A phase 2b, placebo-controlled, randomized, double-blind, multi-center study of GCS-100 in patients with chronic kidney disease caused by diabetes. The study will enroll approximately 375 patients at multiple centers located in the United States. Study duration is 6 months. Patients will be randomly assigned 1:1:1:1 to treatment with placebo (0.9% Sodium Chloride Injection, USP), 1 mg, 3 mg, or 9 mg GCS-100. All doses of study drug will be administered via intravenous (IV) push injection once weekly for 2 months (8 weeks), then every other week for an additional 4 months (16 weeks).