Inclusion Criteria:

• Type 1 or Type 2 diabetes with optimized and stable glycemic control during the 3 months prior to Screening
• Painful distal symmetric sensorimotor polyneuropathy ≥6 months
• Douleur Neuropathique 4 (DN4) score of ≥4
• Use and failure of at least 2 other treatments for neuropathic pain
• Satisfactory diary data during the 7-day Pain Observation period determined by an algorithm that includes diary compliance, overall level of pain and day-to-day variability in pain

Exclusion Criteria:

• Pregnant or lactating
• BMI >40 kg/m2
• Suicidal ideation/behavior as measured by the C-SSRS
• Radiculopathy or other neuropathic conditions, including chemotherapy-induced neuropathy
• Other chronic pain condition(s) that could affect compliance with pain medication restrictions or confound pain assessments
• Known history of opioid abuse or opioid dependence in the past 5 years, or opioid use at a dose of ≥30 MME on 3 or more days a week during the month prior to Screening
• Chronic use of over-the-counter capsaicin on extremities within 3 months of Screening and/or prescription Qutenza use within 6 months of Screening
• Corrected QT interval at Screening using QTcF of ≥480 msec in the presence of a QRS >120 msec
• Any of the following hematology abnormalities at Screening;
• Hemoglobin <11.5 g/dL (female) or <13 g/dL (male)
• Complete blood count outside the normal reference range
• Creatinine >1.5 mg/dL or a calculated creatinine clearance of <60 mL/min
• Serum bilirubin values >2.0 mg/dL (>3.0 mg/dL for hereditary benign hyperbilirubinemia) and serum ALT and/or AST values >1.5 x the upper limit of normal
• HIV positive and/or active hepatitis virus (A, B, or C) infection
• Current or previous (≤1 month of Screening) enrollment in a clinical trial involving treatment with an investigational product