Enantioselective inhibition of apomorphine-induced emesis in the ferret by the neurokinin1 receptor antagonist CP-99,994

Evaluation of Antiemetic Therapy for Hepatic Arterial Infusion Chemotherapy with Oxaliplatin, Fluorouracil, and Leucovorin

Purpose

Our aim was to compare the antiemetic efficacy of the triple combination of aprepitant, dolasetron and dexamethasone with the combination of dolasetron and dexamethasone for chemotherapy-induced nausea and vomiting (CINV) in hepatocellular carcinoma (HCC) patients receiving hepatic arterial infusion chemotherapy (HAIC) with oxaliplatin, fluorouracil and leucovorin (FOLFOX).

Patients and Methods

This was a retrospective study. In the dolasetron plus dexamethasone group (D group), the patients received dolasetron (100 mg, i.v., on day 1) and dexamethasone (10 mg, i.v., on day 1) 30 min before starting administration of chemotherapeutic drugs. In the aprepitant plus dolasetron and dexamethasone group (AD group), the patients received dolasetron and dexamethasone as described above, and aprepitant (125 mg, p.o.) on day 1 followed by 80 mg on days 2 and 3. The primary endpoint was the complete response rate (CR, defined as no emetic episodes and no rescue medication use) during the first cycle of hepatic arterial infusion chemotherapy.

Results

Between January 2018 and August 2019, 302 eligible patients were included: 197 in AD group and 105 in D group. Patients in AD group had significantly higher complete response rates than those in D group during the first cycle (85.8% vs 71.4%, P = 0.003) and all cycles (73.6% vs 49.5%, P<0.001). Patients in AD group had lower rescue therapy (1.5% vs 26.7%, P<0.001) and lower incidence of disruption related to chemotherapy-induced nausea and vomiting (0.5% vs 6.7%, P = 0.002) than patients in D group.

Conclusion

Aprepitant, dolasetron plus dexamethasone is more effective to prevent chemotherapy-induced nausea and vomiting in hepatocellular carcinoma patients treated with FOLFOX-HAIC therapy than dolasetron plus dexamethasone.

A History of Drug Discovery for Treatment of Nausea and Vomiting and the Implications for Future Research

The origins of the major classes of current anti-emetics are examined. Serendipity is a recurrent theme in discovery of their anti-emetic properties and repurposing from one indication to another is a continuing trend. Notably, the discoveries have occurred against a background of company mergers and changing anti-emetic requirements. Major drug classes include: (i) Muscarinic receptor antagonists-originated from historical accounts of plant extracts containing atropine and hyoscine with development stimulated by the need to prevent sea-sickness among soldiers during beach landings; (ii) Histamine receptor antagonists-searching for replacements for the anti-malaria drug quinine, in short supply because of wartime shipping blockade, facilitated the discovery of histamine (H1) antagonists (e.g., dimenhydrinate), followed by serendipitous discovery of anti-emetic activity against motion sickness in a patient undergoing treatment for urticaria; (iii) Phenothiazines and dopamine receptor antagonists-investigations of their pharmacology as "sedatives" (e.g., chlorpromazine) implicated dopamine receptors in emesis, leading to development of selective dopamine (D2) receptor antagonists (e.g., domperidone with poor ability to penetrate the blood-brain barrier) as anti-emetics in chemotherapy and surgery; (iv) Metoclopramide and selective 5-hydroxytryptamine3(5-HT3) receptor antagonists-metoclopramide was initially assumed to act only via D2 receptor antagonism but subsequently its gastric motility stimulant effect (proposed to contribute to the anti-emetic action) was shown to be due to 5-hydroxytryptamine4 receptor agonism. Pre-clinical studies showed that anti-emetic efficacy against the newly-introduced, highly emetic, chemotherapeutic agent cisplatin was due to antagonism at 5-HT3 receptors. The latter led to identification of selective 5-HT3 receptor antagonists (e.g., granisetron), a major breakthrough in treatment of chemotherapy-induced emesis; (v) Neurokinin1receptor antagonists-antagonists of the actions of substance P were developed as analgesics but pre-clinical studies identified broad-spectrum anti-emetic effects; clinical studies showed particular efficacy in the delayed phase of chemotherapy-induced emesis. Finally, the repurposing of different drugs for treatment of nausea and vomiting is examined, particularly during palliative care, and also the challenges in identifying novel anti-emetic drugs, particularly for treatment of nausea as compared to vomiting. We consider the lessons from the past for the future and ask why there has not been a major breakthrough in the last 20 years.

Neurokinin-1 receptor blocker CP-99 994 improved emesis induced by cisplatin via regulating the activity of gastric distention responsive neurons in the dorsal motor nucleus of vagus and enhancing gastric motility in rats

BACKGROUND

Nowadays, chemotherapy induced nausea and vomiting (CINV) is still common in patients with cancer. It was reported that substance P mediated CINV via neurokinin-1 (NK₁ ) receptor and antagonists of NK₁ receptor has been proved useful for treating CINV but the mechanism are not fully understood. This study aimed to examine the role of NK₁ receptor blocker, CP-99 994, when administrated into dorsal motor nucleus of vagus (DMNV), on the cisplatin-induced emesis in rats and the possible mechanism.

METHODS

Rats' kaolin intake, food intake, and bodyweight were recorded every day; gastric contraction activity was recorded in conscious rats through a force transducer implanted into the stomach; gastric emptying was monitored using the phenol red method; single unit extracellular firing in the DMNV were recorded.

KEY RESULTS

DMNV microinjection of CP-99 994 reduced the changes of increased kaolin consumption and suppressed food intake in cisplatin-treated rats; enhanced the gastric contraction activity dose-dependently in control and cisplatin-treated rats but enhanced gastric emptying only in cisplatin-treated rats; reduced the firing rate of gastric distention inhibited (GD-I) neurons but increased the firing rate of GD excited (GD-E) neurons in the DMNV. The effects of CP-99 994 on gastric motility and neuronal activity were stronger in cisplatin-treated rats than those of control rats.

CONCLUSIONS AND INFERENCES

Our results suggested that CP-99 994 could improve emesis induced by cisplatin by regulating gastric motility and gastric related neuronal activity in the DMNV.

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.

The effects of intravenous fosaprepitant and ondansetron for the prevention of postoperative nausea and vomiting in neurosurgery patients: a prospective, randomized, double-blinded study

The incidence of postoperative nausea and vomiting (PONV) is 30–50% after surgery. PONV occurs frequently, especially after craniotomy. In this study, we investigated the preventive effects on PONV in a randomized study by comparing patients who had been administered fosaprepitant, a neurokinin-1 (NK1) receptor antagonist, or ondansetron intravenously. Sixty-four patients undergoing craniotomy were randomly allocated to receive fosaprepitant 150 mg i.v. (NK1 group, n = 32) or ondansetron 4 mg i.v. (ONS group, n = 32) before anesthesia. The incidence of vomiting was significantly less in the NK1 group, where 2 of 32 (6%) patients experienced vomiting compared to 16 of 32 (50%) patients in the ONS group during the first 24 and 48 hours following surgery. Additionally, the incidence of complete response (no vomiting and no rescue antiemetic use) was significantly higher in the NK1 group than in the ONS group, and was 66% versus 41%, respectively, during the first 24 hours, and 63% versus 38%, respectively, during the first 48 hours. In patients undergoing craniotomy, fosaprepitant is more effective than ondansetron in increasing the rate of complete response and decreasing the incidence of vomiting at 24 and 48 hours postoperatively.

