Abstract
Cough is among the most common complaints for which patients worldwide seek medical attention. In a majority of patients with chronic cough (defined as cough of greater than 8 weeks’ duration), successful management results from a thorough evaluation and treatment of underlying causes. In a subgroup of patients, however, cough proves refractory to therapeutic trials aimed at known reversible causes of chronic cough. Such patients are appropriately termed as having refractory chronic cough. At present, safe and effective medications are lacking for this challenging patient population. Currently available therapeutic options are usually ineffective or achieve antitussive effect at the expense of intolerable side effects, typically sedation. Fortunately, the past decade has witnessed great progress in elucidating underlying mechanisms of cough. From that knowledge, aided by the development of validated instruments to measure objective and subjective cough-related end points, numerous antitussive drug development programs have emerged. The most active area of inquiry at present involves antagonists of the purinergic P2X receptors. Indeed, four clinical programs (one in Phase 3 and three in Phase 2) are currently underway investigating antagonists of receptors comprised entirely or partially of the P2X3 subunit as potential antitussive medications. Herein we review the foundation on which P2X receptor antagonists were developed as potential antitussive medications and provide an update on current clinical trials.
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References
Hsiao C-J, Cherry DK, Beatty PC et al (2010) National ambulatory medical care survey: 2007 summary. Natl Health Stat Report 27:1–32
Dicpinigaitis PV, Morice AH, Birring SS et al (2014) Antitussive drugs—past, present, and future. Pharmacol Rev 66:468–512
Irwin RS, French CL, Chang AB et al (2018) Classification of cough as a symptom in adults and management algorithms: chest guideline and expert panel report. Chest 153:196–209
Morice AH, Millqvist E, Bieksiene K et al (2020) ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. Eur Respir J. https://doi.org/10.1183/13993003.01136-2019
Morice AH, Millqvist E, Belvisi MG et al (2014) Expert opinion on the cough hypersensitivity syndrome in respiratory medicine. Eur Respir J 44:1132–1148
Morice AH, Menon MS, Mulrennan SA et al (2007) Opiate therapy in chronic cough. Am J Respir Crit Care Med 175:312–315
Ryan MA, Cohen SM (2016) Long-term follow-up of amitriptyline treatment for idiopathic cough. Laryngoscope 126:2758–2763
Ryan NM, Birring SS, Gibson PG (2012) Gabapentin for refractory chronic cough: a randomised, double-blind, placebo-controlled trial. Lancet 380:1583–1589
Vertigan AE, Kapela SL, Ryan NM et al (2016) Pregabalin and speech pathology combination therapy for refractory chronic cough: a randomized controlled trial. Chest 149:639–648
Burnstock G (1972) Purinergic nerves. Pharmacol Rev 24(3):509–581
Dalziel HH, Westfall DP (1994) Receptors for adenine nucleotides and nucleosides: subclassification, distribution, and molecular characterization. Pharmacol Rev 46(4):449–466
Fredholm BB, Abbracchio MP, Burnstock G, Daly JW, Harden TK, Jacobson KA, Leff P, Williams M (1994) Nomenclature and classification of purinoceptors. Pharmacol Rev 46(2):143–156
Bleehen T, Keele CA (1977) Observations on the algogenic actions of adenosine compounds on the human blister base preparation. Pain 3(4):367–377
Haskell CM, Wong M, Williams A, Lee LY (1996) Phase I trial of extracellular adenosine 5'-triphosphate in patients with advanced cancer. Med Pediatr Oncol 27(3):165–173
Basoglu OK, Pelleg A, Essilfie-Quaye S, Brindicci C, Barnes PJ, Kharitonov SA (2005) Effects of aerosolized adenosine 5'-triphosphate vs adenosine 5'-monophosphate on dyspnea and airway caliber in healthy nonsmokers and patients with asthma. Chest 128(4):1905–1909
Lee WC, Chiang PH, Tain YL, Wu CC, Chuang YC (2012) Sensory dysfunction of bladder mucosa and bladder oversensitivity in a rat model of metabolic syndrome. PLoS ONE 7(9):e45578
Basoglu OK, Barnes PJ, Kharitonov SA, Pelleg A (2015) Effects of aerosolized Adenosine 5'-Triphosphate in smokers and patients with COPD. Chest 148(2):430–435
