Methods: Upon completion of the MENSA or SIRIUS study participants were offered the option to enter MEA115661; a 52-week open-label extension study where all subjects received open-label mepolizumab 100mg administered subcutaneously every 4 weeks as adjunctive therapy. The study objectives were to describe the safety profile of long-term mepolizumab treatment and to evaluate the effects of long-term dosing on clinical markers of asthma control. This post-hoc analysis evaluated the durability of steroid reduction following open-label mepolizumab treatment among the subset of subjects from the SIRIUS study that completed MEA115661. MEA115661 was sponsored by GSK.
Results: Ninety-three percent (n=126) of SIRIUS subjects entered the open-label study MEA115661; 65 subjects previously received mepolizumab and 61 subjects previously received placebo, with 57 and 58 subjects completing MEA115661 respectively. For placebo subjects from SIRIUS the median OCS dose achieved at the end of SIRIUS was 10mg/day and following 52 weeks of mepolizumab treatment in MEA115661 was reduced to 5.0mg/day. For subjects who continued mepolizumab the median OCS dose achieved was 2.5mg/day at the end of SIRIUS and was 2.5mg/day at the end of MEA115661.
Conclusions: This open label extension study adds evidence that the steroid reduction achieved in the 24-week double-blind SIRIUS study was sustained. Additionally subjects initiating mepolizumab treatment in MEA115661 demonstrated improvements similar to that seen in SIRIUS.