Warner-Lambert is now testing a potential drug it calls Zenarestat that could prevent neuropathy. Several medications treat neuropathy pain, but according to Howard Foyt, MD, PhD, director of clinical research, diabetes and metabolic diseases for Warner-Lambert, there is none available for preventing or reducing the risk of neuropathy.
“Right now, doctors prescribe antidepressants, capsaicin or even Neurontin [a Warner-Lambert drug used for the treatment of epilepsy] to treat neuropathy-related pain,” explains Foyt. “None of these affects the natural history of diabetes, or does anything to inhibit the progression of the disease.”
Zenarestat is an aldose reductase inhibitor (ARI) that, according to Warner-Lambert, reduces sorbitol levels in human tissues and improves nerve fiber density. According to Foyt, blood sugar can become sorbitol in a person with diabetes, which can lead to neuropathy, kidney disease and retinopathy complications.
About 60 percent of people with diabetes suffer from some type of nerve damage.
“Zenarestat is a second-generation ARI which has been documented to get into the tissues and nerves, and significantly lower sorbitol levels without causing skin reactions or liver toxicity,” says Foyt.
Nerve conduction velocity (how fast a nerve conducts electrical impulses) increased by 1 to 1.5 meters per second over the 12-month test period in people who took Zenarestat, while a placebo group’s nerve conduction velocity decreased. Additionally, nerve fiber density increased in the Zenarestat group and decreased in the placebo group.
“Any patient with diabetes, even if he or she has excellent glycemic control, is still at risk for neuropathy complications,” says Foyt. “By reducing sorbitol levels, this drug is aimed at further reducing your risk for either the development or progression of diabetic neuropathy.”
Warner-Lambert is in the final stages of testing for Zenarestat. Presently, there is one study in the United States and one in Europe. Based on the results of those studies, Warner-Lambert will apply for FDA approval.