Two years after Gilead Sciences secured the first option on Assembly Biosciences’ entire pipeline, the pharma has decided to pick the first fruits from the pact.
Gilead is paying $35 million upfront for the rights to two treatments for recurrent genital herpes, dubbed ABI-1179 and ABI-5366. Both therapies are inhibitors of helicase-primase, an enzyme involved in replication of the herpes virus.
Both assets are currently in phase 1b trials, where they have demonstrated “strong antiviral activity and improvements in clinical outcomes, including significant reduction in virus-positive lesions,” the companies explained in the Dec. 22 release.
“Both compounds also exhibit pharmacokinetic and safety profiles supportive of once-weekly oral dosing,” the companies noted.
Gilead first took an interest in Assembly back in October 2023, when the drugmaker paid $100 million upfront for opt-in rights on all of Assembly’s current and future programs. The show of faith in the biotech came at a crunch point for Assembly, which had suffered a series of clinical setbacks in previous years, downgrading its goal from curing to controlling hepatitis B before dropping drug candidates altogether in response to safety signals and lackluster efficacy.
Part of Gilead’s $100 million payment to Assembly involved a $15.2 million equity investment in return for a 19.9% stake in Assembly. Gilead also agreed at the time to buy up to a further 29.9% of the biotech's stock.
While ABI-5366 originated at Assembly, ABI-1179 was originally licensed by Gilead to Assembly as part of the agreement.
That 2023 pact—which tied Assembly to Gilead for 12 years—mandated that Gilead pay a $45 million option fee if it chose to license the assets. However, the pharma is only paying $35 million after having handed $10 million in accelerated funding to the biotech as part of an amendment to the agreement a year ago.
Assembly is still in line for up to $330 million in regulatory and commercial milestones from the original agreement, as well as tiered royalties on net sales should any therapies make it to market. Assembly also has the right to opt in to share 40% of the costs and profits of its products in the U.S. instead of receiving milestone payments.
In this morning’s release, Gilead’s virology therapeutic area head Jared Baeten, M.D., Ph.D., put the decision to onboard the two Assembly assets in the context of the pharma’s work to “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,” Baeten added. “Collaborations and partnerships are key in the pursuit of life-changing innovations.”
Assembly’s CEO Jason Okazaki described Gilead’s decision as reflecting “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,” Okazaki added.
Assembly has taken two other candidates into the clinic in the form of a next-gen capsid assembly modulator for hepatitis B and an entry inhibitor for hepatitis D.