Oral administration of aprepitant to prevent postoperative nausea in highly susceptible patients after gynecological laparoscopy

PURPOSE

The use of opioids following surgery is associated with a high incidence of postoperative nausea and vomiting (PONV). We conducted a prospective, randomized, double-blind, placebo-controlled study to investigate the effect of orally administered aprepitant, a neurokinin-1 receptor antagonist, for reducing PONV in patients with fentanyl-based, patient-controlled analgesia (PCA) given intravenously after gynecological laparoscopy.

METHODS

One hundred and twenty female patients (ages 21-60) undergoing laparoscopic hysterectomy were randomly allocated to receive 80 mg (A80 group, n = 40) or 125 mg aprepitant (A125 group, n = 40) or placebo (control group, n = 40) orally 2 h before anesthesia induction. Anesthesia was maintained with isoflurane and remifentanil, and PCA IV using fentanyl and ketorolac were provided for 48 h after surgery. Incidences of nausea, vomiting/retching, and use of rescue antiemetics were recorded at 2, 24, and 48 h after surgery. Complete response was defined as no PONV and no need for rescue treatment.

RESULTS

The incidence of complete response was significantly lower in the A80 and A125 groups than in controls, 56 % and 63 %, vs. 28 %, respectively, P = 0.007 and P = 0.003, respectively, during the first 48 h, and 65 % and 65 % vs. 38 %, respectively, both P = 0.025, during the first 2 h. However, there were no statistically significant differences between A80 and A125 groups in the incidences of complete response and PONV during the study period.

CONCLUSIONS

Aprepitant 80 mg orally was effective in lowering the incidence of PONV in the first 48 h after anesthesia in patients receiving fentanyl-based PCA after gynecological laparoscopy.

The effect of aprepitant for the prevention of postoperative nausea and vomiting in patients undergoing gynecologic surgery with intravenous patient controlled analgesia using fentanyl: aprepitant plus ramosetron vs ramosetron alone

BACKGROUND

The purpose of this study was to evaluate the effect of an aprepitant, neurokinin-1(NK1) receptor antagonist, for reducing postoperative nausea and vomiting (PONV) for up to 24 hours in patients regarded as high risk undergoing gynecological surgery with intravenous patient-controlled analgesia (IV PCA) using fentanyl.

METHODS

In this randomized, open label, case-control study 84 gynecological surgical patients receiving a standardized general anesthesia were investigated. Patients were randomly allocated to receive aprepitant 80 mg P.O. approximately 2-3 hours before operation (aprepitant group) or none (control group). All patients received ramosetron 0.3 mg IV after induction of anesthesia. The incidence of PONV, severity of nausea, and use of rescue antiemetics were evaluated for up to 24 hours postoperatively.

RESULTS

The incidence of nausea was significantly lower in the aprepitant group (50.0%) compared to the control group (80.9%) during the first 24 hours following surgery. The incidence of vomiting was significantly lower in the aprepitant group (4.7%) compared to the control group (42.8%) during the first 24 hours following surgery. In addition, the severity of nausea was less among those in the aprepitant group compared with the control group over a period of 24 hours post-surgery (P < 0.05). Use of rescue antiemetics was lower in the aprepitant group than in the control group during 24 hours postoperatively (P < 0.05).

CONCLUSIONS

In patients regarded as high risk undergoing gynecological surgery with IV PCA using fentanyl, the aprepitant plus ramosetron ware more effective than ramosetron alone to decrease the incidence of PONV, use of rescue antiemetics and nausea severity for up to 24 hours postoperatively.

Consensus recommendations for the prevention of vomiting and nausea following high-emetic-risk chemotherapy

In this update of our 2005 document, we used an evidence-based approach whenever possible to formulate recommendations, emphasizing the results of controlled trials concerning the best use of antiemetic agents for the prevention of emesis and nausea following anticancer chemotherapies of high emetic risk. A three-drug combination of a 5-hydroxytryptamine type 3 receptor (5-HT(3)) receptor antagonist, dexamethasone, and aprepitant beginning before chemotherapy and continuing for up to 4 days remains the standard of care. We address issues of dose, schedule, and route of administration of five selective 5-HT(3) receptor antagonists. We conclude that, for each of these five drugs, there is a plateau in therapeutic efficacy above which further dose escalation does not improve outcome. In trials designed to prove the equivalence of palonosetron to ondansetron and granisetron, palonosetron proved superior in emesis prevention, while adverse effects were comparable. Furthermore, for all classes of antiemetic agents, a single dose is as effective as multiple doses or a continuous infusion. The oral route is as efficacious as the intravenous route of administration.

Antiemetic effect of Xiao-Ban-Xia-Tang, a Chinese medicinal herb recipe, on cisplatin-induced acute and delayed emesis in minks

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao-Ban-Xia-Tang (XBXT), a traditional Chinese herbal medicine, has been used in China for more than 2000 years, and proved to be effective on various cases of vomiting in the clinic.

OBJECTIVE

To investigate the antiemetic effect of XBXT on cisplatin-induced acute and delayed emesis and its effective mechanism on Neurokinin-1 receptor (NK(1)-R) in the new vomiting model of minks.

MATERIALS AND METHODS

Minks were randomly divided into the normal group, cisplatin group, cisplatin + ondansetron group, cisplatin + low-dose XBXT group and cisplatin + high-dose XBXT group. The antiemetic effect of drugs was investigated in the vomiting model of minks induced by cisplatin (6mgkg(-1), i.p.) in 72h observation, and the expression of NK(1)-R in the area postrema and ileum was measured by Western blot.

RESULTS

The frequency cisplatin induces retching and vomiting was significantly reduced by pretreatment with XBXT in a dose-dependent manner during the 0-24-h and 24-72-h periods (P<0.05), and XBXT exhibited effective dose-dependent (P<0.05) inhibition on the increase of expression levels of NK1 receptor in both the ileum and area postrema.

CONCLUSIONS

XBXT has good activity against cisplatin-induced acute and delayed emesis in minks possibly by inhibiting central or peripheral increase of NK(1)-R.

Gingerol inhibits cisplatin-induced vomiting by down regulating 5-hydroxytryptamine, dopamine and substance P expression in minks

OBJECTIVE

To investigate the antiemetic effect of gingerol and its multi-targets effective mechanism on 5-hydroxytryptamine (5-HT), dopamine (DA) and substance P (SP). The antiemetic effect of gingerol was investigated on a vomiting model of mink induced by cisplatin (7.5 mg . kg(-1), i.p.) in 6 h observation. The levels of 5-HT, DA and distribution of substance P in the area postrema and ileum were measured by high performance liquid chromatography (HPLC) and immunohistochemistry respectively. The frequency of cisplatin induced retching and vomiting was significantly reduced by pretreatment with gingerol in a dose-dependent manner (P<0.05). Cisplatin produced a significant increase in 5-HT and DA levels in the area postrema and ileum of minks (P<0.05), and this increase was significantly inhibited by gingerol in a dose-dependent manner (P<0.05). Substance P-immunoreactive was mainly situated in the mucosa and submucosa of ileum as well as in the neurons of area postrema, and gingerol markedly suppressed the increase immunoreactivity of substance P induced by cisplatin in a dose-dependent manner (P<0.05). Gingerol has good activity against cisplatin-induced emesis in minks possibly by inhibiting central or peripheral increase of 5-HT, DA and substance P.

