Study to Evaluate IV CR845 in Hemodialysis Patients With Moderate-to-Severe Pruritus

This is a two-part study. Patients participating in Part A will be consented and trained on the completion of questionnaires about the severity of itching and overall health. Patients will be required to complete questionnaires during their visits to the dialysis center and also while at home on other days. Results of the screening questionnaires will assess eligibility for the study. Additional laboratory tests and measurements for safety will also be completed during the screening period. Patients meeting all criteria for entry into Part A of the study will be randomized to receive either one of three different doses of CR845 or a placebo. Patients will receive the study drug for eight weeks IV after each hemodialysis treatment (i.e. 3 times per week). Assessments for intensity of itch and safety will also be completed during the 8 week treatment period. When patients have completed treatment, a Follow-up visit will be completed 7 days later. Patients participating in Part B will be consented and trained on the completion of questionnaires about itching and overall health. Patients will be required to complete questionnaires during their visits to the dialysis center and also while at home on other days. Laboratory tests and measurements for safety will also be completed during the screening period to determine study eligibility. Patients meeting all criteria for entry into Part B of the study will be randomized to receive either CR845 or a placebo. The dose of CR845 used will have been determined based on the safety and efficacy from Part A. Patients will be dosed with either CR845 or placebo for twelve weeks after each hemodialysis treatment (i.e. 3 times per week). Assessments for intensity of itch and safety will be completed during the treatment period also. When patients have completed treatment, a Follow-up visit will be completed 7 days later.