A Phase I Trial of Allogeneic γδ T Lymphocytes From Haploidentical Donors in Patients With Refractory or Relapsed Acute Myeloid Leukemia

Introduction We report the results of a phase I clinical trial NCT03790072 of an adoptive transfer of γδ T lymphocytes from haploidentical donors in patients with refractory/relapsed acute myeloid leukemia after lymphodepletion regimen. Patients and methods Healthy donor mononuclear cells collected by leukapheresis were consistently expanded to generate products of 10⁹ to 10¹⁰ γδ T cells. Seven patients received donor-derived T cell product at doses of 10⁶/kg (n = 3), 10⁷/kg (n = 3), and 10⁸/kg (n = 1). Results Four patients had bone marrow evaluation at day 28. One patient had a complete remission, one was classified as morphologic leukemia-free state, one had stable disease and one had no evidence of response. In one patient, there was evidence of disease control with repeat infusions up to 100 days after first dosing. There were no treatment-related serious adverse events or treatment-related Common Terminology Criteria for Adverse Events grade 3 or greater toxicities at any dose level. Allogeneic Vγ9Vδ2 T cell infusion was shown to be safe and feasible up to a cell dose of 10⁸/kg. Discussion In agreement with previously published studies, the infusion of allogeneic Vγ9Vδ2 cells was safe. The contribution of lymphodepleting chemotherapy to responses seen cannot be ruled out. Main limitation of the study is the low number of patients and interruption due to COVID-19 pandemic. Conclusion These positive Phase 1 results support progression to phase II clinical trials.