Copyright ©ERS Journals Ltd 2004 Dual tachykinin NK1/NK2 antagonist DNK333 inhibits neurokinin A-induced bronchoconstriction in asthma patients1 Dept of Respiratory Diseases, Ghent University Hospital, 2 Academic Hospital, University of Brussels, Brussels, and 3 CHU-Sart-Tilman, University of Liège, Belgium, 4 Novartis Horsham Research Center, Horsham, UK CORRESPONDENCE: G. F. Joos, Dept of Respiratory Diseases, Ghent University Hospital, De Pintelaan 185, B-9000, Ghent, Belgium. Fax: 0032 92402 341. E-mail: guy.joos@ugent.be Keywords: asthma, bronchoconstriction, DNK333, neurokinin A, substance P, tachykinins
Received: November 7, 2002
This project was supported by a grant from Novartis, Belgium. Part of this paper was presented at the American Thoracic Society International Conference in May 2001, San Francisco, California.
Inhalation of neurokinin A (NKA) causes bronchoconstriction in patients with asthma. In vitro both tachykinin NK1 and NK2 receptors can mediate airway contraction. In this study the authors examined the effects of a single dose of the dual tachykinin NK1/NK2 receptor antagonist, DNK333, on NKA-induced bronchoconstriction in asthma. A total of 19 male adults with mild asthma completed a randomised, double-blind, placebo-controlled, crossover trial. Increasing concentrations of NKA (3.3x109 to 1.0x106 mol·mL1) were inhaled at 1 and 10 h intervals after a single oral dosing with either DNK333 (100 mg) or a placebo. It was observed that DNK333 did not affect baseline lung function but did protect against NKA-induced bronchoconstriction in those patients. The mean log10 provocative concentration causing a 20% fall in forced expiratory volume in one second for NKA was 5.6 log10 mol·mL1 at 1 h after DNK333 treatment and 6.8 log10 mol·mL1 after placebo. This was equivalent to a difference of 4.08 doubling doses, which decreased to a difference of 0.90 doubling doses 10 h after treatment. The results shown in this report indicate that DNK333 blocks neurokinin A-induced bronchoconstriction in patients with asthma. The sensory neuropeptides substance P and neurokinin A are members of the tachykinin peptide family, present within pulmonary sensory nerves and immune cells 1. In the airways they mainly interact with tachykinin (NK1, NK2) receptors to induce bronchoconstriction, bronchial hyperresponsiveness, mucus secretion, vasodilation, increased vascular permeability, and attraction and activation of inflammatory cells 24. Therefore, pharmacological agents that inhibit both NK1 and NK2 receptors may be useful in thetreatment of asthma. Bronchoconstriction is among the most prominent and extensively studied effects caused by tachykinins 57. Patients with asthma are more sensitive than nonasthmatic patients to the bronchoconstrictor effect of substance P and neurokinin A 6, 8, 9. Evidence from studies on guinea-pig airways suggests that both tachykinin NK1 and NK2 receptors may be involved in mediating tachykinin-induced bronchoconstriction 10, 11. Studies on isolated human airways have suggested that tachykinin-induced bronchoconstriction is mainly caused by stimulation of tachykinin NK2 receptors 6. However contraction induced by tachykinins in isolated small- and medium-sized human bronchi is partially mediated by tachykinin NK1 receptors 12, 13. The presence of both tachykinin NK1 and NK2 receptors at the level of airway smooth muscle has been demonstrated by immune histochemistry 14. Limited data exists on clinical trials examining the protective effects of tachykinin receptor antagonists against neurokinin A-induced bronchoconstriction, and up to now results have been less than impressive 15. The dual tachykinin NK1/NK2 antagonist FK 224 had only low potency effects against bronchoconstriction caused by neurokinin A in guinea-pigs and did not protect against neurokinin A-induced bronchoconstriction in patients with asthma 16. The relatively potent tachykinin NK2 receptor antagonists, such as the nonpeptide SR 48968 (saredutant) and the bicyclic peptide MEN 11420 (nepadutant), caused a small but significant inhibition in neurokinin A-induced bronchoconstriction in mild asthmatics 17, 18. In preclinical investigations, a newly identified dual tachykinin NK1/NK2 receptor antagonist, DNK333, was found to bind to cloned human NK1 and NK2 receptors. In addition, DNK333 inhibited bronchoconstriction induced by tachykinin NK1- and NK2-receptor agonists in guinea pigs and squirrel monkeys 1921. The present investigation utilised a randomised, double-blind, placebo-controlled, two-treatment crossover design to examine the effects of DNK333 onneurokinin A-induced bronchoconstriction in patients with asthma.
