OBJECTIVE: To determine reversion rates from chronic migraine to episodic migraine during long-term erenumab treatment.

METHODS: A daily headache diary was completed during the 12-week, double-blind treatment phase of a placebo-controlled trial comparing erenumab 70 mg, 140 mg, and placebo, and weeks 1-12, 21-24, 37-40, and 49-52 of the open-label treatment phase. Chronic migraine to episodic migraine reversion rates were assessed over the double-blind treatment phase; persistent reversion to episodic migraine over 24 weeks (double-blind treatment phase through the first 12 weeks in the open-label treatment phase), long-term persistent reversion to episodic migraine over 64 weeks (double-blind treatment phase plus open-label treatment phase); delayed reversion to episodic migraine through the first 12 weeks of the open-label treatment phase among patients remaining in chronic migraine during the double-blind treatment phase.

RESULTS: In the double-blind treatment phase, 53.1% (95% confidence interval: 47.8-58.3) of 358 erenumab-treated completers had reversion to episodic migraine; monthly reversion rates to episodic migraine were typically higher among patients receiving 140 mg versus 70 mg. Among 181 completers (receiving erenumab for 64 weeks), 98 (54.1% [95% confidence interval: 46.6-61.6]) had reversion to episodic migraine during the double-blind treatment phase; of those, 96.9% (95% confidence interval: 91.3-99.4) had persistent reversion to episodic migraine, 96.8% (95% confidence interval: 91.1-99.3) of whom had long-term persistent reversion to episodic migraine. Delayed reversion to episodic migraine occurred in 36/83 (43.4% [95% confidence interval: 32.5-54.7]) patients; of these, 77.8% (95% confidence interval: 60.9-89.9) persisted in reversion through week 64.

CONCLUSIONS: Patients with reversion to episodic migraine at week 12 will likely persist as episodic migraine with longer-term erenumab; others may achieve delayed reversion to episodic migraine.Clinical trial registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02066415.