(HealthDay News) — The Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib is active in relapsed or refractory mantle-cell lymphoma, with a response rate of 68 percent, according to a study published online June 19 in the New England Journal of Medicine.

Michael L. Wang, M.D., from the University of Texas MD Anderson Cancer Center in Houston, and colleagues conducted a phase 2 study to examine use of oral ibrutinib at a daily dose of 560 mg in 111 patients (mean age, 68 years) with relapsed or refractory mantle-cell lymphoma (86 percent with intermediate- or high-risk disease). Participants were enrolled into two groups based on previous treatment with bortezomib.

The researchers found that mild or moderate diarrhea, fatigue, and nausea were the most common treatment-related adverse events. Grade 3 or higher hematologic events occurred infrequently and included neutropenia, thrombocytopenia, and anemia (in 16, 11, and 10 percent of patients, respectively). The response rate was 68 percent and included a complete response rate of 21 percent and a partial response rate of 47 percent. The response rate was unaffected by prior bortezomib treatment. The estimated median response duration was 17.5 months and the estimated median progression-free survival was 13.9 months. Median overall survival was not reached during follow-up (median of 15.3 months). At 18 months, the estimated rate of overall survival was 58 percent.

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“The BTK inhibitor ibrutinib is a highly active new agent showing durable single-agent activity in relapsed and refractory mantle-cell lymphoma,” the authors write. “The favorable toxicity profile suggests that ibrutinib provides the opportunity for treatment with less intensive and more effective regimens than those currently available.”

The study was partially funded by Pharmacyclics and Janssen Biotech, the manufacturers of ibrutinib.

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