Ibrutinib Active, Safe in Previously Treated Waldenström’s Macroglobulinemia

Ibrutinib was highly active, associated with durable responses, and safe in pretreated patients with Waldenström’s macroglobulinemia, a recent study published in The New England Journal of Medicine has shown.

For the prospective study, researchers sought to evaluate the efficacy and safety of ibrutinib in previously treated patients with Waldenström’s macroglobulinemia, and identify the effect of MYD88^L265P and CXCR4^WHIM mutations, which are highly prevalent in Waldenström’s macroglobulinemia, on outcomes. CXCR4^WHIM mutations are known to confer in vitro resistance to the tyrosine kinase inhibitor.

Researchers enrolled 63 symptomatic patients with Waldenström’s macroglobulinemia who had received at least one previous treatment. All patients received ibrutinib 420mg/day orally until disease progression or unacceptable toxicity.

Results showed that the overall response rate was 90.% and the major response rate was 73.0%. Researchers found that patients with MYD88^L265P and wild-type CXCR4 mutations achieved a 100% overall response rate and 91.2% major response rate, while patients with MYD88^L265PCXCR4^WHIM had an overall and major response rate of 85.7% and 61.9%, respectively.

Patients with wild-type MYD88 and CXCR4 had an overall response rate of 71.4% and a major response rate of 28.6%.

The estimated 2-year progression-free survival rate was 69.1% and the overall survival rate was 95.2%.

In regard to safety, grade 2 or higher ibrutinib-related adverse effects included neutropenia, thrombocytopenia, postprocedural bleeding, epistaxis, and atrial fibrillation.

Reference

1. Treon SP, Tripsas CK, Meid K, et al. Ibrutinib in previously treated Waldenström’s macroglobulinemia. N Engl J Med. 2015; 372:1430-1440.