The objective of this study was to evaluate the safety and efficacy of different lenalidomide starting doses in patients with relapsed/refractory chronic lymphocytic leukemia (CLL). CLL patients were randomized to receive lenalidomide at initial doses of 5, 10, or 15 mg/d (N = 103). Doses were escalated by 5 mg every 28-d up to a maximum of 25 mg/d; dose reductions in up to 5 mg decrements were permitted. The most common grade ≥3 adverse events (AEs) were neutropenia and thrombocytopenia. Ten patients died during therapy (four deaths considered as related to lenalidomide); 12 patients experienced second primary malignancies. The most common cause for treatment discontinuation was AEs. Overall response rates were similar across arms. Progression-free survival and overall survival rates were longer in patients who escalated treatment (to 15 or 20 mg/d) versus those who did not. Lower starting doses allowed subsequent dose escalation of lenalidomide while maintaining an acceptable tolerability profile in patients with relapsed/refractory CLL.

Purpose

Among Bruton's tyrosine kinase inhibitors, acalabrutinib has greater selectivity than ibrutinib, which we hypothesized would improve continuous therapy tolerability. We conducted an open-label, randomized, noninferiority, phase III trial comparing acalabrutinib and ibrutinib in patients with chronic lymphocytic leukemia (CLL).

Methods

Patients with previously treated CLL with centrally confirmed del(17)(p13.1) or del(11)(q22.3) were randomly assigned to oral acalabrutinib 100 mg twice daily or ibrutinib 420 mg once daily until progression or unacceptable toxicity. The primary end point was independent review committee-assessed noninferiority of progression-free survival (PFS).

Results

Overall, 533 patients (acalabrutinib, n = 268; ibrutinib, n = 265) were randomly assigned. At the data cutoff, 124 (46.3%) acalabrutinib patients and 109 (41.1%) ibrutinib patients remained on treatment. After a median follow-up of 40.9 months, acalabrutinib was determined to be noninferior to ibrutinib with a median PFS of 38.4 months in both arms (95% CI acalabrutinib, 33.0 to 38.6 and ibrutinib, 33.0 to 41.6; hazard ratio: 1.00; 95% CI, 0.79 to 1.27). All-grade atrial fibrillation/atrial flutter incidence was significantly lower with acalabrutinib versus ibrutinib (9.4% v 16.0%; P = .02); among other selected secondary end points, grade 3 or higher infections (30.8% v 30.0%) and Richter transformations (3.8% v 4.9%) were comparable between groups and median overall survival was not reached in either arm (hazard ratio, 0.82; 95% CI, 0.59 to 1.15), with 63 (23.5%) deaths with acalabrutinib and 73 (27.5%) with ibrutinib. Treatment discontinuations because of adverse events occurred in 14.7% of acalabrutinib-treated patients and 21.3% of ibrutinib-treated patients.

Conclusion

In this first direct comparison of less versus more selective Bruton's tyrosine kinase inhibitors in CLL, acalabrutinib demonstrated noninferior PFS with fewer cardiovascular adverse events.