Dr. Kreitman on MRD-Negative CRs With Moxetumomab Pasudotox in Hairy Cell Leukemia

Robert J. Kreitman, MD, chief of Clinical Immunotherapy Section in the Laboratory of Molecular Biology at the National Cancer Institute, discusses the association between minimal residual disease (MRD) negativity and complete remission (CR) durations in patients with hairy cell leukemia treated with moxetumomab pasudotox, in an interview during the 2019 Hairy Cell Leukemia Foundation Annual Conference.

Kreitman presented data from combining findings from a phase I and phase III clinical trial that looked at MRD negativity in patients treated with moxetumomab pasudotox. These data demonstrated that patients will have a longer duration of CR when there is no MRD positivity. Kreitman compared several different tests that looked at MRD and found that bone marrow flow cytometry was the most sensitive assay for identifying patients who have a longer CR duration and those who have a shorter duration.

While the assay can predict MRD negativity in patients with hairy cell leukemia, bone marrow biopsies can be challenging to do often in these patients. Biopsies are done several times during treatment, but it would be beneficial to determine the MRD status with each cycle of moxetumomab pasudotox, says Kreitman. Blood flow cytometry is not as sensitive in these patients, where data showed that the blood flow was positive for MRD in 1 of 41 patients assessed from the phase I and phase III trials. Overall, blood flow cytometry cannot be used to discriminate which patients will have a shorter or longer CR duration with moxetumomab pasudotox.

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