Recent advances, trends and economic considerations in the risk assessment, prevention and treatment of postoperative nausea and vomiting

During the last two decades there have been considerable achievements regarding the management of postoperative nausea and vomiting (PONV). Due to the importance of these symptoms in the aim to streamline clinical processes and to improve patient satisfaction, the debate on the best strategies and also research that focuses on PONV continues. This review summarises the recent developments with respect to the management of PONV. Following a brief review on what is already known on the risk assessment, prevention and treatment of PONV, newer trends in the pharmacological prevention (dexamethasone, neurokinin-1 antagonists, multimodal prevention) will be discussed as well as new insights regarding the value of algorithms for the prevention of PONV. Further, pharmacogenetically based algorithms (according to the metaboliser status) as well as new treatment strategies (dexamethasone, multimodal treatment) will be covered. No drug so far can achieve a reduction of PONV of more than one third. Furthermore, all clinical studies consistently demonstrated that a combination treatment has a simple additive effect without any relevant interaction between different drugs or classes of drugs. The relative reduction of approximately 30% can also be expected from dexamethasone and it is likely that the substances presently in development and in an early clinical use (e.g., neurokinin-1 antagonists) will not represent the new panacea. However, they will probably replenish the existing antiemetic portfolio to better cope with high risk patients. Stratified prevention using pharmacogenetic knowledge is still in the early stages. Algorithms need to be customized to the local settings in order to prove efficient. Treatment remains a most important pillar and there is evidence that the principles of combining antiemetics to prolong effects and improve protection can be similarly applied to treatment. Recent developments in the area of PONV are more related to implementing the already existing evidence than based on the introduction of new molecules. New molecules replenish the pharmacological antiemetic portfolio, which is needed due to the limited efficacy of any single agent available so far. The new neurokinin-1 receptor antagonist, aprepitant, and the long lasting 5-HT(3) receptor antagonist palonosetron are the latest developments in this context. Treatment is most important and can also be regarded as a secondary prevention. Due to limited efficacy of single treatment interventions, combination therapy may gain more widespread use in the future.

Single-dose aprepitant vs ondansetron for the prevention of postoperative nausea and vomiting: a randomized, double-blind phase III trial in patients undergoing open abdominal surgery

BACKGROUND

The neurokinin(1) antagonist aprepitant is effective for prevention of chemotherapy-induced nausea and vomiting. We compared aprepitant with ondansetron for prevention of postoperative nausea and vomiting.

METHODS

Nine hundred and twenty-two patients receiving general anaesthesia for major abdominal surgery were assigned to receive a single preoperative dose of oral aprepitant 40 mg, oral aprepitant 125 mg, or i.v. ondansetron 4 mg in a randomized, double-blind trial. Vomiting episodes, use of rescue therapy, and nausea severity (verbal rating scale) were documented for 48 h after surgery. Primary efficacy endpoints were complete response (no vomiting and no use of rescue therapy) 0-24 h after surgery and no vomiting 0-24 h after surgery. The secondary endpoint was no vomiting 0-48 h after surgery.

RESULTS

Aprepitant at both doses was non-inferior to ondansetron for complete response 0-24 h after surgery (64% for aprepitant 40 mg, 63% for aprepitant 125 mg, and 55% for ondansetron, lower bound of 1-sided 95% CI > 0.65), superior to ondansetron for no vomiting 0-24 h after surgery (84% for aprepitant 40 mg, 86% for aprepitant 125 mg, and 71% for ondansetron; P < 0.001), and superior for no vomiting 0-48 h after surgery (82% for aprepitant, 40 mg, 85% for aprepitant, 125 mg, and 66% for ondansetron; P < 0.001). The distribution of peak nausea scores was lower in both aprepitant groups vs ondansetron (P < 0.05).

CONCLUSIONS

Aprepitant was non-inferior to ondansetron in achieving complete response for 24 h after surgery. Aprepitant was significantly more effective than ondansetron for preventing vomiting at 24 and 48 h after surgery, and in reducing nausea severity in the first 48 h after surgery. Aprepitant was generally well tolerated.

A randomized, double-blind comparison of the NK1 antagonist, aprepitant, versus ondansetron for the prevention of postoperative nausea and vomiting

BACKGROUND

Antiemetics currently in use are not totally effective. Neurokinin-1 receptor antagonists are a new class of antiemetic that have shown promise for chemotherapy-induced nausea and vomiting. This is the first study evaluating the efficacy and tolerability of the neurokinin-1 receptor antagonist, aprepitant, for the prevention of postoperative nausea and vomiting.

METHODS

In this multicenter, double-blind trial, we randomly assigned 805 patients receiving general anesthesia for open abdominal surgery to a preoperative dose of aprepitant 40 mg orally, aprepitant 125 mg orally, or ondansetron 4 mg IV. Vomiting, nausea, and use of rescue therapy were assessed over 48 h after surgery. Treatments were compared using logistic regression.

RESULTS

Incidence rates for the primary end point (complete response [no vomiting and no use of rescue] over 0-24 h after surgery, tested for superiority of aprepitant) were not different across groups (45% with aprepitant 40 mg, 43% with aprepitant 125 mg, and 42% with ondansetron). The incidence of no vomiting (0-24 h) was higher with aprepitant 40 mg (90%) and aprepitant 125 mg (95%) versus ondansetron (74%) (P < 0.001 for both comparisons), although between-treatment use of rescue and nausea control was not different. Both aprepitant doses also had higher incidences of no vomiting over 0-48 h (P < 0.001). No statistically significant differences were seen among the side effect profiles of the treatments.

CONCLUSIONS

Aprepitant was superior to ondansetron for prevention of vomiting in the first 24 and 48 h, but no significant differences were observed between aprepitant and ondansetron for nausea control, use of rescue, or complete response.

Discovery of 3-methyl-N-(1-oxy-3',4',5',6'-tetrahydro-2'H-[2,4'-bipyridine]-1'-ylmethyl)benzamide (ABT-670), an orally bioavailable dopamine D4 agonist for the treatment of erectile dysfunction

The goal of this study was to identify a structurally distinct D(4)-selective agonist with superior oral bioavailability to our first-generation clinical candidate 1a (ABT-724) for the potential treatment of erectile dysfunction. Arylpiperazines such as (heteroarylmethyl)piperazine 1a, benzamide 2, and acetamides such as 3a,b exhibit poor oral bioavailability. Structure-activity relationship (SAR) studies with the arylpiperidine template provided potent partial agonists such as 4d and 5k that demonstrated no improvement in oral bioavailability. Further optimization with the (N-oxy-2-pyridinyl)piperidine template led to the discovery of compound 6b (ABT-670), which exhibited excellent oral bioavailability in rat, dog, and monkey (68%, 85%, and 91%, respectively) with comparable efficacy, safety, and tolerability to 1a. The N-oxy-2-pyridinyl moiety not only provided the structural motif required for agonist function but also reduced metabolism rates. The SAR study leading to the discovery of 6b is described herein.

Synthesis and evaluation of 3-aryl piperidine analogs as potent and efficacious dopamine D4 receptor agonists

A series of 3-aryl piperidine analogs with 2-piperidinoalkylamino or 2-piperidinoalkyloxy fused bicyclic rings were prepared and found to be potent and efficacious human dopamine D4 agonists. The synthesis and structure-activity relationship (SAR) studies that led to the identification of these compounds are discussed.

Consensus proposals for the prevention of acute and delayed vomiting and nausea following high-emetic-risk chemotherapy

This paper uses an evidence-based approach whenever possible to formulate recommendations, emphasizing the results of controlled trials concerning the best use of antiemetic agents. We address issues of dose, schedule, and route of administration of five selective 5-HT(3) antagonists. We conclude that for each of these five drugs, there is a plateau in therapeutic efficacy above which further dose escalation does not improve outcome. Furthermore, for all classes of antiemetic agents, a single dose is as effective as multiple doses or a continuous infusion. The oral route is as efficacious as the intravenous route of administration, even with chemotherapy of high emetic risk. Selective antagonists of the type 3 serotonin receptor (5-HT(3)) in combination with dexamethasone and aprepitant are the standard of care for the prevention of emesis following chemotherapy of high emetic risk.

