Pfizer Inc., said today that it is suspending the development of its aldose reductase inhibitor research candidate, zenarestat, which is under development for the treatment of diabetic neuropathy.

Managing the neuropathic complications of diabetes has been, and remains, a difficult challenge for patients, physicians and researchers. There is currently no effective pharmacologic therapy for management of this debilitating medical condition. Pfizer has had a long-standing interest in developing an effective drug therapy for diabetic neuropathy. Drug researchers have evaluated many aldose reductase inhibitors over the years in clinical trials. To date, there are none approved for use in the United States.

Pfizer based its decision to suspend development of zenarestat following its evaluation of recent safety data in two large trials. In a small number of patients in these early phase III trials, zenarestat was noted to have potential renal toxicity, which appears to be dose dependent with the majority of cases at the highest dose (1200 mg/day). However, with regard to efficacy, zenarestat was shown in phase II clinical development to have a beneficial effect on nerve conduction velocity, findings which were confirmed in an interim efficacy analysis of one of these trials. These efficacy findings are important with regard to our overall continuing research programs.

Pfizer has a long history of diabetes research and continues to seek new therapies for this devastating disease. The company is in Phase III development of inhaled insulin, a novel device and formulation that delivers insulin by inhalation. Pfizer also has several novel approaches to other diabetes treatments in early stages of development.