Clinical Profiles of Nalfurafine Hydrochloride for the Treatment of Pruritus Patients.

Nalfurafine hydrochloride is a selective kappa-opioid agonist that has antipruritic effects. Here we describe the clinical trials for treatment of uremic pruritus in dialysis patients and on hepatic pruritus in patients with chronic liver disease. Among cytochrome P-450 (CYP) isoforms in humans, CYP3A4 is the major isoform involved in metabolic decyclopropylmethylation of nalfurafine hydrochloride. Nalfurafine hydrochloride was found to be a substrate for P-glycoprotein (P-gp), but had no inhibitory effects on P-gp-mediated transport. The efficacy of oral nalfurafine hydrochloride at 2.5 and 5 µg for refractory pruritus in hemodialysis patients was observed within the first 7 days of treatment, and the effects persisted for the 52-week treatment period. Nalfurafine hydrochloride is also effective in the treatment of conventional refractory pruritus in peritoneal dialysis patients. Moreover, nalfurafine hydrochloride at 2.5 and 5 µg is effective for the treatment of refractory pruritus in chronic liver disease patients within the first 7 days of drug administration. In all the clinical trials, most adverse drug reactions (ADRs) were mild and resolved quickly and there was no clinical safety problem. Following 52 weeks of treatment, hemodialysis patients did not develop physical or psychological dependence, indicating no addiction risks. In summary, nalfurafine hydrochloride administered orally at doses of 2.5 and 5 µg was safe and effective for treatment of refractory pruritus in patients undergoing hemodialysis or peritoneal dialysis and in chronic liver disease patients.

Recurrence rates of pruritus after the stop of nalfurafine hydrochloride in chronic liver disease: Preliminary prospective confirmatory trial.

AIM: The recurrence rates of pruritus after stopping nalfurafine hydrochloride are unknown in chronic liver disease. METHODS: A prospective confirmatory trial was carried out to determine the recurrence rates of pruritus after cessation of nalfurafine hydrochloride in chronic liver disease. After pretreatment with nalfurafine hydrochloride for 4 weeks or more, 15 consecutive Japanese patients, who confirmed the improvement of pruritus (decrease in the visual analogue scale (VAS) of ≥50 mm), were enrolled in the present study. Patients were classified to the continuous group (continuation of nalfurafine hydrochloride for 4 weeks) or the discontinuous group (cessation of nalfurafine hydrochloride) at the time of consent to study protocol, by self-determination. RESULTS: The recurrence rates (increase in VAS of ≥25 mm after stopping nalfurafine hydrochloride) were 100% (5 of 5 patients) and 0% (0 of 10) in the discontinuous and continuous groups, respectively. In the discontinuous group, 3 patients selected retreatment with nalfurafine hydrochloride as salvage therapy, and they generally recovered to the levels of VAS at the discontinuation of treatment. CONCLUSION: The present prospective trial showed the high recurrence rates of pruritus after the stop of nalfurafine hydrochloride in chronic liver disease.

Predictors of pruritus in patients with chronic liver disease and usefulness of nalfurafine hydrochloride.

AIM: Pruritus is one of the complications of chronic liver disease, and it is important to investigate the predictors. METHODS: Six hundred and seventy-three consecutive Japanese patients with chronic liver disease were retrospectively investigated for itch severity. Furthermore, 138 of all 673 patients were introduced to nalfurafine hydrochloride, and the improvement of itch severity was evaluated. The itch severity was self-assessed using the pruritus scores by Kawashima's criteria and visual analog scale. RESULTS: Two hundred and twenty-nine of the 673 patients (34.0%) were evaluated as 1 point or more of pruritus severity of Kawashima's criteria, and 46 patients (6.8 %) as 3 points or more. Multivariate analysis established that being negative for hepatitis B surface antigen (HBsAg) and presence of hepatocellular carcinoma (HCC) were significant determinants of pruritus (≥1 point of Kawashima's criteria), and being negative for HBsAg and having lower levels of platelet count were significant determinants of severe pruritus (≥3 points). Ninety-three of the 138 patients (67.4%) with nalfurafine hydrochloride indicated improvement of itch, defined as a decrease in VAS of 50 mm or more. There were no significant differences in treatment efficacy of nalfurafine hydrochloride, regardless of the three predictors of pruritus (HBsAg, HCC and platelet count). CONCLUSION: The present retrospective study indicated the predictors for pruritus, based on the large number of patients with chronic liver disease. Furthermore, this study demonstrated that nalfurafine hydrochloride may be useful for pruritus, regardless of the predictors.

Efficacy of nalfurafine hydrochloride in patients with chronic liver disease with refractory pruritus: A randomized, double-blind trial.

