Ibrutinib Plus Rituximab Active in Relapsed, Refractory Mantle Cell Lymphoma

Ibrutinib in combination with rituximab is active and well tolerated in patients with relapsed or refractory mantle cell lymphoma, a new study published online ahead of print in the journal The Lancet Oncology has shown.¹

In a previous phase 2 trial, 68% of patients with mantle cell lymphoma achieved an objective response rate, and 34% of patients had transient lymphocytosis. Therefore, researchers sought to evaluate whether adding rituximab to ibrutinib could target mantle cell lymphoma cells associated with redistribution lymphocytosis, resulting in higher antitumor activity.

For the single-center, open-label, phase 2 study, researchers enrolled 50 patients with mantle cell lymphoma who had any number of previous treatments.

All patients received continuous ibrutinib 560 mg orally daily until disease progression or unacceptable toxicity. Rituximab 375 mg/m² was administered intravenously once weekly for 4 weeks during cycle 1, then on day 1 of cycles 3 through 8, followed by once every other cycle for up to 2 years.

Results showed that at a median follow-up of 16.5 months, the objective response rate was 88% (95% CI, 75.7 – 95.5), with 44% (95% CI, 30.0 – 58.7) achieving a complete response and 44% (95% CI, 30.0 – 58.7) achieving a partial response.

In terms of safety, grade 3 atrial fibrillation occurred in 12% of patients; and grade 4 diarrhea and neutropenia occurred in 1 patient each. Adverse events leading to treatment discontinuation included atrial fibrillation, liver infection, and bleeding. Two patients died while on therapy, with one’s death being potentially related to treatment.

“Our results provide preliminary evidence for the activity of this combination in clinical practice. A phase 3 trial is warranted for more definitive data,” the authors concluded.

Ibrutinib is a kinase inhibitor already approved by the U.S. Food and Drug Administration for the treatment of patients with mantle cell lymphoma who have received at least 1 prior therapy. It is also approved for certain patients with chronic lymphocytic leukemia and Waldenström’s macroglobulinemia.

Reference

1. Wang ML, Lee H, Chuang H, et al. Ibrutinib in combination with rituximab in relapsed or refractory mantle cell lymphoma: a single-centre, open-label, phase 2 trial [published online ahead of print November 27, 2015]. Lancet Oncol. doi: 10.1016/S1470-2045(15)00438-6.