1. 90% of relapsed B-cell acute lymphoblastic leukemia (ALL) patients achieved complete remission 1 month after an infusion of engineered T-cells.
2. All patients developed the cytokine-release syndrome requiring hospitalization.
Evidence Rating Level: 2 (Good)
Study Rundown: ALL is the most common form of childhood cancer. Up to a quarter of children with ALL will have recurrent or refractory disease. This phase II study looked at a new therapy involving engineered T-cells for relapsed B-cell ALL. The T-cells were engineered to target a protein found on the surface of B-cells called CD19. The hope was that these engineered T-cells would target and kill cancerous B-cells.
27 of 30 patients had complete remission 1 month after infusion of the T-cells. At six months of follow-up, there was a 67% event-free survival rate. The results compares favorably with existing treatments for relapsed ALL, which achieve rates of remission of less than 25% and lasting only 4 to 9 weeks. Adverse effects included the cytokine-release syndrome and B-cell aplasia. Excessive cytokine release as a result of massive T-cell activation leads to the cytokine-release syndrome, which can cause life-threatening complications. B-cell aplasia is an expected consequence of the treatment since the engineered T-cells do not discriminate between cancerous and healthy B-cells. In fact, B-cell aplasia may be a useful marker of continued efficacy of the CTL019 T-cells.
Relevant Reading: Chimeric Antigen Receptor- Modified T Cells for Acute Lymphoid Leukemia
In-Depth: This phase II clinical trial treated 30 patients with CTL019 T-cell therapy to evaluate the safety and feasibility of this therapy. There was a higher proportion of CTL019 T-cells in the 27 patients who achieved remission at 1 month versus the 3 who did not. Three patients who initially achieved remission had relapses after losing the CTL019 T-cells. Notably, another three patients had relapses after their leukemia cells stopped expressing CD19.The study achieved an overall survival of 78% (95% CI, 65 to 95). All patients experienced the cytokine-release syndrome, and 27% developed a severe reaction.
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