Safety and Efficacy of Avaren-Fc Lectibody Targeting HCV High-Mannose Glycans in a Human Liver Chimeric Mouse Model

Abstract

Hepatitis C virus (HCV) infection remains a major cause of end-stage liver disease. Here, we show the efficacy and safety of a novel biotherapeutic targeting a HCV glycobiomarker in a mouse model, providing a foundation for a new anti-HCV strategy. BACKGROUND & AIMS: Infection with hepatitis C virus (HCV) remains a major cause of morbidity and mortality worldwide despite the recent advent of highly effective direct-acting antivirals. The envelope glycoproteins of HCV are heavily glycosylated with a high proportion of high-mannose glycans (HMGs), which serve as a shield against neutralizing antibodies and assist in the interaction with cell-entry receptors. However, there is no approved therapeutic targeting this potentially druggable biomarker. METHODS: The anti-HCV activity of Avaren-Fc (AvFc Q7) was evaluated through the use of in vitro neutralization assays as well as an in vivo challenge in the PXB Q8 chimeric human liver mouse model. Drug toxicity was assessed by histopathology, serum alanine aminotransferase, and mouse body weights. RESULTS: AvFc was capable of neutralizing cell culture-derived HCV in a genotype-independent manner, with 50% inhibitory concentration values in the low nanomolar range. Systemic administration of AvFc in a histidine-based buffer was well tolerated; after 11 doses every other day at 25 mg/kg there were no significant changes in body or liver weights or in blood human albumin or serum alanine aminotransferase activity. Gross necropsy and liver pathology confirmed the lack of toxicity. This regimen successfully prevented genotype 1a HCV infection in all animals, although an AvFc mutant lacking HMG binding activity failed. CONCLUSIONS: These results suggest that targeting envelope HMGs is a promising therapeutic approach against HCV infection, and AvFc may provide a safe and efficacious means to prevent recurrent infection upon liver transplantation in HCVrelated end-stage liver disease patients.

Impact of glycoengineering and antidrug antibodies on the anticancer activity of a plant‐made lectin‐Fc fusion protein

“…It should be noted that AvFc manufactured in CHO cells also has increased levels of high‐mannose glycans compared with normal mAbs, though there are fewer and the predominant form is Man5 (data not shown), indicating a greater degree of processing but also suggesting that the increase is due to a property of AvFc and not the production host. The increased presence of high‐mannose glycans may also help to partially explain the relatively low half‐life of AvFc ΔXF in mice and rhesus macaques (≈22 and ≈28 h, respectively, as reported in Dent et al ., 2021 ; Hamorsky et al ., 2019 ) compared with normal mAbs, as antibodies and other Fc‐bearing molecules containing high‐mannose glycans are more rapidly cleared from the organism by the immune system (Goetze et al ., 2011 ). AvFc ΔXF also had a longer half‐life in female mice than AvFc WT (≈14 h for the WT variant, data not shown vs. ≈18.5 h for the ΔXF variant, Figure S2 and Dent et al ., 2021 ), possibly due to the reduction in high‐mannose glycan content compared with the WT (Table 1 ).…”

Hepatitis C Virus Glycan-Dependent Interactions and the Potential for Novel Preventative Strategies

“…An improved mechanistic understanding of the interaction between these molecules and HCV virions is needed for the design of small molecules with improved potency and specificity. The encouraging long-lasting protective effect of a carbohydrate-binding lectin fusion protein in human liver chimeric mice [113] opens perspectives for the development of a pan-genotypic HCV entry inhibitor. As well, recombinant human lectin L-ficolin has been demonstrated to neutralize multiple HCV genotypes in vitro [76,143], further supporting the potential of a lectin-based antiviral strategy with a high barrier to resistance [144].…”

“…Most recently, a fusion protein consisting of an HMG-targeting lectin and the Fc region of a human IgG antibody was shown to bind HCV E2 [112]. Upon further investigation, this lectibody, called AvFc, had low nanomolar inhibitory activity against at least five HCV genotypes tested [113]. The impressive inhibitory concentrations are partially attributed to the multivalent recognition of HMGs due to the dimerization of the lectin via the Fc fusion [113].…”

“…Upon further investigation, this lectibody, called AvFc, had low nanomolar inhibitory activity against at least five HCV genotypes tested [113]. The impressive inhibitory concentrations are partially attributed to the multivalent recognition of HMGs due to the dimerization of the lectin via the Fc fusion [113]. AvFc was formulated for in vivo efficacy testing and, remarkably, was shown to protect human liver chimeric mice against HCV infection for up to 35 days, without apparent toxicity [113].…”

“…The impressive inhibitory concentrations are partially attributed to the multivalent recognition of HMGs due to the dimerization of the lectin via the Fc fusion [113]. AvFc was formulated for in vivo efficacy testing and, remarkably, was shown to protect human liver chimeric mice against HCV infection for up to 35 days, without apparent toxicity [113]. The potent pan-genotypic activity and the efficacy of systemic administration of AvFc provides a strong rationale for evaluation of the lectibody in future trials, particularly for prophylactic use to prevent infection during liver transplant or to protect populations at high risk of HCV infection.…”