Ph 1B B-701 in Combination With Pembrolizumab in Metastatic Transitional Cell Carcinoma of the Urothelial Tract

B-701 is a phage-derived, affinity-matured, human monoclonal antibody (mAb) specific for FGFR3. It is based on a human immunoglobulin G1 (IgG1) framework containing heavy chain VHIII and light chain VκI subgroup sequences.

Pembrolizumab is an mAb that binds to the programmed cell death protein 1 (PD-1) receptor and blocks its interaction with programmed death-ligand 1 (PD-L1) and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the anti-tumor immune response. In syngeneic mouse tumor models, blocking PD-1 activity resulted in decreased tumor growth.