In vitro and in vivo pharmacological characterization of the novel NK₁ receptor selective antagonist Netupitant

Therapeutic antagonism of the neurokinin 1 receptor in endosomes provides sustained pain relief

The hypothesis that sustained G protein-coupled receptor (GPCR) signaling from endosomes mediates pain is based on studies with endocytosis inhibitors and lipid-conjugated or nanoparticle-encapsulated antagonists targeted to endosomes. GPCR antagonists that reverse sustained endosomal signaling and nociception are needed. However, the criteria for rational design of such compounds are ill-defined. Moreover, the role of natural GPCR variants, which exhibit aberrant signaling and endosomal trafficking, in maintaining pain is unknown. Herein, substance P (SP) was found to evoke clathrin-mediated assembly of endosomal signaling complexes comprising neurokinin 1 receptor (NK1R), Gαq/i, and βarrestin-2. Whereas the FDA-approved NK1R antagonist aprepitant induced a transient disruption of endosomal signals, analogs of netupitant designed to penetrate membranes and persist in acidic endosomes through altered lipophilicity and pKa caused sustained inhibition of endosomal signals. When injected intrathecally to target spinal NK1R+ve neurons in knockin mice expressing human NK1R, aprepitant transiently inhibited nociceptive responses to intraplantar injection of capsaicin. Conversely, netupitant analogs had more potent, efficacious, and sustained antinociceptive effects. Mice expressing C-terminally truncated human NK1R, corresponding to a natural variant with aberrant signaling and trafficking, displayed attenuated SP-evoked excitation of spinal neurons and blunted nociceptive responses to SP. Thus, sustained antagonism of the NK1R in endosomes correlates with long-lasting antinociception, and domains within the C-terminus of the NK1R are necessary for the full pronociceptive actions of SP. The results support the hypothesis that endosomal signaling of GPCRs mediates nociception and provides insight into strategies for antagonizing GPCRs in intracellular locations for the treatment of diverse diseases.

Real-world multicenter study of the safety and efficacy of netupitant plus palonosetron fixed-dose combination to prevent chemotherapy-induced nausea and vomiting among Malaysian patients receiving moderately or highly emetogenic chemotherapy

AIM

A large proportion of cancer patients are at high risk for chemotherapy-induced nausea and vomiting (CINV), but the choice of anti-emetics for CINV in Malaysia is limited.

METHODS

This was a real-world study of a fixed-dose combination of netupitant and palonosetron (NEPA) to inhibit CINV in adult patients receiving moderately (MEC) or highly emetogenic chemotherapy (HEC) for solid/hematological malignancies at eight Malaysian centers. Each HEC/MEC cycle received one dose of NEPA + dexamethasone for CINV prevention. Complete response (no emesis, no rescue medication) (CR), no more than mild nausea (severity score ≤ 2.5), and complete control (CR) (no more than mild nausea) during the acute (0-24 h), delayed (25-120 h), and overall (0-120 h) phases post-chemotherapy were measured. Treatment-related adverse events (AEs) were recorded.

RESULTS

During March 2016-April 2018 (NMRR-17-3286-38282), NEPA + dexamethasone was administered to 54 patients (77.8% solid, 22.2% hematological malignancies). Note that 59.3% received HEC, while 40.7% received MEC regimen. During the overall phase of the first cycle, the majority had CR (77.8%), no more than mild nausea (74.1%), and complete control (61.1%). Seventeen patients received two consecutive cycles at any point of chemotherapy cycles. During the overall phases across two consecutive cycles, all patients achieved CR, and the majority reported no more than mild nausea and complete control. No grades 3-4 AEs were reported.

CONCLUSIONS

NEPA had sustained efficacy and tolerability at first administration and across two cycles of MEC/HEC for CINV prevention.

Simulation of the oxidative metabolization pattern of netupitant, an NK1 receptor antagonist, by electrochemistry coupled to mass spectrometry

Considering the frequent use of netupitant in polytherapy, the elucidation of its oxidative metabolization pattern is of major importance. However, there is a lack of published research on the redox behavior of this novel neurokinin-1 receptor antagonist. Therefore, this study was performed to simulate the intensive hepatic biotransformation of netupitant using an electrochemically driven method. Most of the known enzyme-mediated reactions occurring in the liver (i.e., N-dealkylation, hydroxylation, and N-oxidation) were successfully mimicked by the electrolytic cell using a boron-doped diamond working electrode. The products were separated by reversed-phase high-performance liquid chromatography and identified by high-resolution mass spectrometry. Aside from its ability to pinpoint formerly unknown metabolites that could be responsible for the known side effects of netupitant or connected with any new perspective concerning future therapeutic indications, this electrochemical process also represents a facile alternative for the synthesis of oxidation products for further in vitro and in vivo studies.

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Study of the electrochemical behavior of netupitant, an NK₁ receptor antagonist.

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Electrochemical simulation of the phase I oxidative metabolization of netupitant.

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Identification of the generated oxidation species by LC/ESI(+)-MS.

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Separation and identification of electrochemically generated isomers.

Carbohydrate-Based NK1R Antagonists with Broad-Spectrum Anticancer Activity

NK1R antagonists, investigated for the treatment of several pathologies, have shown encouraging results in the treatment of several cancers. In the present study, we report on the synthesis of carbohydrate-based NK1R antagonists and their evaluation as anticancer agents against a wide range of cancer cells. All of the prepared compounds, derived from either d-galactose or l-arabinose, have shown high affinity and NK1R antagonistic activity with a broad-spectrum anticancer activity and an important selectivity, comparable to Cisplatin. This strategy has allowed us to identify the galactosyl derivative 14α, as an interesting hit exhibiting significant NK1R antagonist effect (kinact 0.209 ± 0.103 μM) and high binding affinity for NK1R (IC50 = 50.4 nM, Ki = 22.4 nM by measuring the displacement of [125I] SP from NK1R). Interestingly, this galactosyl derivative has shown marked selective cytotoxic activity against 12 different types of cancer cell lines.

The 2-Pyridyl Problem: Challenging Nucleophiles in Cross-Coupling Arylations

Azine-containing biaryls are ubiquitous scaffolds in many areas of chemistry, and efficient methods for their synthesis are continually desired. Pyridine rings are prominent amongst these motifs. Transition-metal-catalysed cross-coupling reactions have been widely used for their synthesis and functionalisation as they often provide a swift and tuneable route to related biaryl scaffolds. However, 2-pyridine organometallics are capricious coupling partners and 2-pyridyl boron reagents in particular are notorious for their instability and poor reactivity in Suzuki-Miyaura cross-coupling reactions. The synthesis of pyridine-containing biaryls is therefore limited, and methods for the formation of unsymmetrical 2,2'-bis-pyridines are scarce. This Review focuses on the methods developed for the challenging coupling of 2-pyridine nucleophiles with (hetero)aryl electrophiles, and ranges from traditional cross-coupling processes to alternative nucleophilic reagents and novel main group approaches.

