A Clinically Applicable Prediction Model to Improve T Cell Collection in Chimeric Antigen Receptor T Cell Therapy

Abstract

As chimeric antigen receptor (CAR) T cell therapy targeting CD19 has shown favorable outcomes in patients with relapsed or refractory (r/r) mature B cell lymphomas and B cell acute lymphoblastic leukemia (B-ALL), an increasing number of patients are waiting to receive these treatments. Optimized protocols for T cell collection by lymphapheresis for chimeric antigen receptor (CAR) T cell therapy are urgently needed to provide CAR T cell therapy for patients with refractory and progressive disease and/or a low number of lymphocytes owing to prior chemotherapy. The predicted efficiency of CD³⁺ cell collection in apheresis can guide protocols for apheresis, but a clinically applicable model to produce reliable estimates has not yet been established. In this study, we prospectively analyzed 108 lymphapheresis procedures for tisagenlecleucel therapy at 2 centers. The apheresis procedures included 20 procedures in patients with B cell acute lymphoblastic leukemia and 88 procedures in patients with diffuse large B cell lymphoma, with a median age at apheresis of 58 years (range, 1 to 71 years). After lymphapheresis with a median processing blood volume of 10 L (range, 3 to 16 L), a median of 3.2 × 10⁹ CD³⁺ cells (range, .1 to 15.0 × 10⁹ cells) were harvested. Collection efficiency 2 (CE2) for CD³⁺ cells was highly variable (median, 59.3%; range, 11.0% to 199.8%). Multivariate analyses revealed that lower hemoglobin levels, higher circulating CD3+ cell counts, and higher platelet counts before apheresis significantly decreased apheresis CE2. Based on multivariate analyses, we developed a novel formula that estimates CE2 from precollection parameters with high accuracy (r = .56; P < .01), which also suggests the necessary processing blood volume. Our strategy for lymphapheresis should help reduce collection failure, as well as achieve efficient utilization of medical resources in clinical practice, thereby allowing delivery of CAR T cell therapy to more patients in a timely manner.