Investigational drugs for pruritus

Neurokinin-1 antagonist orvepitant for EGFRI-induced pruritus in patients with cancer: a randomised, placebo-controlled phase II trial

OBJECTIVE

To evaluate the efficacy of orvepitant (10 or 30 mg given once daily, orally for 4 weeks), a neurokinin-1 receptor antagonist, compared with placebo in reducing the intensity of epidermal growth factor receptor inhibitor (EGFRI)-induced intense pruritus.

DESIGN

Randomised, double-blind, placebo-controlled clinical trial.

SETTING

15 hospitals in Italy and five hospitals in the UK.

PARTICIPANTS

44 patients aged ≥18 years receiving an EGFRI for a histologically confirmed malignant solid tumour and experiencing moderate or intense pruritus after EGFRI treatment.

INTERVENTION

30 or 10 mg orvepitant or placebo tablets once daily for 4 weeks (randomised 1:1:1).

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary endpoint was change from baseline in mean patient-recorded numerical rating scale (NRS) score (over the last three recordings) at week 4. Secondary outcome measures were NRS score, verbal rating scale score, Skindex-16 and Leeds Sleep Evaluation Questionnaire at each study visit (baseline, weeks 1, 4, 8); rescue medication use; EGFRI dose reduction; and study withdrawal because of intense uncontrolled pruritus.

RESULTS

The trial was terminated early because of recruitment challenges; only 44 of the planned 90 patients were randomised. All patients were analysed for efficacy and safety. Mean NRS score change from baseline to week 4 was -2.78 (SD: 2.64) points in the 30 mg group, -3.04 (SD: 3.06) points in the 10 mg group and -3.21 (SD: 1.77) points in the placebo group; the difference between orvepitant and placebo was not statistically significant. No safety signal was detected. Adverse events related to orvepitant (asthenia, dizziness, dry mouth, hyperhidrosis) were all of mild or moderate severity.

CONCLUSIONS

Orvepitant was safe and well tolerated. No difference in NRS score between the orvepitant and placebo groups was observed at the week 4 primary endpoint. A number of explanations for this outcome are possible.

TRIAL REGISTRATION NUMBER

EudraCT2013-002763-25.

Endogenous opioid system dysregulation in depression: implications for new therapeutic approaches

The United States is in the midst of an opioid addiction and overdose crisis precipitated and exacerbated by use of prescription opioid medicines. The majority of opioid prescriptions are dispensed to patients with comorbid mood disorders including major depressive disorder (MDD). A growing body of research indicates that the endogenous opioid system is directly involved in the regulation of mood and is dysregulated in MDD. This involvement of the endogenous opioid system may underlie the disproportionate use of opioids among patients with mood disorders. Emerging approaches to address endogenous opioid dysregulation in MDD may yield novel therapeutics that have a low or absent risk of abuse and addiction relative to µ-opioid agonists. Moreover, agents targeting the endogenous opioid system would be expected to yield clinical benefits qualitatively different from conventional monaminergic antidepressants. The development of safe and effective agents to treat MDD-associated endogenous opioid dysregulation may represent a distinct and currently underappreciated means of addressing treatment resistant depression with the potential to attenuate the on-going opioid crisis.

Gene Expression of Neurotrophins and Their Receptors in Keloids

The aim of this study was to assess gene expression of neurotrophins and their receptors in keloids. Skin samples of normal skin and keloids were obtained from patients in the control (n = 12) and keloid (n = 12) groups, respectively. Ribonucleic acid was extracted from the skin specimens, purified, evaluated by spectrophotometry, and used to synthesize complementary DNA. Real-time quantitative polymerase chain reaction analysis of 84 human neurotrophin genes and their receptors was performed. Twelve genes, including heat shock 27-kDa protein 1, gastrin-releasing peptide receptor, corticotropin-releasing hormone receptor 2, neuropeptide Y Y2 receptor, interleukin 6 signal transducer, nerve growth factor, metallothionein 3, B-cell chronic lymphocytic leukemia/lymphoma 2, cholecystokinin A receptor, persephin, galanin receptor 2, and fibroblast growth factor receptor 3, were down-regulated in keloid tissue compared with normal skin. The genes 27-kDa heat shock protein 1, gastrin-releasing peptide receptor, corticotropin-releasing hormone receptor 2, nerve growth factor, metallothionein 3, B-cell chronic lymphocytic leukemia/lymphoma 2, and persephin protein were considered priority genes associated with keloid formation.

Synergic Anti-Pruritus Mechanisms of Action for the Radix Sophorae Flavescentis and Fructus Cnidii Herbal Pair

Radix Sophorae Flavescentis (RSF) and Fructus Cnidii (FC) compose a typical herbal synergic pair in traditional Chinese medicine (TCM) for pruritus symptom treatments. The mechanisms of action for the synergy are not understood. This paper aims at predicting the anti-pruritus targets and the main active ingredients for the RSF and FC herbal pair. We demonstrate that the RSF-FC herbal pair can be elucidated by mining the chemical structures of compounds derived from RSF and FC. Based on chemical structure data, the putative targets for RSF and FC were predicted. Additional putative targets that interact with the anti-pruritus targets were derived by mapping the putative targets onto a PPI network. By examining the annotations of these proteins, we conclude that (1) RSF's active compounds are mainly alkaloids and flavonoids. The representative putative targets of the alkaloids are inflammation-related proteins (MAPK14, PTGS2, PTGS2, and F2) and pruritus-related proteins (HRH1, TRPA1, HTR3A, and HTR6). The representative putative targets of the flavonoids are inflammation-related proteins (TNF, NF-κB, F2, PTGS2, and PTGS2) and pruritus-related proteins (NR3C1 and IL2). (2) FC's active compounds are mainly coumarins. Their representative putative targets are CNS-related proteins (AChE and OPRK1) and inflammation-related proteins (PDE4D, TLR9, and NF-κB). (3) Both RSF and FC display anti-inflammatory effects, though they exhibit their anti-pruritus effects in different ways. Their synergy shows that RSF regulates inflammation-related pruritus and FC regulates CNS-related pruritus.

