Pharmacokinetic, Pharmacodynamic and Blood Analytes Associated with Clinical Response and Safety in Relapsed/Refractory Aggressive B-NHL Patients Treated with JCAR017

Introduction:

JCAR017 is a CD19-directed 4-1BB CAR T cell product administered in a defined composition at a precise dose of CD8 and CD4 CAR T cells. TRANSCEND NHL 001 is the first multicenter Phase 1 trial of JCAR017 in relapsed/refractory (R/R) B-cell NHL (NCT02631044). In previously reported interim results (Abramson et al, 14-ICML 2017), JCAR017 demonstrated high CR rates and low rates of cytokine release syndrome (CRS) and neurotoxicity (NT). The accompanying cellular pharmacokinetics (PK), pharmacodynamics (PD), and blood analyte evaluations are reported herein.

Methods:

Patients (pts) on the TRANSCEND NHL 001 trial received lymphodepletion with fludarabine and cyclophosphamide, followed by a single flat dose of JCAR017 at one of two dose levels (DL1, 5x10⁷ CAR T cells; DL2, 1x10⁸ CAR T cells). A small cohort received a 2-dose schedule at DL1. Blood samples were collected and evaluated for PK, PD, and cytokine levels. CAR T cell expansion was evaluated in bone marrow at day 11 (±3 days) after infusion. PK was measured using validated flow cytometry and qPCR-based assays to detect EGFRt (a marker encoded by the CAR transgene and expressed separately) or host cell integrated CAR transgene, respectively. B cell aplasia was assessed by CD19 flow cytometry. Plasma cytokines were evaluated. Cytokines and additional plasma analytes are being evaluated on additional samples and will be presented. Correlations were observed with clinical outcomes, including best overall response, durable response, and all grade NT and CRS. Univariate nonparametric tests were used for statistical analysis, and all reported p-values are 2-sided without multiplicity adjustment.

Results:

Using a data cut-off of May 7, 2017, 55 pts in the DLBCL cohort were evaluable for safety; 54 pts were evaluable for efficacy. Four MCL pts were also evaluated for safety. Blood samples from 59 pts were included in this analysis. Pts receiving DL2 relative to DL1 had higher median C_max and median AUC_0-28 for CD3+/CAR+, CD4+/CAR+, and CD8+ CAR+ T cell subsets in peripheral blood (AUC: DL2 vs DL1 was 1836 vs 461, 350 vs 182, and 1628 vs 114, for CD3, CD4, and CD8, respectively; p < 0.05 for CD8; C_max: DL2 vs DL1 was 99.8 vs 27.9, 15.1 vs 5.2, and 73.1 vs 5.5 cells/μl, respectively). Median time to maximum CD3+ CAR T cell expansion was 15 days (range 8-29) and did not differ between dose levels. JCAR017 cells homed to the bone marrow at relatively similar levels of CD4+ and CD8+ CAR+ T cells to blood.

Median C_max and median AUC_0-28 of CD8+ CAR+ T cells were higher in responding patients and with durable response at month 3 (CD8 C_max median = 20.8 vs 5.5; CD8 AUC median = 235 vs 55 in CR/PR at Month 3 vs PD at Month 3). Of pts evaluable for CAR T cell persistence, 90% and 93% of 29 pts had detectable CD8+ and CD4+ CAR+ T cells, respectively, at month 3; 63% and 58% of 19 pts had detectable CD8+ and CD4+CAR+ T cells, respectively, at month 6. At months 3 and 6, no statistically significant differences in the persistence of CAR T cells were seen in those with durable response or relapse. Most striking, CAR T cells were detectable at time of relapse in 89% of 11 pts with PK, even though B cell aplasia (<1 cell/µl) was demonstrated in nearly all pts 97% (34/35) at month 3, 100% (24/24) at month 6.

Higher C_max and AUC_0-28 at DL2 did not increase CRS or NT. For any NT or for > Gr2 CRS, both CD4+/CAR+ and CD8+/CAR+ median AUCs were 5-10 fold and 3-5 fold higher, respectively, than median DL2 AUC. Higher disease burden and baseline levels of inflammatory cytokines appeared to be associated with higher CAR T cell peak levels, higher cytokine peak levels, and higher incidences of CRS and NT. Preliminary findings suggest that patient factors may result in higher expansion of CAR T cells and the associated CRS and NT.

Conclusions:

Based on current data, JCAR017 has demonstrated increased CAR T cell expansion and persistence and higher durability of response at 3 months at higher dose levels, without increased toxicity. Exploratory analyses suggest that high peak levels of CAR T cells and cytokines in the blood may be associated with NT and CRS and may be influenced by baseline patient factors. CAR T cells are present at the time of relapse, suggesting opportunities for combination approaches.