Gilead Sciences, Inc. and Vir Biotechnology, Inc. announced this week that the companies have entered into a clinical collaboration to evaluate novel therapeutic combination strategies aimed at developing a functional cure for chronic hepatitis B virus (HBV).

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The companies plan to initiate a Phase 2 trial evaluating combination therapy for both treatment-experienced and treatment-naïve people living with HBV. The multi-arm trial will evaluate different combinations of selgantolimod, Gilead’s investigational TLR-8 agonist; VIR-2218, Vir’s investigational small interfering ribonucleic acid (siRNA); and a commercially-sourced, marketed PD-1 antagonist. People in the trial with HBV treatment experience may also receive Gilead’s Vemlidy® (tenofovir alafenamide fumarate, TAF). The primary outcome of the study will be the proportion of patients achieving a functional cure, defined as an off-therapy loss of hepatitis B surface antigen (HBsAg) and HBV DNA from the serum.

Both companies retain full rights to their individual product candidates and will discuss the potential path forward for any future combination studies based on the outcome of the Phase 2 trial.

“Gilead has a two-decade commitment to people with hepatitis B and we have worked tirelessly to bring new treatments forward with the goal of helping to improve their lives,” said Anuj Gaggar, vice president, Clinical Research, Virology at Gilead Sciences. “We believe that selgantolimod and VIR-2218 have the potential to be best-in-class therapeutics and could provide a compelling new combination approach to a functional cure for HBV.”

“We are enthusiastic about this collaboration,” said Phil Pang, M.D., Ph.D., chief medical officer of Vir Biotechnology. “We believe a functional cure for the majority of patients will require a reduction of the levels of circulating viral proteins together with an immune boost to stimulate the production of new T-cells that can bring the infection under control. We believe that this collaboration with Gilead adds a novel and significant new combination to our efforts to find a cure for HBV.”

HBV affects more than 290 million people worldwide. Globally, HBV is a leading cause of liver cancer and each year it is estimated that more than 800,000 people die of HBV-related liver disease. While current antiviral therapies result in sustained HBV viral suppression, they rarely completely clear the virus and therefore people with HBV require lifelong therapy.

The safety and efficacy of selgantolimod and VIR-2218 have not been established. They are investigational compounds, not approved by the U.S. Food and Drug Administration (FDA) or any other regulatory authority.