Nonadherence to inhaled corticosteroids is associated with negative mepolizumab response

Nonadherence to inhaled corticosteroids (ICS) in severe asthma is associated with poor control and may impair response to biologics. The primary objective of the present study was to evaluate ICS nonadherence influence on mepolizumab treatment response in adults with severe eosinophilic asthma.

In this retrospective cohort study, we compared ICS nonadherence rates in mepolizumab responders and nonresponders. 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 dose. Predictors of adherence and mepolizumab response were explored using standard statistics.

A total of 190 participants were included in the analysis (enrolment mean±sd age 52±13 years, 59 (31%) males). There were 153 (80%) responders to mepolizumab who displayed lower median exacerbations than the nonresponders (1 (interquartile range (IQR) 0, 2) versus 4 (IQR 2, 7); p=0.002). ICS nonadherence was detected in 30% and 26% of participants prior to and during mepolizumab treatment respectively. ICS nonadherence was more common in nonresponders 12/23 (52%) than in mepolizumab responders 29/130 (22%), p=0.002. Nonadherent patients had higher exhaled nitric oxide fraction (F _ENO) (ppb) than the adherent patients (median 57 (IQR 35, 81) versus 34 (IQR 21, 61); p=0.009). Pre-mepolizumab nonadherence correlated significantly with on-treatment nonadherence (r=0.75, 95% CI 0.67-0.81; p<0.0001).

ICS nonadherence was associated with negative response to mepolizumab treatment and raised F _ENO levels compared to the adherent group. Our findings support the notion for the need for optimisation of ICS adherence during mepolizumab therapy.