1:Josep Carreras Leukemia Research Institute; 2:Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Portugal; 3:Red Española de Terapias Avanzadas (TERAV) - Instituto de Salud Carlos III (ISCII) (RICORS, RD21/0017/0029); 4:Centro de Investigación Biomédica en Red-Oncología (CIBERONC), Instituto de Salud Carlos III, Barcelona, Spain; 5:Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain

Chimeric Antigen Receptor (CAR)-T cells have emerged as a breakthrough treatment for relapse/refractory (r/r) hematological tumors, showing impressive complete remission rates in B-cell malignancies. However, around 50% of the patients relapse before 1-year post-treatment. T-cell “fitness” is critical to prolong the persistence and activity of the adoptively transferred product. Allogeneic T cells from healthy donors are less dysfunctional or exhausted than autologous patient-derived T cells, enabling a very attractive and cost-effective “off-the-shelf” therapy option. In this context, Delta One T cells (DOTs), a recently described cellular product based on MHC/HLA-independent Vd1⁺ gd T cells generated from the peripheral blood of healthy donors, represent a robust platform of allogeneic effector T cells. Here we generated and pre-clinically validated 4-1BB-based CAR-DOTs directed against the IL-3a chain receptor (CD123), a target antigen widely expressed on acute myeloid leukemia (AML) blasts. CD123CAR-DOTs showed vigorous, superior to control DOTs, cytotoxicity against AML cell lines and primary samples both in vitro and in vivo. Continuous administration of IL-15 supported the long-term persistence of a single-dose CD123CAR-DOTs in patient-derived xenograft models, sustaining their anti-leukemic efficacy as demonstrated in a re-challenge assay in vivo. Our results provide proof-of-concept for an allogeneic next-generation therapy based on CD123CAR-DOTs for r/r AML patients.