Assessment of prolonged safety and tolerability of erenumab in migraine patients in a long-term open-label study (APOLLON).

Background: Efficacy and safety of human monoclonal antibody erenumab used for migraine prophylaxis have been shown in clinical studies. APOLLON is an open-label, multi-center, single arm study, which permits dose adjustments of erenumab and includes an option for a drug holiday. The findings contribute to the accumulating long-term evidence regarding erenumab's tolerability and safety profile in individuals experiencing episodic and chronic migraines.

Methods: The study population consisted of adult patients with episodic or chronic migraine, who had successfully completed the HER-MES study (NCT03828539). Patients were treated with erenumab for 128 weeks at a flexible dose of either 70 mg or 140 mg. Treatment discontinuation attempts were allowed as voluntary single treatment interruption ('drug holiday') of up to 24 weeks.

Results: 701 patients were enrolled in APOLLON. The exposure associated incidence rate (EAIR) of adverse events (AEs) (N = 601) per 100 subject years was 101.71 (95% CI [92.28; 111.14]) meaning a patient could expect having about one adverse event per each year of treatment. EAIR was higher in females (n = 524, EAIR: 104.40, 95% CI [93.93; 114.86]) than in males (n = 77, EAIR: 86.55, 95% CI [65.39; 107.71]) and increased with initial monthly migraine days (MMD) and prior prophylactic treatment failures. A total of 155 patients discontinued erenumab treatment during open-label treatment phase. Of these, 29 were due to AEs (4.1% of total cohort) and out of these 65.5% (N = 19) were considered treatment-related. Safety parameters were in line with HER-MES data and did not reveal new safety signals. Drug holidays were realized by 108 patients (15.4%), of which 64.8% (N = 70) returned to treatment. The mean number of monthly headache days (MHDs), MMDs, and days with acute headache medication significantly increased during drug holiday. After resumption of erenumab treatment, a rapid reduction of the migraine parameters was observed.

Conclusions: APOLLON provides long-term safety and tolerability data confirming the beneficial safety profile of erenumab over a period of 128 weeks. In addition, reversibility of migraine deterioration during drug holiday was shown and most patients returned to their treatment with similar response rates compared to initial treatment.

Trial registration: ClinicalTrials.gov ID: NCT04084314 ( https://clinicaltrials.gov/study/NCT04084314 ), First submitted: 2019-09-06.