Identification of optimal contemporary antiemetic prophylaxis for doxorubicin-cyclophosphamide chemotherapy in Chinese cancer patients: post-hoc analysis of 3 prospective studies

OBJECTIVE

Chemotherapy-induced nausea and vomiting (CINV) are common with doxorubicin-cyclophosphamide (AC) chemotherapy. Recommended antiemetic regimens incorporate neurokinin-1 receptor antagonist (NK1RA), 5-hydroxytryptamine type-3 receptor antagonist (5HT3RA), corticosteroid, and dopamine antagonists. This post-hoc analysis compared results of 3 prospective antiemetic studies conducted among Chinese breast cancer patients who received (neo)adjuvant AC, in order to identify optimal antiemetic prophylaxis.

METHODS

A total of 304 patients were included: Group 1, ondansetron/dexamethasone (D1); Group 2, aprepitant/ondansetron/dexamethasone (D1); Group 3, aprepitant/ondansetron/dexamethasone (D1-3); Group 4, aprepitant/ondansetron/dexamethasone (D1-3)/olanzapine; and Group 5, netupitant/palonosetron/dexamethasone (D1-3). Antiemetic efficacies of Groups 3, 4, and 5 during cycle 1 of AC were individually compared with Group 1. In addition, emesis outcomes of patients in Groups 3 and 5, and those of Groups 2 and 3, were compared.

RESULTS

When comparing efficacies of a historical doublet (5HT3RA/dexamethasone) with triplet antiemetic regimens (NK1RA/5HT3RA/dexamethasone) with/without olanzapine, complete response (CR) percentages and quality of life (QOL) in overall phase of cycle 1 AC were compared between Group 1 and the other groups: Group 1 vs. 3, 41.9% vs. 38.3% (P = 0.6849); Group 1 vs. 4, 41.9% vs. 65.0% (P = 0.0107); and Group 1 vs. 5, 41.9% vs. 60.0% (P = 0.0460). Groups 4 and 5 achieved a better QOL. When comparing netupitant-based (Group 3) with aprepitant-based (Group 5) triplet antiemetics, CR percentages were 38.3% vs. 60.0%, respectively (P = 0.0176); Group 5 achieved a better QOL. When comparing 1 day (Group 2) vs. 3 day (Group 3) dexamethasone, CR percentages were 46.8% and 38.3%, respectively (P = 0.3459); Group 3 had a worse QOL.

CONCLUSIONS

Aprepitant-containing triplets were non-superior to doublet antiemetics. Netupitant-containing triplets and adding olanzapine to aprepitant-containing triplets were superior to doublets. Netupitant/palonosetron/dexamethasone was superior to aprepitant/ondansetron/dexamethasone. Protracted administration of dexamethasone provided limited additional benefit.

Asymmetric Synthesis of Merck's Potent hNK1 Antagonist and Its Stereoisomers via Tandem Acylation/[3,3]-Rearrangement of 1,2-Oxazine N-Oxides

An asymmetric total synthesis of Merck's hNK₁ antagonist and three of its stereoisomers was accomplished in 10 steps. The synthesis involves a stereoselective assembly of 1,2-oxazine N-oxide by the [4 + 2]-cycloaddition, site-selective C-H oxygenation using a novel tandem acylation/[3,3]-rearrangement process and the reductive 1,2-oxazine ring contraction into a pyrrolidine ring as key stages. Using this strategy, the fused pyrrolidine subunit was constructed with exceptionally high regio- and stereoselectivities. The approach described here can be used to access enantiopure 3,4-disubstituted prolinols, which are frequently found in pharmaceutically relevant molecules and organocatalysts.

Efficacy and safety of multiple doses of NEPA without dexamethasone in preventing nausea and vomiting induced by multiple-day and high-dose chemotherapy in patients with non-Hodgkin's lymphoma undergoing autologous hematopoietic stem cell transplantation: a phase IIa, multicenter study

Despite the availability of several antiemetics, clinical findings show that control of chemotherapy-induced nausea and vomiting (CINV) continues to be a serious concern for hematological patients, mainly for those receiving multiple-day (MD) and high-dose (HD) chemotherapy (CT). For CINV prophylaxis, 5-hydroxytryptamine type-3 receptor antagonists (5HT₃-RAs) and neurokinin 1 receptor antagonists (NK₁-RAs) are usually administered together with dexamethasone, which may increase the risk of serious infections in patients undergoing myeloablative treatment. The rationale of this multicenter, open-label and phase IIa study was to explore the efficacy of multiple doses of NEPA (netupitant/palonosetron) given as an every-other-day regimen without dexamethasone in preventing CINV in patients with relapsed-refractory aggressive non-Hodgkin’s lymphoma (R/R-NHL), eligible for autologous stem cell transplantation (ASCT) and treated with MD-HD-CT. Seventy patients participated to the study. According to the adopted Fleming one-stage design, the primary endpoint of this study was achieved. The CR values were 87.1% (primary endpoint, overall phase: days 1–8), 88.6% (acute phase: days 1–6), and 98.6% (delayed phase: days 7–8), while complete control (CR with no more than mild nausea) was 85.7% (overall phase), 88.6% (acute phase), and 95.7% (delayed phase). Moderate and severe episodes of nausea were reported by less than 10% of patients in the overall phase and less than 5% in both the acute and delayed phases. Regarding safety, NEPA was well tolerated with only one adverse event (constipation) evaluated as possibly related to NEPA administration. In conclusion, our study demonstrated that multiple alternate dosing of NEPA without the addition of dexamethasone is highly effective for preventing nausea and vomiting in this difficult setting, with a good tolerability profile.

Δ9-THC and related cannabinoids suppress substance P- induced neurokinin NK1-receptor-mediated vomiting via activation of cannabinoid CB1 receptor

Δ⁹-THC suppresses cisplatin-induced vomiting through activation of cannabinoid CB₁ receptors. Cisplatin-evoked emesis is predominantly due to release of serotonin and substance P (SP) in the gut and the brainstem which subsequently stimulate their corresponding 5-HT₃-and neurokinin NK₁-receptors to induce vomiting. Δ⁹-THC can inhibit vomiting caused either by the serotonin precursor 5-HTP, or the 5-HT₃ receptor selective agonist, 2-methyserotonin. In the current study, we explored whether Δ⁹-THC and related CB₁/CB₂ receptor agonists (WIN55,212-2 and CP55,940) inhibit vomiting evoked by SP (50 mg/kg, i.p.) or the NK₁ receptor selective agonist GR73632 (5 mg/kg, i.p.). Behavioral methods were employed to determine the antiemetic efficacy of cannabinoids in least shrews. Our results showed that administration of varying doses of Δ⁹-THC (i.p. or s.c.), WIN55,212-2 (i.p.), or CP55,940 (i.p.) caused significant suppression of SP-evoked vomiting in a dose-dependent manner. When tested against GR73632, Δ⁹-THC also dose-dependently reduced the evoked emesis. The antiemetic effect of Δ⁹-THC against SP-induced vomiting was prevented by low non-emetic doses of the CB₁ receptor inverse-agonist/antagonist SR141716A (<10 mg/kg). We also found that the NK₁ receptor antagonist netupitant can significantly suppress vomiting caused by a large emetic dose of SR141716A (20 mg/kg). In sum, Δ⁹-THC and related cannabinoids suppress vomiting evoked by the nonselective (SP) and selective (GR73632) neurokinin NK₁ receptor agonists via stimulation of cannabinoid CB₁ receptors.

