Treatment with the Immunomodulator AIC649 in Combination with Entecavir Produces Antiviral Efficacy in the Woodchuck Model of Chronic Hepatitis B

Abstract

As current interventions for chronic hepatitis B (CHB) rarely induce cure, more effective drugs are needed. Short-term treatment of woodchucks with the novel immunomodulator AIC649, a parapoxvirus-based stimulator of toll-like receptor 9 dependent and independent pathways, has been shown to reduce viral DNA and surface antigen via a unique, biphasic response pattern. The present study evaluated long-term AIC649 treatment in combination with Entecavir for potency and safety in woodchucks. AIC649 monotreatment induced modest reductions in serum viral DNA and surface and e antigens that were associated with the same biphasic response pattern previously observed. Entecavir monotreatment reduced transiently viremia but not antigenemia, while AIC649/Entecavir combination treatment mediated superior viral control. Undetectability of viral antigens and elicitation of antibodies in AIC649/Entecavir-treated woodchucks correlated with the expression of interferons and suppression of viral replication in liver. Combination treatment was well tolerated, and liver enzyme elevations were minor and transient. It was concluded that the AIC649-mediated effects were most likely based on an improvement and/or reconstitution of antiviral immune responses that are typically deficient in CHB. As a combination partner to Entecavir, the antiviral efficacy of AIC649 was markedly enhanced. This preclinical study supports future evaluation of AIC649 for treatment of human CHB.

Combination Treatment with the Vimentin-Targeting Antibody hzVSF and Tenofovir Suppresses Woodchuck Hepatitis Virus Infection in Woodchucks

“…Overall, these results indicated a variability in the individual responsiveness to hzVSF that may depend on the levels of WHV cccDNA at treatment initiation, but primarily show that the durability of the treatment response was dependent on markedly reduced levels of WHV replication, either naturally attained by the underlying immune response (in the absence of testing for the presence of an unlikely WHV genome mutation) or induced by TAF. This is comparable to other woodchuck studies in which agonism of toll-like receptors 7 and 9 in combination with entecavir produced superior effects over monotreatment with each drug, albeit only in subsets of animals [56,78,81]. A more pronounced effect of Myrcludex B on HBV DNA serum loads when provided in combination with PegIFN-α2a to HBV/HDV co-infected patients has been also observed [22].…”

“…Serum WHV DNA levels were assayed quantitatively by slot-blot hybridization and real-time PCR, as described previously [ 54 , 56 ]. The lower limit of detection (LLOD) of the PCR assay was 600 WHV genomic equivalents (ge) or copy numbers per mL serum.…”

Involvement of Innate Immune Receptors in the Resolution of Acute Hepatitis B in Woodchucks

“…Thus, it is conceivable that the prolonged presence and/or the higher levels of WHV surface and e antigens in woodchucks with CHB progression than during AHB resolution interfere more with the activation of RNA than DNA receptor pathways. This is further supported by the antiviral effects mediated by RNA receptor agonism in vitro (TLR3) and in vivo (TLR3/7/8/9 or RIG-I), with the latter often resulting in reduced or undetectable viremia and antigenemia levels, and antibody seroconversion in at least subsets of animals (31,33,35,39,56). Future studies should focus on understanding how HBV/WHV in the setting of CHB progression avoids efficient detection by PRRs and the induction of an innate immune response that is different to the receptor pathway activation and strong immune response induction during AHB resolution.…”

“…Activation of PRRs further shapes the adaptive immune response against viral infections, including HBV (27-29). The antiviral properties of selected PRRs after activation by agonist molecules have been preclinically evaluated for possible treatment of patients with CHB (8,30,31). GS-9620, the firstin-class oral TLR7 agonist developed for the treatment of CHB generated CTL and NK-cell responses following the induction of IFN-a and ISGs in HBV-infected chimpanzees and in WHVinfected woodchucks (32,33).…”

“…GS-9688, a TLR8 agonist, also mediated sustained antiviral effects in a subset of woodchucks (35). AIC649, an inactivated parapoxvirus ovis particle preparation that activates antigen-presenting cells (APCs) mainly via TLR9, suppressed viral replication in woodchucks as a single agent; however, the combination of AIC649 and ETV produced superior antiviral effects (31). Likewise, CpG 21798, a synthetic oligodeoxynucleotide containing CpG motifs for the activation of TLR9, modulated WHV replication and delayed viral relapse after treatment discontinuation, but only when provided together with ETV to woodchucks (36).…”