Allogeneic CD5-specific CAR-T therapy for relapsed/refractory T-ALL: a phase 1 trial

Refractory or relapsed T cell acute lymphoblastic leukemia (r/r T-ALL) patients have poor prognoses, due to the lack of effective salvage therapies. Recently, CD7-targeting chimeric antigen receptor (CAR)-T therapies show efficacy in patients with r/r T-ALL, but relapse with CD7 loss is common. This study evaluates a CD5-gene-edited CAR-T cell therapy targeting CD5 in 19 r/r T-ALL patients, most of whom had previously failed CD7 CAR-T interventions. CAR-T products were derived from previous transplant donors (Cohort A) or newly matched donors (Cohort B). Primary endpoints were dose-limiting toxicity at 21 days and adverse events within 30 days. Secondary endpoints were responses, pharmacokinetics and severe adverse events after 30 days. A total of 16 received infusions, 10 at target dose of 1 × 10⁶ kg^-1. All encountered grade 3-4 cytopenias and one had a grade 3 infection within 30 days. All patients (100%) achieved complete remission or complete remission with incomplete blood count recovery by day 30. At a median follow-up of 14.3 months, four received transplantation; three were in remission and one died of infection. Of 12 untransplanted patients, 2 were in remission, 3 relapsed, 5 died of infection and 2 of thrombotic microangiopathy. CAR-T cells persisted and cleared CD5⁺ T cells. CD5^- T cells, mostly CD5-gene-edited, increased but remained below normal levels. These results suggest this CD5-specific CAR-T intervention has a high remission rate for T-ALL patients. Evidence also suggests the risk of late-onset severe infection may be mitigated with consolidative transplantation. This study provides insights that could help to optimize this promising intervention. ClinicalTrials.gov registration: NCT05032599 .