This study will evaluate the safety and tolerability of treatment with CTP-499 starting with 600 milligrams (mg) once a day (QD) for 2 weeks followed by 600 mg twice a day (BID) for 2 weeks in non-dialysis patients associated with moderate chronic kidney disease defined as an estimated Glomerular Filtration Rate or eGFR that is 30-59 mL/min/1.73m2