The safety of rolapitant for the treatment of nausea and vomiting associated with chemotherapy

Introduction: Chemotherapy-induced nausea and vomiting is a significant clinical issue that affects patients' quality of life as well as treatment decisions. Significant improvements in the control of chemotherapy-induced nausea and vomiting have occurred in the past 15 years with the introduction of new antiemetic agents 5-HT3, receptor antagonists, neurokinin-1 receptor antagonists, and olanzapine. Oral (aprepitant, 2003; netupitant, 2014; rolapitant, 2015) neurokinin-1 receptor antagonists have been developed along with intravenous formulations (fosaprepitant, NEPA, rolapitant, HTX-019) for the prevention of chemotherapy-induced nausea and vomiting.Areas covered: This review presents a description of the safety and efficacy of rolapitant along with a comparison to the other oral and intravenous formulations of the neurokinin-1 receptor antagonists.Expert opinion: Oral rolapitant has been demonstrated in clinical trials to be safe and effective in controlling chemotherapy-induced nausea and vomiting in patients receiving moderately and highly emetogenic chemotherapy. Rolapitant has a longer half-life (180 h) than other commercially available NK-1 receptor antagonists and does not induce or inhibit CYP34A, unlike the other NK-1 receptor antagonists. Future studies may determine if these may be important clinical issues.

Neurokinin-1 receptor antagonists: review of their role for the prevention of chemotherapy-induced nausea and vomiting in adults

Introduction: The addition of neurokinin-1 receptor antagonists (NK₁RAs) to standard prophylaxis of 5-hydroxytryptamine-3 RA (5-HT₃RA) plus dexamethasone more effectively prevents chemotherapy-induced nausea and vomiting (CINV) associated with highly and moderately emetogenic chemotherapy. Areas covered: This review presents the evidence base for the use of oral and intravenous (IV) NK₁RAs, focusing on the pharmacologic and clinical properties as a class, and highlighting differences between agents. A PubMed literature search was conducted from 2000 to 2018. Expert opinion: Adherence to international antiemetic guidelines remains a clinical challenge. Strategies to simplify antiemetic regimens and facilitate their administration may improve compliance and treatment outcomes. The use of fixed-combination antiemetics offers clinical utility, in combining an NK₁RA with a 5-HT₃RA in a single oral dose. The use of long-lasting NK₁RAs and administering CINV prophylaxis closer to the time of chemotherapy may also assist with guideline and treatment compliance, diminishing the need for home-based administration, and potentially reducing resource utilization. The availability of IV and oral formulations of NK₁RAs and NK₁RA-5-HT₃RA fixed combinations offers further utility, particularly for those patients unsuited for oral administration. However, safety considerations with respect to injection site toxicity and hypersensitivity reactions of the new NK₁RA IV formulations deserve close attention.

Fixed Combination Antiemetic: A Literature Review on Prevention of Chemotherapy-Induced Nausea and Vomiting Using Netupitant/Palonosetron

BACKGROUND

Prevention of chemotherapy-induced nausea and vomiting (CINV) can be improved with guideline-consistent use of antiemetics. However, adherence to antiemetic guidelines remains often insufficient. Therefore, new strategies that improve adherence are needed.

OBJECTIVES

To review the latest antiemetic guideline recommendations and provide an update on the use of NEPA, a fixed combination antiemetic composed of the neurokinin-1 receptor antagonist (RA) netupitant and the 5-hydroxytryptamine-3 RA palonosetron (Akynzeo®).

METHODS

Analysis of the literature was performed, including guidelines, published literature, congress data on NEPA, and relevant articles on CINV.

FINDINGS

Nurses are in a unique position to promote guideline-consistent antiemetic prophylaxis and are central in the education of patients and caregivers. Thus, nurses’ continuous education on antiemetic treatments is key for the prevention and management of CINV. NEPA offers a simplified antiemetic therapy with the potential to increase guideline adherence.

A dose-finding randomized Phase II study of oral netupitant in combination with palonosetron .75 mg intravenous for the prevention of chemotherapy-induced nausea and vomiting in Japanese patients receiving highly emetogenic chemotherapy

Objective

Netupitant is a novel, selective neurokinin-1 receptor antagonist used for prevention of chemotherapy-induced nausea and vomiting, a distressing side effect of chemotherapy. This double-blind, randomized, Phase II study investigated the dose-response of oral netupitant in Japanese patients receiving highly emetogenic chemotherapy.

Methods

Chemotherapy-naïve patients were randomized (1:1:1) to a single oral netupitant 30-, 100- or 300-mg dose before chemotherapy initiation. Patients received concomitant palonosetron (0.75 mg intravenously [i.v.] Day 1) and dexamethasone (9.9 mg i.v. Day 1, 8 mg orally Days 2-4).

Results

Overall, 402 patients (30 mg: 134; 100 mg: 135; 300 mg: 133) were treated and evaluable for efficacy and safety. The primary endpoint of overall (0-120 h after chemotherapy administration) complete response (CR) rate (no emesis, no rescue medication) was 64.2%, 60.0% and 54.9% in the 30-, 100- and 300-mg arms, respectively, without statistical significance for dose-response. The safety profile of netupitant was comparable in the three arms. The plasma concentrations of netupitant and its metabolites increased with the dose increase from 30 mg to 300 mg.

Conclusions

No dose-response relationship of netupitant in terms of overall CR rate was observed in this study. Netupitant was well tolerated at all doses without clinically harmful safety signals observed.

Clinical trial registration

JapicCTI-142 483.

Crystal structures of the human neurokinin 1 receptor in complex with clinically used antagonists

Neurokinins (or tachykinins) are peptides that modulate a wide variety of human physiology through the neurokinin G protein-coupled receptor family, implicated in a diverse array of pathological processes. Here we report high-resolution crystal structures of the human NK₁ receptor (NK₁R) bound to two small-molecule antagonist therapeutics – aprepitant and netupitant and the progenitor antagonist CP-99,994. The structures reveal the detailed interactions between clinically approved antagonists and NK₁R, which induce a distinct receptor conformation resulting in an interhelical hydrogen-bond network that cross-links the extracellular ends of helices V and VI. Furthermore, the high-resolution details of NK₁R bound to netupitant establish a structural rationale for the lack of basal activity in NK₁R. Taken together, these co-structures provide a comprehensive structural basis of NK₁R antagonism and will facilitate the design of new therapeutics targeting the neurokinin receptor family.

Neurokinin receptors are G protein-coupled receptors. Here the authors present three crystal structures of the neurokinin 1 receptor (NK₁R) in complex with small-molecule antagonists including aprepitant and netupitant and observe that these clinically approved compounds induce a conformational change in the receptor.

Effectiveness of Antiemetic Regimens for Highly Emetogenic Chemotherapy-Induced Nausea and Vomiting: A Systematic Review and Network Meta-Analysis

BACKGROUND

It is important to control chemotherapy-induced nausea and vomiting (CINV) to maintain dose intensity and patients' quality of life. The National Comprehensive Cancer Network guidelines suggest combination therapy of antiemetic agents. The growing number of antiemetic regimens, and in particular the growing use of regimens containing antagonists to the Nk-1 receptor (NK1RAs) and the antipsychotic drug olanzapine (OLZ), call for the re-evaluation of the optimal regimen for CINV. This study assessed the efficacy and safety of antiemetic regimens for highly emetogenic chemotherapy, using Bayesian network meta-analysis.

