China-based Cosunter Pharmaceutical has presented Phase II data showing its oral hepatitis B surface antigen (HBsAg) inhibitor GST-HG131 achieved mean 0.9 log reduction in surface antigen levels, with 76.5% of chronic hepatitis B patients reaching below 100 IU/mL threshold after twelve weeks of treatment, supporting functional cure potential. The first-in-class (FIC) small molecule demonstrated maximum 1.64 log reduction with a favourable safety profile, earning a breakthrough therapy designation (BTD) from China's National Medical Products Administration (NMPA) in July 2025. Low surface antigen levels correlate with reduced hepatocellular carcinoma risk and improved immune reactivation sensitivity, positioning GST-HG131 as a key component in functional cure combination strategies against hepatitis B virus (HBV) infections.

The company plans to combine GST-HG131 with HBV core protein allosteric modulator GST-HG141, targeting covalently closed circular DNA (CCCDNA) depletion and viral replication suppression through complementary mechanisms. The all-oral regimen holds national innovative drug trial approval under the optimised review pathway, with superior patient compliance over injectable alternatives. Cosunter highlighted the clinical validation of decade-long research efforts, with multinational pharmaceutical companies expressing partnership interest following data presentation.

PharmCube's NextBiopharm® database shows that GST-HG131 is leading its drug class globally in terms of development. Click here to request a free trial for NextBiopharm®.