Serotonin and Anticancer Drug-induced Emesis

Cytotoxic drug-induced nausea and vomiting are the side effects most feared by cancer patients. Emesis is an instinctive defense reaction caused by the somato-autonomic nerve reflex, which is integrated in the medulla oblongata. Emesis caused by anticancer drugs is associated with an increase in the concentration of serotonin (5-HT) (5-HT) in the intestinal mucosa and brainstem. 5-HT released from the enterochromaffin (EC) cells, which synthesize and secrete 5-HT, stimulates the 5-HT receptors on the adjacent vagal afferent nerves. The depolarization of the vagal afferent nerves stimulates the vomiting center in the brainstem and eventually induces a vomiting reflex. 5-HT released from EC cells appears to mediate the cisplatin-induced emesis sensitive to 5-HT(3) receptor antagonists. The precise role of 5-HT in the occurrence of vomiting has not been fully elucidated. The present review describes the role of 5-HT in anticancer drug-induced emesis from the viewpoint of 5-HT release and afferent vagal nerve activity. Various models and methods for predicting emesis are also evaluated.

Discovery of 2-(4-Pyridin-2-ylpiperazin-1-ylmethyl)-1H-benzimidazole (ABT-724), a Dopaminergic Agent with a Novel Mode of Action for the Potential Treatment of Erectile Dysfunction

A new class of agents with potential utility for the treatment of erectile dysfunction has been discovered, guided by the hypothesis that selective D4 agonists are erectogenic but devoid of the side effects typically associated with dopaminergic agents. The lead agent 2-(4-pyridin-2-ylpiperazin-1-ylmethyl)-1H-benzimidazole (1, ABT-724) was discovered by optimization of a series of benzimidazole arylpiperazines. This highly selective D4 agonist was found to be very potent and efficacious in vivo, eliciting penile erections in rats at a dose of 0.03 micromol/kg, with a positive response rate of 77% erectile incidence. Even at high doses, it was devoid of side effects in animal models of central nervous system behaviors, emesis, or nausea. The structure-activity relationship of the parent benzimidazole series leading to 1 is described, with the detailed in vitro and in vivo profiles described. Distinctive structural features were discovered that are associated with D4 selective agonism in this series of analogues.

Demonstration of the efficacy and safety of a novel substance P (NK1) receptor antagonist in major depression

The efficacy and safety of a selective NK(1) antagonist, L-759274, was investigated in outpatients with diagnosis of major depressive disorder with melancholic features, following evidence obtained with the novel compound aprepitant that Substance P (NK(1)) antagonists may provide a unique mechanism of antidepressant activity. A randomized, double-blind placebo-controlled study was carried out. Patients, male or female, aged 18-60, scoring >/=25 points on total of first 17 items of 21-item Hamilton Depression Scale (HAMD), and scoring >/=4 (moderately ill) on Clinical Global Impressions-Severity Scale were randomized to oral L-759274 40 mg daily (n=66) or placebo (n=62) for 6 weeks. For patients receiving L-759274, improvement (mean decrease from baseline) in HAMD-17 total score was 10.7 points, compared with a mean 7.8 point improvement in patients receiving placebo (p<0.009). Mean scores for item 1 of HAMD-17 (depressed mood) also improved to a greater extent in the active group compared with the placebo group (0.3 points, p<0.058). Compared with placebo, mean scores on Clinical Global Impressions-Improvement Scale improved significantly by the end of the trial (p=0.009). L-759274 was generally safe and well-tolerated. The incidence of sexual side effects was on par with that observed in patients receiving placebo, and the incidences of gastrointestinal effects were low. Antidepressant actions have now been observed with two different highly selective NK(1) antagonists (aprepitant and L-759274). NK(1) antagonism is a replicated and generally well-tolerated antidepressant mechanism.

Brain penetration of aprepitant, a substance P receptor antagonist, in ferrets

The pharmacokinetics, metabolism, and brain penetration of the neurokinin 1 (NK1) receptor antagonist (substance P receptor antagonist), aprepitant (MK-0869), were examined in ferrets. This species exhibits human-type NK1receptor pharmacology and is of proven value in the identification of clinically useful drugs for the treatment of chemotherapy-induced nausea and vomiting in humans. After a single p.o. dose of aprepitant at 1 or 2 mg/kg, plasma levels of the compound were between approximately 200 and 270 ng/ml, 24 h after dosing. In the brain cortex, concentrations of aprepitant reached between approximately 80 and 150 ng/g of tissue 24 h after dosing. The predominant radioactive component present in the plasma and the brain of ferrets at 24 or 48 h after a single oral dose of [14C]aprepitant at 3 mg/kg was the parent compound itself. The slow plasma clearance of aprepitant ( approximately 1.5 ml/min/kg) and its abundance in ferret brain were in accord with its efficacy in blocking the retching and vomiting at 24 and 48 h postdose when ferrets were challenged with the emetic anticancer drug, cisplatin. When aprepitant and some of its metabolites were assessed for their in vitro binding affinity to the human NK1receptor, aprepitant demonstrated the highest affinity. Collectively, these data suggested that aprepitant, rather than its metabolites, was responsible, primarily, for the antiemetic activity of this compound in the male ferret.

Identification of the degradation product of ezlopitant, a non-peptidic substance P antagonist receptor, by hydrogen deuterium exchange, electrospray ionization tandem mass spectrometry (ESI/MS/MS) and nuclear magnetic resonance (NMR) spectroscopy

The degradation product of ezlopitant was isolated from low specific activity material and identified by solution phase hydrogen/deuterium (H/D) exchange and electrospray ionization tandem mass spectrometry (ESI/MS/MS) to be an isopropyl peroxide analog of ezlopitant. The structure of the degradant was further confirmed by nuclear magnetic resonance (NMR) spectroscopy utilizing complete 1H and 13C assignments. Studies were also performed to identify the factors responsible for the oxidative degradation of ezlopitant, which included salt form, storage conditions and salt formation solvent. Of all the variable studies over a 3 weeks period, only a change in the salt form prevented this oxidative degradation.

Roles of substance P and NK(1) receptor in the brainstem in the development of emesis

The emetic response is primarily a protective reflex occurring in a wide variety of vertebrates in response to the ingestion of toxic compounds. The role of the nuclei in the brainstem, including the area postrema, nucleus tractus solitarius, the dorsal motor nucleus of the vagus, and the central pattern generator for vomiting, as well as the involvement of the abdominal visceral innervation relevant to the emetic reflex, have all been discussed by many researchers. The introduction of serotonin 5-HT(3)-receptor antagonists into clinical practice allowed for a dramatic improvement in the management of vomiting. However, vomiting still remains a significant problem. The mechanism of the emetic response is even more complicated than was first thought. This review attempts to bring together some of the evidence suggesting the roles of substance P and its receptor, neurokinin NK(1) receptor, in the brainstem nuclei in the development of emesis. Accordingly, NK(1)-receptor antagonists might represent novel drugs for the management of major types of emesis.

Application of LC-NMR for the study of the volatile metabolite of MK-0869, a substance P receptor antagonist

LC-NMR was applied to identify the polar volatile metabolite of MK-0869. MK-0869, a morpholine-based compound containing a triazolone ring, is a very potent NK(1) receptor antagonist. Currently, it is in development as an anti-emesis agent in chemotherapy treatments. The primary metabolites of MK-0869, M1 and M2, are non-polar and lack the triazolone ring. Incubation of [14C]M1 with liver microsomes from male rats produced a very polar and volatile metabolite, M3. Analysis was not possible by LC-MS or by conventional NMR because of poor ionization, small molecular weight and volatility, leaving chemical derivatization and LC-NMR as alternative methods. Reduction of M3 with NaBH(4) resulted in a derivative that had the same retention time as p-fluorophenylethylene glycol on HPLC. A small aliquot of the solution containing M3 was passed through the LC of the LC-NMR system, which was connected on-line with a radioactivity detector. The simultaneous UV and radioactivity chromatograms thus identified the chromatographic UV peak that was associated with the metabolite. Analysis was carried out by stop-flow on another portion of this fraction. From the chemical derivatization and the analysis by LC-NMR, M3 is shown to be p-fluoro-alpha-hydroxyacetophenone. Further studies using LC-NMR showed that M3 could be generated from both M1 and M2 in NADPH-dependant reactions catalyzed by microsomes containing recombinant human CYP2C19, CYP1A2 or CYP3A4.

