 This 12 month double-blind, randomized, placebo-controlled, parallel group efficacy and safety study will enroll 400 adult diabetic subjects with diabetic peripheral neuropathy DPN to investigate the effect of diepalrestat BNV-222 150 mg, 300 mg, or placebo on MNCV and patients perception of nerve function over 12 months as measured by VAS scales and composite clinical outcome patient reported scales that evaluate numbness, tingling, cramping, paresthesiae, hyperesthesia, coldness, weakness and spontaneous pain perception of upper and lower extremities, and the effects on other measures of nerve motor and sensory conduction. Subjects will be assessed at screening and baseline, with office visits every 12 weeks, for a total of 6 visits. Subjects will be assessed by testing motor nerve conduction velocity and other assessments at each office visit. A subgroup of 24 patients will be selected for pharmacokinetic PK testing for up to 48 hours with additional blood draws on Day 7 and 14. This study will investigate the ability of diepalrestat to reduce the ongoing deterioration of nerve function which is a hallmark of the DPN process. 