Safety, Tolerability and Preliminary Efficacy of AZD5213 in Combination With Pregabalin in Subjects With PDN and Good Pain Reporting Ability

Inclusion Criteria: 1\. Male or female, age 18 to 75 years, inclusive, at Screen. 2. Subjects must provide informed consent in accordance with local regulations before the conduct of any study-related procedures. The informed consent should reflect the protocol stipulations concerning the use of contraception. 3. Diagnosis of Type 1 or Type 2 diabetes mellitus for at least 1 year prior to Screen. 4. Diabetes-related painful neuropathy for at least 6 months prior to Screen. 5. Pain that began in the feet and is symmetric or nearly symmetric. 6. Diabetes has been clinically stable for at least 2 months prior to Screen, and between Screen and baseline (Day 35). 7. At Screen and baseline, score of at least 4 on Item 5 ("average pain") of the modified Brief Pain Inventory for patients with painful diabetic peripheral neuropathy (BPI-DPN). 8. Able to participate in all scheduled evaluations and to complete all required tests and procedures. 9. In the opinion of the investigator, the subject must be considered likely to comply with the study protocol and to have a high probability of completing the study. Exclusion Criteria: 1\. Known or suspected hypersensitivity to pregabalin. 2. Clinically important illness or infection (e.g., chronic, persistent, or acute infection) within 30 days prior to screen or between screen adn baseline. 3. Presence of any psychiatric or neurologic disorder or any other disorder or symptom, if, in the judgement of the investigator, the disorder or symptom is likely to confound interpretation of drug effect or affect the subject's ability to complete the study. Any clinically important abnormality, as determined by investigator at Screen or baseline, in physical or neurologic examination, vital sign, ECG, or clinical laboratory test results that could be detrimental to the subject, or could affect the subject's ability to complete the study. 4. Initiation or change in intensity or frequency of non-pharmacologic therapy for PDN, including psychotherapy, physical therapy, massage, acupuncture, acupressure, or chiropractic care, within 3 months prior to baseline).