METHODS

Randomized trials that compared different antiemetic regimens were included. We strictly followed Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The main outcomes were the odds ratio (OR) for overall complete response (absence of vomiting). We conducted network meta-analysis within a Bayesian model to combine the direct and indirect evidence. Safety was assessed from the trial description. All statistical tests were two-sided.

RESULTS

We systematically reviewed 27 randomized control trials (13,356 participants), which compared 12 different antiemetic regimens: serotonin-3 receptor antagonist (5HT3), 5HT3 + dexamethasone (Dex), palonosetron (PAL), PAL + Dex, PAL at 0.75 mg (PAL0.75), PAL0.75 + Dex, NK1RA + 5HT3 + Dex, NK1RA + PAL + Dex, an oral combination of netupitant and palonosetron (NEPA) + Dex, OLZ + 5HT3 + Dex, OLZ + PAL + Dex, and OLZ + NK1RA + 5HT3 + Dex. An NK1RA + 5HT3 + Dex regimen and an NK1RA + palonosetron + Dex regimen gave a higher complete response (CR) rate than the reference regimen, 5HT3 + Dex (OR, 1.75; 95% credibility interval [95% CrI], 1.56-1.97, and OR, 2.25; 95% CrI, 1.66-3.03, respectively). A regimen containing NEPA was more effective in producing CR than conventional regimens without NEPA or olanzapine. Further analysis, based on the surface under the cumulative ranking probability curve, indicated that olanzapine-containing regimens were the most effective in producing CR.

CONCLUSION

Our meta-analysis supports the conclusion that olanzapine-containing regimens are the most effective for CINV of highly emetogenic chemotherapy. We confirmed that NK1RA + PAL + Dex is the most effective of conventional regimens. Substituting olanzapine for an Nk-1 receptor antagonist may offer a less costly and more effective alternative for patients.

IMPLICATIONS FOR PRACTICE

Nausea and vomiting during chemotherapy often pose difficulties for patients and doctors, making it hard to continue the proper therapy and to maintain the quality of life. This article gives insights into the optimal choice of medicine to treat nausea during chemotherapy. The findings reported here provide readers with a robust efficacy ranking of antinausea medicine, which can be used as a reference for the best possible treatment. Furthermore, the 70% less costly drug, olanzapine, is suggested to be equally effective to aprepitant in reducing nausea and vomiting. The possibility of offering a cost-effective treatment to a wider range of the population is discussed.

The Neurokinins: Peptidomimetic Ligand Design and Therapeutic Applications

The neurokinins are indisputably essential neurotransmitters in numerous pathoand physiological events. Being widely distributed in the Central Nervous System (CNS) and peripheral tissues, their discovery rapidly promoted them to drugs targets. As a necessity for molecular tools to understand the biological role of this class, endogenous peptides and their receptors prompted the scientific community to design ligands displaying either agonist and antagonist activity at the three main neurokinin receptors, called NK1, NK2 and NK3. Several strategies were implemented for this purpose. With a preference to small non-peptidic ligands, many research groups invested efforts in synthesizing and evaluating a wide range of scaffolds, but only the NK1 antagonist Aprepitant (EMENDT) and its prodrug Fosaprepitant (IVEMENDT) have been approved by the Food Drug Administration (FDA) for the treatment of Chemotherapy-Induced and Post-Operative Nausea and Vomiting (CINV and PONV, respectively). While non-peptidic drugs showed limitations, especially in side effect control, peptidic and pseudopeptidic compounds progressively regained attention. Various strategies were implemented to modulate affinity, selectivity and activity of the newly designed ligands. Replacement of canonical amino acids, incorporation of conformational constraints, and fusion with non-peptidic moieties gave rise to families of ligands displaying individual or dual NK1, NK2 and NK3 antagonism, that ultimately were combined with non-neurokinin ligands (such as opioids) to target enhanced biological impact.

Anti-emetic Action of the Brain-Penetrating New Ghrelin Agonist, HM01, Alone and in Combination With the 5-HT3 Antagonist, Palonosetron and With the NK1 Antagonist, Netupitant, Against Cisplatin- and Motion-Induced Emesis in Suncus murinus (House Musk Shrew)

Ghrelin has well-known activity to stimulate appetite and weight gain. Evidence suggests that ghrelin may also have effects in reducing chemotherapy-induced emesis via growth hormone secretagogue receptors (GHS-R1A) in the brain. However, it is not known whether the stimulation of GHS-R1A has broad inhibitory anti-emetic effects. In the present studies, we used Suncus murinus to investigate the potential of the new and novel orally bioavailable brain-penetrating GHS-R1A mimetic, HM01 (1-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-3-methyl-3-[(4R)-1-Methyl-3,3-dimethyl-4-piperidyl]urea), to reduce emesis induced by a variety of emetic challenges. HM01 (1 to 30 mg/kg, p.o.) antagonized emesis induced by cisplatin (30 mg/kg, i.p.) and by motion (4 cm horizontal displacement, 1 Hz) but was ineffective against emesis induced by nicotine (5 mg/kg, s.c.) and copper sulfate (120 mg/kg by intragastric gavage). In other experiments, HM01 (3 mg/kg, p.o.) enhanced the anti-emetic control of a regimen of palonosetron (0.01 mg/kg, p.o.) alone and palonosetron (0.01 mg/kg p.o.) plus netupitant (1 mg/kg, p.o.). HM01 (10 mg/kg, p.o.) also had positive effects in increasing feeding and drinking in nicotine-treated animals, and it shortened the latency to drink in animals treated with cisplatin. These data indicate that brain-penetrating GHS-R1A agonists may have use alone and/or in combination with standard anti-emetic regimens for the treatment of chemotherapy-induced nausea and vomiting and motion sickness.

Peptide welding technology - A simple strategy for generating innovative ligands for G protein coupled receptors

Based on their high selectivity of action and low toxicity, naturally occurring peptides have great potential in terms of drug development. However, the pharmacokinetic properties of peptides, in particular their half life, are poor. Among different strategies developed for reducing susceptibility to peptidases, and thus increasing the duration of action of peptides, the generation of branched peptides has been described. However, the synthesis and purification of branched peptides are extremely complicated thus limiting their druggability. Here we present a novel and facile synthesis of tetrabranched peptides acting as GPCR ligands and their in vitro and vivo pharmacological characterization. Tetrabranched derivatives of nociceptin/orphanin FQ (N/OFQ), N/OFQ related peptides, opioid peptides, tachykinins, and neuropeptide S were generated with the strategy named peptide welding technology (PWT) and characterized by high yield and purity of the desired final product. In general, PWT derivatives displayed a pharmacological profile similar to that of the natural sequence in terms of affinity, pharmacological activity, potency, and selectivity of action in vitro. More importantly, in vivo studies demonstrated that PWT peptides are characterized by increased potency associated with long lasting duration of action. In conclusion, PWT derivatives of biologically active peptides can be viewed as innovative pharmacological tools for investigating those conditions and states in which selective and prolonged receptor stimulation promotes beneficial effects.

