By: Greg Wolfe, Ph.D., Senior Consultant, Clinical & Scientific Assessment, Kantar Health and Jay Grisolano, Ph.D., Senior Director, Clinical & Scientific Assessment, Kantar Health
Immunotherapies such as checkpoint inhibitors have had a dramatic impact on treatment paradigms for many tumor types over the past few years, and their full potential is far from being realized. Hot on the heels of checkpoint inhibitors are engineered, adoptive T-cell therapies that represent another promising advancement. These “living drugs” certainly have the potential to lead to yet another paradigm shift in anticancer therapies. Chimeric antigen receptor (CAR) technology, one type of adoptive T-cell therapy, took center stage yesterday at the 2016 American Society of Hematology (ASH) annual meeting.
With the CAR T-cell approach, T-cells (typically patient-derived) are transduced with an engineered receptor that typically comprises an extracellular domain that recognizes a specific epitope on cancer cells (typically from a B-cell-derived monoclonal antibody), coupled with the intracellular CD3ζ domain derived from the T-cell receptor and one or more co-stimulatory signaling domains. Patients receive “preparative chemotherapy” to achieve lymphodepletion and/or myeloablation to minimize regulatory T-cells and myeloid-derived suppressor cells that inhibit immune-mediated attack, and then genetically modified T-cells that attack cancer cells are infused into the patient.
Kite Pharma is developing KTE-C19 (axicabtagene ciloleucel), an investigational therapy where patients’ T-cells are genetically modified to express a chimeric antigen receptor designed to target the antigen CD19, a protein expressed on the cell surface of B-cell lymphomas and leukemias. The intracellular portion of the KTE-C19 contains the CD3ζ signaling domain in tandem with the co-stimulatory CD28 signaling domain.
Results of the evaluation of KTE-C19 in patients with chemotherapy-refractory diffuse large B-cell lymphoma (DLBCL) from the Phase II portion of the ZUMA-1 trial were presented by Dr. Sattva S. Neelapu yesterday in the Late-Breaking Abstract session of the ASH 2016 annual meeting. The ZUMA-1 trial (NCT02348216) is a single-arm, open-label, multicenter, Phase I/II trial designed to evaluate the safety and efficacy of KTE-C19 in refractory aggressive non-Hodgkin’s lymphoma (NHL). Patients with DLBCL, primary mediastinal B-cell lymphoma (PMBCL), and transformed follicular lymphoma (TFL) were enrolled in the trial. Safety was the primary endpoint in the Phase I portion of the study, and overall response rate was the primary endpoint of the Phase II portion with secondary endpoints that included duration of response, progression-free survival, and overall survival. Results of the Phase I portion of ZUMA-1 were reported previously1 and demonstrated ongoing complete responses in 43% of treated patients at 12 or more months. The Phase II portion of the study has two cohorts based on tumor type: DLBCL (cohort 1) or PMBCL/TFL (cohort 2). Preliminary results from the first prespecified interim analysis of KTE-C19, which included DLBCL patients (cohort 1), from ZUMA-1 were presented.2
Patients (n=111) were enrolled and leukapheresed to collect T-cells for production of KTE-C19. Patients subsequently received a conditioning regimen of cyclophosphamide (500 mg/m2) and fludarabine (30 mg/m2) x three days. KTE-C19 manufacture was accomplished with an average turnaround time of 17 days, a 99% success rate, and 101 patients each received a single infusion of KTE-C19 (2 x106 cells/kg). Patients had a median age of 59 and had received a median of three prior therapies. Of 73 treated DLBCL patients, the best overall response rate (ORR) with a one-month follow-up was 68%, including a complete response (CR) rate of 33%. At a three-month follow-up, the best ORR improved to 76% with a CR rate of 47%, which compares favorably to historical control (p=0.0001), and thus the primary endpoint of the study was achieved. There was a 39% durable CR rate at the three-month assessment. Grade ≥3 adverse events were reported in 93% of DLBCL patients and included cytokine release syndrome in 10 patients (14%) and neurologic events in 18 patients (25%); most of these adverse events were reversible. One KTE-C19-related Grade 5 event was reported in a DLBCL patient.
DLBCL is the most commonly occurring subtype of NHL, with an incidence of 28,449 in 2016 according to Kantar Health’s CancerMPact® Patient Metrics.3 There is a great need for effective treatment options for this patient population as outcomes are quite poor for patients with refractory DLBCL. A recent meta-analysis recently reported an ORR of 26% and median overall survival of 6.6 months based on currently available therapies.4 Efficacy results from the ZUMA-1 study trial far exceed historical controls, like this meta-analysis, and thus ZUMA-1 results generated considerable excitement at ASH 2016. ZUMA-1 is the first multicenter study of anti-CD19 CAR T-cells in refractory, aggressive NHL, and this study demonstrated the successful implementation of management strategies for treatment emergent adverse events associated with this technology. Additional data from ZUMA-1 were presented at ASH 2016 from patients with PMBCL and TFL (cohort 2), and results were equally as encouraging.5
KTE-C19 will likely play an important role in the future treatment of DLBCL and other aggressive NHL subtypes. The U.S. Food and Drug Administration (FDA) awarded KTE-C19 Breakthrough Therapy Designation (BTD) in December 2015. On December 4, 2016, Kite announced that they initiated a rolling submission of a U.S. Biologic License Application (BLA) to the FDA based on the results of ZUMA-1, and completion of the filing is expected by the end of the first quarter of 2017. The BLA is for treatment of relapsed patients with aggressive B-cell NHL who are ineligible for autologous stem cell transplant (ASCT). This submission represents the first BLA filing for a CAR-T therapy. With approval likely, Kite plans to commercially launch KTE-C19 in 2017. Kite also plans a regulatory submission to the European Medicines Agency (EMA) for KTE-C19 in 2017. Earlier this year, the EMA granted Kite access to Priority Medicines (PRIME) regulatory support for axicabtagene ciloleucel for the treatment of refractory DLBCL.
Kite is also sponsoring clinical trials to evaluate KTE-C19 in other B-cell malignancies including indolent NHL, mantle cell lymphoma, acute lymphocytic leukemia, and chronic lymphocytic leukemia. In September 2016, Kite, in collaboration with Roche/Genentech, initiated ZUMA-6, a Phase I/II study designed to evaluate safety and efficacy of KTE-C19 administered in combination with atezolizumab for treatment of patients with refractory DLBCL. The future looks bright for this CAR T-cell product.