There were a number of landmark approvals by the US Food and Drug Administration (FDA) in 2017 for cancer therapies, among them, the approval of the first two chimeric antigen receptor (CAR) T-cell therapies for cancer: tisagenlecleucel (in August) and axicabtagene ciloluecel (in October).1 CAR T-cells are a type of adoptive cell therapy or immunotherapy, in which the patient’s own immune cells are genetically engineered to target a tumor-associated antigen, in this case CD19. In tisagenlecleucel, CD19 proteins on B cells are targeted in the treatment of B-cell precursor acute lymphoblastic leukemia. Axicabtagene ciloluecel, the second anti-CD19 CAR T-cell therapy, was approved for the treatment of refractory, aggressive B-cell non-Hodgkin lymphoma.
Tisagenlecleucel
Tisagenlecleucel was approved for the treatment of pediatric patients up to 25 years of age with B-cell precursor acute lymphoblastic leukemia (ALL) whose disease is refractory to treatment or who have relapsed after second-line therapy or beyond.2 Approval was based on the pivotal ELIANA trial, a single-arm, global phase 2 trial conducted at 25 centers worldwide during April 2015 through April 2017. Patients were eligible for enrollment if they had relapsed or refractory B-cell ALL and were at least 3 years of age at screening and no older than 21 years of age at diagnosis, had at least 5% lymphoblasts in the bone marrow at screening, had tumor expression of CD19, had adequate organ function, and a Karnofsky (adult) or Lansky (child) Performance Status of ≥50 (with the worst allowable score, 50, indicating a patient who requires considerable assistance and frequent medical care [Karnofsky] and lying around much of the day, but gets dressed; no active playing but participates in all quiet play and activities [Lansky]). Exclusion criteria included previous receipt of anti-CD19 therapy, concomitant genetic syndromes associated with bone marrow failure, previous malignancy, and/or active or latent hepatitis B or C virus (HBV/HCV) infection.
The overall remission rate (ORR) was evaluated in 75 patients who were given a single dose of tisagenlecleucel (a median weight-adjusted dose of 3.1 x 106 transduced viable T cells per kg of body weight) within 14 days of completing a lymphodepleting chemotherapy regimen. The confirmed ORR after at least 3 months of follow-up, as assessed by independent central review, was 81%, which included 60% of patients in complete remission (CR) and 21% in complete remission with incomplete hematologic recovery, all of whom were negative for minimal residual disease.
The most common adverse events (AEs) associated with tisagenlecleucel treatment were cytokine release syndrome (CRS), hypogammaglobulinemia, infection, pyrexia, decreased appetite, headache, encephalopathy, hypotension, bleeding episodes, tachycardia, nausea, diarrhea, vomiting, viral infectious disorders, hypoxia, fatigue, acute kidney injury, and delirium. AEs were of grade 3/4 severity in 84% of patients.3
To combat serious safety issues, including CRS and neurologic toxicities, the FDA approved tisagenlecleucel with a Risk Evaluation and Mitigation Strategy (REMS) that, in part, requires health care providers who administer the drug to be trained in their management. It also requires the facility where treatment is administered to have immediate, onsite access to the drug tocilizumab, which was approved in conjunction with tisagenlecleucel for the treatment of patients who experience CRS.
In addition to information about the REMS, the prescribing information details warnings and precautions relating to several other common toxicities. These include hypersensitivity reactions, serious infections, prolonged cytopenias, and hypogammaglobulinemia.
Patients should be monitored for signs and symptoms of infection and treated appropriately. Viral reactivation can occur after tisagenlecleucel treatment, so patients should be screened for HBV, HCV, and human immunodeficiency virus before collection of cells.
The administration of myeloid growth factors is not recommended during the first 3 weeks after infusion or until CRS has resolved. Immunoglobulin levels should be monitored after treatment and hypogammaglobulinemia managed using infection precautions, antibiotic prophylaxis, and immunoglobulin replacement according to standard guidelines.
