A Trial in Painful Diabetic Peripheral Neuropathy With GRT3983Y

Change From Baseline in the Mean of the Daily Average Pain Intensity Scores (on an 11-point NRS) Over the Entire 12-week Maintenance

Time frame: Baseline, Daily scores over entire 12 week maintenance

Proportion of Subjects Achieving Various Levels of Pain Improvement (Including 30% and 50%) Based on the Percent Change From Baseline to the Last 7 Days of the 12-week Maintenance on an 11-point NRS (Responder Analysis).

Time frame: Baseline, Last 7 days of 12-week maintenance

Change From Baseline in the Mean of the Daily Average Pain Intensity Scores (on an 11-point NRS) Over Each Week of Maintenance.

Time frame: Baseline; daily scores over each week of maintenance

Change From Baseline of the Weekly Mean of Night Pain Intensity (on an 11-point NRS).

Time frame: Baseline; weekly mean

Change From Baseline of the Weekly Mean of Current Pain Intensity (on an 11-point NRS) in the Evening and in the Morning, Respectively.

Time frame: Baseline, weekly mean

Brief Pain Inventory Scores: Changes From Baseline to Day 8, Day 15, Day 22, Day 29, Day 43, Day 57, Day 71, Day 85, Day 99, and Day 113 (Final Visit).

Time frame: Baseline, weekly mean

Neuropathic Pain Symptoms Inventory: Changes From Baseline to Day 8, Day 15, Day 22, Day 29, Day 43, Day 57, Day 71, Day 85, Day 99 and Day 113 (Final Visit)