We describe the pharmacological and pharmacokinetic profiles of SCH 486757, a nociceptin/orphanin FQ peptide (NOP) receptor agonist that has recently entered human clinical trials for cough. SCH 486757 selectively binds human NOP receptor (Ki=4.6±0.61nM) over classical opioid receptors. In a guinea pig capsaicin cough model, SCH 486757 (0.01–1mg/kg) suppressed cough at 2, 4, and 6h post oral administration with a maximum efficacy occurring at 4h equivalent to codeine, hydrocodone, dextromethorphan and baclofen. The antitussive effects of SCH 486757 (3.0mg/kg, p.o.) was blocked by the NOP receptor antagonist J113397 (12mg/kg, i.p.) but not by naltrexone (10mg/kg, p.o.). SCH 486757 does not produce tolerance to its antitussive activity after a 5-day BID dosing regimen. After acute and chronic dosing paradigms, SCH 486757 (1mg/kg) inhibited capsaicin-evoked coughing by 46±9% and 40±11%, respectively. In a feline mechanically-evoked cough model, SCH 486757 produces a maximum inhibition of cough and expiratory abdominal electromyogram amplitude of 59 and 61%, respectively. SCH 486757 did not significantly affect inspiratory electromyogram amplitude. We examined the abuse potential of SCH 486757 (10mg/kg, p.o.) in a rat conditioned place preference procedure which is sensitive to classical drugs of abuse, such as amphetamine and morphine. SCH 486757 was without effect in this model. Finally, SCH 486757 displays a good oral pharmacokinetic profile in the guinea pig, rat and dog. We conclude that SCH 486757 has a favorable antitussive profile in preclinical animal models.

The adenosine A(2A) receptor has been implicated in the underlying biology of various neurological and psychiatric disorders, including Parkinson's disease (PD) and depression. Preladenant and SCH 412348 [7-[2-[4-2,4-difluorophenyl]-1-piperazinyl]ethyl]-2-(2-furanyl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine] are potent competitive antagonists of the human A(2A) receptor (K(i) = 1.1 and 0.6 nM, respectively) and have >1000-fold selectivity over all other adenosine receptors, making these compounds the most selective A(2A) receptor antagonists reported to date. Both compounds attenuate hypolocomotion induced by the A(2A) receptor agonist CGS-21680 [2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosine], suggesting that they inhibit A(2A) receptor activity in vivo. Their high degree of selectivity and robust in vivo activity make preladenant and SCH 412348 useful tools to investigate the role of the A(2A) receptor system in animal models of PD and depression. Oral administration of preladenant and SCH 412348 (0.1-1 mg/kg) to rats potentiated 3,4-dihydroxy-L-phenylalanine (L-Dopa)-induced contralateral rotations after 6-hydroxydopamine lesions in the medial forebrain bundle and potently attenuated the cataleptic effects of haloperidol. Preladenant (1 mg/kg) inhibited L-Dopa-induced behavioral sensitization after repeated daily administration, which suggests a reduced risk of the development of dyskinesias. Finally, preladenant and SCH 412348 exhibited antidepressant-like profiles in models of behavioral despair, namely the mouse tail suspension test and the mouse and rat forced swim test. These studies demonstrate that preladenant and SCH 412348 are potent and selective A(2A) receptor antagonists and provide further evidence of the potential therapeutic benefits of A(2A) receptor inhibition in PD (with reduced risk of dyskinesias) and depression (one of the primary nonmotor symptoms of PD).

