Chimeric antigen receptor (CAR)-modified T cells with anti-CD19 specificity are a highly effective novel immune therapy for relapsed/refractory acute lymphoblastic leukemia. Cytokine release syndrome (CRS) is the most significant and life-threatening toxicity. To improve understanding of CRS, we measured cytokines and clinical biomarkers in 51 CTL019-treated patients. Peak levels of 24 cytokines, including IFNγ, IL6, sgp130, and sIL6R, in the first month after infusion were highly associated with severe CRS. Using regression modeling, we could accurately predict which patients would develop severe CRS with a signature composed of three cytokines. Results were validated in an independent cohort. Changes in serum biochemical markers, including C-reactive protein and ferritin, were associated with CRS but failed to predict development of severe CRS. These comprehensive profiling data provide novel insights into CRS biology and, importantly, represent the first data that can accurately predict which patients have a high probability of becoming critically ill. SIGNIFICANCE: CRS is the most common severe toxicity seen after CAR T-cell treatment. We developed models that can accurately predict which patients are likely to develop severe CRS before they become critically ill, which improves understanding of CRS biology and may guide future cytokinedirected therapy. Cancer Discov;6(6);

SUMMARY A patient with refractory multiple myeloma received an infusion of CTL019 cells, a cellular therapy consisting of autologous T cells transduced with an anti-CD19 chimeric antigen receptor, after myeloablative chemotherapy (melphalan, 140 mg per square meter of body-surface area) and autologous stem-cell transplantation. Four years earlier, autologous transplantation with a higher melphalan dose (200 mg per square meter) had induced only a partial, transient response. Autologous transplantation followed by treatment with CTL019 cells led to a complete response with no evidence of progression and no measurable serum or urine monoclonal protein at the most recent evaluation, 12 months after treatment. This response was achieved despite the absence of CD19 expression in 99.95% of the patient’s neoplastic plasma cells. (Funded by Novartis and others; ClinicalTrials.gov number, NCT02135406.)

Pancreatic ductal adenocarcinoma (PDAC) is resistant to T-cell-mediated immunotherapy. We engineered T cells to transiently express a messenger RNA encoding a chimeric antigen receptor (CAR) specific for mesothelin, a protein that is overexpressed by PDAC cells. We performed a phase I study to evaluate the safety and efficacy of adoptive cell therapy with autologous mesothelin-specific CAR T cells (CARTmeso cells) in 6 patients with chemotherapy-refractory metastatic PDAC. Patients were given intravenous CARTmeso cells 3 times weekly for 3 weeks. None of the patients developed cytokine release syndrome or neurologic symptoms and there were no dose-limiting toxicities. Disease stabilized in 2 patients, with progression-free survival times of 3.8 and 5.4 months. We used F-2-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography/computed tomography imaging to monitor the metabolic active volume (MAV) of individual tumor lesions. The total MAV remained stable in 3 patients and decreased by 69.2% in 1 patient with biopsy-proven mesothelin expression; in this patient, all liver lesions had a complete reduction in FDG uptake at 1 month compared with baseline, although there was no effect on the primary PDAC. Transient CAR expression was detected in patients' blood after infusion and led to expansion of new immunoglobulin G proteins. Our results provide evidence for the potential antitumor activity of messenger RNA CARTmeso cells, as well as PDAC resistance to the immune response.

PURPOSE The anti-CD19 chimeric antigen receptor T-cell therapy tisagenlecleucel (CTL019) has an 81% response rate in children with relapsed or chemotherapy refractory (r/r) B-cell acute lymphoblastic leukemia (ALL). Cytokine release syndrome (CRS) is a life-threatening treatment-related toxicity that limits the full therapeutic potential in adults. We report outcomes for adults with r/r ALL treated with an optimized CTL019 dosing and CRS management strategy. METHODS Adults with r/r B-cell ALL received CTL019 in 1 of 2 trials. Patients received lymphodepletion followed by CTL019 as either a one-time infusion or fractionated infusions split over 3 days (day 1, 10%; day 2, 30%; day 3, 60%), which allowed for day 2 and day 3 doses to be held for early CRS. Total planned CTL019 dose varied with adaptive protocol modifications in response to efficacy and CRS toxicity. RESULTS Thirty-five adults with r/r ALL received CTL019 in 1 of 3 dosing cohorts. The low-dose cohort (n = 9) received single or fractionated dosing and had manageable toxicity with a 33% complete remission (CR) rate. In the high-dose single infusion cohort, 3 of 6 patients with refractory CRS concurrent with culture-positive sepsis died, and 3 achieved CR. The 20 patients in the high-dose fractionated (HDF) cohort had a 90% CR rate and manageable CRS. The HDF cohort had the highest survival, with a 2-year overall survival of 73% (95% CI, 46% to 88%) and event-free survival of 49.5% (95% CI, 21% to 73%). CONCLUSION Fractionated dosing of CTL019 with intrapatient dose modification optimizes safety without compromising efficacy in adults with r/r ALL.

Purpose Graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (alloSCT) has been associated with low numbers of circulating CD4+CD25+FoxP3+ regulatory T-cells(Tregs). Because Tregs express high levels of the IL-2 receptor, they may selectively expand in vivo in response to doses of IL-2 insufficient to stimulate T-effector T-cell populations, thereby preventing GvHD. Experimental Design We prospectively evaluated the effects of ultra low-dose (ULD) IL-2 injections on Treg recovery in pediatric patients after alloSCT and compared this recovery with Treg reconstitution post alloSCT in patients without IL-2. Sixteen recipients of related(n=12) or unrelated(n=4) donor grafts received ULD-IL-2 post HSCT (100,000–200,000 IU/m2 3×weekly), starting