Late Breaking Abstract - Long-term safety & durability of mepolizumab in life-threatening/seriously debilitating severe eosinophilic asthma (SEA): COSMEX

Background: Safety & durability of mepolizumab were limited in pts with the most severe form of SEA. Objective: To assess the long-term safety & durability of mepolizumab in these SEA pts. Methods: COSMEX was an open-label extension of COSMOS (a 52-wk extension of mepolizumab Ph3 trials)*. Pts had life-threatening/seriously debilitating asthma prior to Ph3 trials (≥1 intubation [lifetime]; ≥1 hospitalisation or ≥3 exacerbations [12m prior]; OCS dose ≥10mg [randomisation]; %predFEV1 ≤50% + ACQ-5 score ≥3 or SGRQ score ≥60) & improved on mepolizumab (≥50% reduction in exacerbations/OCS dose & investigator-confirmed improvement) during the previous studies. Coprimary endpoints: frequency of AEs & exacerbation rate; other endpoint: OCS reduction. Results: 339 pts entered COSMEX. Total mepolizumab exposure over COSMEX was 718pt-yr (mean 25m[range 2–39m] & over COSMEX & previous studies was 1202pt-yr [mean 43m (range 14–57m)]). See table for coprimary endpoint results; no new safety signals seen. Exacerbation & OCS reductions achieved in the previous studies were sustained over COSMEX (median OCS dose maintained at 0–5mg/day). Conclusions: In these SEA pts, the safety profile of mepolizumab was similar to previous shorter-term trials, with no new safety signals; long-term treatment provided sustained & consistent exacerbation & OCS reductions for up to 4.5yrs. Funding: GSK [201312/NCT02135692]