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11/30/2011
Botulinum toxins function similarly, but aren't interchangeable
Coral Gables, Fla. Although many forms of botulinum toxin available worldwide function similarly, the products are not interchangeable, as they have different protein sizes, diffusion characteristics, potencies and effects, says Fredric S. Brandt, M.D., a Coral Gables, Fla., dermatologist.
Botulinum toxins function similarly, but aren't interchangeable

Coral Gables, Fla. Although many forms of botulinum toxin available worldwide function similarly, the products are not interchangeable, as they have different protein sizes, diffusion characteristics, potencies and effects, says Fredric S. Brandt, M.D., a Coral Gables, Fla., dermatologist.

In addition to Botox (onabotulinumtoxinA, Allergan) and Dysport (abobotulinumtoxinA, Medicis), there's PurTox (Mentor), for which data have been submitted to the Food and Drug Administration, Dr. Brandt says. Xeomin (incobotulinumtoxinA, Merz) is FDA-approved for therapeutic and aesthetic indications, and RT001 (botulinumtoxinA, Revance) is a topical gel currently under investigation.

All varieties of botulinum toxin A contain the same 150 kilodalton active molecule, Dr. Brandt says. All presently FDA-approved botulinum toxins also include nonactive complexing proteins including hemagglutinin and nontoxic nonhemagglutinin proteins.


Botox surrounds the 150 kDa active molecule with 900 kDa of complexing proteins. "Dysport has less of the nonactive proteins than Botox does," he says. Botox includes no sugar, although Dysport includes lactose and Xeomin includes sucrose.

The fact that Botox contains more complexing proteins than Dysport leads some experts to believe that perhaps Botox will diffuse less after injection, Dr. Brandt says. Some people also believe Dysport may provide a quicker onset of action.

Unlike Botox and Dysport, Xeomin and PurTox use no complexing proteins or other proteins besides the active molecule itself, Dr. Brandt says. However, "It may not mean much because a lot of evidence shows that once you mix the powders in a vial, with sodium chloride, everything becomes disassociated," he says.

Some botulinum toxins use different measuring units. In particular, "One unit of Xeomin will be equivalent to one unit of Botox clinically," Dr. Brandt says. "That should be the same with PurTox."

Conversely, he says 2.5 units of Dysport are clinically equivalent to one unit of Botox. "With Dysport, you're using more units, but they're not really the same units," he says. "In other words, if you're using one unit of Botox, you'd have to use about 2.5 units of Dysport."
RT001

The Revance topical product uses a proprietary TransMTS peptide carrier to transport the 150 kDa active molecule through the skin to the targeted muscle, Dr. Brandt says. The peptide carries the active molecule through the intercellular area between stratum corneum cells. The peptide also uses an energy-dependent pathway to carry the active molecule through cells.

In 11 phase 2 studies performed in crow's feet, the product achieved response rates up to 89 percent, Dr. Brandt says. Based on patient and investigator assessments, patients who responded achieved an average bilateral improvement of two points on a five-point scale (in which zero = no improvement; P<0.0001). Additionally, he says, the product's effects on lateral canthal lines at rest lasted a median of 113 days.


"These studies also showed no evidence of diffusion away from the target muscle, and no effects on any other cranial nerves," he says. "Additional studies were done to measure whether or not the large botulinum toxin molecule can penetrate the skin on its own." Taken together, he says these studies show RT001 appears safe and effective in the study population.

At press time, Revance had submitted the phase 2 data to the FDA, and a phase 3 study had not yet begun, Dr. Brandt says. The topical product likely will prove best suited for superficial musculature such as that involved in crow's feet and perioral wrinkles and for hyperhidrosis and areas that require broader coverage, such as the forehead and platysmal bands, he says.

Other options

Other botulinum toxins available internationally include Neuronox (Medy-Tox), which is manufactured in South Korea, Dr. Brandt says.

Prosigne (CBTX-A, Lanzhou Biological Products Institute) is available in China. It uses different complexing proteins than Botox and Dysport, Dr. Brandt says.

"Linurase (Prollenium Medical Technologies Inc.) is another botulinum type A toxin. It contains no serum albumin and is undergoing testing in Canada. It's said to have the same unit dosing as Botox," Dr. Brandt says.

CNBTX-A (Nanfeng Medical Science and Technology Development Co. Ltd.) is available in China. According to Dr. Brandt, it comes freeze-dried in packages of 55 or 100 units and also uses the same unit dosing as Botox.

Disclosures: Dr. Brandt is a consultant and investigator for Allergan and Medicis. He is an investigator for Anika Therapeutics, Mentor, Suneva, Merz, Isolagen/Fibrocell, Contura, Revance, Galderma and Teoxane Laboratories.

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