Difelikefalin

Korsuva / Kapruvia

Difelikefalin is a small synthetic tetrapeptide that selectively activates the kappa-opioid receptor (KOR). Its defining feature is that it is deliberately designed to be peripherally restricted: it is hydrophilic and does not readily cross the blood-brain barrier, so it engages kappa-opioid receptors on peripheral sensory neurons and immune cells without producing the central nervous-system effects — sedation, euphoria, dependence — associated with traditional mu-opioid drugs. This separates the anti-itch and anti-inflammatory benefits of kappa-opioid signaling from the classic risks of opioids. Its approved use is chronic kidney disease-associated pruritus (CKD-aP), the intense, often debilitating itching experienced by many patients on hemodialysis. This itching is poorly understood but appears to involve an imbalance between mu- and kappa-opioid tone and a component of neural and immune activation; kappa-opioid agonism helps rebalance this and dampens the itch signal. In the pivotal KALM trials, intravenous difelikefalin given after dialysis sessions significantly reduced itch intensity and improved itch-related quality of life compared with placebo. It was approved by the FDA in 2021 (Korsuva) and in the EU (Kapruvia) for moderate-to-severe CKD-associated pruritus in adults on hemodialysis. Difelikefalin is administered by a clinician as an intravenous injection into the dialysis circuit at the end of each hemodialysis session, which fits neatly into existing dialysis routines. Its most common side effects reflect residual kappa-opioid activity and include dizziness, altered mental status, and gait disturbances, so patients are monitored accordingly. An oral formulation has been studied for other itch conditions, but the approved product is the intravenous dialysis form. It is a prescription medicine used within nephrology care, not a self-administered peptide.