Hairy Cell Leukemia

Phase 2 Study of Ibrutinib in Classic and Variant Hairy Cell Leukemia

Phase 2 Study of Ibrutinib in Classic and Variant Hairy Cell Leukemia

June 24, 2021

The treatment options for patients with r/r hairy cell leukemia are limited. Ibrutinib has shown activity in a variety of B-cell malignancies. In a phase 2 clinical trial, published in the journal Blood on June 24, 2021, investigators reported on the utility of ibrutinib in heavily pretreated hairy cell leukemia.  The primary outcome measure was overall response rate at 32 weeks.  There was also an assessment at 48 weeks.  Secondary endpoints included progression free survival, as well as overall survival.  

37 patients were enrolled in 2 dosing cohorts.  24 patients received 420 mg while 13 patients received 840 mg.  The median duration of follow-up is 3.5 years.  The overall response rate at 32 weeks was 24% and improved to 36% at 48 weeks.  The overall response rate was 54%.  36-month progression free survival was 73% while overall survival was 85%. 

Diarrhea was the most common adverse event seen in 59% while fatigue was seen in 54%.  Anemia was seen in 43% while thrombocytopenia was seen in 41%.  Neutropenia was reported at 35%. 

The authors concluded “Ibrutinib can be safely administered to patients with HCL with objective responses and results in prolonged disease control. Although the initial primary outcome objective of the study was not met, the observation of objective responses in heavily pretreated patients coupled with a favorable PFS suggests that ibrutinib may be beneficial in these patients. “