AIMS: Patients with chronic liver disease sometimes develop cholestasis, which induces severe whole-body pruritus that may disrupt daily activities and sleep. To determine the efficacy of nalfurafine hydrochloride (5 µg), which is a selective κ-opioid receptor agonist, in improving pruritus, we undertook a double-blind placebo-controlled study in patients with chronic liver disease with refractory pruritus. Nalfurafine hydrochloride at 2.5 µg was also used to evaluate the dose-response relationship. METHODS: In total, 318 subjects were randomly assigned to receive the placebo or nalfurafine hydrochloride (2.5 or 5 µg) given orally once daily for 84 consecutive days. Pruritus was assessed based on the visual analog scale and pruritus scores. RESULTS: Changes in the visual analog scale at week 4 (last observation carried forward) were significantly greater in the nalfurafine hydrochloride groups at 28.56 and 27.46 mm in the 2.5 µg and 5 µg groups, respectively, compared to 19.25 mm in the placebo group (P = 0.0022 and 0.0056, respectively). The major adverse drug reactions (ADRs) included pollakiuria (including nocturia), somnolence, insomnia (including middle insomnia), and constipation. Most ADRs were mild. CONCLUSIONS: Nalfurafine hydrochloride (2.5 or 5 µg daily) was effective in the treatment of refractory pruritus in patients with chronic liver disease. Furthermore, no clinically significant ADRs were observed at either dose.

Nalfurafine hydrochloride, a selective κ opioid receptor agonist, has no reinforcing effect on intravenous self-administration in rhesus monkeys.

Nalfurafine hydrochloride [(E)-N-[17-(cyclopropylmethyl)-4,5α-epoxy-3,14-dihydroxymorphinan-6ß-yl]-3-(furan-3-yl)-N-methylprop-2-enamide monohydrochloride; nalfurafine] is used in Japan as an antipruritic for the treatment of intractable pruritus in patients undergoing hemodialysis or with chronic liver disease. It is a potent and selective agonist at the κ opioid receptor, but also has weak and partial agonist activity at µ opioid receptors. Opioids, especially those acting at µ receptors, carry a risk of abuse. This is an important factor in the consideration of therapeutic risk vs. benefit in clinical use and the potential for misuse as a public health problem. It is therefore necessary to carefully evaluate the reinforcing effects of nalfurafine. To this end, we investigated intravenous self-administration of nalfurafine in rhesus monkeys. The number of self-administration of nalfurafine at doses of 0.0625, 0.125 and 0.25 µg/kg/infusion was not higher than that of saline in rhesus monkeys that frequently self-administered pentazocine (0.25 mg/kg/infusion). These results indicate that nalfurafine has no reinforcing effect in rhesus monkeys in the intravenous self-administration paradigm.

Nalfurafine Hydrochloride, a κ-Opioid Receptor Agonist, Induces Melanophagy via PKA Inhibition in B16F1 Cells.

Selective autophagy controls cellular homeostasis by degrading unnecessary or damaged cellular components. Melanosomes are specialized organelles that regulate the biogenesis, storage, and transport of melanin in melanocytes. However, the mechanisms underlying melanosomal autophagy, known as the melanophagy pathway, are poorly understood. To better understand the mechanism of melanophagy, we screened an endocrine-hormone chemical library and identified nalfurafine hydrochlorides, a κ-opioid receptor agonist, as a potent inducer of melanophagy. Treatment with nalfurafine hydrochloride increased autophagy and reduced melanin content in alpha-melanocyte-stimulating hormone (α-MSH)-treated cells. Furthermore, inhibition of autophagy blocked melanosomal degradation and reversed the nalfurafine hydrochloride-induced decrease in melanin content in α-MSH-treated cells. Consistently, treatment with other κ-opioid receptor agonists, such as MCOPPB or mianserin, inhibited excessive melanin production but induced autophagy in B16F1 cells. Furthermore, nalfurafine hydrochloride inhibited protein kinase A (PKA) activation, which was notably restored by forskolin, a PKA activator. Additionally, forskolin treatment further suppressed melanosomal degradation as well as the anti-pigmentation activity of nalfurafine hydrochloride in α-MSH-treated cells. Collectively, our data suggest that stimulation of κ-opioid receptors induces melanophagy by inhibiting PKA activation in α-MSH-treated B16F1 cells.

Factors Related to Sleeping Disorder Due to Pruritus in Patients with Chronic Liver Disease.

