Diabetic foot ulcers are sores on the feet that occur in 15% of diabetic patients some time during their lifetime. Once an ulcer develops, the risk of lower-extremity amputation is increased 8-fold in people with diabetes. New treatments that improve the number of ulcers that heal and/or speed up healing are urgently needed. Initial studies with a new drug called Nexagon® (developed by CoDa Therapeutics, Inc.) support the concept that healing of diabetic foot ulcers can be improved with topical application of Nexagon®. Further research will be undertaken to assess the safety and activity of Nexagon® when applied to diabetic foot ulcers at various doses. A proposed randomized controlled trial will randomly allocate (e.g., by the toss of a coin) 24 people with diabetic foot ulcers to Nexagon® (one of three different doses) or vehicle (substance containing no medication) to be applied to their ulcer three times over four weeks. Participants will be followed over four weeks to monitor their response to the treatment, specifically with regards to the amount of healing that occurs.