Abstract
This is a pivotal, multicenter, open-label study of moxetumomab pasudotox, a recombinant CD22-targeting immunotoxin, in hairy cell leukemia (HCL), a rare B cell malignancy with high CD22 expression. The study enrolled patients with relapsed/refractory HCL who had ≥2 prior systemic therapies, including ≥1 purine nucleoside analog. Patients received moxetumomab pasudotox 40 µg/kg intravenously on days 1, 3, and 5 every 28 days for ≤6 cycles. Blinded independent central review determined disease response and minimal residual disease (MRD) status. Among 80 patients (79% males; median age, 60.0 years), durable complete response (CR) rate was 30%, CR rate was 41%, and objective response rate (CR and partial response) was 75%; 64 patients (80%) achieved hematologic remission. Among complete responders, 27 (85%) achieved MRD negativity by immunohistochemistry. The most frequent adverse events (AEs) were peripheral edema (39%), nausea (35%), fatigue (34%), and headache (33%). Treatment-related serious AEs of hemolytic uremic syndrome (7.5%) and capillary leak syndrome (5%) were reversible and generally manageable with supportive care and treatment discontinuation (6 patients; 7.5%). Moxetumomab pasudotox treatment achieved a high rate of independently assessed durable response and MRD eradication in heavily pretreated patients with HCL, with acceptable tolerability.
Highlights
Patients with hairy cell leukemia (HCL), a rare B cell malignancy characterized by high CD22 expression, typically present with pancytopenia and increased susceptibility to infection [1]
The current study evaluated the rate of durable complete response with moxetumomab pasudotox in patients with multiply relapsed HCL
The primary end point was durable complete response, defined as complete response assessed by blinded independent central review with maintenance of hematologic remission for more than 180 days
Summary
Patients with hairy cell leukemia (HCL), a rare B cell malignancy characterized by high CD22 expression, typically present with pancytopenia and increased susceptibility to infection [1]. Many patients achieve long-term complete remission with the purine nucleoside analogs pentostatin or cladribine [2,3,4], ~50% will relapse by 16
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