Ibrutinib potentiates CTL019 cell expansion and engraftment, which correlates with clinical response. Ex vivo proliferation of total T cells during test expansion (A) and of CTL019 cells during clinical manufacturing (evaluated at day 9 after CD3/CD28-induced activation) (B) derived from patients with CLL and stratified by clinical response (n = 16 no response [NR], n = 7 partial response [PR], n = 7 CR) and by treatment (n = 3 pretreated with ibrutinib) compared with adults with ALL (n = 7). (C) In vivo engraftment of autologous CTL019 cells from the above CLL patients expressed as maximum expansion of adoptively transferred lymphocytes (copies of anti-CD19 CAR per microgram of genomic [g]DNA) in the first 90 days postinfusion. (D) Spearman ρ correlation shown between ex vivo expansion potential and in vivo proliferative capacity (maximum copies of anti-CD19 CAR per microgram of gDNA within 90 days after infusion) of adoptively transferred CTL019 cells in matched CLL patients (n = 30). *P < .05, **P < .01; error bars show mean ± standard error as determined by a 2-tailed Student t test. n.s., not statistically significant.