Guidance on treatment endpoints and study design for clinical trials aiming to achieve cure in chronic hepatitis B and D: Report from the 2022 AASLD-EASL HBV-HDV Treatment Endpoints Conference

Representatives from academia, industry, regulatory agencies, and patient advocacy groups convened under the American Association for the Study of Liver Diseases (AASLD) and the European Association for the Study of the Liver (EASL) in June 2022 with the primary goal of achieving consensus on chronic HBV and HDV treatment endpoints to guide clinical trials aiming to "cure" HBV and HDV. Conference participants reached an agreement on some key points. The preferred primary endpoint for phase II/III trials evaluating finite treatments for chronic hepatitis B (CHB) is a "functional" cure, defined as sustained HBsAg loss and HBV DNA less than the lower limit of quantitation (LLOQ) 24 weeks off-treatment. An alternate endpoint would be "partial cure" defined as sustained HBsAg level < 100 IU/mL and HBV DNA < LLOQ 24 weeks off-treatment. Clinical trials should initially focus on patients with HBeAg positive or negative CHB, who are treatment-naive or virally suppressed on nucleos(t)ide analogs. Hepatitis flares may occur during curative therapy and should be promptly investigated and outcomes reported. HBsAg loss would be the preferred endpoint for chronic hepatitis D, but HDV RNA < LLOQ 24 weeks off-treatment is a suitable alternate primary endpoint of phase II/III trials assessing finite strategies. For trials assessing maintenance therapy, the primary endpoint should be HDV RNA < LLOQ assessed at on-treatment week 48. An alternate endpoint would be ≥2 log reduction in HDV RNA combined with normalization of alanine aminotransferase level. Suitable candidates for phase II/III trials would be treatment-naiive or experienced patients with quantifiable HDV RNA. Novel biomarkers (hepatitis B core-related antigen [HBcrAg] and HBV RNA) remain exploratory, while nucleos(t)ide analogs and pegylated interferon still have a role in combination with novel agents. Importantly, patient input is encouraged early on in drug development under the FDA/EMA patient-focused drug development programs.