A Targeted R-Spondin Mimetic Induces Hepatocyte-Specific Activation of Wnt Signaling and Cell Proliferation in Mice.

BACKGROUND AND AIMS: Injection of an antibody-based WNT mimetic or R-spondin (RSPO) protein in mice has been reported to activate Wnt signaling in the liver. Furthermore, a therapeutic hepatocyte-targeted RSPO mimetic antibody, SZN-043, has entered a multiple ascending dose phase 1b trial in patients with severe alcoholic hepatitis. To address key questions regarding therapeutic Wnt signaling agonism and RSPO-based therapy, impacts of different Wnt-activating treatments to the liver gene expression landscape and metabolic zonation were investigated. METHODS: Naive mice were treated with a WNT mimetic, RSPO2, or in combination to assess their impacts on metabolic zonation in the liver. To address its hepatocyte specificity, the effects of SZN-043 on liver cell transcriptome were investigated using single-cell RNA sequencing in a 14-day daily injection study followed with washout periods. Its effect on hepatocyte proliferation was investigated in a subsequent study using Edu labeling to track cell proliferation. RESULTS: SZN-043 injection, compared with Wnt/β-catenin signaling activation through co-injection of a WNT mimetic and RSPO2, induced strong pathway activation specifically in hepatocytes. Sustained SZN-043 treatment led to bona fide zonal metabolic gene expression profile changes. However, unlike the effects from Wnt pathway-activating mutations, the agonist-based treatment effects are quickly reversed after treatment cessation. SZN-043 also induced robust hepatocyte proliferation that was transient and zone-biased. We also identified and assessed several serum pharmacodynamic biomarker candidates in a preclinical setting. CONCLUSION: This work provides insights into Wnt signaling agonism applications for liver regeneration, particularly the mechanism and dynamics of SZN-043 activity, thus supporting its further clinical investigation.