Recent studies have revealed that the R-spondins (RSPOs) can mediate with Lgr4 and Lgr5 proteins/Frizzled/LRP receptor complexes as an independent (noncanonical) control of the Wnt pathway. Several lines of evidence supported that RSPOs play a positive role in the regulation of Wnt/beta-catenin signalling. We have identified an anti-RSPO3 antibody (DBPR117; hB1) using a rational design approach. DBPR117 was identified as an ideal candidate to be developed as a therapeutic antibody. DBPR117 was well characterized in a variety of assays including the binding assays, in vitro bioassays, in vivo PDX (patient-derived xenograft), lung cancer or colon cancer CDX (cell line-derived xenograft) models. DBPR117 is capable of binding specifically to the human RSPO3 with novel amino acid sequences in the complementary determining regions (CDRs). DBPR117 showed efficacy in human colon and lung cancers with RSPO3 fusion/overexpression. We are currently evaluating whether antagonizing RSPO3 by DBPR117 would synergize with anti-PD-L1 antibody to combat cancers using syngeneic murine models.
