Trajectories of Adherence to Biologics in Patients With Inflammatory Bowel Diseases: A Large-Scale Multi-Regional Italian Study Through the VALORE Distributed Database

: This study aimed to identify and describe trajectories of adherence to biologics in patients with IBDs and to identify adherence determinants in the Italian real-world setting. We conducted a retrospective cohort study across 12 Italian regions, including new users of biologics with inflammatory bowel diseases (IBDs), between 2010 and 2019 and followed them for 3 years. We assessed adherence longitudinally, and we identified trajectories using nonparametric methods. To identify determinants of adherence, we used multinomial multivariate regression models. We included 20 150 subjects in the final cohort, mostly male (56%), < 65 years old (92%), and with Crohn's disease (58%). We identified three trajectories of adherence to biologics for IBDs: one group (19% of the cohort) maintained high adherence throughout the observation period, while the largest group (46%) initially reduced adherence, stabilizing around 70%. The remaining group (35%) gradually decreased adherence over the entire follow-up, reaching 20%. Being female (odds ratio (OR) 1.52, 95% confidence interval (CI) 1.40-1.65), older (OR 1.44, 95% CI 1.21-1.70), and having adalimumab as index drug were each positively associated with low adherence compared to high adherence. In contrast, starting treatment with a biosimilar (OR 0.47, 95% CI 0.42-0.52) was negatively associated with low adherence. Our findings highlight that one in three patients with IBDs gradually reduced adherence to biologics within the first 3 years of treatment. Differences were observed according to the initial biologic dispensed and patient characteristics such as sex and age, with females and older patients positively associated with low adherence.