This is a safety and efficacy trial of ranirestat(AS-3201) which is an aldose reductase inhibitor in patients with diabetic sensorimotor polyneuropathy.

Inclusion Criteria:

• Patients with the following may enter:

Clinical signs and symptoms (footpain, numbness, tingling, weakness, etc.) of symmetrical distal Diabetic Sensorimotor Polyneuropathy with diagnosis by Nerve Conduction Tests and/or Quantitative Sensory Test.

• 18 to 70 years old of either sex and any race
• Type I or Type II, insulin-dependent or non insulin-dependent diabetes for at least six months prior to study entry
• Healthy in general
• No hospitalizations for diabetic control or episodes of ketoacidosis for three months prior to screening
• Female patients of childbearing potential must have a negative serum pregnancy test

Exclusion Criteria:

• Known non-diabetic causes of neuropathic symptoms
• Diabetic patients with no neuropathy or severe neuropathy
• Used any Aldose Reductase Inhibitors within one year of screening
• Clinically significant illness including unstable cardiac, pulmonary, hematologic, hepatic, renal, or neoplastic disease
• A history of systemic carcinoma within five years of screening
• A history of epilepsy or serious head injury
• A history or evidence of drug or alcohol abuse
• Test positive at screening for hepatitis B surface antigen or hepatitis C antibody or have a history of a positive result, or patients with evidence of significant hepatic insufficiency
• A history of known or suspected diagnosis of AIDS, or have tested seropositive for HIV antibody or antigen previously