A non-ligand surrogate agonist antibody that enhances canonical Wnt signaling and bone regeneration

The Wnt signaling pathway promotes tissue regeneration and is a promising therapeutic target for treatment of osteolytic bone diseases. Here we report the discovery of a novel type of canonical Wnt agonist antibody that does not operate as a ligand surrogate. The antibody increases Wnt/{beta}-catenin signaling with or without exogenously provided Wnt ligands. It binds to a site on the P3 domain of LRP6 that is distinct from where the Wnt3a ligand and the DKK1 antagonist bind. The agonist effect persists in the presence of DKK1 and is further amplified by R-spondin even when Wnt ligands are not provided, suggesting a potential use for this antibody in ligand-low or insufficient settings. The antibody induces osteoblastic differentiation and mineralization in vitro and restores bone loss in vivo in a myeloma-derived intrafemoral mouse model, opening a potential path for therapeutic development in osteolytic diseases caused by cancer and aging.