Gilead Sciences inked a partnership with Assembly Biosciences that will focus on developing antiviral therapies for diseases like herpes, hepatitis B and hepatitis D, the company announced Tuesday.

Gilead will pay $100 million upfront as part of the 12-year deal, including $84.8 million upfront and $15.2 as an initial equity investment. 

Gilead will also contribute potential regulatory, commercial and collaboration extension payments in the future if the company decides to advance any programs under the deal. As such, Assembly Bio is eligible to receive up to $330 million per candidate in milestones.

Through the partnership, Gilead will build upon Assembly Bio’s small molecule antiviral portfolio, which includes candidates like ABI-4334, a hepatitis B virus (HBV) treatment, as well as a long-acting helicase primase inhibitor ABI-5366 for herpes simplex virus (HSV).

In a statement, Tomas Cihlar, SVP of virology research at Gilead, noted that the partnership will help Gilead tackle the next wave of innovation in virology as the company seeks to address the unmet needs of people affected by serious viral infections around the world.

“Collaborations and partnerships are key in the pursuit of the next wave of transformative innovations,” Cihlar said in a statement. “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.”

Going forward, Assembly Bio will head the research and development efforts, while Gilead will take the lead of discovery, research, development and commercialization once it has decided to advance a candidate.

Assembly Bio CEO Jason Okazaki noted in a statement that the new deal with Gilead will work to address significant unmet medical needs in herpesviruses, viral hepatitis and beyond.

“[W]e believe the shared expertise and promising investigational therapies that both organizations contribute to this collaboration have the potential to deliver significant advances to patients,” Okazaki said. 

Throughout 2023, Gilead has been busy making deals. 

The Assembly Bio partnership followed the announcement of a collaboration between Gilead and Tentarix in August. That three-year agreement is focusing on developing cancer and inflammatory disease candidates through Tentarix’s proprietary Tentacles platform.

Gilead also picked up XinThera earlier this year in an acquisition that would expand its oncology and inflammation pipeline.

The pharma reported growth in its Q2 earnings report in August, with total revenues rising 5% to $6.6 billion during the quarter. Its cell therapy products saw the biggest jump of 27%, while its liver disease portfolio grew 4%.

The company is slated to release its latest earnings report on November 7 after the markets close.