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Moxetumomab Pasudotox Therapy Under Study in Resistant Hairy Cell Leukemia

By: Hillary Ojeda
Posted: Thursday, March 19, 2020

According to an article published in The Oncologist, treatment with moxetumomab pasudotox—a biologic containing an antibody fragment binding to CD22 and attached to a portion of Pseudomonas exotoxin A—may lead to increased rates of complete remission and minimal residual disease (MRD) in patients with hairy cell leukemia. To diminish tumor burden in patients with this rare type of chronic lymphocytic leukemia, Robert J. Kreitman, MD, and Ira Pastan, MD, both of the National Institutes of Health, Bethesda, Maryland, are conducting a phase I trial of the recombinant immunotoxin in combination with rituximab.

“[Moxetumomab pasudotox] is unique in its achievement of MRD-negative complete remission in this chemoresistant population, without chemotherapy-type toxicities,” the authors commented.

In a phase I dose-escalation trial, the efficacy of moxetumomab pasudotox was examined in 49 patients with relapsed or refractory hairy cell leukemia. An international pivotal phase III trial assessed the drug’s efficacy in 80 patients. For the phase I trial, dose escalation was done in three or four patients, each at 5, 10, 20, 30, 40, and 50 μg/kg every other day for three doses, followed by a fixed‐dose cohort. The phase III trial used a single-arm non–placebo-controlled trial structure including a treatment of the biologic at 40 μg/kg every other day for three doses.

In phase I, 64% of 33 patients receiving the highest dose level achieved complete remission—many lacked MRD. Of the 11 patients without MRD, 10 were still in complete remission after a median of 42 months. In phase III testing, a total of 41% had complete remission, and 82% (27 of 33 patients) had MRD-negative disease. A total of 4 of the 27 patients relapsed during the follow-up period.

Disclosure: The study authors’ disclosure information can be found at theoncologist.onlinelibrary.wiley.com.



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