Patients treated with tisagenlecleucel should also be monitored for life for secondary malignancies, should not be treated with live vaccines from 2 weeks before the start of lymphodepleting chemotherapy until immune recovery after tisagenlecleucel infusion, and should be aware of the potential for neurological events to impact their ability to drive and use dangerous machinery.4
Tisagenlecleucel is marketed as Kymriah by Novartis Pharmaceuticals. The recommended dose is 1 infusion of 0.2-5 x 106 CAR-positive viable T cells per kilogram of body weight intravenously (for patients ≤50kg) and 0.1-2.5 x 108 cells/kg (for patients >50kg), administered 2-14 days after lymphodepleting chemotherapy.
Axicabtagene ciloleucel
Axicabtagene ciloleucel was approved for the treatment of adult patients with certain types of relapsed or refractory large B-cell lymphoma, including diffuse large B-cell lymphoma (DLBCL), primary mediastinal B-cell lymphoma (PMBCL), high-grade B-cell lymphoma, and DLBCL arising from follicular lymphoma.5 It is not indicated for the treatment of patients with primary central nervous system lymphoma.
Approval followed positive results from the phase 2 single-arm, multicenter ZUMA-1 trial.6 Patients were included if they were aged 18 years of age and older, had histologically confirmed aggressive B-cell non-Hodgkin lymphoma that was chemotherapy refractory, had received adequate previous therapy, had at least 1 measurable lesion, had completed radiation or systemic therapy at least 2 weeks before, had resolved toxicities related to previous therapy, and had an Eastern Cooperative Oncology Group Performance Status of 0 (asymptomatic) or 1 (symptomatic), an absolute neutrophil count of ≥1000/µL, a platelet count of ≥50,000/µL, and adequate hepatic, renal and cardiac function. They were treated with a single infusion of axicabtagene ciloleucel after lymphodepleting chemotherapy.
Patients who had received previous CD19-targeted therapy, who had concomitant genetic syndromes associated with bone marrow failure, who had previous malignancy, and who had active or latent HBV/HCV infection were among those excluded from the study.
Patients were enrolled in 2 cohorts; those with DLBCL (n = 77) and those with PMBCL or transformed follicular lymphoma (n = 24). The primary endpoint was objective response rate, and after a primary analysis at a minimum of 6 months follow-up, the objective response rate was 82%, with a CR rate of 52%. Among patients who achieved CR, the median duration of response was not reached after a median follow-up of 7.9 months.
A subsequent updated analysis was performed when 108 patients had been followed for a minimum of 1 year. The objective response rate was 82%, and the CR rate was 58%, with some patients having CR in the absence of additional therapies as late as 15 months after treatment. At this updated analysis, 42% of patients continued to have a response, 40% of whom remained in CR.
The most common grade 3 or higher AEs included febrile neutropenia, fever, CRS, encephalopathy, infections, hypotension, and hypoxia. Serious AEs occurred in 52% of patients and included CRS, neurologic toxicity, prolonged cytopenias, and serious infections. Grade 3 or higher CRS or neurologic toxicities occurred in 13% and 28% of patients, respectively. Three patients died during treatment.
To mitigate the risk of CRS and neurologic toxicity, axicabtagene ciloleucel is approved with an REMS that requires appropriate certification and training before hospitals are cleared to administer the therapy.
Other warnings and precautions in the prescribing information relate to serious infections (monitor for signs and symptoms and treat appropriately), prolonged cytopenias (monitor blood counts), hypogammaglobulinemia (monitor immunoglobulin levels and manage appropriately), secondary malignancies (life-long monitoring), and the potential effects of neurologic events on a patient’s ability to drive and operate dangerous machinery (avoid for at least 8 weeks after infusion).7
Axicabtagene ciloleucel is marketed as Yescarta by Kite Pharma Inc. The recommended dose is a single intravenous infusion with a target of 2 x 106 CAR-positive viable T cells per kilogram of body weight, preceded by fludarabine and cyclophosphamide lymphodepleting chemotherapy.