From receptor binding kinetics to signal transduction; a missing link in predicting in vivo drug-action

An important question in drug discovery is how to overcome the significant challenge of high drug attrition rates due to lack of efficacy and safety. A missing link in the understanding of determinants for drug efficacy is the relation between drug-target binding kinetics and signal transduction, particularly in the physiological context of (multiple) endogenous ligands. We hypothesized that the kinetic binding parameters of both drug and endogenous ligand play a crucial role in determining cellular responses, using the NK1 receptor as a model system. We demonstrated that the binding kinetics of both antagonists (DFA and aprepitant) and endogenous agonists (NKA and SP) have significantly different effects on signal transduction profiles, i.e. potency values, in vitro efficacy values and onset rate of signal transduction. The antagonistic effects were most efficacious with slowly dissociating aprepitant and slowly associating NKA while the combination of rapidly dissociating DFA and rapidly associating SP had less significant effects on the signal transduction profiles. These results were consistent throughout different kinetic assays and cellular backgrounds. We conclude that knowledge of the relationship between in vitro drug-target binding kinetics and cellular responses is important to ultimately improve the understanding of drug efficacy in vivo.

Recent developments in the clinical pharmacology of rolapitant: subanalyses in specific populations

Knowledge of the involvement of the neurokinin substance P in emesis has led to the development of the neurokinin-1 receptor antagonists (NK-1 RAs) for control of chemotherapy-induced nausea and vomiting (CINV), in combination with serotonin type 3 receptor antagonists and corticosteroids. The NK-1 RA rolapitant, recently approved in oral formulation, has nanomolar affinity for the NK-1 receptor, as do the other commercially available NK-1 RAs, aprepitant and netupitant. Rolapitant is rapidly absorbed and has a long half-life in comparison to aprepitant and netupitant. All three NK-1 RAs undergo metabolism by cytochrome P450 (CYP) 3A4, necessitating caution with the concomitant use of CYP3A4 inhibitors, but in contrast to aprepitant and netupitant, rolapitant does not inhibit or induce CYP3A4. However, rolapitant is a moderate inhibitor of CYP2D6, and concomitant use with CYP2D6 substrates with narrow therapeutic indices should be avoided. Aprepitant, netupitant, and rolapitant have all demonstrated efficacy in the control of delayed CINV in patients receiving moderately and highly emetogenic chemotherapy in randomized controlled trials, including over multiple cycles of chemotherapy. We reviewed recent post hoc analyses of clinical trial data demonstrating that rolapitant is efficacious in the control of CINV in patient populations with specific tumor types, namely, breast cancers, gastrointestinal/colorectal cancers, and lung cancers. In addition, we show that rolapitant has efficacy in the control of CINV in specific age groups of patients receiving chemotherapy (<65 and ≥65 years of age). Overall, the safety profile of rolapitant in these specific patient populations was consistent with that observed in primary analyses of phase 3 trials.

Profile of Antiemetic Activity of Netupitant Alone or in Combination with Palonosetron and Dexamethasone in Ferrets and Suncus murinus (House Musk Shrew)

Background and Aims: Chemotherapy-induced acute and delayed emesis involves the activation of multiple pathways, with 5-hydroxytryptamine (5-HT; serotonin) playing a major role in the initial response. Substance P tachykinin NK₁ receptor antagonists can reduce emesis induced by disparate emetic challenges and therefore have a clinical utility as broad inhibitory anti-emetic drugs. In the present studies, we investigate the broad inhibitory anti-emetic profile of a relatively new NK₁ receptor antagonist, netupitant, alone or in combination with the long acting 5-HT₃ receptor antagonist, palonosetron, for a potential to reduce emesis in ferrets and shrews.

Materials and Methods: Ferrets were pretreated with netupitant and/or palonosetron, and then administered apomorphine (0.125 mg/kg, s.c.), morphine (0.5 mg/kg, s.c.), ipecacuanha (1.2 mg/kg, p.o.), copper sulfate (100 mg/kg, intragastric), or cisplatin (5–10 mg/kg, i.p.); in other studies netupitant was administered to Suncus murinus before motion (4 cm horizontal displacement, 2 Hz for 10 min).

Results: Netupitant (3 mg/kg, p.o.) abolished apomorphine-, morphine-, ipecacuanha- and copper sulfate-induced emesis. Lower doses of netupitant (0.03–0.3 mg/kg, p.o.) dose-dependently reduced cisplatin (10 mg/kg, i.p.)-induced emesis in an acute (8 h) model, and motion-induced emesis in S. murinus. In a ferret cisplatin (5 mg/kg, i.p.)-induced acute and delayed emesis model, netupitant administered once at 3 mg/kg, p.o., abolished the first 24 h response and reduced the 24–72 h response by 94.6%; the reduction was markedly superior to the effect of a three times per day administration of ondansetron (1 mg/kg, i.p.). A single administration of netupitant (1 mg/kg, p.o.) plus palonosetron (0.1 mg/kg, p.o.) combined with dexamethasone (1 mg/kg, i.p., once per day), also significantly antagonized cisplatin-induced acute and delayed emesis and was comparable with a once-daily regimen of ondansetron (1 mg/kg, p.o.) plus aprepitant (1 mg/kg, p.o.) in combination with dexamethasone (1 mg/kg, i.p.).

Conclusion: In conclusion, netupitant has potent and long lasting anti-emetic activity against a number of emetic challenges indicating broad inhibitory properties. The convenience of protection afforded by the single dosing of netupitant together with palonosetron was demonstrated and also is known to provide an advantage over other therapeutic strategies to control emesis in man.

Netupitant, a Potent and Highly Selective NK1 Receptor Antagonist, Alleviates Acetic Acid-Induced Bladder Overactivity in Anesthetized Guinea-Pigs

Introduction. Tachykinins potently contract the isolated urinary bladder from a number of animal species and play an important role in the regulation of the micturition reflex. On the guinea-pig isolated urinary bladder we examined the effects of a new potent and selective NK1 receptor antagonist (netupitant) on the contractions induced by a selective NK1 receptor agonist, SP-methylester (SP-OMe). Moreover, the effects of netupitant and another selective NK1 antagonist (L-733,060) were studied in anesthetized guinea-pigs using two experimental models, the isovolumetric bladder contractions and a model of bladder overactivity induced by intravesical administration of acetic acid (AA). Methods and Results. Detrusor muscle strips were mounted in 5 mL organ baths and isometric contractions to cumulative concentrations of SP-OME were recorded before and after incubation with increasing concentrations of netupitant. In anesthetized female guinea-pigs, reflex bladder activity was examined under isovolumetric conditions with the bladder distended with saline or during cystometry using intravesical infusion of AA. After a 30 min stabilization period, netupitant (0.1-3 mg/kg, i.v.) or L-733,060 (3-10 mg/kg, i.v.) were administered. In the detrusor muscle, netupitant produced a concentration-dependent inhibition (mean pKB = 9.24) of the responses to SP-OMe. Under isovolumetric conditions, netupitant or L-733,060 reduced bladder contraction frequency in a dose-dependent manner, but neither drug changed bladder contraction amplitude. In the AA model, netupitant dose-dependently increased intercontraction interval (ICI) but had no effect on the amplitude of micturition (AM). L-733,060 dose-dependently increased ICI also but this effect was paralleled by a significant reduction of AM. Conclusion. Netupitant decreases the frequency of reflex bladder contractions without altering their amplitude, suggesting that this drug targets the afferent limb of the micturition reflex circuit and therefore may be useful clinically in treating bladder overactivity symptoms.

