Persistent post-treatment FeNO and long-term FEV1 trajectories in patients with asthma treated with dupilumab: a single-center retrospective study

Background Long-term lung function trajectories during dupilumab treatment remain insufficiently characterized. We characterized post-treatment FEV1 trajectories in patients with asthma who continued dupilumab for 3 years and explored whether persistent fractional exhaled nitric oxide (FeNO) was associated with a less favorable trajectory. Methods This single-center retrospective study included 41 of 60 patients with physician-confirmed asthma who initiated dupilumab for asthma at Niigata University between March 2019 and August 2022 and continued treatment for 3 years. Post-treatment FEV1 slopes were estimated using values obtained at 4 months, 1 year, 2 years and 3 years. Decliners were defined as patients with an annual FEV1 slope more negative than − 30 mL/year. Persistent FeNO was defined as FeNO ≥ 20 ppb at ≥ 2 of the 1-, 2-, and 3-year visits. Maintenance treatment was assessed throughout follow-up, and 3-year prescription-based adherence and ICS exposure were evaluated in 38 patients with complete prescription records. Results Seventeen patients were classified as decliners. Both groups showed an early increase in FEV1; thereafter, FEV1 gradually decreased in decliners but remained relatively stable in non-decliners. Persistent FeNO was associated with a less favorable FEV1 slope and remained associated with decliner status after adjustment for age and baseline % FEV1 (adjusted OR, 21.8; 95% CI, 2.61–183; p = 0.004). FeNO at 1 year was inversely correlated with post-treatment FEV1 slope (Spearman’s ρ = −0.329; p = 0.036). No significant between-group differences were observed in 3-year prescribed ICS intensity, prescription-based ICS exposure, or prescription-based adherence. Conclusions In this selected cohort of patients with asthma who continued dupilumab for 3 years, long-term post-treatment FEV1 trajectories were heterogeneous. Persistent post-treatment FeNO was associated with a less favorable FEV1 trajectory. These exploratory findings require validation in larger prospective studies.