Hypoimmune CD19 CAR T cells evade allorejection in patients with cancer and autoimmune disease

Off-the-shelf CAR T cells need to reliably escape allogeneic immune responses to become universal medicines. The primary T cell product SC291 was engineered with a CD19 CAR, T cell receptor alpha constant (TRAC) knockout, and the hypoimmune (HIP) edits of HLA depletion and CD47 overexpression. Here, we report exploratory immune analyses from the ARDENT (NCT05878184) and GLEAM (NCT06294236) trials with HIP-edited CD19 CAR T cells. Although there was an alloimmune response against HLA-replete subpopulations of SC291, we observed no de novo immune response against fully edited HIP CAR T cells in all patients, irrespective of the dose or the patient’s disease. The lack of antibodies against the HLA-replete CAR T cells was identified as a marker for deep tissue CD19 cell depletion, and all patients without such antibodies for 60 days showed concomitant B cell depletion in peripheral blood. The immune data presented support the reliability of the HIP concept to evade allorejection.