Inclusion Criteria:

Key Inclusion Criteria:

• Have a clinical diagnosis of diabetes mellitus type I or II for at least 12 months prior to the study.
• Have received a diagnosis of sensorimotor diabetic neuropathy from a neurologist (a doctor who specializes in disorders of the nervous system) or endocrinologist (a doctor who specializes in diabetes).
• Have reduced nerve conduction velocity in any lower extremity nerve: peroneal, tibial or sural due to diabetic polyneuropathy
• If female and of childbearing potential, agree to use a medically acceptable physical barrier method during the study.
• Have blood pressure < 140/90 mm Hg
• Body mass index (BMI) < 38 kg/m2

Key Exclusion Criteria:

Subjects with the following are NOT eligible to participate in this study:

• Have moderate to severe ischemic heart disease, any history of congestive heart failure, or have had a myocardial infarction (heart attack) within the previous 6 months.
• Have chronic foot or leg ulcers for >1 month, gangrene in the legs, or any previous amputation of the lower extremity.
• Have a history of cancer within the past 5 years (except for curable non-melanoma cancer of the skin, superficial bladder cancer in complete remission, or any other cancer that has been in complete remission for at least 5 years).
• Have colon polyps. If patients have a history of benign colonic polyps that have been removed, they must have evidence of a normal colonoscopy within the last 12 months.
• Require any drug that depresses patients' immune systems (such as methotrexate, cyclophosphamide, or cyclosporine) when they receive the study drug and for 30 days afterwards.
• Have a known disorder that affects patients' immune systems (such as HIV/AIDS, hepatitis B virus [HBV], hepatitis C virus [HCV], sarcoidosis, tuberculosis, rheumatoid arthritis, or autoimmune disorders).