Kinetic binding and activation profiles of endogenous tachykinins targeting the NK1 receptor

Ligand-receptor binding kinetics (i.e. association and dissociation rates) are emerging as important parameters for drug efficacy in vivo. Awareness of the kinetic behavior of endogenous ligands is pivotal, as drugs often have to compete with those. The binding kinetics of neurokinin 1 (NK1) receptor antagonists have been widely investigated while binding kinetics of endogenous tachykinins have hardly been reported, if at all. Therefore, the aim of this research was to investigate the binding kinetics of endogenous tachykinins and derivatives thereof and their role in the activation of the NK1 receptor. We determined the binding kinetics of seven tachykinins targeting the NK1 receptor. Dissociation rate constants (k_off) ranged from 0.026±0.0029min^-1 (Sar⁹,Met(O₂)¹¹-SP) to 0.21±0.015min^-1 (septide). Association rate constants (k_on) were more diverse: substance P (SP) associated the fastest with a k_on value of 0.24±0.046nM^-1min^-1 while neurokinin A (NKA) had the slowest association rate constant of 0.001±0.0002nM^-1min^-1. Kinetic binding parameters were highly correlated with potency and maximal response values determined in label-free impedance-based experiments on U-251 MG cells. Our research demonstrates large variations in binding kinetics of tachykinins which correlate to receptor activation. These findings provide new insights into the ligand-receptor interactions of tachykinins and underline the importance of measuring binding kinetics of both drug candidates and competing endogenous ligands.

Management of acute and delayed chemotherapy-induced nausea and vomiting: role of netupitant-palonosetron combination

Purpose

The purpose of this review is to summarize and discuss the recently published data (both original studies and reviews) on the oral medication NEPA, consisting of netupitant (a neurokinin-1 receptor antagonist [NK1RA], 300 mg dose) and palonosetron (5-hydroxytryptamine [serotonin or 5HT] type 3 receptor antagonist [5HT₃RA], 0.5 mg dose), in the prevention of the acute and delayed nausea and vomiting in patients receiving highly or moderately emetogenic chemotherapy.

Methods

This review was based on the very limited number of available published trials consisting of two Phase III studies and one Phase II dose-selecting trial.

Results

These studies demonstrated some therapeutic benefits of NEPA over related chemotherapy-induced nausea and vomiting (CINV) prophylaxis management, as well as its beneficial safety profile. In particular, compared with single-dose 0.5 mg palonosetron, the complete response rates for all phases of CINV for the first cycle of highly emetogenic chemotherapy (with cisplatin), as well as anthracycline–cyclophosphamide-based moderately emetogenic chemotherapy, were significantly higher for single-dose NEPA. The high efficacy of NEPA in terms of prevention of CINV continued throughout repeated cycles of highly and moderately emetogenic therapies.

Conclusion

It is currently recommended that patients who are administered highly emetogenic chemotherapy regimens should obtain a three-drug combination consisting of NK1RA, 5HT₃RA, and dexamethasone. The recently available oral combination of NEPA plus dexamethasone provides an additional pharmacological management option that could be considered in this scenario.

Rolapitant for the treatment of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting is a significant clinical issue which affects patient's quality of life and treatment decisions. Significant improvements in the control of chemotherapy-induced nausea and vomiting have occurred in the past 15 years with the introduction of new antiemetic agents 5-HT3, receptor antagonists, neurokinin-1 (NK-1) receptor antagonists, and olanzapine. Aprepitant was the first NK-1 receptor antagonist introduced (2003) for the prevention of chemotherapy-induced nausea and vomiting in combination with a 5-HT3 receptor antagonist and dexamethasone. A second NK-1 receptor antagonist netupitant was approved for use in October 2014. Phase III clinical trials of an additional NK-1 receptor antagonist rolapitant have been completed, and the data have been submitted for regulatory approval. A description of rolapitant and its role in chemotherapy-induced nausea and vomiting will be presented, along with a comparison of the other neurolinin-1 receptor antagonists aprepitant and netupitant.

In vitro and in vivo pharmacological characterization of Pronetupitant, a prodrug of the neurokinin 1 receptor antagonist Netupitant

The aim of the present study was to investigate the pharmacological activity of Pronetupitant, a novel compound designed to act as prodrug of the NK1 antagonist Netupitant. In receptor binding experiments Pronetupitant displayed high selectivity for the NK1 receptor. In a calcium mobilization assay performed on CHONK1 cells Pronetupitant (100 nM, 15 min preincubation) behaved as an NK1 antagonist more potent than Netupitant (pK(B) 8.72 and 7.54, respectively). In the guinea pig ileum bioassay Pronetupitant antagonized the contractile effect of SP showing a similar potency as Netupitant (pK(B)≈9). Similar results were obtained with 5 min preincubation time while at 2 min only Pronetupitant produced significant effects. In vivo in mice the intrathecal injection of 0.1 nmol SP elicited the typical scratching, biting and licking (SBL) nociceptive response. This effect of SP was dose dependently (0.1-10 mg/kg) antagonized by Pronetupitant given intravenously 2 h before the peptide. Superimposable results were obtained using Netupitant. Pharmacokinetic studies performed in rats demonstrate that Pronetupitant, after i.v. administration, is quickly (few minutes) and completely converted to Netupitant. Collectively the present results indicated that Pronetupitant acts in vitro as selective NK1 antagonist more potent than Netupitant. However based on the short half-life measured for Pronetupitant in rats, the in vivo action of Pronetupitant can be entirely interpreted as due to its conversion to Netupitant.

Drug-drug interaction profile of components of a fixed combination of netupitant and palonosetron: Review of clinical data

Neurokinin-1 (NK₁) receptor antagonists (RAs) are commonly coadministered with serotonin (5-HT₃) RAs (e.g. palonosetron (PALO)) to prevent chemotherapy-induced nausea/vomiting. Netupitant/palonosetron (NEPA), an oral fixed combination of netupitant (NETU)—a new NK₁ RA—and PALO, is currently under development. In vitro data suggest that NETU inhibits CYP3A4 and is a substrate for and weak inhibitor of P-glycoprotein (P-gp). This review evaluates potential drug–drug interactions between NETU or NEPA and CYP3A4 substrates/inducers/inhibitors or P-gp substrates in healthy subjects. Pharmacokinetic (PK) parameters were evaluated for each drug when NETU was coadministered with PALO (single doses) and when single doses of NETU or NEPA were coadministered with CYP3A4 substrates (erythromycin (ERY), midazolam (MID), dexamethasone (DEX), or oral contraceptives), inhibitors (ketoconazole (KETO)), or inducers (rifampicin (RIF)), or a P-gp substrate (digoxin (DIG)). Results showed no relevant PK interactions between NETU and PALO. Coadministration of NETU increased MID and ERY exposure and significantly increased DEX exposure in a dose-dependent manner; NETU exposure was unaffected. NEPA coadministration had no clinically significant effect on oral contraception, although levonorgestrel exposure increased. NETU exposure increased after coadministration of NEPA with KETO and decreased after coadministration with RIF; PALO exposure was unaffected. NETU coadministration did not influence DIG exposure. In conclusion, there were no clinically relevant interactions between NETU and PALO, or NEPA and oral contraceptives (based on levonorgestrel and ethinylestradiol exposure). Coadministration of NETU or NEPA with CYP3A4 inducers/inhibitors/substrates should be done with caution. Dose reduction is recommended for DEX. Dose adjustments are not needed for NETU coadministration with P-gp substrates.

