Ascletis Pharma Inc. announced positive interim data from the Phase IIb expansion cohort (the "Expansion Cohort") of subcutaneously administered PD-L1 antibody ASC22 (Envafolimab) for functional cure of chronic hepatitis B (CHB). The Expansion Cohort is a randomized, single-blind, placebo-controlled and multi-center clinical trial and planned to enroll approximately 50 CHB patients with baseline hepatitis B surface antigen (HBsAg) =100 IU/mL who would be treated with 1.0 mg/kg ASC22 or placebo (at a ratio of approximately 4:1) once every two weeks (Q2W) for 24-week treatment plus 24-week follow-up. All patients in both ASC22 and placebo cohorts received nucleot(s)ide analogues (NAs) as a background therapy.

In the second quarter of 2023, Ascletis successfully completed the enrollment of 49 CHB patients, including 40 patients in ASC22 cohort and 9 patients in placebo cohort. Interim analysis was conducted when approximately 50% of the enrolled patients completed 24-week treatment of ASC22 or placebo. The interim analysis included 25 patients who completed 24-week treatment (19 patients in ASC22 cohort and 6 patients in placebo cohort).

Topline results indicated that in ASC22 cohort, 4 patients (4/19, 21.1%) achieved HBsAg loss at the end of 24-week treatment. In contrast, there were no patients (0/6, 0%) achieving HBsAg loss at the end of 24-week treatment in the placebo cohort. ASC22 was generally safe and well tolerated.

Most of ASC22 drug related adverse effects were Grade 1 or 2. CHB remains to be a significantly unmet medical need globally, with approximately 86 million people in China and 1.59 million people in the U.S. infected with hepatitis B virus (HBV)[1].