Non-adherence to inhaled corticosteroids is associated with negative mepolizumab response

Background Non-adherence to inhaled corticosteroids (ICS) in severe asthma is associated with poor control and may impair response to biologics. Primary objective To evaluate ICS non-adherence influence on mepolizumab treatment response in adults with severe eosinophilic asthma. Methods In this retrospective cohort study we compared ICS non-adherence rates in mepolizumab responders and non-responders. Adherence was determined using a prescription possession ratio (PPR) of ≥75% to indicate adherence. Mepolizumab response was assessed using the positive response criteria of a ≥50% reduction in exacerbations and/or in the maintenance oral corticosteroid (OCS) dose. Predictors of adherence and mepolizumab response were explored using standard statistics. Results A total of 190 participants were included in the analysis [enrolment mean age 52±13 years, 59 (31%) males]. There were 153 (80%) responders to mepolizumab who displayed lower median exacerbations than the non-responders [1 (2, 0) versus 4 (7, 2) (p=0.002)]. ICS non-adherence was detected in 30% and 26% of participants prior to and during mepolizumab treatment respectively. ICS non-adherence was more common in non-responders 12/23 (52%) than in mepolizumab responders 29/130 (22%), p=0.002. Non-adherent patients had higher FeNO (parts per billion) than the adherent patients [median 57 (81, 35) versus 34 (61, 21) (p=0.009). Pre-mepolizumab non-adherence correlated significantly with on treatment non-adherence [r= 0.75, 95% CI (0.67 to 0.81), p<0.0001]. Conclusions ICS non-adherence was associated with negative response to mepolizumab treatment and raised FeNO levels compared to the adherent group. Our findings support the notion for the need for optimisation of ICS adherence during mepolizumab therapy.