This is a 3-part study (Zebra 1, 2A and 2B) that will explore safety and therapeutic potential of Zibotentan in acute and chronic renal complications of Scleroderma. Trial duration will be 52 weeks for Zebra 1 and 2A (1 or 2 weeks for ZEBRA 2B with 1 year follow up data). Scleroderma (Systemic sclerosis) is a multisystem rheumatic disease that results in vascular damage and fibrosis of target organs.This project will focus specifically on the evaluation and treatment of renal disease in scleroderma.