American Association for Cancer Research
ccr-23-3052_supplementary_figure_11_suppsf11.pptx (69.48 kB)

Supplementary Figure 11 from CB307: A Dual Targeting Costimulatory Humabody VH Therapeutic for Treating PSMA-Positive Tumors

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posted on 2024-04-15, 07:21 authored by Sophie Archer, Phillip M. Brailey, Minjung Song, Phillip D. Bartlett, Ines Figueiredo, Bora Gurel, Christina Guo, Verena Brucklacher-Waldert, H. Lorraine Thompson, Jude Akinwale, Samantha E. Boyle, Christine Rossant, Neil R. Birkett, Julia Pizzey, Mark Maginn, James Legg, Richard Williams, Colette M. Johnston, Philip Bland-Ward, Johann S. de Bono, Andrew J. Pierce

Supplementary Figure 11: Vipivotide tetraxetan does not interfere with CB307 activity



CD137 is a T- and NK-cell costimulatory receptor involved in consolidating immunologic responses. The potent CD137 agonist urelumab has shown clinical promise as a cancer immunotherapeutic but development has been hampered by on-target off-tumor toxicities. A CD137 agonist targeted to the prostate-specific membrane antigen (PSMA), frequently and highly expressed on castration-resistant metastatic prostate cancer (mCRPC) tumor cells, could bring effective immunotherapy to this immunologically challenging to address disease. We designed and manufactured CB307, a novel half-life extended bispecific costimulatory Humabody VH therapeutic to elicit CD137 agonism exclusively in a PSMA-high tumor microenvironment (TME). The functional activity of CB307 was assessed in cell-based assays and in syngeneic mouse antitumor pharmacology studies. Nonclinical toxicology and toxicokinetic properties of CB307 were assessed in a good laboratory practice (GLP) compliant study in cynomolgus macaques. CB307 provides effective CD137 agonism in a PSMA-dependent manner, with antitumor activity both in vitro and in vivo, and additional activity when combined with checkpoint inhibitors. A validated novel PSMA/CD137 IHC assay demonstrated a higher prevalence of CD137-positive cells in the PSMA-expressing human mCRPC TME with respect to primary lesions. CB307 did not show substantial toxicity in nonhuman primates and exhibited a plasma half-life supporting weekly clinical administration. CB307 is a first-in-class immunotherapeutic that triggers potent PSMA-dependent T-cell activation, thereby alleviating toxicologic concerns against unrestricted CD137 agonism.