Safety and Efficacy Study for the Treatment of Painful Diabetic Neuropathy

Inclusion Criteria: * Age ≥ 18 years to ≤ 75 years * Documented history of Type I or II diabetes with current treatment control (glycosylated hemoglobin A1c of ≤ 10.0% at Screening) and currently on oral medication and/or insulin * Diagnosis of painful diabetic peripheral neuropathy in both lower extremities * Lower extremity pain for at least 6 months * Visual analog scale (VAS) score of ≥ 40 mm at Initial Screening (0 mm = no pain - 100 mm very severe pain) * Symptoms from the Brief Pain Neuropathy Screening (BPNS) is ≤ 5 point difference between legs at Initial Screening * The average daily pain intensity score of the Daily Pain and Sleep Interference Diary completed after medication wash-out is ≥ 4 with a standard deviation ≤ 2 * The physical examination component of the Michigan Neuropathy Screening Instrument Score (MNSI) is ≥ 3 at Screening * Stable treatment of diabetes for at least 3 months with no anticipated changes in medication regimen, and no new symptoms associated with diabetes * If female of childbearing potential, negative urine pregnancy test at screening and using acceptable method of birth control during the study Exclusion Criteria: * Peripheral neuropathy caused by condition other than diabetes * Other pain more severe than neuropathic pain * Progressive or degenerative neurological disorder * Myopathy * Inflammatory disorder of the blood vessels (inflammatory angiopathy, such as Buerger's disease) * Active infection * Chronic inflammatory disease (e.g., Crohn's disease, rheumatoid arthritis) * Positive HIV or HTLV at Screening * Active Hepatitis B or C as determined by Hepatitis B core antibody (HBcAB), antibody to Hepatitis B antigen (IgG and IgM; HbsAb), Hepatitis B surface antigen (HBsAg) and Hepatitis C antibodies (Anti-HCV) at Screening * Subjects with known immunosuppression or currently receiving immunosuppressive drugs, chemotherapy or radiation therapy * Stroke or myocardial infarction within last 3 months * Ophthalmologic conditions pertinent to proliferative retinopathy or conditions that preclude standard ophthalmologic examination * Specific laboratory values at Screening including: Hemoglobin \< 8.0 g/dL, WBC \< 3,000 cells per microliter, platelet count \<75,000/mm3, Creatinine \> 2.0 mg/dL; AST and/or ALT \> 3 times the upper limit of normal or any other clinically significant lab abnormality which in the opinion of the investigator should be exclusionary * Uncontrolled hypertension as defined as sustained systolic blood pressure (SBP) \> 200 mmHg or diastolic BP (DBP) \> 110 mmHg at Screening * Patients with a recent history (\< 5 years) of or new screening finding of malignant neoplasm except basal cell carcinoma or squamous cell carcinoma of the skin (if excised and no evidence of recurrence); patients with family history of colon cancer in any first degree relative are excluded unless they have undergone a colonoscopy in the last 12 months with negative findings * Subjects requiring \> 81 mg daily of acetylsalicylic acid; If ≥ 81 mg are taken at screening, subjects may be enrolled if willing/able to switch to another medication * Use of any opioids; subjects may be enrolled if willing and able to discontinue use of these drugs 14 days prior to starting the 7 Day Daily Pain and Sleep Interference Diary and refrain from taking these drugs for the duration of the study * Subjects requiring regular COX-2 inhibitor drug(s) or non-specific COX-1/COX-2 inhibiting drugs, or high dose steroids (excepting inhaled steroids).Subjects may be enrolled if willing/able to undergo medication wash-out prior to the first dosing and to refrain from taking these drugs for the duration of the study; * Major psychiatric disorder in within last 6 months * Body mass index (BMI) \> 45 kg/m2 at Screening * Any lower extremity amputation * Use of an investigational drug or treatment in past 6 months * Unable or unwilling to give informed consent