Objective This study evaluated cases of pruritus, which is known to be associated with sleep disorder, in chronic liver disease (CLD) patients. Methods Questionnaires were given to 339 enrolled CLD outpatients in winter (November 2019 to March 2020) and again in summer (April to October 2020) (median interval: 104 days). Relative changes in symptoms shown by a visual analogue scale (VAS) and Kawashima's pruritus score between winter and summer were evaluated in Study 1 (n=199), while Study 2 examined the clinical features of patients with sleep disorder based on the results of the second questionnaire (n=235, median age 70 years old; 141 men, liver cirrhosis 37%). Results Study 1. There was a significant relationship in VAS between daytime and nighttime for each season, as well as between winter and summer for each time period (p<0.001). A comparison of Kawashima's pruritus scores for the daytime and nighttime showed no significant seasonal differences (p=0.436 and 0.828, respectively). When Kawashima's score increased, so did the average VAS for both daytime (0:1:2:3:4=0.4±0.2:1.4±0.9:3.0±1.8:5.9±2.1:6.2±2.3) and nighttime (0:1:2:3:4=0.3±0.1:1.4±1.5:3.5±2.3:6.7±2.6:6.9±1.8) (p<0.001 for both). Study 2. Twenty subjects (8.5%) complained of sleep disorder. An elevated FIB-4 index (≥3.07) showed a good predictive value for sleep disorder (p<0.01). The cut-off for the daytime and nighttime VAS values for existing sleep disorder were 1.6 [area under the curve (AUC) 0.901] and 3.4 (AUC 0.931). The respective sensitivity, specificity, and positive and negative predictive values for sleep disorder based on Kawashima's score (≥2) were 0.85, 0.28, 0.10, and 0.95 for the daytime and 1.00, 0.29, 0.12, and 1.00 for the nighttime. Conclusion Intervention against pruritus is recommended in CLD patients with a high Kawashima's score (≥2) in any season, especially with an elevated FIB-4 index.

Post-marketing surveillance study of the safety and efficacy of nalfurafine hydrochloride (Remitch® capsules 2.5 µg) in 3,762 hemodialysis patients with intractable pruritus.

BACKGROUND: Intractable pruritus in hemodialysis patients can significantly decrease their quality of life and is also associated with poor vital prognosis. Although combined multiple causes of intractable pruritus in these patients have been identified, no existing treatments are proven to be sufficiently effective. We conducted a post-marketing surveillance to follow-up and assess the safety and efficacy of nalfurafine, a selective κ-opioid receptor agonist, for the treatment of intractable pruritus in patients undergoing hemodialysis. PATIENTS AND METHODS: Hemodialysis patients with intractable pruritus from institutions in Japan who received oral nalfurafine hydrochloride between January 2010 and December 2013 were enrolled in the surveillance. Surveillance was completed in July 2015. Safety data during 1 year after nalfurafine treatment onset, and efficacy data of nalfurafine evaluating the first 12-week treatment period and the following period until 1 year after the initial dose of nalfurafine (using global assessment of the itch improvement by the physician, Visual Analog Scale, and the Shiratori's severity scores) were collected and analyzed. RESULTS: In total, 3,762 patients were analyzed for safety. Adverse drug reactions were experienced by 402/3,762 (10.69%) patients. The most frequent adverse drug reactions were insomnia (127/3,762 [3.38%] patients), constipation (34 [0.90%]), somnolence (32 [0.85%]), dizziness (23 [0.61%]), nausea (13 [0.35%]), and malaise (9 [0.24%]). No patients developed dependence on nalfurafine. Nalfurafine was effective in 82.50% (2,880/3,491) of patients during the first 12 weeks and in 84.95% (2,167/2,551) on treatment during the subsequent period until 1 year after nalfurafine treatment initiation. Statistically significant decreases were reported in the Visual Analog Scale and the Shiratori's severity scores (p<0.001). CONCLUSION: Oral nalfurafine hydrochloride (from 2.5 µg/day to a maximum of 5.0 µg/day) continues to be safe and effective for the treatment of intractable pruritus in hemodialysis patients in real-world clinical settings.

Nalfurafine hydrochloride to treat pruritus: a review.

Uremic pruritus has a great negative influence on quality of life in hemodialysis (HD) patients and, importantly, negatively affects mortality risk. Recently, nalfurafine hydrochloride, an opioid κ-selective agonist, has been officially approved for resistant pruritus in HD patients on the basis of a well-evidenced clinical trial in Japan. From clinical observation, it has been suggested that the upper neuron system plays a role in its pathogenesis. According to previous experimental results, using mice injected with opioids, dynorphin suppresses itch through binding κ-opioid receptors, suggesting that κ-opioid opioid receptor agonists act as potential therapeutic reagents for pruritus in HD patients. In Japan, a large-scale placebo-controlled study was performed to examine the efficacy and safety of oral nalfurafine hydrochloride for intractable pruritus in 337 HD patients. Two daily doses of 2.5 or 5 µg nalfurafine or placebo were orally administered for 2 weeks, and clinical responses were analyzed. The results showed that the mean decrease in the visual analog scale for pruritus from baseline was 22 mm in the 5 µg nalfurafine hydrochloride group (n=114) and 23 mm in the 2.5 µg group (n=112). These reductions were statistically significant compared with 13 mm, which is the mean decrease of visual analog scale in the placebo group (n=111), demonstrating that nalfurafine is an effective and safe drug for uremic pruritus in HD patients. Moreover, another open-label trial (n=145) examining the long-term effect of 5 µg oral nalfurafine revealed the maintenance of the antipruritic effect of nalfurafine for 52 weeks. In addition, on the basis of recent data showing κ-opioid receptor expression in the epidermis of atopic dermatitis and psoriasis, nalfurafine hydrochloride also can be potentially used for these two skin diseases.