Gilead Secures Arenavirus Vaccine Programs from Hookipa for $10 Million

Gilead Sciences has acquired exclusive ownership of two arenavirus-based immunotherapy programs for hepatitis B (HBV) and human immunodeficiency virus (HIV) from Hookipa Pharma. The transaction is the result of a long-standing collaboration between the two companies.
Under the terms of the agreement, Gilead will pay a total of $10 million to take full control of the HB-400 and HB-500 programs. Of that amount, $3 million is due at the close of the deal, with the remaining $7 million to be paid in three stages as the transfer is completed. The deal was signed on May 21, as disclosed in a May 22 filing with the Securities and Exchange Commission.
The HB-400 candidate, a therapeutic vaccine for chronic HBV, entered a Phase 1a/1b clinical trial in 2023. The HB-500 candidate, designed for HIV, is currently in an early-stage trial. As part of the new agreement, Hookipa will be responsible for winding down the HB-500 study. This trial had aimed to enroll approximately 30 participants and was previously scheduled to conclude in November 2025, according to ClinicalTrials.gov.

Both HB-400 and HB-500 utilize arenaviral backbones—specifically, lymphocytic choriomeningitis virus and pichinde virus—to deliver antigens targeting HBV and HIV, respectively.
The programs stem from a 2022 agreement between Gilead and Hookipa. At that time, Gilead made an upfront payment of $15 million and invested an additional $5 million in Hookipa equity. The 2022 pact included provisions for a $10 million program completion fee, up to $162.5 million in development milestones, and as much as $65 million in commercialization payments.
Gilead’s collaboration with Hookipa began in 2018 when it first licensed arenaviral immunization technologies from the biotech for use against HBV and HIV. In 2021, Gilead initially chose not to take an HIV candidate into the clinic. The company later revised its position, leading to the 2022 agreement that produced the HB-400 and HB-500 programs.
In addition to its development-stage assets, Gilead currently markets the antiretroviral drugs Biktarvy and Descovy, which together contributed to a combined $19.6 billion in HIV-related sales last year. The company also markets Vemlidy for HBV.
The HB-400 candidate represents a potential new offering in HBV, following recent announcements by other companies in the space. Vir Biotechnology and GSK have both discontinued efforts to develop “functional cures” for HBV this year, although GSK continues to work on an alternative candidate.

Hookipa Pharma, based in New York, has experienced recent business setbacks. These include the cancellation of a proposed merger with Poolbeg Pharma in February and workforce reductions following the termination of a collaboration with Roche on its HB-700 program for KRAS-mutated cancers.
Gilead’s acquisition of the HB-400 and HB-500 programs concludes its arenavirus collaboration with Hookipa and grants it full rights to the two therapeutic vaccine candidates.