Phenotypic and Functional Attributes of Lentivirus-modified CD19-specific Human CD8+ Central Memory T Cells Manufactured at Clinical Scale

A key determinant of the therapeutic potency of adoptive T-cell transfer is the extent to which infused cells can persist and expand in vivo. Ex vivo propagated virus-specific and chimeric antigen receptor (CAR)-redirected antitumor CD8(+) effector T cells derived from CD45RA(-) CD62L(+) central memory (TCM) precursors engraft long-term and reconstitute functional memory after adoptive transfer. Here, we describe a clinical scale, closed system, immunomagnetic selection method to isolate CD8(+) TCM from peripheral blood mononuclear cells (PBMC). This method uses the CliniMACS device to first deplete CD14(+), CD45RA(+), and CD4(+) cells from PBMC, and then to positively select CD62L(+) cells. The average purity and yield of CD8(+) CD45RA(-) CD62L(+) TCM obtained in full-scale qualification runs were 70% and 0.4% (of input PBMC), respectively. These CD8(+) TCM are responsive to anti-CD3/ CD28 bead stimulation, and can be efficiently transduced with CAR encoding lentiviral vectors, and undergo sustained expansion in interleukin (IL)-2/IL-15 over 3-6 weeks. The resulting CD8(+) TCMderived effectors are polyclonal, retain expression of CD62L and CD28, exhibit CAR-redirected antitumor effector function, and are capable of huIL-15-dependent in vivo homeostatic engraftment after transfer to immunodeficient NOD/Scid IL-2RgCnull mice. Adoptive therapy using purified TCM cells is now the subject of a Food and Drug Administration-authorized clinical trial for the treatment of CD19(+) B-cell malignancies, and 3 clinical cell products expressing a CD19-specific CAR for IND # 14645 have already been successfully generated from lymphoma patients using this manufacturing platform.