EHA 2018 | Durable responses seen with moxetumomab pasudotox in R/R HCL

On Saturday 16^th June an oral abstract session took place at the 23^rd Congress of the European Hematology Association (EHA). Abstract S856 was presented by Francis Giles, Developmental Therapeutics Consortium, Chicago, US, on the use of moxetumomab pasudotox in heavily pretreated patients with relapsed/refractory (R/R) hairy cell leukemia (HCL) (NCT01829711).

Study Overview

• The study was single-arm, open-label at 34 centers across 14 countries
• N = 80 patients received 40 μg/kg IV on Days 1,3 and 5 of 28-day treatment cycles until disease progression or unacceptable toxicity
• The primary endpoint was the rate of durable complete response (CR) that was defined by CR with hematologic remission of ≥181 days
• The secondary endpoints were overall response rate (ORR), CR rate, progression-free survival (PFS), duration of response (DOR), tolerability and safety

Key Findings

• The durable CR as assessed by a blinded independent review was 30% (95% CI, 20%–41%)
• 34% (n = 27) of patients demonstrated CR with MRD-negativity according to immunohistochemistry (95% CI, 24%–45%)
• The ORR as assessed by a blinded independent review was 75% (95% CI, 64%–84%)
• 80% achieved hematologic remission with a median onset of 1.1 months
• The median duration of hematologic remission from CR was not reached
• Most frequent treatment-related adverse events (AEs) Grade ≥3 was lymphocyte count decrease (7.5%) and hemolytic uremic syndrome (5%)

The findings of this study demonstrated that moxetumomab pasudotox had durable responses in patients with R/R HCL. Dr Giles concluded that moxetumomab pasudotox also eradicated MRD in a substantial proportion of patients.