Extension Study of Vebicorvir for Chronic HBV Does Not Achieve Meaningful SVR Rates

Assembly Biosciences provided an update on the ongoing open-label Phase 2 extension study (Study 211) of vebicorvir (VBR, or ABI-H0731) in patients with chronic HBV infection. Study 211 is exploring whether sustained virologic response (SVR) could be achieved after discontinuing therapy in virologically-suppressed patients who had received at least 12-18 months of combination treatment with core inhibitor VBR and a nucleos(t)ide analogue reverse transcriptase inhibitor (NrtI). Study patients who met the treatment stopping criteria discontinued therapy and have been assessed monthly for safety and relapse. The study has not achieved meaningful SVR rates as 39 of 41 patients have now relapsed.

Among the patients who have discontinued treatment, 22 of the 23 with HBeAg negative HBV have relapsed (SVR = 4% at last visit), defined as off-treatment quantifiable HBV DNA by the COBAS TaqMan (2.0) assay (lower limit of quantification = 20 IU/mL). Sixteen of these patients relapsed at post-treatment Week 4, three at post-treatment Week 12, and three patients at post-treatment Week 16. Among the HBeAg positive patients, 17 of 18 relapsed at post-treatment Week 4 (SVR = 6% at last visit). Assembly Bio continues to collect and analyze study data and intends to submit more detailed findings to a future medical meeting.

“With the addition of our first-generation core inhibitor, vebicorvir, to NrtI, we were able to drive viral suppression deeper in patients with chronic HBV infection to levels below the limits of our highly sensitive assays for six months or more. Patients like these normally face a lifetime of therapy, so we took the pioneering step to test whether their virologic response could be sustained off treatment. As we had previously indicated, we believe an SVR24 rate of at least 15% would have marked a meaningful first advance in HBV finite therapy, but preliminary results have shown that we will fall short of that mark. While we are just beginning to analyze the data and this is not the outcome we were hoping for, we firmly believe it was the right experiment to conduct, and the learnings will inform the field and our ongoing development programs,” John McHutchison, AO, MD, Chief Executive Officer and President of Assembly Biosciences, said.