Pharmacological characterization of tachykinin tetrabranched derivatives

BACKGROUND AND PURPOSE

Peptide welding technology (PWT) is a novel chemical strategy that allows the synthesis of multibranched peptides with high yield, purity and reproducibility. Using this technique, we have synthesized and pharmacologically characterized the tetrabranched derivatives of the tachykinins, substance P (SP), neurokinin A (NKA) and B (NKB).

EXPERIMENTAL APPROACH

The following in vitro assays were used: calcium mobilization in cells expressing human recombinant NK receptors, BRET studies of G-protein - NK1 receptor interaction, guinea pig ileum and rat urinary bladder bioassays. Nociceptive behavioural response experiments were performed in mice following intrathecal injection of PWT2-SP.

KEY RESULTS

In calcium mobilization studies, PWT tachykinin derivatives behaved as full agonists at NK receptors with a selectivity profile similar to that of the natural peptides. NK receptor antagonists display similar potency values when tested against PWT2 derivatives and natural peptides. In BRET and bioassay experiments PWT2-SP mimicked the effects of SP with similar potency, maximal effects and sensitivity to aprepitant. After intrathecal administration in mice, PWT2-SP mimicked the nociceptive effects of SP, but with higher potency and a longer-lasting action. Aprepitant counteracted the effects of PWT2-SP in vivo.

CONCLUSIONS AND IMPLICATIONS

The present study has shown that the PWT technology can be successfully applied to the peptide sequence of tachykinins to generate tetrabranched derivatives characterized with a pharmacological profile similar to the native peptides. In vivo, PWT2-SP displayed higher potency and a marked prolongation of action, compared with SP.

Netupitant/Palonosetron

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, call The Formulary at 800-322-4349. The April 2015 monograph topics are edoxaban, diclofenac sodium injectable, olaparib, antihemophilic factor porcine, and blinatumomab. The Safety MUE is on edoxaban.

Profile of netupitant/palonosetron (NEPA) fixed dose combination and its potential in the treatment of chemotherapy-induced nausea and vomiting (CINV)

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The use of a combination of a 5-hydroxytryptamine-3 (5-HT3) receptor antagonists, dexamethasone, and a neurokinin-1 (NK-1) receptor antagonist has significantly improved the control of acute and delayed emesis in single-day chemotherapy. Palonosetron, a second generation 5-HT3 receptor antagonist with a different half-life, different binding capacity, and a different mechanism of action than the first generation 5-HT3 receptor antagonists, appears to be the most effective agent in its class. Netupitant, is a new NK-1 receptor antagonist with a high binding affinity, a long half-life of 90 hours, is metabolized by CYP3A4, and is an inhibitor of CYP3A4. NEPA is an oral fixed-dose combination of netupitant and palonosetron which has recently been employed in Phase II and Phase III clinical trials for the prevention of CINV in patients receiving moderately and highly emetogenic chemotherapy (MEC and HEC). The clinical trials demonstrated that NEPA (300 mg of netupitant plus 0.50 mg of palonosetron) significantly improved the prevention of CINV compared to the use of palonosetron alone in patients receiving either HEC or MEC. The clinical efficacy was maintained over multiple cycles of chemotherapy. NEPA (Akynzeo(®)) has recently been approved by the Food and Drug Administration (FDA) to treat nausea and vomiting in patients undergoing cancer chemotherapy.

Review of oral fixed-dose combination netupitant and palonosetron (NEPA) for the treatment of chemotherapy-induced nausea and vomiting

Current guidelines recommend the combination of a neurokinin-1 (NK1) receptor antagonist (RA) and a 5-hydroxytryptamine-3 (5-HT3) RA, together with corticosteroids, in order to prevent chemotherapy-induced nausea and vomiting with anthracycline-cyclophosphamide and highly emetogenic chemotherapy, and it is to be considered with moderately emetogenic chemotherapy. Netupitant and palonosetron (NEPA) is a fixed-dose combination of netupitant, a novel, highly selective NK1 RA, and palonosetron, a new-generation 5-HT3 RA, targeting two major emetic pathways in a single oral capsule. In clinical trials, NEPA administered on day 1 together with dexamethasone was highly effective and well tolerated in the prevention of chemotherapy-induced nausea and vomiting in patients with solid tumors undergoing moderately emetogenic chemotherapy or highly emetogenic chemotherapy. NEPA offers maximal convenience, and as a simple guideline-based regimen, has the potential to improve adherence to guidelines.

Synergistic effect of 5-hydroxytryptamine 3 and neurokinin 1 receptor antagonism in rodent models of somatic and visceral pain

Synergistic activity has been observed between serotonergic 5-hydroxytryptamine 3 (5-HT3) and tachykinergic neurokinin 1 (NK1) receptor-mediated responses. This study investigated the efficacy of a 5-HT3 antagonist, palonosetron, and a NK1 antagonist, netupitant, alone or in combination in rodent models of somatic and visceral colonic hypersensitivity. In a rat model of experimental neuropathic pain, somatic hypersensitivity was quantified by the number of ipsilateral paw withdrawals to a von Frey filament (6g). Electrophysiologic responses were recorded in the dorsal horn neurons after mechanical or thermal stimuli. Acute colonic hypersensitivity was induced experimentally in rats by infusing dilute acetic acid (0.6%) directly into the colon. Colonic sensitivity was assessed by a visceromotor behavioral response quantified as the number of abdominal contractions in response to graded isobaric pressures (0-60 mm Hg) of colorectal distension. Palonosetron or netupitant was administered alone or in combination via oral gavage. When dosed alone, both significantly reduced somatic sensitivity, decreased the evoked response of spinal dorsal horn neurons to mechanical or thermal stimulation, and caused significant (P < 0.05) inhibition of colonic hypersensitivity in a dose-dependent manner. The combined administration of palonosetron and netupitant at doses that were ineffective alone significantly reduced both somatic and visceral sensitivity and decreased the evoked response of spinal dorsal horn neurons to mechanical or thermal stimulation. In summary, the combination of palonosetron with a NK1 receptor antagonist showed synergistic analgesic activity in rodent models of somatic and visceral hypersensitivity, and may prove to be a useful therapeutic approach to treat pain associated with irritable bowel syndrome.

