CLL-492 Real-World Adherence to First-Line Ibrutinib and Acalabrutinib Single-Agent Among Patients With Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Context

Treatment guidelines recommend Bruton's tyrosine kinase inhibitors (BTKi) ibrutinib (once-daily) and acalabrutinib (twice-daily) as preferred regimens for chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). However, data are limited for adherence, which has been demonstrated as being higher in chronic diseases for once-daily versus twice-daily regimens and thus may inform treatment effectiveness.

Objective

To compare refill adherence between CLL/SLL patients treated with first-line (1L) ibrutinib or acalabrutinib single-agent.

Methods

Specialty pharmacy electronic medical records from academic integrated care networks (01/01/2017-11/30/2020) were used. Adult CLL/SLL patients with ≥12 months of data availability without antineoplastic agent use before ibrutinib or acalabrutinib single-agent initiation (index date) were included. Adherence was measured by the proportion of days covered (PDC) and medication possession ratio (MPR) during fixed periods of time during the ibrutinib/acalabrutinib line of therapy (LOT), which lasted until the earliest of second-line treatment initiation, death, or end of data. PDC and MPR were calculated as the sum of days of supply (DOS) divided by the duration of the period of interest; PDC calculations shifted forward prescriptions with overlapping DOS; MPR counted all DOS. The proportion of adherent patients (PDC/MPR ≥80%) was compared between ibrutinib versus acalabrutinib using logistic regression models adjusted for baseline characteristics.

Results

Among 288 and 80 patients treated with ibrutinib and acalabrutinib, mean age was 70.9 and 73.2 years, 35.8% and 45.0% were female, and mean LOT duration was 19.3 and 10.1 months, respectively. At all time points (first 3, 6, 9, and 12 months of the LOT), patients treated with ibrutinib were more likely to be adherent based on the proportion of patients with PDC/MPR ≥80% (odds ratio [OR] ranges=1.58-2.17 and 1.64-2.37); while results did not reach statistical significance at 3 and 12 months, they did at 6 months (PDC: 76.4% [ibrutinib] versus 60.0% [acalabrutinib], OR [95%CI]=2.17 [1.12-4.21]; MPR: 76.8% versus 60.0%, OR=2.20 [1.13-4.28]) and 9 months (PDC: 66.5% versus 46.3%, OR =2.05 [1.02-4.12]; MPR: 69.2% versus 46.3%, OR=2.37 [1.18-4.77]).

Conclusions

CLL/SLL patients initiating 1L ibrutinib single-agent had higher adherence than those initiating 1L acalabrutinib single-agent. Characterization of BTKi adherence rates may inform treatment effectiveness in the real-world.