FDA Approves New Treatment for Hairy Cell Leukemia

Adults with relapsed or refractory hairy cell leukemia (HCL) now have a new treatment option. The US Food and Drug Administration just approved moxetumomab pasudotox (Lumoxiti, AstraZeneca) for adults with relapsed or refractory HCL who “received at least 2 prior systemic therapies, including treatment with a purine nucleoside analog. The drug is the first of a type of treatment known as CD22-directed cytotoxin.

Richard Pazdur, MD, director of the FDA's Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research is quoted in the approval as stating, "[Moxetumomab pasudotox] fills an unmet need for patients with hairy cell leukemia whose disease has progressed after trying other FDA-approved therapies. This therapy is the result of important research conducted by the National Cancer Institute that led to the development and clinical trials of this new type of treatment for patients with this rare blood cancer.”

The approval of the treatment is based on a single-arm, open-label clinical trial made up of 80 participants (63 male; median age 60 years) who had previously received treatment with at least 2 systemic therapies, including a purine nucleoside analog. For the trial, participants received 40 µg/kg intravenously on days 1, 3, and 5 of 28-day cycles, for up to 6 cycles. Participants underwent a median number of 3 therapies (range, 2-11). A total of 39 participants (49%) had more than 3 prior therapies and 60 participants (75%) had prior rituximab.

Thirty-percent of participants in the trial were able to achieve durable complete response (CR), which was defined as "maintenance of hematologic remission for more than 180 days after achievement of CR." The overall response rate (those participants with partial or complete response) was 75%.

The most frequent treatment-related adverse events seen during the trial were nausea (28%), peripheral edema (26%), headache (21%), and pyrexia (20%); 8% of the participants had infections and 3% had neutropenia that was deemed treatment-related.

A Boxed Warning accompanies the approval, advising both patients and providers to be aware of the risk of the development of grade 3/4 capillary leak syndrome, symptoms of which include difficulty breathing, weight gain, hypotension, or swelling of arms, legs and/or face. Furthermore, the warning includes a risk of hemolytic uremic syndrome. During the trial, 7 participants (9%) had capillary leak syndrome (grade 2: n = 5; grade 4: n = 2), 7 (9%) had hemolytic uremic syndrome (grade 2: n = 2; grade 3: n = 3; grade 4: n = 2), and 4 (5%) had both. The investigators reported that the conditions were manageable and reversible (with no plasma exchange in hemolytic uremic syndrome).

Adequate fluid intake and blood chemistry values should be monitored in patients taking the drug. Other serious warnings include: decreased renal function, infusion-related reactions and electrolyte abnormalities. Women who are breastfeeding should not be given Moxetumomab pasudotox.

The FDA granted this application Fast Track and Priority Review designations. Moxetumomab pasudotox also received Orphan Drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases.