Approval follows weeks after firm pays government $375M to settle misbranding charge.

FDA has approved Allergan’s botulinum toxin product Botox® for the prophylactic treatment of headaches in adults with chronic migraine. Approval comes within weeks of the firm agreeing to pay $375 million to the U.S. government and another $225 million in settlement of civil claims after it pleaded guilty to a Botox misbranding charge.

Allergan claims Botox is the first clinically studied prophylactic treatment to be cleared by FDA specifically for prophylactic use in adults with chronic migraine. The firm estimates the condition affects some 3.2 million people in the U.S., while migraine is ranked by WHO as the 19th most debilitating disease. The new approval was based on data from the Phase III Preempt program, which comprised two double-blind, placebo-controlled trials involving 1,384 adults in North America and Europe.

Results from the studies found that Botox therapy resulted in a significant reduction in the frequency of headache days compared with placebo. Patients treated with Botox also reported a cumulative reduction in headache hours of up to 134 hours, compared with up to 95 hours reported by placebo patients. The drug was approved in the U.K. for the prophylactic treatment of chronic migraine in July.

Botox was first approved by FDA 21 years ago for treatment of the eye disorders strabismus and blepharospasm. The drug is now approved for 21 indications in some 80 countries, Allergan states. In the U.S. Botox has been sanctioned to treat the abnormal head position and neck pain that accompany cervical dystonia in adults.

It is separately approved for treating symptoms associated with severe underarm sweating, and for treating increased muscle stiffness in adult patients with upper limb spasticity. Botox is currently in Phase III trials as a treatment for neurogenic and idiopathic overactive bladder. The drug is separately in development for treating benign prostatic hyperplasia and for juvenile cerebral palsy. Approvals for both these indications are projected for post 2012. A next-generation targeted Botox is being developed for the treatment of pain. In addition to its approved and developmental therapeutic applications, Botox Cosmetic was cleared by FDA in 2002 for use in temporarily improving the appearance of moderate to severe glabellar lines.

The misbranding charge to which Allergan pleaded guilty in September related to the firm’s marketing practice for Botox during 2000-2005. This resulted in the drug having intended, but off-label uses, including the therapeutic treatment of headache, pain, spasticity, and juvenile cerebral palsy. In March FDA approved Botox for the treatment of increased muscle stiffness in the elbow, wrist, and fingers resulting from upper limb spasticity. It was this off-label use during 2000-2005 that represented the bulk of the misbranding investigation, Allergan states.

In 2009 sales of Botox Therapeutic represented 15% of Allergan’s product sales, with Botox Cosmetic accounting for a further 14%. The firm predicts net Botox product sales of between $1,360 million and $1,390 million in 2010.

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