Evaluation of monovalent versus biparatopic CD3xPSMA bispecific antibodies for t-cell mediated killing of prostate tumor cells with minimal cytokine release.

person Ben Buelow TeneoBio, Inc., Menlo Park, CA info_outline Ben Buelow, Starlynn Clarke, Kevin Dang, Jacky Li, Chiara Rancan, Yuping Li, Preethi Sankaran, Duy Pham, Aarti Balasubramani, Laura Davison, Katherine Harris, Brett Jorgensen, Ute Schellenberger, Nathan Trinklein, Harshad Ugamraj, Lawrence Fong, Wim Van Schooten, Shelley Force Aldred

Authors person Ben Buelow TeneoBio, Inc., Menlo Park, CA info_outline Ben Buelow, Starlynn Clarke, Kevin Dang, Jacky Li, Chiara Rancan, Yuping Li, Preethi Sankaran, Duy Pham, Aarti Balasubramani, Laura Davison, Katherine Harris, Brett Jorgensen, Ute Schellenberger, Nathan Trinklein, Harshad Ugamraj, Lawrence Fong, Wim Van Schooten, Shelley Force Aldred Organizations TeneoBio, Inc., Menlo Park, CA, Teneobio, Inc., Menlo Park, CA, University of California, San Francisco, San Francisco, CA, UCSF, San Francisco, CA, University of California San Francisco, San Francisco, CA Abstract Disclosures Research Funding Pharmaceutical/Biotech Company U.S. National Institutes of Health Background: Castration resistant prostate cancer (CRPC) remains an incurable disease and new treatments are needed. Therapies directed against Prostate specific membrane antigen (PSMA) -such as radiolabeled antibodies, chimeric antigen receptor T cells (CAR-Ts) and T-cell engaging bispecific antibodies (T-BsAbs)- have shown promising efficacy but also induce significant toxicity. In particular T-cell redirection leads to efficient killing of tumor cells but induces cytokine release-related toxicities. We have developed a panel of monovalent and biparatopic CD3xPSMA bispecific antibodies that eliminate prostate tumor cells while minimizing cytokine release. Methods: Antibodies targeting CD3 and PSMA were generated in transgenic rats (UniRat™, OmniFlic™) followed by deep sequencing of the antibody repertoire from draining lymph nodes in immunized animals, and high-throughput gene assembly/expression. PSMA x CD3 T-BsAbs were assembled and evaluated for stability, pharmacokinetics, and T cell activation and ability to eliminate PSMA+ tumor cells in vitro and in vivo . Results: Bispecific CD3xPSMA Abs. incorporating either monovalent or biparatopic anti-PSMA binding domains activated T-cells in the presence of PSMA (plate-bound or cell surface), while no T cell activation occurred in the absence of either PSMA antigen or bispecific antibody. Potent/selective cytotoxicity against PSMA+ cells was observed in co-cultures of primary human T cells and tumor cells treated with CD3xPSMA T-BsAbs. Similar results were observed in in vivo Xenograft models of prostate cancer. Strikingly, CD3xPSMA bispecifics containing a novel low affinity anti-CD3 domain produced similar levels of tumor cytotoxicity compared to those with a traditional high affinity anti-CD3 domain, but with reduced cytokine production. Conclusions: We have created novel CD3xPSMA bispecific antibodies incorporating both monovalent and biparatopic anti-PSMA binding domains that mediate T-cell killing of PSMA+ tumor cells with minimal production of cytokines. Such T-BsAbs may improve safety, efficacy, and opportunities for combination therapy to treat CRPC.