236 Intrinsically disordered region (IDR) engineered CAR-T cells show increased signaling, tumor killing and high antigen sensitivity against solid and liquid tumors compared to 3^rd generation CAR-T’s

<h3>Background</h3> Current 2^nd or 3^rd generation CAR-Ts are unable to detect low levels of antigens presented on liquid or solid tumors. We have leveraged IDR (intrinsically disordered region) that causes signaling condensation to engineer IDR-CAR-T cells with increased signaling in the synapse, cytotoxicity and high antigen sensitivity compared to 3^rd generation CAR-Ts in both solid tumors and blood cancers. <h3>Methods</h3> We selected well characterized IDR domains that are known to induce condensation in cellular systems and fused them to the C-terminus of the 3^rd generation CARs containing CD28, 41BB and CD3z domains. scFVs against CD19 or CD22 or HER2 were engineered into IDR CARs and evaluated in corresponding CD19 or CD22 leukemia and lymphoma or HER2 solid tumor models. IDR CAR-T functional assessments included membrane-proximal signaling, tonic signaling, cytokine production, in vitro cytotoxicity, and in-vivo exhaustion, and in-vivo anti-tumor activity against corresponding tumor antigens expressed in hematologic and solid tumor models. <h3>Results</h3> The IDRs from FUS, TAF15, and EWS increased CAR condensation and phosphorylation of CD3z and LAT in the synapse. No antigen-independent tonic signaling or any increased CAR-T exhaustion compared to 3^rd generation CAR-Ts was observed. The FUS IDR-CAR-Ts showed the highest potency and increased antigen sensitivity against CD19 and HER2 low and CD22 intermediate tumors compared to the control 3^rd generation CAR-Ts both in-vitro and in-vivo tumor models. Based on these proof of concept studies, Synaptimmune is developing the next generation of IDR CAR-T cells with increased synapse formation and T cell signaling, against both antigen low refractory blood cancers and solid tumors where antigen expression is limited and increased antigen sensitivity by CAR-Ts is desired. <h3>Conclusions</h3> The above IDR-CAR-T data in antigen low blood cancers and solid tumors warrant clinical investigation for the treatment of antigen low refractory blood cancers and solid tumors where tumor antigen is limited. Synaptimmune Therapeutics currently has an exclusive option to license the Yale’s IP covering the invention of IDR-CAR T. <h3>Acknowledgements</h3> We acknowledge the support of Yale University and Yale Ventures in supporting our work.