Deruxtecan-based antibody-drug conjugate targeting TCR-Vβ2 for the treatment of cutaneous T cell lymphoma

Summary: A challenge in the development of effective and safe immunotherapies for T cell lymphomas and leukemias malignancies is the lack of a unique marker on malignant vs healthy T cells. We observed that malignant T cells from advanced cutaneous T cell lymphoma (CTCL) patients express a clone-defining T cell receptor (TCR), with Vβ2 being the most common Vβrepresented variable region of the >20 Vβ families. Since each Vβ gene is expressed by only a small fraction (~3–9%) of the overall T cell population, a patient-matched Vβ-specific immunotherapy may be a safer strategy for eliminating CTCL cells. [MG1] We have previously generated anti-Vβ2 chimeric antigen receptor (CAR)-T cells using purified T cells from healthy donors as a potential patient-matched Vβ-specific immunotherapy. However, to overcome the production cost and logistical challenges of generating CAR-T immunotherapies, we have now developed antibody-drug conjugate (ADC) prototypes using different conjugation strategies and payloads. Using a Lysolight internalization assay, we show that a Fc-dead inactivated humanized anti-Vβ2 antibody is readily internalized in any target cells Lysolight internalization assay. We then conjugated deruxtecan (Dxd), a topoisomerase 1 inhibitor and a derivative of exatecan, to the anti-Vβ2 antibody via lysine modification at a drug-antibody ratio of ~2.5. We show that these anti-Vβ2-Dxd ADC prototype can effectively and specifically kill Vβ2 Jurkat cells <i>in vitro</i>. Finally, to assess the anti-Vβ2-Dxd ADC prototype <i>in vivo</i>, a complimentary mouse xenograft models using NSG mice was were generated by intravenous (retro-orbital) or subcutaneous injection of luciferase-expressing Vβ2+ Jurkat cells. <i>In vivo</i> preclinical imaging revealed that tumor burden growth was substantially suppressed in mice treated with the anti-Vβ2-Dxd ADC prototype (1 or 2 mg/kg i.p.) when compared to untreated mice. Overall, we demonstrate a potential strategy to rapidly generate and assess Dxd ADCs targeting TCRVβs for the treatment of Vβ+ clonal CTCL and other T cell malignancies. Davis Li¹, Julia Lewis¹, Haoxiang Zheng¹, Joohyung Lee¹, Kacie Carlson¹, Michael Girardi¹ 1. Dermatology, Yale University, New Haven, CT, United States. Translational Studies: Preclinical