Synthesis of a novel class of non-peptide NK-2 receptor ligand, derived from 1-phenyl-3-pyrrol-1-ylindan-2-carboxamides

A series of trans,trans-1-phenyl-3-pyrrol-1-ylindan-2-carboxamide derivatives has been synthesized in eight steps starting from cinnamic acid or 3,3-diphenylpropionic acid. The trans,trans configuration of these carboxamides has been established by X-ray analysis and by NOE experiments in NMR. These new compounds were evaluated for their potential NK-1, NK-2 and NK-3 receptors binding affinity. The N,N-disubstituted carboxamides bound selectively on NK-2 receptors.

Prospective evaluation of antiemetic outcome following high-dose chemotherapy with hematopoietic stem cell support

Considerable progress has been made in improving the control of chemotherapy-induced emesis. The impact of available antiemetic options for patients receiving stem cell transplants is unclear, as few prospective data have been collected. We prospectively evaluated antiemetic outcome in patients receiving stem cell transplantation over a 7-day period following the initiation of chemotherapy. The primary endpoints were the number of emetic episodes and the extent of nausea measured on a four-point scale. Eighty-two patients were evaluated. Ninety-five percent of patients had nausea during the first week of treatment; 80% had at least one emetic episode. The percentage of patients with emesis was as follows: day 1: 13%, day 2: 21%, day 3: 30%, day 4: 38%, day 5: 44%, day 6: 39%, day 7: 18%. In multivariate analysis, gender, emesis with prior chemotherapy, history of morning or motion sickness, type of transplant (auto vs allo), use of total body irradiation, or use of dexamethasone did not effect emesis control. Most patients receiving high-dose chemotherapy experience incompletely controlled emesis. Control of nausea and emesis progressively worsened with each subsequent day following initiation of chemotherapy, reaching a nadir on day 5. New treatment approaches are needed to improve emesis control in this patient population.

An orally active, water-soluble neurokinin-1 receptor antagonist suitable for both intravenous and oral clinical administration

1-(5-[[(2R,3S)-2-([(1R)-1-[3,5-Bis(trifluoromethyl)phenyl]ethyl]oxy)-3-(4-fluorophenyl)morpholin-4-yl]methyl]-2H-1,2,3-triazol-4-yl)-N,N-dimethylmethanamine hydrochloride 3 is a high affinity, orally active, h-NK(1) receptor antagonist with a long central duration of action and a solubility in water of >100 mg/mL. The construction of the 5-dimethylaminomethyl 1,2,3-triazol-4-yl unit, which incorporates the solubilizing group of 3, was accomplished by thermal rearrangement of a propargylic azide in the presence of dimethylamine. Compound 3 is highly effective in pre-clinical tests that are relevant to clinical efficacy in emesis and depression.

Substance P: a new era, a new role

Substance P has been extensively studied and is considered the prototypic neuropeptide of the more than 50 known neuroactive molecules. The understanding of substance P has evolved beyond the original concept as the pain transmitter of the dorsal horn. Animal and genetic research, recent developments of nonpeptide substance P antagonists, and important changes in the understanding of neurotransmission have each contributed to the current understanding of substance P After 7 decades, the physiologic role of substance P is known as a modulator of nociception, involved in signaling the intensity of noxious or aversive stimuli. Genetic studies in mice and development of substance P antagonists provide more recent results that support the redefinition of the central role of substance P Evidence suggests that this neuropeptide is an integral part of central nervous system pathways involved in psychologic stress.

Narrow-bore high-performance liquid chromatography in combination with ionspray tandem mass spectrometry for the determination of the substance P receptor antagonist ezlopitant and its two active metabolites in plasma

A simple, but highly sensitive and specific, assay was developed for the quantitative determination of ezlopitant and its two active metabolites in human plasma using narrow-bore reversed-phase high-performance liquid chromatography (HPLC) coupled with electrospray tandem mass spectrometry (ES-MS-MS). Ezlopitant, its two pharmacologically active metabolites, an alkene analogue (CJ-12 458) and a benzyl alcohol analogue (CJ-12 764), and their corresponding trideuterated internal standards (I.S.), were extracted from plasma with methyl tert.-butyl ether (MTBE). The dried MTBE extracts were reconstituted and analyzed using a narrow-bore (2.1 mm I.D.) YMC basic HPLC column and a mobile phase of acetonitrile-20 mM ammonium acetate, pH 5 (60:40, v/v). Column effluent was monitored by pneumatically assisted electrospray tandem mass spectrometry. Multiple reaction monitoring (MRM) using the parent to product ions was used to quantify ezlopitant and its two active metabolites. The assay exhibited a linear dynamic range of 0.1-100 ng/ml. Average absolute recoveries from plasma were approximately 71, 80 and 99% for ezlopitant and its two active metabolites CJ-12 485 and CJ-12 764, respectively. The precision (RSD %) and accuracy (Deviation %) values for the method were within +/- 12% and +/- 15%, respectively, for all analytes. Sample analysis times were less than 5 min from one injection to the next. The assay proved to be suitable for pharmacokinetics studies.

Potential of substance P antagonists as antiemetics

The introduction of serotonin 5-HT3 receptor antagonists into clinical practice allowed for a dramatic improvement in the management of nausea and vomiting. Despite this, postoperative and chemotherapy-induced emesis remains a significant, unresolved issue in many patients even when a combination of antiemetic drugs is used. Numerous neurotransmitters have been implicated in triggering emesis; however, the tachykinin substance P, by virtue of its localisation within both the gastrointestinal vagal afferent nerve fibres and brainstem emetic circuitry, and its ability to induce vomiting when administered intravenously, is thought to play a key role in emetic responses. Because substance P is the most likely endogenous ligand for the neurokinin-1 (NK1) receptor, the development of nonpeptide NK1 receptor antagonists led scientists to evaluate these compounds as antiemetics. The five NK1 receptor inhibitors that have been studied initially in humans are: vofopitant (GR-205171), CP-122721, ezlopitant (CJ-11974), MK-869 (L-754030) and its prodrug L-758298. Except for monotherapy in acute cisplatin-induced emesis, this new class of drugs has proven to be highly effective in the control of both chemotherapy-induced nausea and vomiting, and postoperative nausea and vomiting. No major adverse event was reported in the preliminary trials. Further investigation is mandatory in order to assess the optimal treatment regimen and to make sure the wide spectrum activity of the NK1 receptor inhibitors does not cause significant adverse effects in the context of the treatment of nausea and vomiting.

