Dr. Werschler

Current off-label use hasn't shown any particular clinical advantage for Xeomin (incobotulinumtoxinA, Merz) over Botox (onabotulinumtoxinA, Allergan) or Dysport (abobotulinumtoxinA, Medicis), but the new toxin will broaden clinicians' aesthetic options and may spur price competition in the U.S.

The unit-to-unit equivalence to Botox is one of Xeomin's purported advantages over Dysport, says W. Philip Werschler, M.D., F.A.A.D., F.A.A.C.S., assistant clinical professor of medicine/dermatology, University of Washington, Seattle.

Toxin categories

Xeomin was approved by the Food and Drug Administration (FDA) in July 2010 for the treatment of cervical dystonia and blepharospasm. It became available in October 2010. Xeomin has not yet been approved for an aesthetic indication. Botox and Dysport are FDA-approved for aesthetic applications.

"While Xeomin might be used off-label by some dermatologists, there is no particular significant, scientific or clinical-trial proven advantage in using it off-label compared to Botox or Dysport," says Dr. Werschler, who has used Xeomin in Europe and conducted training programs for Merz internationally.

The currently available botulinum toxin type A toxins fall into two categories, according to Dr. Werschler. Both Botox and Dysport are complexed toxins, while Xeomin and PurTox (Mentor, currently in clinical trials) are known as "naked" toxins.

"Botox and Dysport both have the active toxin molecule, which is a protein that has a light chain and a heavy chain," he says. "In Botox and Dysport, in addition to the active (protein) ingredient, there are stabilizing proteins, hemagglutinin and nonhemagglutinin proteins, that are wrapped around it. There is some ongoing debate as to whether or not the proteins serve any vital function."

PurTox and Xeomin are not complexed, or surrounded to these carrier or chaperone proteins.

"Theoretically, there is an advantage of not having a complexing protein because the more protein mass that there is, the more likely the chances a person could potentially develop antibodies to it, which could block the effectiveness of the toxin," Dr. Werschler says.

Botox equivalent?

Xeomin is designed to have efficacy across a range of applications and doses with transparency between Botox and Xeomin. Dr. Werschler says a number of clinical trials evaluating Xeomin use aesthetically and therapeutically for various applications and dosages show a therapeutic efficacy with nearly identical dose/response data curves. Before Botox had a cosmetic indication, many dermatologists used it off-label because no alternatives were available.

"Now that there are two toxins on the market with an aesthetic indication and a proven track record of safety and efficacy on-label, it would behoove dermatologists and plastic surgeons to not use a product that doesn't have a cosmetic indication," Dr. Werschler says. "While Xeomin has the same active ingredient and it seems to have the same efficacy as Botox, it is still awaiting aesthetic approval by the FDA."

Treatment tips

Because Xeomin is unit-to-unit equivalent with Botox, dermatologists do not need retraining to use it.

"They don't have to relearn the dosing schedule and it should make the learning curve essentially flat," Dr. Werschler says. An aesthetic approval could come with some labeling changes, depending on FDA requirements, he says. These toxins are approved on-label for only the glabella, or frown line, indication.

"I am waiting until we have labels for forehead and crow's feet and other aesthetic indications. I don't know if Merz will look for that kind of a label to come to market (with Xeomin), but that would be an advantage because they would be able to advertise for that and have some market distinction," Dr Werschler says.

Xeomin can be used in combination with other products.

"Because there is no difference clinically in the use of Xeomin and Botox, in cases in which dermatologists would use Botox plus Restylane (hyaluronic acid, Medicis) or Juvéderm (cross-linked hyaluronic acid, Allergan), or Radiesse (calcium hydroxylapatite, Merz) they could also use Xeomin," he says. "It's the same thing — I don't see any safety issues or concerns with combining Xeomin and dermal fillers for concurrent use in facial aesthetic indications."

Disclosures: Dr. Werschler is a consultant for Merz, Allergan and Medicis.