Selinexor Combined with Ibrutinib Demonstrates Tolerability and Safety in Advanced B-Cell Malignancies: A Phase I Study

Purpose: Dual blockade of Bruton's tyrosine kinase with ibrutinib and selinexor has potential to deepen responses for patients with chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Patients and Methods: In this phase I study (clinicaltrials.gov: NCT02303392), adult patients with CLL/NHL, relapsed/refractory to ≥1 prior therapy were enrolled. Patients received weekly oral selinexor and daily oral ibrutinib in 28-day cycles until progression or intolerance. Primary objective was to determine MTD. Results: Included patients had CLL (n = 16) or NHL (n = 18; 9 Richter transformation, 6 diffuse large B-cell lymphoma, and 3 mantle cell lymphoma). Median prior therapies were 4 (range = 1–14) and 59% previously received ibrutinib. The established MTD was 40 mg of selinexor (days 1, 8, 15) and 420 mg daily ibrutinib. Common nonhematologic adverse events were fatigue (56%), nausea (53%), anorexia (41%), and diarrhea (41%) and were mostly low grade. Overall response rate was 32%. An additional 47% achieved stable disease (SD), some prolonged (up to 36 months). Median progression-free survival for patients with CLL and NHL was 8.9 [95% confidence interval (CI), 3.9–16.1] and 2.7 (95% CI, 0.7–5.4) months, respectively. For patients with CLL who did not receive prior ibrutinib, only 20% (1/5) progressed. Estimated 2-year overall survival was 73.7% (95% CI, 44.1–89.2) and 27.8% (95% CI, 10.1–48.9) for patients with CLL and NHL, respectively. Conclusions: The selinexor and ibrutinib combination has demonstrated tolerability in patients with relapsed/refractory CLL/NHL. Responses were durable. Notable responses were seen in patients with CLL with minimal prior therapy. Future study of this combination will focus on efforts to deepen remissions in patients with CLL receiving ibrutinib therapy.