The emetic and anti-emetic effects of the capsaicin analogue resiniferatoxin in Suncus murinus, the house musk shrew

1. In SUNCUS: murinus the ultrapotent capsaicin analogue resiniferatoxin (RTX) induced an emetic response in the dose range 1 - 1000 microg kg(-1), s.c. The latency was inversely related to dose and ranged from 41.2+/-4.4 min. (1 microg kg(-1), s.c.) to 2.7+/-0.6 min. (1000 microg kg(-1), s.c.). 2. The emetic response to RTX (10 or 100 microg kg(-1), s.c.) was blocked or markedly reduced by pre-treatment with RTX (100 microg kg(-1), s.c.), 8-OH-DPAT (100 microg kg(-1), s.c.), morphine (2 mg kg(-1), s.c.), neonatal capsaicin (100 mg kg(-1), s.c.) and the NK(1) receptor antagonist CP-99,994 (10 - 20 mg kg(-1), s.c.) but not by the 5-HT(3) receptor antagonist tropisetron (200 microg kg(-1), s.c.). 3. RTX (100 microg kg(-1), s.c.) induced c-fos-like immunoreactivity in the area postrema and parts of the nucleus tractus solitarius. This pattern is consistent with the proposal that the emetic effect is mediated via one or both of these structures and an involvement of substance P is discussed. 4. RTX (10 and 100 microg kg(-1), s.c.) had broad-spectrum antiemetic effects in Suncus as indicated by its ability to block or markedly reduce the emetic response to motion (1 Hz, 4 cm lateral, 10 min.), cisplatin (20 mg kg(-1), i.p.), intragastric copper sulphate (40 mg kg(-1), p.o.), nicotine (10 mg kg(-1), s.c.) and RTX (100 microg kg(-1), s.c.) itself. 5. It is proposed that the site of the anti-emetic effect is in the nucleus tractus solitarius and mechanisms involving the modulation of substance P release are discussed. 6. The general utility of SUNCUS: for investigations of vanilloid receptors is reviewed in the light of the exquisite sensitivity of the emetic reflex in this species to resiniferatoxin.

A new class of antiemetics: the NK-1 receptor antagonists

Emesis is one of the most unpleasant and debilitating side effects of anticancer chemotherapy. In acute emesis (vomiting occurring 0-24 hours after chemotherapy administration), the 5-HT3 receptor antagonists and corticosteroids are highly effective, with few significant side effects, and can safely be combined. Delayed emesis (vomiting occurring >24 hours after chemotherapy administration), however, is both not well understood and less well controlled. Studies have yielded conflicting results concerning the use of 5-HT3 receptor antagonists alone in delayed emesis. The data of NK-1 receptor antagonists in the control of acute emesis, although promising, need confirmation in a properly designed study.

The novel NK1 receptor antagonist MK-0869 (L-754,030) and its water soluble phosphoryl prodrug, L-758,298, inhibit acute and delayed cisplatin-induced emesis in ferrets

The anti-emetic profile of the novel brain penetrant tachykinin NK1 receptor antagonist MK-0869 (L-754,030) 2-(R)-(1-(R)-(3,5-bis(trifluoromethyl)phenylethoxy)-3-(S)-(4-fluor o)phenyl-4-(3-oxo-1,2,4-triazol-5-yl)methylmorpholine and its water soluble prodrug, L-758,298, has been examined against emesis induced by cisplatin in ferrets. In a 4 h observation period, MK-0869 and L-758,298 (3 mg/kg i.v. or p.o.) inhibited the emetic response to cisplatin (10 mg/kg i.v.). The anti-emetic protection afforded by MK-0869 (0.1 mg/kg i.v.) was enhanced by combined treatment with either dexamethasone (20 mg/kg i.v.) or the 5-HT3 receptor antagonist ondansetron (0.1 mg/kg i.v.). In a model of acute and delayed emesis, ferrets were dosed with cisplatin (5 mg/kg i.p.) and the retching and vomiting response recorded for 72 h. Pretreatment with MK-0869 (4-16 mg/kg p.o.) dose-dependently inhibited the emetic response to cisplatin. Once daily treatment with MK-0869 (2 and 4 mg/kg p.o.) completely prevented retching and vomiting in all ferrets tested. Further when daily dosing began at 24 h after cisplatin injection, when the acute phase of emesis had already become established, MK-0869 (4 mg/kg p.o. at 24 and 48 h after cisplatin) prevented retching and vomiting in three out of four ferrets. These data show that MK-0869 and its prodrug, L-758,298, have good activity against cisplatin-induced emesis in ferrets and provided a basis for the clinical testing of these agents for the treatment of emesis associated with cancer chemotherapy.

The effect of the NK1 receptor antagonist CP-99,994 on emesis and c-fos protein induction by loperamide in the ferret

The site of the anti-emetic action of the neurokinin1 receptor antagonist CP-99,994 was studied in the ferret using the centrally acting opiate receptor agonist loperamide at a dose (0.5 mg/kg s.c.) which induced emesis in all animals tested. CP-99,994 (1 mg/kg, s.c.x2) abolished the emetic response (retching and vomiting) and the behaviours (licking, wet dog shakes, mouth scratching and gagging) induced by loperamide over a 2-h observation period. The enantiomer of this compound CP-100,263 (1 mg/kg, s.c.x2) did not have any significant effect on emesis or related behaviours. Loperamide (0.5 mg/kg s.c.) administration (but not its vehicle) resulted in dense fos-like immunoreactivity (FLI) mainly throughout the rostro-caudal extent of the nucleus tractus solitarius but not the area postrema. Although CP-99,994 (1 mg/kgx2) abolished the loperamide-induced emesis, it did not have any statistically significant effect on FLI in the brainstem. In loperamide and CP-100,263 (1 mg/kg, s.c.x2) treated animals FLI was comparable to that in animals treated with loperamide and CP-99,994. The results from this study taken together with those from previous studies indicate that loperamide exerts its emetic effect via nucleus tractus solitarius dendrites projecting into the area postrema. The lack of significant effect of CP-99,994 on the FLI induced by loperamide in this nucleus suggests that it is acting at a site "deep" in the nucleus tractus solitarius or elsewhere. The marked reduction in behaviours associated with loperamide administration by CP-99,994 provides a preliminary indication that NK1 receptor antagonist (as represented by CP-99,994) may in the clinic have effects on behaviours induced by emetic agents in addition to their previously described effects on retching and vomiting.

Discovery of the antidepressant and anti-emetic efficacy of substance P receptor (NK1) antagonists

The development of small-molecule antagonists of the substance P (SP)-preferring tachykinin NK1 receptor during the past decade represents an important opportunity to exploit these molecules as novel therapeutic agents. On the basis of its anatomical localization and function, SP has been implicated in diverse pathophysiologies; of these, diseases of the CNS have been examined in the greatest detail. Although SP is best known as a pain neurotransmitter, it also controls vomiting and various behavioural, neurochemical and cardiovascular responses to stress. Recent clinical trials have confirmed the efficacy of NK1 receptor antagonists to alleviate depression and emesis but, surprisingly, not pain. Thus, multiple clinical trials, targeted to appropriate patient populations, are necessary to define the therapeutic potential of novel neurotransmitter ligands.

The tachykinin NK1 receptor in the brain: pharmacology and putative functions

After its discovery in 1931, substance P (SP) remained the only mammalian member of the family of tachykinin peptides for several decades. Tachykinins thus refer to peptides sharing the common C-terminal amino acid sequence Phe-X-Gly-Leu-Met x NH2. In recent years the family of mammalian tachykinins has grown with the isolation of two novel peptides from bovine and porcine central nervous system (CNS), neurokinin A and neurokinin B. In parallel with the identification of multiple endogenous tachykinins several classes of tachykinin receptors were discovered. The receptors described so far are named tachykinin NK1 receptor, tachykinin NK2 receptor and tachykinin NK1 receptor, respectively. The present review focuses on the pharmacology and putative function of tachykinin NK1 receptors in brain. The natural ligand with the highest affinity for the tachykinin NK1 receptor is SP itself. The C-terminal sequence is essential for activity, the minimum length of a fragment with reasonable affinity for the tachykinin NK1 receptor is the C-terminal hexapeptide. A rapid advance of knowledge was caused by development of non-peptidic tachykinin NK1 receptor antagonists. This area is under rapid development and a variety of different chemical classes of compounds are involved. Species-dependent affinities of tachykinin NK1 receptor antagonists reveal two clusters of compounds, targeting the tachykinin NK1 receptor subtype found in guinea pig, human or ferret or the one in rat or mouse, respectively. The most recently developed compounds are highly selective, enter the brain and are orally bioavailable. Distinct behavioural effects in experimental animals suggest the involvement of tachykinin NK1 receptors in nociceptive transmission, basal ganglia function or anxiety and depression. Recent clinical trials in man showed that tachykinin NK1 receptor antagonists are effective in treating depression and chemotherapy-induced emesis. Therefore, it is well possible that tachykinin NK1 receptor antagonists will be clinically used for treatment of specific CNS disorders within a short period of time.

