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Gilead and Assembly Biosciences to develop next-generation therapeutics for serious viral diseases

Gilead Sciences and Assembly Biosciences, a biotechnology company developing innovative antiviral therapeutics targeting serious viral diseases, have entered into a 12-year partnership to advance the research and development of novel antiviral therapies, with an initial focus in Assembly Bio’s established areas of herpesviruses, hepatitis B virus (HBV) and hepatitis D virus (HDV).

Assembly Bio’s current portfolio of small molecule antiviral therapeutics includes both clinical and preclinical programs, including next-generation core inhibitor ABI-4334 for the treatment of HBV, long-acting helicase-primase inhibitor ABI-5366 for herpes simplex virus (HSV), an orally bioavailable HDV entry inhibitor ABI-6250, and a pan-herpes polymerase inhibitor program.

“Advancing the next wave of innovation in virology remains a core focus for Gilead as we seek to address the unmet needs of people affected by serious viral infections around the world,” said Tomas Cihlar, Senior Vice President of Virology Research, Gilead.

“Collaborations and partnerships are key in the pursuit of the next wave of transformative innovations. We are excited to announce this partnership with Assembly Bio to synergize our efforts on advancing and accelerating the discovery and development of novel antiviral therapeutics.”

“We are thrilled to partner with Gilead to address significant unmet medical needs in herpesviruses, viral hepatitis and beyond,” said Jason Okazaki, chief executive officer and president of Assembly Bio.

“With Gilead’s established success in developing and commercializing antiviral medicines and Assembly Bio’s advanced virology research capabilities, we believe the shared expertise and promising investigational therapies that both organizations contribute to this collaboration have the potential to deliver significant advances to patients.

“This transaction represents a critical step in Assembly Bio’s path to becoming a fully-integrated biotechnology company and we are eager to begin working with our new partner.”

Under the terms of the agreement, Assembly Bio will receive $100 million, consisting of an $84.8 million upfront payment and a $15.2 million equity investment from Gilead. Gilead’s initial equity investment at a premium represents 19.9 percent of the outstanding voting stock of Assembly Bio as of the date of closing. In addition, subject to certain conditions, Gilead has agreed to purchase up to 29.9 percent of Assembly Bio’s outstanding voting stock at a premium.

Gilead may opt-in to obtain exclusive rights for each of Assembly Bio’s current and future programs, including two preclinical programs targeting HSV and transplant-associated herpesviruses that Gilead is licensing to Assembly Bio, upon payment of an opt-in fee of at least $45 million per program after clinical proof-of-concept is achieved. If Gilead opts-in to any current or future program under the collaboration, Assembly Bio is eligible to receive up to $330 million per program in potential regulatory and commercial milestones, in addition to royalties ranging from the high single digits to high teens.

During the term of the collaboration, Assembly Bio will also be eligible to receive three separate $75 million collaboration extension payments at prespecified timepoints during the collaboration term to help fund future research and development.

Following Gilead’s exercise of its option for an Assembly Bio program, Assembly Bio will have the right to opt-in to share profits and costs in the United States. For future new programs, Assembly Bio will also have an option to co-promote those products in the United States.

Assembly Bio will be primarily responsible for the research and development efforts on the collaboration programs, including the two contributed Gilead programs, prior to Gilead’s potential opt-in. Following Gilead’s opt-in, Gilead will control discovery, research, development and commercialization on the optioned program(s).

Gilead has the right to appoint two individuals to Assembly Bio’s Board of Directors.


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