A Study to Assess the Long-term Safety and Efficacy of Erenumab (AMG 334) in Chronic Migraine Prevention.

An Open-label Extension (OLE) Study to Assess the Long-term Safety and Efficacy of AMG 334

To assess the long-term safety and efficacy of erenumab.

This was a multicenter, 52-week, open-label study designed to assess the long-term safety and efficacy of erenumab in adults with chronic migraine. Participants who completed the 12-week double-blind treatment of the parent Study 20120295 (NCT02066415) and met all Study 20130255 eligibility criteria were eligible for enrollment into this study. Enrollment occurred within 14 days after the parent study's week 12 visit.

The initial dose used in the study was erenumab 70 mg every month (QM). The protocol was subsequently amended to increase the dose to erenumab 140 mg QM (Protocol Amendment 2). Participants who had already completed the week 28 visit (ie, midpoint of the study) at the time of Protocol Amendment 2 continued to receive open-label erenumab 70 mg QM for the remainder of the study. Participants who enrolled but had not completed the week 28 visit at the time of Protocol Amendment 2 increased the open-label erenumab dose from 70 mg QM to 140 mg QM at the next visit. All participants who enrolled after Protocol Amendment 2 received open-label erenumab 140 mg QM throughout the study.

Participants may elect to participate in a separate clinical home use (CHU) substudy to assess subjects' ability to self-administer 140 mg of erenumab for in-home use using either two prefilled syringes (PFS) or two prefilled autoinjector/pens (AI/pens). Enrollment in the 12-week substudy occurred at either week 12 or week 40 of study 20130255. Participants were randomized to self-administer erenumab using either the PFS or AI/pen on CHU days 29 and 57 at home.

Inclusion Criteria:

1. Subject has provided informed consent prior to initiation of any study-specific activities/procedures
2. Completed the 12-week study visit and did not end IP early during the double-blind treatment period of the AMG 334 20120295 (NCT02066415) parent study, and is appropriate for continued treatment.

Exclusion Criteria:

1. Development of any unstable or clinically significant medical condition, laboratory or electrocardiogram (ECG) abnormality following randomization into the parent study, that in the opinion of the investigator, would pose a risk to subject safety or interfere with the study evaluation, procedures or completion.
2. Systolic blood pressure (BP) 160 mm Hg and/or diastolic BP 100 mm Hg or greater at screening/Day 1.
3. Subject who used excluded concomitant medications between week 8 and week 12 of the parent study