Pharmacological, pharmacokinetic and clinical profiles of Difelikefalin (KORSUVA<sup>®</sup> IV Injection Syringe for Dialysis), a peripheral kappa opioid receptor agonist

Difelikefalin (KORSUVA^® IV Injection Syringe for Dialysis) is a novel kappa opioid receptor (KOR) agonist. In September 2023, difelikefalin was approved for the treatment of pruritus in hemodialysis patients. Pruritus is a major symptom that significantly reduces the quality of life of hemodialysis patients, even with improved dialysis techniques, dialysis membranes, and dialysate solutions. The factors that contribute to pruritus include dry skin, accumulation of uremic toxins, overproduction of chemical mediators and altered immune function, and disruption of the opioid balance. In nonclinical studies, difelikefalin showed highly selective for KOR and antipruritic effects in animal models of histamine- and substance P-induced itching. It also showed anti-inflammatory effects by suppressing cytokine release in human monocyte-derived macrophages and TNFα and IL-1β induced by lipopolysaccharide administration in mice. In the phase 3 clinical trial in Japanese hemodialysis patients, difelikefalin showed significant improvement compared to placebo in the primary endpoint of the change from baseline in the weekly mean NRS score at week 4. It also improved sleep disturbance and itch-related quality of life, and the improvement in itch was sustained up to 58 weeks. Furthermore, there was no increase in adverse drug reactions with long-term treatment, and no delayed adverse events were observed. In conclusion, the novel KOR agonist difelikefalin is expected to be a new treatment option for pruritus on dialysis.