A Study to Investigate the Analgesic Efficacy of AZD2423 Compared With Placebo After 28 Days Treatment in Patients With Painful Diabetic Polyneuropathy

Change From Baseline to Days 24-28 in Numerical Rating Scale (NRS) Worst Pain Score.

Last Observation Carried Forward (LOCF). Twice daily, the participants rated their Worst pain intensity during the past 12 hours on an Numerical Rating Scale (NRS) 0-10, 0=No pain, 10=Worst pain imaginable.

Time frame: Baseline (mean of Day -5 to Day -1) to the mean of Day 24 to Day 28

Number of Participants With at Least 30% Decrease From Baseline in Numerical Rating Scale (NRS) Average Pain Score at Day 28.

Last Observation Carried Forward (LOCF). Numerical Rating Scale(NRS) Average Pain score reduction=(change from baseline at Day 28/baseline)\*100. Responder= NRS Average Pain score reduction ≥30% (yes/no)

Time frame: Baseline (mean of Day -5 to Day -1) to Day 28

Number of Participants With at Least 50% Decrease From Baseline in Numerical Rating Scale (NRS) Average Pain Score at Day 28.

Last Observation Carried Forward (LOCF). Numerical Rating Scale (NRS) Average Pain score reduction=(change from baseline at Day 28/baseline)\*100. Responder= NRS Average Pain score reduction ≥50% (yes/no)

Time frame: Baseline (mean of Day -5 to Day -1) to Day 28

Change From Baseline to Day 29 in Neuropathic Pain Symptom Inventory Scale (NPSI) Total Score.

Last Observation carried Forward (LOCF). Scale consists of 10 Neuropathic Pain Symptom Inventory Scale (NPSI) pain symptom descriptors wiht a recall period of 24 hours. Each descriptor is rated on a Numerical Rating Scale (NRS) 0-10; 0=No (symptom), 10=Worst (symptom) imaginable. The NPSI Total Score was calculated as the sum of 10 of the NPSI descriptors. Range for total score 0 -100. Higher total score implicates worse symptoms.