Real-world Comparison of Adherence Between Patients with Chronic Lymphocytic Leukemia Treated with Single-agent Ibrutinib or Acalabrutinib In First Line

Introduction:
Ibrutinib and acalabrutinib are both Bruton’s tyrosine kinase inhibitors (BTKis) used to treat chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Since studies in chronic diseases have demonstrated better treatment adherence with once-daily compared to twice-daily regimens, we wanted to compare adherence rates between patients treated with single-agent ibrutinib (once-daily) versus acalabrutinib (twice-daily) as first-line (1L) therapy for CLL/SLL.
Methods:
Specialty pharmacy electronic medical records from academic and community integrated care networks were used. The study included adult patients with CLL/SLL who initiated 1L single-agent ibrutinib or acalabrutinib between 01/01/2018-11/30/2020 (index date). Single-agent use was defined as receiving no other antineoplastic agents within 28‚Äâdays of ibrutinib or acalabrutinib initiation. A washout period of ‚â•12 months (also used as the baseline period to evaluate patient characteristics) without any use of antineoplastic agents was used to confirm use as 1L therapy.
Discussion:
In this real-world study, patients with CLL/SLL who initiated 1L once-daily ibrutinib had higher adherence than those initiating a twice-daily regimen of acalabrutinib. Given the importance of sustained adherence in achieving disease control in CLL, dosing frequency may be an important consideration for providers (in addition to other factors such as efficacy, tolerability, safety, and past experience treating patients with the medication) when selecting treatment options in the frontline setting.
Results:
Among 1,374 and 140 patients treated with ibrutinib and acalabrutinib, respectively, mean age was 70.7 and 72.1‚Äâyears, 35.7% and 42.9% were female, and the mean (median) LOT duration was 27.5 (28.9) and 20.7 (21.1) months. During the first 3, 6, 9, and 12 months of the LOT and during the entire LOT duration, ibrutinib-treated patients were more likely to be adherent than acalabrutinib-treated patients based on the proportion of patients with PDC/MPR ‚â•80% (OR ranges=1.04-1.76 for PDC and 1.03-1.58 for MPR). Results reached statistical significance at 6 months (PDC: 75.9% for ibrutinib vs 63.6% for acalabrutinib, OR [95% CI]=1.76 [1.16, 2.67], P=0.008; MPR: 76.8% vs 66.9%, OR [95% CI]=1.58 [1.03, 2.42], P=0.036) and for the entire LOT duration (PDC: 53.0% vs 41.4%, OR [95% CI]=1.53 [1.07, 2.20], P=0.021; MPR: 58.7% vs 47.1%, OR [95% CI]=1.50 [1.05, 2.15], P=0.027).