Neurokinin-1 receptor antagonist orvepitant is an effective inhibitor of itch-associated response in a Mongolian gerbil model of scratching behaviour

Data suggest that substance P could play an important role in pruritus, and therefore, blockade of the neurokinin (NK)-1 receptor might be antipruritic. Thus, we explored in the Mongolian gerbil the effect on scratching behaviour, induced by intra-dermal injection of the NK-1 receptor-specific agonist GR73632, of oral administration of the NK-1 receptor antagonist orvepitant. Orvepitant at all doses tested (0.1-10 mg/kg p.o.) produced a profound inhibition of GR73632 (30 nmol i.d.) induced hindlimb scratching; the minimum effective dose of orvepitant in this model was identified as ≤0.1 mg/kg. The data generated supported the proposition that the antipruritic potential of orvepitant should be evaluated in clinical trials.

Salvinorin A analogues PR-37 and PR-38 attenuate compound 48/80-induced itch responses in mice

BACKGROUND AND PURPOSE

The opioid system plays a crucial role in several physiological processes in the CNS and in the periphery. It has also been shown that selective opioid receptor agonists exert potent inhibitory action on pruritus and pain. In this study we examined whether two analogues of Salvinorin A, PR-37 and PR-38, exhibit antipruritic properties in mice.

EXPERIMENTAL APPROACH

To examine the antiscratch effect of PR-37 and PR-38 we used a mouse model of compound 48/80-induced pruritus. In order to elucidate the mechanism of action of tested compounds, specific antagonists of opioid and cannabinoid receptors were used. The effect of PR-37 on the CNS was assessed by measuring motor parameters and exploratory behaviours in mice.

KEY RESULTS

PR-37 and PR-38, jnjected s.c., significantly reduced the number of compound 48/80-induced scratching behaviours in mice in a dose- and time-dependent manner. PR-38 was also active when orally administered. The antiscratch activity of PR-37 was blocked by the selective κ opioid receptor antagonist, nor-binaltorphimine, and that of PR-38 by the selective μ opioid receptor antagonist, β-funaltrexamine.

CONCLUSION AND IMPLICATIONS

In conclusion, a novel framework for the development of new antipruritic drugs derived from salvinorin A has been validated.

[Drug-induced pruritus]

BACKGROUND

Pruritus, especially chronic pruritus, has long been underestimated and leads to high psychological strain in the affected patients. Even today, in spite of receiving increased attention, the underlying etiology cannot always be identified.

METHODS

We review potential underlying pathologic mechanisms of drug-induced pruritus, focusing among others on current dermato-oncological medications in terms of their pruritogenic risks.

RESULTS

Acute pruritus must be distinguished from chronic pruritus which lasts for a minimum of 6 weeks. There are various therapeutic approaches for drug-induced pruritus. As a first step, the drug causing the pruritus has to be identified; then the intake of that drug has to be ceased or modified. This may not always be possible, as in the case of chemotherapy agents.

CONCLUSIONS

With regard to the demographic development of the population with increasing life expectancy and the resulting increasing polypharmacy, drugs will have to be taken into account as a possible cause for pruritus more often in the future. It would be desirable to routinely assess pruritus as a possible adverse effect in regulatory drug studies.

Aprepitant and fosaprepitant: a 10-year review of efficacy and safety

Chemotherapy-induced nausea and vomiting (CINV) is a common adverse event associated with anticancer treatment that can have a significant adverse impact on patient health-related quality of life and that can potentially undermine the effectiveness of chemotherapy. Traditional regimens to prevent CINV generally involved a combination of a corticosteroid plus a 5-hydroxytryptamine (5HT3) receptor antagonist (RA). In the past 10 years, antiemetic treatment has greatly advanced with the availability of the neurokinin-1 receptor antagonist (NK1 RA) aprepitant and its prodrug fosaprepitant. NK1 RAs have a different mechanism of action in CINV than corticosteroids and 5HT3 RAs, thus their use can complement traditional antiemetic drugs and can enhance control of CINV. This review examined accumulated data regarding the safety and efficacy of aprepitant and fosaprepitant over the decade since the first regulatory approval. Data from key studies of aprepitant and fosaprepitant in the prevention of CINV in patients receiving moderately and highly emetogenic chemotherapy were explored, as were recommendations in currently available guidelines for their use. In addition, their use as antiemetic therapy in special patient populations was highlighted. Future perspectives on potential uses of aprepitant and fosaprepitant for indications other than CINV are presented.

NK-1 Antagonists and Itch

Substance P (SP) is an important mediator of pro-inflammatory mechanisms in the skin. It targets multiple cells such as keratinocytes, mast cells, and fibroblasts which are involved in the cutaneous generation of pruritus. This suggests that SP is an interesting target for therapy. In fact, in recent case reports and case series, SP antagonists demonstrated a significant antipruritic effect in acute and chronic pruritus such as drug-induced pruritus, paraneoplastic pruritus, prurigo nodularis, cutaneous T-cell lymphoma, and brachioradial pruritus.