Netupitant and palonosetron trigger NK1 receptor internalization in NG108-15 cells

Current therapy for chemotherapy-induced nausea and vomiting includes the use of both 5-HT₃ and NK₁ receptor antagonists. Acute emesis has largely been alleviated with the use of 5-HT₃ receptor antagonists, while an improvement in preventing delayed emesis has been achieved with NK₁ receptor antagonists. Delayed emesis, however, remains a problem with a significant portion of cancer patients receiving highly emetogenic chemotherapy. Like other drugs in its class, palonosetron, a 5-HT₃ receptor antagonist, has shown efficacy against acute emesis. However, palonosetron has also shown consistent improvement in the suppression of delayed emesis. Since both 5-HT₃ and NK₁ receptor antagonists are often simultaneously administered to patients, the question remains if palonosetron’s effect on delayed emesis would remain distinct when co-administered with an NK₁ receptor antagonist. Recent mechanistic studies using NG108-15 cells have shown that palonosetron and netupitant, an NK₁ receptor antagonist currently in phase 3 clinical trials, exhibited synergistic effects when inhibiting the substance P response. The present studies showed that both netupitant and palonosetron-induced NK₁ receptor internalization in NG108-15 cells and that when used together receptor internalization was additive. Palonosetron-induced NK₁ receptor internalization was dependent on the presence of the 5-HT₃ receptor. Results provide a possible explanation for palonosetron’s enhancement of the inhibition of the SP response and suggest that the effect of palonosetron and NK₁ receptor antagonists on prevention of delayed emesis could be additive.

Role of neurokinin 1 receptors in dextran sulfate-induced colitis: studies with gene-deleted mice and the selective receptor antagonist netupitant

OBJECTIVE AND DESIGN

The function of the neurokinin 1 (NK1) receptor was investigated in the DSS-induced mouse colitis model using NK1 receptor-deficient mice and the selective antagonist netupitant.

SUBJECTS

Colitis was induced by oral administration of 20 mg/ml DSS solution for 7 days in C57BL/6 and Tacr1 KO animals (n = 5-7).

TREATMENT

During the induction, one-half of the C57BL/6 and Tacr1 KO group received one daily dose of 6 mg/kg netupitant, administered intraperitoneally, the other half of the group received saline, respectively.

METHODS

Disease activity index (DAI), on the basis of stool consistency, blood and weight loss, was determined over 7 days. Histological evaluation, myeloperoxidase (MPO) measurement, cytokine concentrations and receptor expression analysis were performed on the colon samples.

RESULTS

NK1 receptors are up-regulated in the colon in response to DSS treatment. DSS increased DAI, histopathological scores, BLC, sICAM-1, IFN-γ, IL-16 and JE in wildtype mice, which were significantly reduced in NK1 receptor-deficient ones. NK1 receptor antagonism with netupitant significantly diminished DAI, inflammatory histopathological alterations, BLC, IFN-γ, IL-13 and IL-16 in wildtype mice, but not in the NK1-deficient ones. MPO was similarly elevated and netupitant significantly decreased its activity in both groups.

CONCLUSIONS

NK1 receptor antagonism could be beneficial for colitis via inhibiting different inflammatory mechanisms.

Netupitant PET imaging and ADME studies in humans

Netupitant is a new, selective NK1 receptor antagonist under development for the prevention of chemotherapy-induced nausea and vomiting. Two studies were conducted to evaluate the brain receptor occupancy (RO) and disposition (ADME) of netupitant in humans. Positron emission tomography (PET) imaging with the NK1 receptor-binding-selective tracer [(11) C]-GR205171 was used to evaluate the brain penetration of different doses of netupitant (100, 300, and 450 mg) and to determine the NK1 -RO duration. A NK1 -RO of 90% or higher was achieved with all doses in the majority of the tested brain regions at Cmax, with a long duration of RO. The netupitant minimal plasma concentration predicted to achieve a NK1 -RO of 90%, C90% , in the striatum was 225 ng/mL; after administration of netupitant 300 mg, concentrations exceeded the C90% . In the ADME study, a single nominal dose of [(14) C]-netupitant 300 mg was used to assess its disposition. Absorption was rapid and netupitant was extensively metabolized via Phase I and II hepatic metabolism. Elimination of >90% was predicted at day 29 and was principally via hepatic/biliary route (>85%) with a minor contribution of the renal route (<5%). In conclusion, these studies demonstrate that netupitant is a potent agent targeting NK1 receptors with long lasting RO. In addition, netupitant is extensively metabolized and is mainly eliminated through the hepatic/biliary route and to a lesser extent via the kidneys.

Efficacy and safety of repeated dosing of netupitant, a neurokinin-1 receptor antagonist, in treating overactive bladder

AIM

NK-1 receptors in sensory nerves, the spinal cord and bladder smooth muscle participate in complex sensory mechanisms that regulate bladder activity. This study was designed to assess the efficacy and safety of a new NK-1 receptor antagonist, netupitant, in patients with OAB.

METHODS

This was a phase II, multicenter, double-blind study in which adults with OAB symptoms >6 months were randomized to receive 1 of 3 doses of netupitant (50, 100, 200 mg) or placebo once daily for 8 weeks. The primary efficacy endpoint was percentage change from baseline in average number of daily micturitions at week 8. Urinary incontinence, urge urinary incontinence (UUI), and urgency episodes were also assessed.

RESULTS

The primary efficacy endpoint was similar in the treatment groups (-13.85 for placebo to -16.17 in the netupitant 200 mg group) with no statistically significant differences between netupitant and placebo. The same was true for most secondary endpoints although a significant difference for improvement in UUI episodes and a trend for the greatest decrease in urgency episodes were seen in the netupitant 100 mg group. Netupitant was well tolerated with most treatment emergent adverse events (AEs) being mild. While the overall incidence of AEs increased with netupitant dose, there was no evidence for this dose dependency based on relationship to treatment, intensity, or time to onset.

CONCLUSIONS

The study failed to demonstrate superiority of netupitant versus placebo in decreasing OAB symptoms, despite a trend favoring netupitant 100 mg. There were no safety concerns with daily administration of netupitant over 8 weeks.

Effect of netupitant, a highly selective NK₁ receptor antagonist, on the pharmacokinetics of midazolam, erythromycin, and dexamethasone

PURPOSE

Netupitant is a new highly selective neurokinin-1 receptor antagonist being studied for the prevention of nausea and vomiting in patients undergoing chemotherapy. In vitro studies suggest that netupitant inhibits the cytochrome P-450 isoenzyme 3A4 (CYP3A4). Because netupitant may be used with a variety of drugs, which may be substrates of CYP3A4, two studies were designed to establish the potential risk for drug-drug interaction with three different CYP3A4 substrates: midazolam, erythromycin, and dexamethasone.

METHODS

Both trials were three-period crossover studies performed in healthy subjects. In the first study, 20 subjects received netupitant and either midazolam or erythromycin. In the second study, 25 subjects received netupitant and dexamethasone. Serial blood samples were collected over the course of the two studies and pharmacokinetic parameters were determined for all analytes.

RESULTS

Netupitant, by inhibiting the CYP3A4, increased the C max and AUCinf of midazolam by 40 and 144 %, respectively, and the C max and AUCinf of erythromycin by 30 %. Netupitant was shown to increase the exposure to dexamethasone in a dose-dependent manner with the mean increase in AUC and C max by 72 and 11 %, respectively, on day 1 and by 138 and 75 %, respectively, on day 4 when co-administered with 300 mg of netupitant.

CONCLUSIONS

The results of these studies suggest that netupitant is a moderate inhibitor of CYP3A4 and therefore, co-administration with drugs that are substrates of CYP3A4 may require dose adjustments. Treatments were well tolerated in both studies.