Efficacy and tolerability of generic pirfenidone after switch from Esbriet® in idiopathic pulmonary fibrosis: a real-world observational study

BACKGROUND: ) to a generic formulation affects treatment efficacy or tolerability. METHODS: for ≥ 6 months before switching to generic pirfenidone. Pulmonary function was assessed at three time points: 6 months before the switch (T - 6), at switch (T0), and 6 months after (T + 6). The primary endpoint was the within-patient percentage change in FVC over two consecutive 6-month periods (T - 6 → T0 vs T0 → T + 6), analysed within a pre-specified equivalence framework (± 5 percentage points). Secondary endpoints included DLCO changes and treatment-related adverse events (AEs), analysed at the patient level using paired comparisons. RESULTS: Sixty-five patients (median age 77.0 years [72.3-80.0] years, 78% male) had complete functional follow-up. The mean percentage decline in FVC was - 1.9% before the switch and - 1.7% after the switch. The estimated between-period difference in FVC change was 0.2 percentage points (95% CI - 1.1 to 1.5), fully contained within the pre-specified equivalence margins. Similar findings were observed for DLCO, with no significant difference between periods. Overall, 43% of patients experienced at least one AE during treatment. Gastrointestinal AEs were the most frequent, but paired analyses showed no significant difference in patient-level AE occurrence between branded and generic periods. No severe AEs or treatment discontinuations were observed. CONCLUSIONS: In this real-world cohort of patients with IPF, switching from branded to generic pirfenidone was not associated with clinically meaningful differences in lung function decline or treatment tolerability.