Induced pluripotent stem-cell-derived CD19-directed chimeric antigen receptor natural killer cells in B-cell lymphoma: a phase 1, first-in-human trial

Background FT596 is an induced pluripotent stem-cell (iPSC)-derived chimeric antigen receptor (CAR) natural killer (NK) cell therapy with three antitumour modalities: a CD19 CAR; a high-affinity, non-cleavable CD16 Fc receptor; and interleukin-15-interleukin-15 receptor fusion. In this study, we aimed to determine the recommended phase 2 dose (RP2D) and evaluate the safety and tolerability of FT596 as monotherapy and in combination with rituximab. We also aimed to evaluate the antitumour activity and characterise the pharmacokinetics of FT596 as monotherapy and in combination with rituximab. Methods In this phase 1, first-in-human trial, we evaluated FT596 in patients with relapsed or refractory B-cell lymphoma at nine sites in the USA. Patients who had received at least one previous systemic therapy and had no curative treatment options were eligible for inclusion. FT596 was administered after conditioning chemotherapy without rituximab (regimen A) or combined with rituximab (regimen B). The study consisted of a dose-escalation phase using a 3 + 3 design, with dose escalation commencing at 3 x 107 viable cells as a single dose on day 1 and done independently for individual regimens. A treatment cycle consisted of conditioning chemotherapy with cyclophosphamide (500 mg/m(2)) and fludarabine (30 mg/m(2)) intravenously on days -5 to -3, followed by FT596 administered at various doses and schedules, without (regimen A) or with (regimen B) a single dose of rituximab (375 mg/m(2)) intravenously on day -4. Supportive care was determined by the treating investigator. Patients were observed for dose-limiting adverse events for 28 days. Patients who tolerated therapy and derived clinical benefit could receive subsequent cycles of study treatment, with modification of conditioning chemotherapy dose if clinically indicated. The dose-expansion phase evaluated additional patients at selected doses and dosing schedules that had been found to be tolerable. The primary endpoints of the study were the incidence and nature of dose-limiting toxicities within each dose-escalation cohort to determine the maximum tolerated dose or maximum assessed dose to establish the RP2D and the incidence, nature, and severity of adverse events, with severity determined according to National Cancer Institute Common Toxicity Criteria and Adverse Events version 5<middle dot>0. The trial was registered with ClinicalTrials.gov, NCT04245722. Findings Between March 19, 2020, and Jan 12, 2023, 86 patients with B-cell lymphoma received FT596 on regimen A (n=18) or regimen B (n=68). 22 (26%) of 86 patients were female and 72 (84%) of 86 patients were White. Patients had received a median of four previous lines of therapy (range 1-11) and 33 (38%) of 86 patients had received previous CAR T-cell therapy. The maximum tolerated dose was not reached. Cytokine release syndrome was reported in one (6%) of 18 patients (maximum grade 1) on regimen A and nine (13%) of 68 patients on regimen B (six with maximum grade 1 and three with grade 2). Neurotoxicity was not observed. Interpretation FT596 was well tolerated as monotherapy or with rituximab and induced deep and durable responses in patients with indolent and aggressive lymphomas and the RP2D was preliminarily identified to be 1<middle dot>8 x 109 cells for three doses per cycle. This study supports that cell therapy using iPSC-derived, gene-modified NK cells is a potent platform for cancer treatment and suggests that such a platform might address limitations of currently available immune cell therapies, including manufacturing time, heterogeneity, access, and cost. Funding Fate Therapeutics. Copyright (c) 2025 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.