The site of the anti-emetic action of tachykinin NK1 receptor antagonists may exist in the medullary area adjacent to the semicompact part of the nucleus ambiguus

NK1 receptor antagonists have been shown to act centrally and to produce a broad-spectrum anti-emetic action. To determine precisely the site of this action, we microinjected GR205171, an NK1 receptor antagonist, into the left medulla oblongata in decerebrate paralyzed dogs. The right medulla was transected 2.5 mm rostral to the obex to eliminate the emetic function of that half. Fictive retching induced by vagal stimulation was still observed after each of 32 injections (0.5-5 microgram in 1-30 microliter) in the area ventrolateral to the solitary complex in six dogs. Retching was also observed for 30 min or more after all but 2 of 30 injections (0.5-1 microgram in 0.5-1 microliter) in the area dorsal to the retrofacial nucleus in 17 dogs. In contrast, retching disappeared within 5-30 min after each of 20 injections (0.5-1 microgram in 1 microliter) in the area adjacent to the semicompact part of the nucleus ambiguus (scAMB) in 15 dogs. The threshold dose for abolition of the retching response was examined in seven dogs and was about 0.1 ng in 1 microliter. The maximum velocity of salivation occurred before the onset of retching and significantly decreased after its abolition. These results suggest that the site of the anti-emetic action of NK1 receptor antagonists may lie in a limited area adjacent to the scAMB, and that neurons in the site induce prodromal signs and retching in a sequential manner.

Inhibition of emesis by tachykinin NK1 receptor antagonists in Suncus murinus (house musk shrew)

The anti-emetic potential of CP-122,721 ((+)-2S,3S)-3-(2-methoxy-5-trifluoromethoxybenzyl)amino-2-phenylpi peridine), CP-99,994 ((+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine), CP-100,263 ((-)-(2R,3R)-3-(2-methoxybenzylamino)-2-phenylpiperidine), RP 67580 ((3R, 7aR)-7,7-diphenyl-2-[1-imino-2-(2-methoxyphenyl)ethyl] po-hydroisoindol-4-one), FK 888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-in-dole-3-yl)carbonyl-L-propyl] -N-methyl-N-phenylmethyl-1-3-(2-naphthyl)-alaninamide) and GR 82334 ([D-Pro9[spiro-g-lactam]Leu10]-physalaemin-(1-11)) was investigated to inhibit nicotine (5 mg/kg, s.c.)-, copper sulphate pentahydrate (120 mg/kg, intragastric)- and motion (4 cm horizontal displacement at 1 Hz for 5 min)-induced emesis in Suncus murinus. A 30 min intraperitoneal pre-treatment with CP-122,721, CP-99,994, RP 67580 and FK 888 significantly (P < 0.05) antagonized nicotine-induced emesis with ID50 values of 2.1, 2.3, 13.5 and 19.2 mg/kg, respectively CP-100,263, the less active enantiomer of CP-99,994, was inactive at doses up to 10 mg/kg. Infusion of GR 82334, CP-122,721, CP-99,994 and FK 888 into the dorsal vagal complex of the hindbrain also antagonized nicotine-induced emesis yielding ID50 values of 1.1, 3.0, 3.3 and 58.0 microg/dorsal vagal complex, respectively RP 67580 and CP-100,263 were inactive. RP 67580 and FK 888 failed to antagonize copper sulphate-induced emesis but CP-122,721 and CP-99,994 were active yielding ID50 values of 2.2 and 3.0 mg/kg, i.p., respectively. CP-99,994 also completely prevented motion-induced emesis at 10 mg/kg, i.p. (P < 0.05) and RP 67580 produced a significant reduction of motion-induced emesis at 10 mg/kg, i.p. (P < 0.05). These studies provide evidence of a central site of action of tachykinin NK1 receptor antagonists to inhibit nicotine-induced emesis in S. murinus and confirm the broad profile of inhibitory action. The rank order of potency of the antagonists following the intra-dorsal vagal complex administration suggests that the S. murinus tachykinin NK1 receptor has a unique pharmacological profile.

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) in the ferret

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) has been investigated in the ferret. The PDE IV inhibitors studied were: RS14203, R-rolipram and CT-2450 (i.e. (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl ]N'-ethylurea), in addition to the less active enantiomers S-rolipram and CT-3405. Following oral administrations, different emetic profiles were observed with time. Emesis induced by RS14203 exhibited a dose-response relationship but no such relationship was seen for R-rolipram or CT-2450. The incidence of emesis was positively influenced by the dose of PDE IV inhibitors administered, allowing a rank order of potency: RS14203 > R-rolipram > S-rolipram > CT-2450 > CT-3405. PDE IV inhibitor-induced emesis was abolished by the tachykinin NK1 receptor antagonist, CP-99,994. No peripheral release of substance P by PDE IV inhibitors seems to be involved in triggering the emetic reflex since L-743,310, which only has peripheral NK1 receptor antagonist activity, was without effect. The implication of 5-HT3 receptors in PDE IV inhibitor-induced emesis was variable. Our results suggest that the PDE IV inhibitors studied are mixed peripheral-central emetogens. PDE IV inhibition itself could be plausible mechanism of action of these agents. However, whether emesis is mediated via a specific isoform of PDE IV remains to be established.

Randomized phase II study of the neurokinin 1 receptor antagonist CJ-11,974 in the control of cisplatin-induced emesis

PURPOSE

To determine the efficacy and safety of the neurokinin type 1 receptor antagonist CJ-11,974 for the control of high-dose cisplatin-induced emesis.

PATIENTS AND METHODS

A double-blind, randomized, phase II design with a group sequential stopping rule was used in this study. Sixty-one patients with cancer who were receiving cisplatin at a dose of at least 100 mg/m2 for the first time were enrolled. All patients received granisetron 10 microg/kg and dexamethasone 20 mg intravenously 30 minutes before they were given cisplatin. Patients were randomly assigned to two groups: group 1 received CJ-11,974 100 mg, and group 2 received placebo orally 30 minutes before and 12 hours after cisplatin and then twice daily on days 2 through 5 after cisplatin. The primary end point was the percentage of patients who developed delayed emesis (emesis on the second to fifth days after cisplatin).

RESULTS

Thirty patients were enrolled in group 1, and 31 patients were enrolled in group 2. Fifty-eight patients were assessable for efficacy. Complete control of emesis (expressed as the percentage of patients who had no emesis) was as follows: day 1, 85.7% (group 1) and 66.7% (group 2) (P = .090); days 2 through 5, 67.8% (group 1) and 36.6% (group 2) (P = .0425, adjusted); days 1 through 5, 64.3% (group 1) and 30% (group 2) (P = .009). Patients in group 1 experienced significantly less nausea than patients in group 2 on day 1 (P = .024). Treatment was well tolerated in both groups.

CONCLUSION

We conclude from this exploratory phase II trial that CJ-11,974 is superior to placebo in controlling cisplatin-induced delayed emesis and may provide additive benefit in acute emesis and nausea control when combined with a 5-hydroxytryptamine-3 receptor antagonist and dexamethasone. Additional larger trials are indicated to confirm the clinical value of CJ-11,974.

