ASC42 is an in-house developed, selective, potent farnesoid X receptor (FXR) agonist. ASC42 is an oral tablet formulation developed with in-house proprietary technology and is stable at room temperature.

Both in vitro primary human hepatocyte (PHH) cells and in vivo AAV/HBV mouse studies demonstrated that ASC42 significantly inhibited serum hepatitis B surface antigen (HBsAg) and HBV pregenomic RNA (pgRNA), indicating that ASC42 has therapeutic potential to functionally cure CHB.

Nucleot(s)ide analogues (direct antiviral drugs) inhibit only reverse transcription of HBV RNA into HBV DNA and do not inhibit the transcription of HBV cccDNA (covalently closed circular DNA) into HBV RNA, thus have no inhibitory effect on HBsAg. As an FXR agonist, ASC42 has unique mechanism of action against HBV: ASC42 inhibits the transcription of HBV cccDNA into HBV RNA, which in turn inhibits the translation of HBV RNA into HBsAg. ASC42 may also reduce HBV cccDNA stability.

ASC42 is the second investigational new drug of Ascletis for HBV functional cure. Another investigational new drug for HBV functional cure is PD-L1 antibody ASC22, which is currently in Phase IIb study and has demonstrated good safety and preliminary efficacy in HBsAg reduction in Phase IIa study.

"We are excited about ASC42 IND approval for CHB," said Dr. Jinzi J. Wu, Founder, Chairman and CEO of Ascletis, "This is a key milestone for our CHB functional cure pipeline. The potential synergy between ASC42 and ASC22 or Pegasys^® is promising for our effort on CHB functional cure."