Background: Previous studies have demonstrated that nociceptin/orphanin FQ (N/OFQ), the endogenous peptide ligand for the G-protein-coupled NOP receptor, inhibits cough in experimental models. SCH 225288 is a nonpeptide, orally active NOP agonist that may provide the foundation for the development of novel treatments for cough. Methods: First we characterized the selectivity of SCH 225288 in human receptor binding assays. Afterwards, the antitussive activity of SCH 225288 was studied in three mechanistically distinct cough models. Specifically, we observed the cough-suppressant effect of SCH 225288 in a guinea pig capsaicin irritant-evoked cough model, a feline mechanically induced cough model and finally in a canine Bordetella bronchiseptica disease model. Results: SCH 225288 selectively binds human NOP receptor (Ki = 0.38 ± 0.02 nmol/l) over classical opioid receptors (COR). In a guinea pig capsaicin cough model, SCH 225288 (0.1–1 mg/kg) suppressed cough at 2, 4, and 6 h after oral administration. The antitussive effect of SCH 225288 (3.0 mg/kg, p.o.) was blocked by the NOP antagonist J113397 (12 mg/kg, i.p.) but not by the classical opioid receptor (COR) antagonist, naltrexone (3.0 mg/kg, i.p.). In the anesthetized cat, we evaluated the effects of SCH 225288 given either intravenously or via the intravertebral artery against the increases in cough number and respiratory expiratory and inspiratory muscle (rectus abdominis and parasternal) electromyographic (EMG) activities due to perturbations of the intrathoracic trachea. SCH 225288 (0.03–3.0 mg/kg, i.v.) inhibited both cough number and abdominal EMG amplitudes. Similarly, SCH 225288 (0.001–0.3 mg/kg) administered intra-arterially also diminished cough number and abdominal EMG amplitudes. No significant effect of the drug was noted on parasternal EMG activity. Finally, we studied the antitussive actions of SCH 225288 (1.0 mg/kg) in a canine B. bronchiseptica disease model. In this model, dogs were challenged intranasally with B. bronchiseptica. Comparisons were made between a vehicle group, an SCH 225288 (1.0 mg/kg, p.o., q.d.) and a butorphanol (0.6 mg/kg, p.o., b.i.d.) group on the mean change in cough scores from baseline values and days 6–9 after B. bronchiseptica challenge. SCH 225288 (1.0 mg/kg, p.o., q.d.) displayed a positive antitussive tendency (p = 0.06) to inhibit B. bronchiseptica cough whereas butorphanol (0.6 mg/kg, p.o., b.i.d.) was devoid of antitussive activity. Conclusions: Taken together, the present data show that SCH 225288 is a potent and effective antitussive agent in animal models of cough. Furthermore, these findings indicate that NOP agonists represent a promising new therapeutic approach for the treatment of cough without the side effect liabilities associated with opioid antitussives.

Department of Neurobiology, Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA. (RAH, GBV, JEL, MEC-W, GAH, LEP, CF, YZ, EMP, JCH) Department of Neurobiology, Schering-Plough Research Institute, San Raffaele Science Park, Via Olgettina, 58, 20132, Milan, Italy. (RB, AF, SF, FI, EN, AR) Department of Chemical Research, Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA. (BRN, AWS) JPET Fast Forward. Published on March 30, 2009 as DOI:10.1124/jpet.108.149617

The objective of the present experiments was to study the effects of pulmonary inflammation induced by subacute Sulfur-dioxide (SO2) exposure on capsaicin-induced responses in isolated primary vagal sensory neurons and cough. Additionally, we examined the effects of SO2 exposure on respiratory function and lung histology. All experiments were conducted 24 h after 4 days of subacute SO2 (1000 ppm, 3 h/day for 4 days) exposure. In in vitro experiments, intracellular Ca2+ concentrations were measured in single nodose ganglia cells isolated from SO2 treated and control guinea pigs, using a fluorescence-based methodology. In nodose ganglia cells from SO2-exposed animals, intracellular Ca2+ responses evoked by capsaicin (1×10−7 and 1×10−6 M) were significantly augmented (87% and 59%, respectively) compared to nodose ganglia from control animals. In vivo experiments, cough responses induced by a submaximal dose of aerosolized capsaicin (30 μM) were increased approximately 50% in SO2 exposed animals compared to control animals. The enhanced cough response produced by SO2 was inhibited by the corticosteroid, dexamethasone (10 mg/kg, p.o. b.i.d for 4 days and 10 mg/kg, p.o. once on day 5). In separate experiments, guinea pigs exposed to SO2 displayed a decrease in respiratory frequency and minute ventilation and an increase in enhanced pause (PenH), a surrogate measure for pulmonary obstruction. Associated with the SO2-induced increase in cough and changes in respiratory parameters was an increase in BAL neutrophils. BAL neutrophil counts were 5±4 and 691±141 cells×103/ml for air and SO2-exposed animals, respectively. The neutrophillic inflammation induced by SO2 was attenuated by dexamethasone treatment. Finally, staining for collagen, smooth muscle and goblet cells showed inflammation, remodeling and goblet cell metaphasia in the SO2-exposed animals. Our results demonstrate that SO2 exposure enhances TRPV1 receptor function at the level of the nodose ganglia. This effect occurs in parallel with an increase sensitivity of the cough response to capsaicin.