s proven track record in developing and commercializing antiviral medicines, exercising this option is an important step forward as they take control of ABI-5366 and ABI-1179 and advance closer to delivering long-awaited new treatment options to patients suffering from recurrent genital herpes.”

Under the terms of the 2023 collaboration agreement between Gilead and Assembly Bio, Assembly Bio will receive a $35 million payment for Gilead’s exercise of the combined HSV program option, which comprises both ABI-5366 and ABI-1179. The $35 million payment reflects a $45 million option fee, net of $10 million 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 $330 million 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.