Study design This was a three-site, randomised, double-blind, placebo-controlled, crossover trial with a 1- to 4-week washout interval. The investigation was performed at three different university hospital departments of respiratory diseases. The protocol was approved by the ethics committee at each of these centres. Eligible patients provided written informed consent before entry into the study.
Patient selection Patients were excluded from the study if they had a significant smoking history (i.e. patients who had smoked within 1 yr of screening, or who had smoked >10 pack yr), an active lung disease other than allergic asthma, a respiratory tract infection, or an asthma exacerbation within 4 weeks prior to screening. Other exclusion criteria included the use of antiasthmatic agents (other than salbutamol/terbutaline) or nonsteroidal anti-inflammatory drugs within 4 weeks of the screening visit, a systemic disease within 3 months prior to screening, clinically significant laboratory abnormalities, a history of noncompliance to medical regimens, or a history of drug or alcohol abuse.
Study protocol During treatment period I, eligible patients were randomised to receive a single dose of either DNK333 (100 mg, orally) or a placebo in the morning, provided in identical bottles each containing 10 mL of solution. Prior to receiving the treatment, their baseline FEV1 measured and was required to be within 15% of that observed during screening in order for patients to proceed with testing. Otherwise, patient testing was rescheduled (maximum of three attempts). Measures obtained included predose laboratory tests and predose and postdose ECG measurements. At 1 h, after dosing and prior to receiving the first neurokinin A challenge, patients' FEV1 were measured. Neurokinin A challenges were performed 1 and 10 h after the single dose of DNK333 or placebo was administered. Additional blood samples were obtained 30 minutes before and immediately after the neurokinin A challenges to determine the plasma level ofDNK333. Patients returned 2472 h postdose for safety assessments. A 1- to 4-week washout period followed treatment period I. During treatment period II, patients received the alternative treatment to that given in treatment period I. All tests and follow-up procedures were repeated as performed in treatment period I.
Neurokinin A inhalation challenge tests Neurokinin A (MW 1133.34; Peninsula, St Helens, UK) was diluted in saline containing 1% human serum albumin (Behringwerke, Marburg, Germany). The neurokinin A dilutions were prepared on the morning of each challenge and kept on ice until nebulisation. Aerosols were produced using a Mallinckrodt jet nebuliser (Mallinckrodt Diagnostica, Petten, The Netherlands) 17. The patient inhaled this aerosol from the bag in 2 min by quiet tidal breathing through a 3-way valve and a mouthpiece until the collapse of the bag. Supplemental oxygen was supplied (4 L·min1, inspiratory oxygen fraction=0.995) through the mouthpiece. The patients performed the inhalation in a sitting position with their nose occluded by a clip. Nebulisations of the different concentrations were initiated at 10-min intervals and continued until their FEV1 fell 20% below the respective postdiluent baseline at either 3 or 7 min after start of inhalation. The neurokinin A challenge was stopped when PC20 NKA could be calculated. If FEV1 did not reach a 20% fall after inhalation of neurokinin A at 1.0x106 mol·mL1, testing was stopped. In these patients, a PC20 value of 3.3x106 (0.5 log higher on the log10 scale) was assigned.
Pharmacokinetic and safety measures
Statistical analysis
Patients A total of 19 male patients, with an average age of 27.9±7.19 yrs, were randomised, and all completed the study. Their mean±sd baseline FEV1 was 4.02±0.78 L, which was 93.6% of the predicted value. Their mean±sd PC20 for methacholine (mg·mL1), was 2.26±2.16 (table 1
DNK333 and baseline lung function A single dose of DNK333 did not alter baseline lung function measured 1 h after dosing and before the neurokinin A challenge. At 1 h, postdosing, FEV1 was higher in the DNK333 group when compared with placebo. The treatment difference (DNK333 minus placebo) was 0.098 L with an associated 95% confidence interval (CI) of 0.0090.206. A p-value of 0.071 indicates that this difference was not statistically significant.
Effect of DNK333 on neurokinin A-induced bronchoconstriction
Of the 19 patients who completed the study, 14 patients completed the neurokinin A challenge at the 10-h postdose time point. At the 10 h postdose, the log10 PC20 NKA was similar after DNK333 or placebo (p=0.13) Due to the nature of the data, a sensitivity analysis was done to confirm the results of the ANOVA. This was a nonparametric equivalent method using the Wilcoxon rank-sum test based on within patient period differences. The results confirmed the results from the ANOVA presented above. In particular, at 1 h postdosing, there was a significant difference between DNK333 and placebo in PC20 for NKA (p<0.001), while at 10 h postdosing, there was no significant difference (p=0.10).
