Background: ZUMA-1 is a pivotal, multicenter trial of axi-cel, an autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy, for the treatment of patients with refractory, aggressive NHL. The objective response rate (ORR) was 82% with a 54% rate of complete response and 44% of responses were ongoing at the time of the primary analysis (Locke et al. AACR 2017. #9986). Grade ≥ 3 cytokine release syndrome (CRS) and neurologic events (NE) occurred in 13% and 28% of patients, respectively. A safety expansion cohort was added to further characterize mechanisms underlying CRS and NE associated with CAR T cell therapy and to evaluate the impact of prophylactic use of tocilizumab and levetiracetam on the rates of these adverse events (AEs).

Methods: Patients (≥ 18 years) must have had an Eastern Cooperative Oncology Group performance status of 0-1 and refractory or relapsed transplant ineligible disease. Patients received low-dose conditioning of 500 mg/m² cyclophosphamide and 30 mg/m² fludarabine for 3 days followed by axi-cel at a target dose of 2 × 10⁶ CAR T cells/kg. Patients also received prophylactic treatment with 750 mg of levetiracetam twice a day on day 0 and 8 mg/kg of tocilizumab on day 2 post axi-cel infusion. To evaluate the mechanisms of NE, paired serum and cerebrospinal fluid (CSF) were obtained for all patients prior to conditioning chemotherapy and after axi-cel infusion (day 5).

Results: As of April 26, 2017, 31 patients received axi-cel. Median age was 51 years (range, 21-74), 52% were male, 65% had stage III-IV disease, 74% were refractory to ≥ second-line therapy, and 19% relapsed ≤ 12 months after autologous stem cell transplant. Most patients (97%) experienced at least 1 grade ≥ 3 AE. The most common grade ≥ 3 AEs were neutropenia/neutrophil count decreased (71%), anemia (55%), thrombocytopenia/platelet count decreased (52%), leukopenia/white blood cell count decreased (35%), febrile neutropenia (29%), encephalopathy (23%), and hypotension (23%). One patient (3%) experienced a grade ≥ 3 (grade 4) CRS. Grade 3 and 4 NE occurred in 29% and 6% of patients, respectively. One patient died of cerebral edema; there were no other deaths due to AE.

Updated efficacy, safety, subgroups, and paired blood/serum/CSF biomarker associative analyses will be presented.

Conclusions: Early use of tocilizumab may reduce the incidence of severe CRS but not NE in patients treated with CAR T cell therapy. These data provide evidence that the underlying pathophysiology of NE may differ from that of CRS. Understanding the mechanisms of NE may help to further improve the benefit:risk profile for CAR T cell therapy.

Drs Locke and Neelapu contributed equally to this work.

Locke: Kite Pharma: Consultancy; Cellular Biomedicine Group Inc: Consultancy. Neelapu: Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Poseida: Research Funding; Cellectis: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Jacobson: Pharmacyclics, LLC: Consultancy; Kite Pharma: Consultancy. Braunschweig: Kite Pharma: Equity Ownership. Oluwole: Kite Pharma: Consultancy. Siddiqi: Seattle Genetics: Speakers Bureau; Juno: Other: Steering committee for JCAR017; Pharmacyclics, an AbbVie Company: Other: Steering committee for ibrutinib, Speakers Bureau. Timmerman: Celgene: Consultancy; Seattle Genetics: Consultancy; Kite …