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

The purpose of this study is to evaluate the safety and tolerability, as assessed by incidence of AEs, of 0.5 μg/kg IV difelikefalin in adolescent participants on HD (3 times weekly) with moderate-to-severe pruritus over 12 weeks. Additionally, difelikefalin plasma concentrations (Cmax and Ctrough) after multiple administrations will be evaluated at a few selected time points and the efficacy of difelikefalin in improving itching and health-related QoL will be investigated as exploratory. Study details include: * The study duration for a single participant will be up to 17 to 18 weeks. * The treatment duration for each participant will be up to 12 weeks. * The visit frequency will be 3 times weekly (during HD visits). Trial Population: Participants in this study must: * Be male or female adolescent participants ≥12 to \<18 years of age at the time of informed consent/assent * Have CKD-aP on HD (at least 3 hours in duration 3 times weekly, for at least 12 weeks prior to the informed consent procedure) * Be able to continue HD without changing its frequency or method * Have a mean value WI-NRS score during the run-in period of \>4.0 (moderate-to-severe pruritus) Participants in this study must not: * Be planned to receive a kidney transplant during the study * Have known severe hepatic impairment (e.g., Child-Pugh Class C) or concurrent hepatic cirrhosis, serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \>3 times the reference upper limit of normal (ULN), significant systolic or diastolic heart failure, or concurrent malignancy (except excised basal cell or squamous cell carcinoma of the skin, or carcinoma in situ that has been excised or resected completely) Number of Participants: At least 18 participants evaluable for the primary safety endpoint will be enrolled in the study. Note: Enrolled means participants, or their legally acceptable representatives, agreement to participate in a clinical study following completion of the informed consent process and screening. A participant will only be considered enrolled if the informed consent/assent is not withdrawn prior to participating in any study activity after screening including the run-in period. Study Arms and Duration: * This is a single-arm, open-label study. All participants will receive IV difelikefalin at a dose of 0.5 μg/kg of dry body weight after each HD treatment 3 times weekly for 12 weeks. * The study includes a screening period of up to 4 weeks (including a 7-day run-in period during the week prior to enrolment), a study treatment period of 12 weeks, and a follow-up period of 7 (up to 10) days. * If for any reason difelikefalin is interrupted for more than 1 week, the participant should be withdrawn from the study intervention.