Abstract 5611: CRB-601: A highly potent and selective integrin αvβ8 blocking antibody with anti-tumoral properties

Abstract TGFβ is a secreted protein produced by tumors that promotes cancer progression primarily via the suppression of both the innate and adaptive immune systems. This makes TGFβ a promising immunotherapeutic target in cancer. It is ubiquitously expressed in a latent (L-TGFβ) form and the latent form has been shown to promote an immune suppressive phenotype within the tumor microenvironment. Integrin αvβ8 specifically binds to L-TGFβ. This interaction is essential for the activation of L-TGFβ-mediated signals in a variety of immune cell types. Interestingly, it has been recently shown that integrin αvβ8-mediated TGFβ activation can active directly through L-TGFβ and does not require the release of active TGFβ (1). Inhibition of integrin αvβ8-mediated TGFβ activation has been shown to block immunosuppressive regulatory T cell differentiation and enhance the recruitment of cytotoxic T cells into the tumor microenvironment (2). Here, we demonstrate by Surface Plasmon Resonance (SPR) that CRB-601, our selective inhibitor of integrin αvβ8 monoclonal antibody candidate, has a high affinity and specificity for the integrin αvβ8 complex. Moreover, in comparison to competitor molecules, such as ADWA-11, CRB-601 substantially blocks TGFβ activation in a reporter cell assay system. Additionally, using syngeneic mouse models, we evaluated the anti-tumoral properties of CRB-601 as a monotherapy, as well as in combination with immune checkpoints therapies. Findings from this study highlight the importance of integrin αvβ8 blockade in mediating the immune landscape within the tumor and leads to an enhanced response to immune checkpoint therapy. In conclusion, CRB-601 is a potent and selective integrin αvβ8 blocking monoclonal antibody that enhances the activity of immune checkpoint inhibitors in vivo and holds promise as a potential combination partner for immunotherapy. Investigational New Drug (IND) enabling studies are currently underway. References: 1: Campbell MG. et al. (2020) Cyro-EM reveals integrin-mediated TGF-β activation without release from latent TGF-β. Cell 180, 490-501. 2: Mariathasan S. et al. (2018) TGFbeta attenuates tumour response to PD-L1 blockade by contributing to exclusion of T cells. Nature 554, 544-48. Citation Format: Andrew Kolodziej, Eric Haines, Richard Morse, Eugene Zhukovsky. CRB-601: A highly potent and selective integrin αvβ8 blocking antibody with anti-tumoral properties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5611.