Credit: Charles Haymond
An anti-CD19 chimeric antigen receptor (CAR) T-cell therapy can elicit complete responses (CRs) in heavily pretreated patients with acute lymphoblastic leukemia (ALL), results of a phase 1 trial suggest.
More than half of the 21 patients enrolled achieved a CR, and most of those patients went on to hematopoietic stem cell transplant (HSCT).
All 10 patients who underwent HSCT remain leukemia-free at a median follow-up of 10 months.
The CAR T cells did prompt some serious adverse effects, but all effects were fully reversible.
Crystal L. Mackall, MD, of the National Cancer Institute in Bethesda, Maryland, and her colleagues reported these results in The Lancet.
The phase 1 study enrolled patients ages 1 to 30 years who had relapsed or refractory ALL or non-Hodgkin lymphoma. Twenty patients had B-cell ALL, and 1 had diffuse large B-cell lymphoma (DLBCL). All of the patients had been heavily pretreated, and 8 had received a prior HSCT.
Patients received a conditioning regimen of cyclophosphamide and fludarabine, followed by a single infusion of CAR T cells: either 1×10⁶ CAR-transduced T cells per kg or 3×10⁶ CAR-transduced T cells per kg.
The CAR T cells were produced from each patient’s own peripheral blood mononuclear cells, modified using a gammaretroviral vector encoding the CAR, as well as a CD28 costimulatory moiety. After the dose-escalation phase, an expansion cohort was treated at the maximum-tolerated dose.
Twenty-one patients were enrolled and infused, but 2 of them did not receive the prescribed dose of CAR T cells, as the assigned dose could not be generated. The maximum-tolerated dose was 1×10⁶ CAR T cells per kg.
All toxicities were fully reversible. The most common non-hematologic grade 3 adverse events were fever (n=9), hypokalemia (n=9), fever and neutropenia (n=8), and cytokine release syndrome (n=3). Grade 4 cytokine release syndrome occurred in 3 patients.
At day 28, 12 patients had achieved a minimal residual disease (MRD)-negative CR. One patient had an MRD-positive CR, 1 had an MRD-positive CR with incomplete count recovery, and 3 patients had stable disease. Four patients, including the one with DLBCL, progressed.
Ten of the patients with an MRD-negative CR subsequently underwent HSCT, and all 10 remained disease-free with a median follow-up of 10 months.
“The results show that this treatment is feasible in many patients with ALL and can eradicate chemoresistant disease with an acceptable toxicity profile,” said Gary Schiller, MD, of the University of California, Los Angeles, who was not involved in this study.
“Further, the findings demonstrate substantially higher response rates than seen in the literature for the most recently approved agent for refractory ALL. CD19-CAR therapy represents a potentially important new tool to address the urgent need for new treatment modalities in these patients.”
Researchers previously reported positive results with this therapy in patients with chemotherapy-refractory DLBCL.
