OBJECTIVES: Migraine prophylaxis is an area of large unmet medical needs. Although some patients may benefit from medications currently used for migraine prophylaxis, poor tolerability and variable efficacy lead to poor adherence in daily practice and call for alternative therapies with improved long-term tolerability and safety profiles. This study assesses the impact of erenumab, the first CGRP receptor-blocking treatment available, on the migraine burden of successfully treated chronic migraine patients with 15 or more MMDs at baseline who have previously failed two to four prophylactic migraine treatments. METHODS: A reduction of monthly migraine days (MMDs) from baseline of 50% or more is often used as response criterion in clinical trials as per the IHS guidelines. We compared the migraine burden of erenumab responders prior to treatment with their reported trial outcomes in the third month of erenumab treatment. With the absence of a diagnostic tool and of a universally accepted response definition for a real world setting, a pre-defined MMD reduction compared to baseline can be used to identify migraine patient eligible for continuous reimbursed treatment with a well-tolerated CGRP antagonist. RESULTS: Erenumab responders showed an average migraine burden of 18.57 and 20.50 MMDs at baseline in the erenumab 70 mg and 140 mg group, respectively. This burden was reduced by 65.3% (-12.12 MMDs) for the 70 mg group and 75.1% (-15.40 MMDs) for 140 mg, resulting in an average monthly disease burden after treatment with Erenumab 70 mg and 140 mg of 6.45 MMDs and 5.10 MMDs, respectively. CONCLUSIONS: Treatment with erenumab can significantly reduce the migraine burden in responders at 3 months. On average, CM patients effectively treated with erenumab could gain two weeks of migraine-free time per month and reduce their migraine burden by up to 75%, i.e. to less than one week per month.