Ascletis Pharma Inc. announced dosing of the first patient in the Phase IIb Expansion Cohort (the "Expansion Cohort") of subcutaneously administered PD-L1 antibody ASC22 (Envafolimab) for functional cure of chronic hepatitis B (CHB). After the pre-Phase III clinical trial meeting with Center for Drug Evaluation (CDE) of China National Medical Products Administration (NMPA) in June 2022, the pathway to the registration, including patient population, dose, treatment duration, etc. of ASC22 (Envafolimab) for functional cure of CHB has been agreed.

The Expansion Cohort will enroll 50 CHB patients with baseline hepatitis B surface antigen (HBsAg) =100 IU/mL who will be treated with 1.0 mg/kg ASC22 or placebo (with the ration of 4:1) in combination with Nucleot(s)ide analogues (NAs) for 24-week treatment plus 24-week follow-up. The objective is to confirm whether the functional cure rate of ASC22 is similar to the data presented at oral session of the International Liver Congress™ 2022 (ILC 2022) held by the European Association for the Study of the Liver (EASL) in June 2022, which showed that 42.9% (3/7) of patients with baseline HBsAg=100 IU/mL obtained functional cure. The enrollment of 50 CHB patients of the Expansion Cohort is expected to be completed in early 2023.

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]. NAs inhibit only reverse transcription of HBV RNA into HBV DNA and do not inhibit the transcription of HBV cccDNA into HBV RNA, thus have no inhibitory effect on HBsAg. ASC22 (Envafolimab) is the most advanced clinical-stage immunotherapy in the world for CHB functional cure, i.e. HBsAg loss, through blocking PD-1/PD-L1 pathway.

Ascletis presented the latest Phase IIb clinical trial results of ASC22 in patients with CHB at oral session of EASL ILC 2022 in June 2022, which showed that 42.9% (3/7) patients with baseline HBsAg=100 IU/mL obtained sustained HBsAg loss and no rebound has occurred up to now since the last dosing of ASC22 (Envafolimab), indicating a potential functional cure of CHB. For tumor indications, Envafolimab has been approved for treatment of adults with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) advanced solid tumors by China NMPA in November 2021.