Safety and Tolerability of Difelikefalin in Adolescents on Haemodialysis With Moderate-to-Severe Pruritus

Rationale: * People with long term kidney disease who are on haemodialysis (a procedure for removing waste products from the blood) commonly develop a condition that makes their skin very itchy. * Difelikefalin is a medicine that can treat the itching related to long term kidney disease. * Clinical studies have shown difelikefalin to reduce itching in adults on haemodialysis, while being safe and tolerable. * The current study is being done in adolescents aged 12 to 17 years on haemodialysis who have moderate to severe itching related to long term kidney disease to assess if difelikefalin is safe in this age group. The aims of the study are: Main aim: To assess the safety of difelikefalin in adolescents who are on haemodialysis and have itching related to long term kidney disease Secondary aim: To measure the amount of difelikefalin that enters the blood in adolescents who are on haemodialysis and have itching related to long term kidney disease Study Design At least 18 adolescents, aged 12 to 17 years, who are on haemodialysis and have itching related to long term kidney disease will take part in this study. All study participants will receive difelikefalin 3 (or up to 4) times weekly for up to 12 weeks. The study duration for a participant is up to 17 to 18 weeks; during this period, participants will visit the clinic 3 times weekly (during their haemodialysis visits).