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the normal body pH of around 7. The enzyme is very sensitive to pH and is active only at the levels found in lysosomes.
Gustafson said the enzyme could be administered in the following manner: Before injecting the enzyme, a physician would increase the acidity of the target area by administering an anesthetic such as lidocaine, which has a pH of about 5. As the anesthetic wore off and the pH returned to normal, the enzyme would stop working-a process that takes about 20 minutes. At that point, the enzyme becomes an inactive protein in the body.
Gustafson said this procedure would allow the enzyme to target cellulite and minimize unwanted affects on other tissue. “By making it conditionally active, we can make it very safe,” he said.
Halozyme developed the enzyme, known as HTI-501, entirely in-house, so if it is successful in people-a big if at this point-the enzyme could be a very profitable product for the 12-year-old company.
Halozyme had expected to begin human tests of its enzyme in 2009 but the company delayed those studies in order to evaluate a second enzyme, matrix metalloproteinase 1, which also snips collagen but is activated by temperature. This enzyme would be injected at room temperature, its active state, and then would become deactivated by the higher temperature within the body.
In theory, “you could cool the area you are treating with an ice pack ahead of the injection and keep it cool for as long as you want the [enzyme] to degrade the collagen,” spokesman Robert Uhl tells me. He says the company is in the process of determining which enzyme looks best for various conditions, including cellulite, fibrosis and scarring, and which to move forward.
Gustafson said he couldn’t put date on when the company would begin human studies. “We are working to get the right formulation and have that put in place this year,” he said.
Clearly, the cellulite program is at an early stage compared to Halozyme’s programs in diabetes and cancer; important questions about safety and efficacy need to be answered. But if the cellulite shots work as well in people as they seem to in pigs, Halozyme may have a hit on its hands. This is a story we’ll be tracking.