DNK333 plasma concentration and neurokinin A-induced bronchoprotection
Safety and adverse events
In this study the dual tachykinin NK1/NK2 receptor antagonist DNK333 inhibited neurokinin A-induced bronchoconstriction in patients with asthma. A protective effect was observed at 1 h but not at 10 h postdose. The tachykinin receptor antagonist did not affect baseline lung function and was well tolerated. This is the first report of a tachykinin receptor antagonist demonstrating a large inhibition of neurokinin A -induced bronchoconstriction in patients with asthma. The protective effect of DNK333 was evident in 15 out of the 18 patients investigated, by a significant rightward shift of the dose-response curve for neurokinin A 1 h following treatment withDNK333. The degree of bronchoprotection offered by DNK333 against a challenge with neurokinin A was much larger than in studies with other tachykinin receptor antagonists. Using a similar study protocol the less potent dual tachykinin NK1/NK2 receptor antagonist FK224 had noeffect on neurokinin A-induced bronchoconstriction in patients with asthma 16. The tachykinin NK2 receptor antagonists SR48968 (saredutant) and MEN11420(nepadutant) were evaluated in similar patient groups and with similar study methodology, but had a rather limited protective effect on the bronchoconstrictor effect of inhaled neurokinin A 17, 18. The shift in the concentration response curve for neurokinin A was 35 in the studies with the tachykinin NK2 receptor antagonists, whereas in the present study a shift of at least 1620 was observed. Moreover, this amount of shift is an underestimated value, since in most patients a 20% decrease in FEV1 was not observed on the treatment day with DNK333. DNK333 is a dual NK1/NK2 tachykinin receptor antagonist. In ligand binding studies DNK333 binds to cloned human tachykinin NK1 and NK2 receptors with similar affinity (inhibitory concentration at 50% values 4.8 and 5.5 nM) 19. At the start of our study the specificity of DNK333 for tachykinin receptors had been studied in vivo in animals and in vitro on human colonic mucosa cells. From these data it appeared that DNK333 was a specific tachykinin antagonist that did not affect cholinergic responses. So a methacholine provocation arm was not included in this study 20, 21. The inhibiting effect of DNK333 on neurokinin A-induced bronchoconstriction in patients with asthma suggests that both tachykinin NK1 and NK2 receptors are involved in the bronchoconstrictor effect of inhaled neurokinin A. Although tachykinin NK2 receptors mediate most of the direct smooth muscle contracting effect of neurokinin A 6, it has become clear in recent years that tachykinin NK1 receptors can contribute to tachykinin-induced bronchoconstriction in man. Indeed, tachykinin NK1 receptors were found to be involved in tachykinin-induced contraction of small and medium sized human isolated airways 12, 13. This correlates with the demonstration by immune histochemistry of the presence of both tachykinin NK1 and NK2 receptors at the level of airway smooth muscle 14. Moreover, an important part of the bronchoconstrictor effect of inhaled neurokinin A is indirect and probably mediated by tachykinin NK1 receptors located on inflammatory and/or neuronal cells 23, 24. So, based on the available evidence, it is to be expected that a dual tachykinin NK1/NK2 tachykinin receptor antagonist offers a better protection against neurokinin A-induced bronchoconstriction than a tachykinin NK2 receptor antagonist. This study does not allow however to determine the relative contribution of each tachykinin receptor subtype to the bronchoconstrictor effect of neurokinin A in asthma. It may be interesting in future experiments to employ a tachykinin NK1 and a tachykinin NK2 receptor antagonist and their combination to study the relative contribution of each tachykinin receptor. Plasma concentrations of DNK333 did not correlate withthe magnitude of the protective effect of DNK333. Inthe current investigation, no relationship was observed between the plasma drug concentration and the magnitude ofbronchoprotection at either 1 or 10 h postdosing. One possible reason for the absence of such a correlation is that the blood sampling and the neurokinin A inhalation challenge did not occur close enough together in time to observe a relationship. Another possible explanation for the absence of a correlation is that DNK333 concentrations and bronchoprotection relate to different compartments of the body (i.e. plasma or the central compartments in the lungs). Bronchoprotection and DNK333 concentrations may be correlated inthe lungs, but we do not know the relationship between plasma and lung concentrations of the drug. Our study indicates that the dual tachykinin neurokinin 1/neurokinin 2 receptor antagonist DNK333 exerts significant protection against tachykinin-related bronchoconstriction in patients with asthma. These findings provide further evidence of an important role of both neurokinin 1 and neurokinin 2receptors in tachykinin-induced airway constriction in asthmatic patients. Given the significant level of bronchoprotection observed with DNK333 clinical trials examining the efficacy and safety of this agent in patients with asthma are warranted.
The authors gratefully acknowledge the invaluable assistance of V. Collart, J. Sele and that of the medical, laboratory, and technical personnel at Ghent University Hospital, Academic Hospital, University of Brussels, and the CHU-Sart-Tilman, University of Liège. The authors would also like to thank all Novartis colleagues who contributed to the planning, execution, and evaluation of this study.
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