Effect of the capsid assembly modulator (CAM) ALG-000184 on HBsAg Levels in subjects with HBeAg positive chronic hepatitis B (CHB)

ABSTRACT

Background: ALG-000184 is a prodrug of ALG-001075, a novel, potent, pan-genotypic Class II CAM. CAMs are thought to have two mechanisms of action (MoA). The primary MoA affects pgRNA encapsidation resulting in inhibition of HBV DNA/RNA replication, as confirmed in CHB subjects receiving ALG-000184. The secondary MoA, which occurs at higher concentrations, regulates the establishment and replenishment of cccDNA, resulting in lowering of HBsAg, an effect that has not been reported to date with ALG- 000184. Method(s) ALG-000184-201 is a multi-part, multicenter, doubleblind, randomized, placebo-controlled study. In healthy volunteers (HVs), single doses up to 500 mg and multiple doses up to 250 mg were well tolerated with linear PK (Gane E., HBV TAG and APASL 2021). In treatment naive (TN) subjects with CHB, daily oral doses of 10-100 mg ALG-000184 for 28 days were well tolerated with linear PK and were associated with profound reductions of DNA/RNA regardless of HBeAg status or dose (Yuen MF, EASL 2022). Plasma exposures required to engage the secondary MoA are expected to be achieved at the 300 mg dose level. Data from a 300 mg cohort treated for 28 days are described here. Data from another ongoing cohort treated with 300 mg for 12 weeks will be presented at the conference. Result(s) Ten subjects were randomized to 300 mg ALG-000184 for 28 days and two to placebo. Two subjects randomized to ALG- 000184 were replaced due to missing data due to Covid-19 lockdown. Subjects were Asian, HBeAg positive, and genotype B or C. Mean baseline HBV DNA and RNA levels were 8.4 log10 IU/mL and 7.3 log10 copies/mL, respectively. One subject experienced a serious adverse event (AE) of pneumothorax>8 weeks after last dose which was considered unlikely related to study drug. No subjects prematurely discontinued study drug. All treatment emergent AEs were Grade <= 2 except for 4 Grade >= 3 alanine aminotransferase (ALT) elevations, which an independent ALT Flare Committee assessed as not related to study drug toxicity. PK was similar to HBeAg negative and HV cohorts following body weight adjustment. Subjects dosed with 300 mg ALG-000184 experienced mean declines of 4.0 log10 IU/mL and 2.6 log10 copies/mL in HBV DNA and RNA levels, respectively, at Day 28. Three of 7 evaluable subjects who received ALG-000184 had HBsAg declines>0.2 log10 IU/mL (0.23-0.78 log10 IU/mL). One subject receiving ALG-000184 had unquantifiable HBsAg throughout the study. Additionally, one HBeAg positive subject in a prior 100 mg cohort had plasma exposures equivalent to the 300 mg dose level and experienced a 0.5 log10 IU/mL HBsAg decline. Conclusion(s) In TN HBeAg positive CHB subjects, 300 mg ALG- 000184 for 28 days was well tolerated, exhibited predictable PK and resulted in rapid and substantial declines in HBV DNA and RNA. Notably, 3 of 7 evaluable subjects from this cohort experienced HBsAg declines of up to 0.78 log10 IU/mL. These data suggest that ALG-000184 can engage the secondary MoA of CAM II. Cohorts evaluating 300 mg over longer durations are planned or ongoing.