The tachykinin NK1 receptor antagonist GR205171 abolishes the retching activity of neurons comprising the central pattern generator for vomiting in dogs

Tachykinin NK1 receptor antagonists are known to act centrally and to have broad-spectrum antiemetic effects, but their precise site of action has not yet been defined. To identify this site, the effects of the NK1 receptor antagonist GR205171 on the activities of neurons comprising the central pattern generator (CPG) for vomiting were observed in decerebrate paralyzed dogs. A non-respiratory neuron in each of nine dogs was considered to be a CPG neuron based on its response to abdominal vagal stimulation, its location in the CPG area in the reticular formation dorsomedial to the retrofacial nucleus, its firing patterns in prodromal and retching phases and its response to apomorphine. In response to vagal stimulation at 3-10 Hz, the firing of these neurons transiently increased at the onset of stimulation (fast component), gradually increased again (slow component), and finally developed into rhythmic bursts synchronous with retching bursts of the phrenic and abdominal muscle nerves. GR205171 (25-50 microg/kg, i.v.) abolished the slow component and retching bursts in the neurons, and the retching activities of both nerves, but did not change the fast component. The responses of these neurons to repetitive pulse-train vagal stimulation exhibited a vigorous 'wind-up' and finally developed into retching bursts. Both the 'wind-up' phenomenon and retching bursts disappeared after the application of GR205171. These results suggest that the site of the antiemetic action of NK1 receptor antagonists is located in the CPG or in the pathway connecting the solitary nucleus to the CPG.

Structural optimization affording 2-(R)-(1-(R)-3, 5-bis(trifluoromethyl)phenylethoxy)-3-(S)-(4-fluoro)phenyl-4- (3-oxo-1,2,4-triazol-5-yl)methylmorpholine, a potent, orally active, long-acting morpholine acetal human NK-1 receptor antagonist

Structural modifications requiring novel synthetic chemistry were made to the morpholine acetal human neurokinin-1 (hNK-1) receptor antagonist 4, and this resulted in the discovery of 2-(R)-(1-(R)-3, 5-bis(trifluoromethyl)phenylethoxy)-3-(S)-(4-fluoro)phenyl-4-(3-ox o-1 ,2,4-triazol-5-yl)methyl morpholine (17). This modified compound is a potent, long-acting hNK-1 receptor antagonist as evidenced by its ability to displace [125I]Substance P from hNK-1 receptors stably expressed in CHO cells (IC50 = 0.09 +/- 0.06 nM) and by the measurement of the rates of association (k1 = 2.8 +/- 1.1 x 10(8) M-1 min-1) and dissociation (k-1 = 0.0054 +/- 0.003 min-1) of 17 from hNK-1 expressed in Sf9 membranes which yields Kd = 19 +/- 12 pM and a t1/2 for receptor occupancy equal to 154 +/- 75 min. Inflammation in the guinea pig induced by a resiniferatoxin challenge (with NK-1 receptor activation mediating the subsequent increase in vascular permeability) is inhibited in a dose-dependent manner by the oral preadmininstration of 17 (IC50 (1 h) = 0.008 mg/kg; IC90 (24 h) = 1.8 mg/kg), indicating that this compound has good oral bioavailbility and peripheral duration of action. Central hNK-1 receptor stimulation is also inhibited by the systemic preadministration of 17 as shown by its ability to block an NK-1 agonist-induced foot tapping response in gerbils (IC50 (4 h) = 0.04 +/- 0.006 mg/kg; IC50 (24 h) = 0.33 +/- 0.017 mg/kg) and by its antiemetic actions in the ferret against cisplatin challenge. The activity of 17 at extended time points in these preclinical animal models sets it apart from earlier morpholine antagonists (such as 4), and the piperidine antagonists 2 and 3 and could prove to be an advantage in the treatment of chronic disorders related to the actions of Substance P. In part on the basis of these data, 17 has been identified as a potential clinical candidate for the treatment of peripheral pain, migraine, chemotherapy-induced emesis, and various psychiatric disorders.

A neurokinin-1 receptor antagonist reduced hypersalivation and gastric contractility related to emesis in dogs

The roles of tachykinin neurokinin-1 (NK1) receptors in the induction of fictive retching, hypersalivation, and gastric responses associated with emesis induced by abdominal vagal stimulation were studied in paralyzed, decerebrated dogs. Vagal stimulation induced gradual increases in salivary secretion and activity of the parasympathetic postganglionic fibers to the submandibular gland, relaxation of the gastric corpus and antrum, and fictive retching. However, hypersalivation and increased nerve activity were suppressed and antral contractility was enhanced during fictive retching. An NK1 receptor antagonist, GR-205171, abolished the enhancement of antral contractility and fictive retching but had no effect on corpus and antral relaxation. Hypersalivation and increased nerve activity were inhibited by GR-205171 but were not completely abolished. Reflex salivation by lingual nerve stimulation was unaffected. These results suggest that GR-205171 acts on the afferent pathway in the bulb and diminishes hypersalivation and antral contraction related to emesis as well as fictive retching but does not affect gastric relaxation or hypersalivation induced by the vagovagal, vagosalivary, and linguosalivary reflexes.

Anti-emetic effects of a novel NK-1 receptor antagonist HSP-117 in ferrets

We have developed a non-peptide compound, HSP-117, antagonist of the tachykinin NK-1 receptor. Binding of 3H-substance P (SP) to the membranes of IM-9 cells was inhibited by the antagonists HSP-117 and CP-99,994, the inhibitory activity of HSP-117 being about 50-fold that of CP-99,994. The SP-induced firing responses of single neuron activity in slices of the nucleus tractus solitarius of ferrets were inhibited by 10 microM HSP-117. Intracerebroventricular injection of HSP-117 significantly inhibited retching and vomiting induced by copper sulphate and morphine and the inhibitory effect of HSP-117 on emesis was greater than that of CP-99,994. These results indicate that (1) HSP-117 is a potent anti-emetic agent, blocking NK-1 receptors in the nucleus tractus solitarius and (2) NK-1 receptors in the nucleus tractus solitarius play an important role in emesis induced by broad-spectrum emetic stimuli.

Derivation of a three-dimensional pharmacophore model of substance P antagonists bound to the neurokinin-1 receptor

Constrained systematic search was used in an exhaustive conformational analysis of a structurally diverse set of substance P (SP) antagonists to identify a unique hypothesis for their bound conformation at the neurokinin-1 receptor. In this conformation, two aromatic groups essential for high affinity adopt a perpendicular or edge-on arrangement. This pharmacophore hypothesis for the receptor-bound conformation was used in a comparative molecular field analysis (CoMFA) of an expanded set of SP antagonists, and the predictive ability of the resulting three-dimensional quantitative structure-activity relationship (3D-QSAR) was evaluated against a test set of SP antagonists different from those in the training set. This CoMFA model based on the Constrained Search alignment yielded significant cross-validated, conventional, and predictive r2 values equal to 0.70, 0.93, and 0.82, respectively. For comparison, the SP antagonists were forced into an alternative poorer alignment in which the two aromatic rings were parallel and then subjected to a CoMFA analysis. Both the parallel and perpendicular arrangements of the aromatic rings are seen in X-ray structures of SP antagonists and have been proposed as candidates for the receptor-bound conformation. The parallel (or stacked) conformation yielded a poorer correlation with a cross-validated r2 = 0.57, a conventional r2 = 0.90, and a predictive r2 = 0.78. Our results indicate that although both alignments could generate a reasonable CoMFA correlation, the stacked conformation is unlikely to be the receptor-bound conformation, as the covalent structure of the antagonists precludes a common geometry in which the aromatic rings are stacked.