Depletion of high-content CD14 + cells from apheresis products is critical for successful transduction and expansion of CAR T cells during large-scale cGMP manufacturing.

With the US Food and Drug Administration (FDA) approval of four CD19- and one BCMA-targeted chimeric antigen receptor (CAR) therapy for B cell malignancies, CAR T cell therapy has finally reached the status of a medicinal product. The successful manufacturing of autologous CAR T cell products is a key requirement for this promising treatment modality. By analyzing the composition of 214 apheresis products from 210 subjects across eight disease indications, we found that high CD14 ⁺ cell content poses a challenge for manufacturing CAR T cells, especially in patients with non-Hodgkin's lymphoma and multiple myeloma caused by the non-specific phagocytosis of the magnetic beads used to activate CD3 ⁺ T cells. We demonstrated that monocyte depletion via rapid plastic surface adhesion significantly reduces the CD14 ⁺ monocyte content in the apheresis products and simultaneously boosts the CD3 ⁺ content. We established a 40% CD14 ⁺ threshold for the stratification of apheresis products across nine clinical trials and demonstrated the effectiveness of this procedure by comparing manufacturing runs in two phase 1 clinical trials. Our study suggests that CD14 ⁺ content should be monitored in apheresis products, and that the manufacturing of CAR T cells should incorporate a step that lessens the CD14 ⁺ cell content in apheresis products containing more than 40% to maximize the production success.
Competing Interests: P.S.A. has received research funding from ATARA Biotherapeutics; has served on the Scientific Advisory Board or as consultant to ATARA Biotherapeutics, Bayer, Carisma Therapeutics, Imugene, and Takeda Therapeutics; and has patents, royalties, and intellectual property on mesothelin-targeted CARs and other T cell therapies, method for detection of cancer cells using virus, and pending patent applications on T cell therapies. E.L.S. has patents, royalties, and intellectual property on BCMA-targeted CARs and serves as consultant for BMS. I.R. has intellectual property rights from Juno Therapeutics.
(© 2021.)