Ascletis Pharma Inc. (HKEX: 1672), a China-based R&D driven biotech company, announced on Thursday its positive interim data from the Phase IIb expansion cohort of subcutaneously administered PD-L1 antibody ASC22 (Envafolimab) for functional cure of chronic hepatitis B (CHB).

The Expansion Cohort, a randomised, single-blind, placebo-controlled and multi-centre clinical trial (ClinicalTrials.gov: NCT04465890), planned to enrol around 50 CHB subjects with baseline hepatitis B surface antigen (HBsAg) less than 100 IU/mL who are to 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 subjects in both ASC22 and placebo cohorts received nucleot(s)ide analogues (NAs) as a background therapy. During the second quarter of 2023, the company successfully completed the enrolment of 49 CHB patients, which included 40 subjects in ASC22 cohort and nine subjects in placebo cohort.

Interim analysis was carried out when around 50% of the enrolled subjects completed 24-week treatment of ASC22 or placebo. The interim analysis covered 25 subjects who completed 24-week treatment (19 patients in ASC22 cohort and six patients in placebo cohort). Topline results revealed that in ASC22 cohort, four subjects (4/19, 21.1%) achieved HBsAg loss at the end of 24-week treatment, while there were no subjects (0/6, 0%) achieving HBsAg loss at the end of 24-week treatment in the placebo cohort.

The product was generally safe and well tolerated and the majority of ASC22 drug related adverse effects were Grade 1 or 2.