Study to Evaluate the Efficacy and Safety of Erenumab (AMG 334) in Migraine Prevention

The study is composed of an initial screening phase (up to 3 weeks), a 4-week baseline phase, a 12-week double-blind treatment phase (DBTP), an open-label treatment phase (OLTP) for up to 256 weeks, and an 8-week safety follow-up (12 weeks after the last dose of investigational product \[IP\]). In the DBTP participants were to be randomized in a 3:2:2:2 ratio to placebo, erenumab 7 mg, erenumab 21 mg, or erenumab 70 mg. During the open-label treatment phase, participants were to receive erenumab 70 mg QM from week 12 to week 264. After implementation of Protocol Amendment 3 (07 April 2016), participants remaining in the OLTP increased their dose to erenumab 140 mg QM up to week 264. The safety follow-up increased from an 8-week safety follow-up to a 12-week safety follow-up (16 weeks after the last dose of investigational product). During the OLTP participants enrolled at sites in the United States could enroll in an optional clinical home use (CHU) substudy, per a country-specific protocol amendment dated 20 June 2016. Participants in the CHU substudy were to be randomized 1:1 into 1 of 2 treatment groups: erenumab 140 mg using a prefilled syringe or erenumab 140 mg using an autoinjector/pen. Day 1 of the CHU substudy corresponded with any OLTP study visit up through Week 256, as long as the participant had received at least 2 doses of erenumab 140 mg. During the CHU substudy, participants initially self-administered IP under site supervision on substudy day 1, and then self-administered IP at home on substudy days 29 and 57.