Safety and efficacy of the oral TLR8 agonist selgantolimod in individuals with chronic hepatitis B under viral suppression

•Currently there is no finite cure for chronic HBV infection. •Combination therapy with immune modulators and other HBV-specific agents are being explored. •The immune modulator selgantolimod is an oral agonist of Toll-like receptor 8. •Selgantolimod once-weekly was given to individuals with chronic HBV for 6 months. •Six months after treatment, a minority experienced serologic changes associated with durable cure. Background & Aims Selgantolimod (GS-9688) is a Toll-like receptor 8 (TLR8) agonist that suppresses HBV in vitro. In a phase II study, we evaluated the safety and efficacy of weekly selgantolimod treatment in virally suppressed individuals with chronic HBV taking oral antiviral treatment. Methods Forty-eight patients were randomized into two cohorts (hepatitis B e antigen [HBeAg]-positive and -negative [n = 24 each]) to receive oral selgantolimod 3 mg, 1.5 mg, or placebo (2:2:1) once weekly for 24 weeks while maintaining oral antivirals. The primary efficacy endpoint was the percentage of patients with a ≥1 log10 IU/ml decline in hepatitis B surface antigen (HBsAg) from baseline to week 24. Post-treatment, patients continued on oral antivirals for 24 weeks. Results The primary endpoint was reached by one participant, who was HBeAg-negative and received selgantolimod 1.5 mg. In contrast with placebo-treated patients (n = 9), only selgantolimod-treated patients (n = 39 total) had HBsAg declines greater than 0.1 log10 IU/ml at weeks 24 (18%, 7/39) and 48 (26%, 10/39), HBsAg loss (5%, 2/39 through 48 weeks), or HBeAg loss (16%, 3/19 through 48 weeks). The most common adverse events in selgantolimod-treated groups were nausea (46%), upper respiratory tract infection (23%), and vomiting (23%). Gastrointestinal disorders were mostly mild and transient. Selgantolimod induced transient dose-dependent increases in serum cytokines, including IL-12p40, IFN-γ, and IL-1RA, as well as rapid redistribution of some circulating immune cell subsets. Conclusion Oral selgantolimod up to 3 mg once weekly for 24 weeks was generally safe and well tolerated and led to serologic changes associated with progression to durable cure in two individuals by week 48. ClinicalTrials.gov Identifier NCT03491553. Impact and implications The only robust criterion for stopping treatment in chronic hepatitis B is loss of hepatitis B surface antigen (known as functional cure), which is rare during nucleos(t)ide analogue therapy. It is likely that novel antiviral and immunomodulatory therapies will be needed to achieve finite functional cure. Selgantolimod is an oral Toll-like receptor 8 agonist that has shown antiviral activity in vitro as well as safety in a phase I clinical trial with weekly dosing. In this phase II study, selgantolimod therapy was associated with transient increases in serum cytokines, rapid redistribution of circulating immune cell subsets, modest reductions in HBsAg and HBeAg levels, and occasional loss of HBsAg (5%) and HBeAg (16%) among participants with chronic hepatitis B on nucleos(t)ide analogue therapy with viral suppression. Our results support continued development of selgantolimod as a component of a future hepatitis B cure regimen. Selgantolimod (GS-9688) is a Toll-like receptor 8 (TLR8) agonist that suppresses HBV in vitro. In a phase II study, we evaluated the safety and efficacy of weekly selgantolimod treatment in virally suppressed individuals with chronic HBV taking oral antiviral treatment. Forty-eight patients were randomized into two cohorts (hepatitis B e antigen [HBeAg]-positive and -negative [n = 24 each]) to receive oral selgantolimod 3 mg, 1.5 mg, or placebo (2:2:1) once weekly for 24 weeks while maintaining oral antivirals. The primary efficacy endpoint was the percentage of patients with a ≥1 log10 IU/ml decline in hepatitis B surface antigen (HBsAg) from baseline to week 24. Post-treatment, patients continued on oral antivirals for 24 weeks. The primary endpoint was reached by one participant, who was HBeAg-negative and received selgantolimod 1.5 mg. In contrast with placebo-treated patients (n = 9), only selgantolimod-treated patients (n = 39 total) had HBsAg declines greater than 0.1 log10 IU/ml at weeks 24 (18%, 7/39) and 48 (26%, 10/39), HBsAg loss (5%, 2/39 through 48 weeks), or HBeAg loss (16%, 3/19 through 48 weeks). The most common adverse events in selgantolimod-treated groups were nausea (46%), upper respiratory tract infection (23%), and vomiting (23%). Gastrointestinal disorders were mostly mild and transient. Selgantolimod induced transient dose-dependent increases in serum cytokines, including IL-12p40, IFN-γ, and IL-1RA, as well as rapid redistribution of some circulating immune cell subsets. Oral selgantolimod up to 3 mg once weekly for 24 weeks was generally safe and well tolerated and led to serologic changes associated with progression to durable cure in two individuals by week 48.