A randomized phase 2b study of subcutaneous PD-L1 antibody ASC22 in virally-suppressed, HBeAg negative chronic hepatitis B patients

Background and Aims: Studies have shown that blocking the programmed cell death-1/programmed cell death ligand 1 pathway may lead to a potential cure for HBV infections. ASC22 (envafolimab) is a humanized, single-domain programmed cell death ligand 1 antibody administered subcutaneously. This study aimed to evaluate the efficacy and safety of ASC22 in virally suppressed patients with chronic hepatitis B on nucleos(t)ide analogs. Approach and Results: This randomized, single-blind, phase IIb trial enrolled patients with chronic hepatitis B in 2 cohorts for a 24-week treatment with ASC22 or placebo (PBO) once every 2 weeks and 24-week follow-up. In total, 60, 59, and 30 patients were treated with 1.0, 2.5 mg/kg ASC22, and PBO, respectively. The mean changes in HBsAg from baseline at weeks 24 and 48 were −0.309 ( p < 0.001) and −0.272 ( p < 0.023) log 10 IU/mL in the 1.0 mg/kg ASC22 group, −0.231 ( p = 0.007) and −0.205 ( p = 0.12) log 10 IU/mL in the 2.5 mg/kg ASC22 group, and −0.003 and −0.063 log 10 IU/mL in the PBO group, respectively (intent-to-treat population). Three out of 10 patients with baseline HBsAg levels ≤100 IU/mL in the 1.0 mg/kg group obtained on-treatment HBsAg loss. Most adverse events were mild (97.9%). There were no study drug–related serious adverse events in the 1.0 mg/kg ASC22 group. Conclusions: Subcutaneous administration of 1.0 mg/kg ASC22 once every 2 weeks for 24 weeks was shown to be safe and well-tolerated in virally suppressed patients with chronic hepatitis B on nucleos(t)ide analogs and can induce HBsAg decline, especially in patients with HBsAg ≤100 IU/mL.