Evaluation of Adherence and Persistence Differences Between Adalimumab Citrate-Free and Citrate Formulations for Patients with Immune-Mediated Diseases in the United States

Abstract

Introduction: Our aim was to evaluate patient adherence and persistence with citrate-free adalimumab (ADA-CF), introduced in 2018 to reduce injection-site pain, compared with citrate-containing adalimumab (ADA-C). Methods: This was a retrospective cohort study using a US claims database (IBM® MarketScan® Commercial and Medicare Supplemental Claims Database) from February 2018 to January 2020. Patients at least 18 years of age who were naïve to adalimumab 6 months before the index date (date of first adalimumab claim) and with at least 12 months of continuous medical and pharmacy coverage were eligible for the study. Adherence was assessed by determining the proportion of days covered (PDC) and the percentage of patients with PDC ≥ 80% during the 12-month follow-up period. Persistence was evaluated by measuring the rate of discontinuation and days to discontinuation (i.e., time on treatment) from the index date over the 12-month follow-up period. Continuous adherence outcomes (PDC) were evaluated using linear regression models. Binary adherence outcomes (PDC ≥ 80%) were assessed using logistic regression models. Kaplan–Meier analysis and Cox proportional hazards models were used to assess persistence outcomes. Results: There were 2195 and 1005 patients in the ADA-CF and ADA-C cohorts, respectively, with most using adalimumab for rheumatoid arthritis (ADA-CF 29.7%, ADA-C 27.2%) and psoriasis (ADA-CF 24.5%, ADA-C 31.9%). Significantly greater adherence was achieved with ADA-CF compared with ADA-C (mean PDC [standard deviation] 0.68 [0.30] vs 0.61 [0.32], P < 0.0001). A significantly greater percentage of patients receiving ADA-CF (47.2%) vs ADA-C (39.6%) had PDC ≥ 80% (P < 0.0001). The discontinuation rate was significantly lower for the ADA-CF cohort (46.4%) compared with ADA-C (55.9%, P < 0.0001), resulting in a 27% lower likelihood of discontinuation during the 12-month follow-up period (hazard ratio 0.73; 95% confidence interval 0.66, 0.82; P < 0.0001) and longer time on treatment (260 vs 232 days, P < 0.0001). Conclusion: Adherence and persistence are significantly improved with ADA-CF compared with ADA-C.