SAN FRANCISCO – A growing number of immunotherapy options for adults with acute lymphocytic leukemia (ALL) – rituximab, inotuzumab ozogamicin, blinatumomab and chimeric antigen receptor (CAR) T-cell therapy – have improved remission rates, but their collective effects on patient outcomes remain to be seen,, said at the National Comprehensive Cancer Network Annual Congress: Hematologic Malignancies.
The main challenge for the field is deciding when and how to use a variety of therapies, he said. “How are we going to put these together? What’s the order?” he asked. “Are we going to be able to decrease the need for allogeneic stem cell transplant? And, obviously, that’s the goal.”
About 30%-50% of adults with ALL exhibit CD20-positive cells, making them potentially treatable with rituximab. Data show a better event-free survival rate and a reduced relapse rate when rituximab is added to standard chemotherapy as compared with standard chemotherapy alone, Dr. Maloney of the clinical research division at the Fred Hutchinson Cancer Research Center, Seattle, noted (). But the improvement was only “modest,” he said.
The anti-CD22 antibody inotuzumab ozogamicin has produced complete remission in 81% of relapsed or refractory ALL patients, compared with those getting standard therapy (). Dr. Maloney said it seems well tolerated, but there is concern about an increase in veno-occlusive disease in patients who have undergone or will undergo an allogeneic stem cell transplant.
Blinatumomab produces moderate response rates and minimal residual disease–negative remissions, but delivery of the drug is “cumbersome,” requiring a 4-week continuous infusion, he said. The drug seems to be more effective in those with a lower burden of disease, he noted.
CAR T-cell therapy has produced MRD-negative complete responses in 94% of patients, based on results from a clinical trial at Fred Hutchinson. And using the chemotherapy drug fludarabine in combination with this therapy “dramatically” boosts the peak number of the CAR T cells and how long they persist, Dr. Maloney said. Still, CAR T-cell therapy is a work-intensive treatment requiring cells harvested from the patient, and the procedure often brings on cytokine-release syndrome and neurotoxicity, though both adverse events are typically reversible, he said.
It may be that using fewer CAR T cells can reduce toxicity without compromising treatment response, he said.
Questions remain over whether to transplant patients who are in remission after CAR T-cell therapy. “This is a hot debate,” he said. The decision will likely depend on their prior therapy, whether they’ve had a prior transplant, and the how robust the CAR T-cell expansion has been, he said.
Dr. Maloney reports financial relationships with Celgene, Gilead Sciences, Kite Pharma, and Roche.