OnabotulinumtoxinA for treatment of chronic migraine: results from the double-blind, randomized, placebo-controlled phase of the PREEMPT 2 trial.

OBJECTIVES This is the second of a pair of studies designed to evaluate the efficacy and safety of onabotulinumtoxinA (BOTOX) for prophylaxis of headaches in adults with chronic migraine. METHODS PREEMPT 2 was a phase 3 study, with a 24-week, double-blind, placebo-controlled phase, followed by a 32-week, open-label phase. Subjects were randomized (1:1) to injections of onabotulinumtoxinA (155U-195U; n = 347) or placebo (n = 358) every 12 weeks for two cycles. The primary efficacy endpoint was mean change in headache days per 28 days from baseline to weeks 21-24 post-treatment. RESULTS OnabotulinumtoxinA was statistically significantly superior to placebo for the primary endpoint, frequency of headache days per 28 days relative to baseline (-9.0 onabotulinumtoxinA/-6.7 placebo, p < .001). OnabotulinumtoxinA was significantly favoured in all secondary endpoint comparisons. OnabotulinumtoxinA was safe and well tolerated, with few treatment-related adverse events. Few patients (3.5% onabotulinumtoxinA/1.4% placebo) discontinued due to adverse events. CONCLUSIONS The results of PREEMPT 2 demonstrate that onabotulinumtoxinA is effective for prophylaxis of headache in adults with chronic migraine. Repeated onabotulinumtoxinA treatments were safe and well tolerated.