Assembly Biosciences provides update on Study 211 of vebicorvir

Assembly Biosciences provided an update on the ongoing open-label Phase 2 extension study, or Study 211, of vebicorvir in patients with chronic HBV infection. Study 211 is exploring whether sustained virologic response, or 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 nucleoside analogue reverse transcriptase inhibitor, or 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, defined as off-treatment quantifiable HBV DNA by the COBAS TaqMan assay. 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. Assembly Bio continues to collect and analyze study data and intends to submit more detailed findings to a future medical meeting. Assembly Bio's Phase 2 trials, Study 201 and 202, demonstrated that the addition of VBR to NrtI therapy achieved a more rapid and deeper level of viral suppression than seen with NrtI alone and with a similar safety and tolerability profile. Based on these data, Assembly Bio has reached agreement with the Chinese regulatory body, National Medical Products Administration, Center for Drug Evaluation, and continues discussions with the FDA, on a Phase 3 registrational program for VBR plus NrtI as a chronic suppressive therapy for certain patient populations with chronic HBV infection. The company expects to initiate Phase 3 CST trials in the first half of 2021 in collaboration with BeiGene for the partnered China territory as part of the global registration program. Assembly Bio also continues to advance ABI-H2158 and ABI-H3733, which have demonstrated in preclinical studies 10-fold and 40- to 50-fold higher potency, respectively, than VBR in inhibiting the formation of new cccDNA. A multi-center, randomized, placebo-controlled Phase 2 trial is evaluating 2158 with entecavir versus placebo with entecavir in treatment naive HBeAg positive patients with chronic HBV infection. Additionally, a Phase 1 trial of 3733 is evaluating safety, tolerability, and pharmacokinetics following single ascending dose and multiple ascending dose administrations in healthy subjects. During the first half of 2021, Assembly Bio also intends to initiate a Phase 2 trial to evaluate the triple combination of VBR, Arbutus Biopharma's RNAi therapeutic AB-729 and NrtI in patients with chronic HBV infection. Combining multi-drug regimens with non-overlapping mechanisms has the potential to generate higher response rates in certain HBV patient populations and potentially shorten their duration of treatment. The Company also anticipates initiating a triple combination study in the first half of 2021 to evaluate the addition of interferon to VBR and NrtI.