Smith JA, Kitt M, Butera P, Ford A (2016) The effect of P2X3 antagonism (AF-219) on experimentally evoked cough in healthy volunteers and chronic cough patients. Thorax 71(Suppl 3):A17
Fowles HE, Rowland T, Wright C, Morice A (2017) Tussive challenge with ATP and AMP: does it reveal cough hypersensitivity? Eur Respir J 49(2):1601452
Morice AH, Kitt MM, Ford AP, Tershakovec AM, Wu WC, Brindle K, Thompson R, Thackray-Nocera S, Wright C (2019) The effect of gefapixant, a P2X3 antagonist, on cough reflex sensitivity: a randomised placebo-controlled study. Eur Respir J 54(1):1900439
Lambrecht G (2000) Agonists and antagonists acting at P2X receptors: selectivity profiles and functional implications. Naunyn Schmiedebergs Arch Pharmacol 362(4–5):340–350
Kumahashi N, Naitou K, Nishi H, Oae K, Watanabe Y, Kuwata S, Ochi M, Ikeda M, Uchio Y (2011) Correlation of changes in pain intensity with synovial fluid adenosine triphosphate levels after treatment of patients with osteoarthritis of the knee with high-molecular-weight hyaluronic acid. Knee 18(3):160–164
Ferguson DR, Kennedy I, Burton TJ (1997) ATP is released from rabbit urinary bladder epithelial cells by hydrostatic pressure changes–a possible sensory mechanism? J Physiol 505(Pt 2):503–511
Vlaskovska M, Kasakov L, Rong W, Bodin P, Bardini M, Cockayne DA, Ford AP, Burnstock G (2001) P2X3 knock-out mice reveal a major sensory role for urothelially released ATP. J Neurosci 21(15):5670–5677
Lommatzsch M, Cicko S, Müller T, Lucattelli M, Bratke K, Stoll P, Grimm M, Dürk T, Zissel G, Ferrari D, Di Virgilio F, Sorichter S, Lungarella G, Virchow JC, Idzko M (2010) Extracellular adenosine triphosphate and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 181(9):928–934
Huang YJ, Maruyama Y, Dvoryanchikov G, Pereira E, Chaudhari N, Roper SD (2007) The role of pannexin 1 hemichannels in ATP release and cell-cell communication in mouse taste buds. Proc Natl Acad Sci USA 104(15):6436–6441
Birder L, Kullmann FA, Lee H, Barrick S, de Groat W, Kanai A, Caterina M (2007) Activation of urothelial transient receptor potential vanilloid 4 by 4alpha-phorbol 12,13-didecanoate contributes to altered bladder reflexes in the rat. J Pharmacol Exp Ther 323(1):227–235
Gevaert T, Vriens J, Segal A, Everaerts W, Roskams T, Talavera K, Owsianik G, Liedtke W, Daelemans D, Dewachter I, Van Leuven F, Voets T, De Ridder D, Nilius B (2007) Deletion of the transient receptor potential cation channel TRPV4 impairs murine bladder voiding. J Clin Invest 117(11):3453–3462
Seminario-Vidal L, Okada SF, Sesma JI, Kreda SM, van Heusden CA, Zhu Y, Jones LC, O'Neal WK, Penuela S, Laird DW, Boucher RC, Lazarowski ER (2011) Rho signaling regulates pannexin 1-mediated ATP release from airway epithelia. J Biol Chem 286(30):26277–26286
Xia J, Lim JC, Lu W, Beckel JM, Macarak EJ, Laties AM, Mitchell CH (2012) Neurons respond directly to mechanical deformation with pannexin-mediated ATP release and autostimulation of P2X7 receptors. J Physiol 590(10):2285–2304
Pinheiro AR, Paramos-de-Carvalho D, Certal M, Costa MA, Costa C, Magalhães-Cardoso MT, Ferreirinha F, Sévigny J, Correia-de-Sá P (2013) Histamine induces ATP release from human subcutaneous fibroblasts, via pannexin-1 hemichannels, leading to Ca2+ mobilization and cell proliferation. J Biol Chem 288(38):27571–27583
Kennedy C (2015) ATP as a cotransmitter in the autonomic nervous system. Auton Neurosci 191:2–15
Yamamoto K, Sokabe T, Ohura N, Nakatsuka H, Kamiya A, Ando J (2003) Endogenously released ATP mediates shear stress-induced Ca2+ influx into pulmonary artery endothelial cells. Am J Physiol 285(2):H793–H803
Tarran R, Button B, Boucher RC (2006) Regulation of normal and cystic fibrosis airway surface liquid volume by phasic shear stress. Annu Rev Physiol 68:543–561
Weigand LA, Ford AP, Undem BJ (2012) A role for ATP in bronchoconstriction-induced activation of guinea pig vagal intrapulmonary C-fibres. J Physiol 590(16):4109–4120
Zimmermann H, Zebisch M, Sträter N (2012) Cellular function and molecular structure of ecto-nucleotidases. Purinergic Signal 8(3):437–502
Surprenant A, North RA (2009) Signaling at purinergic P2X receptors. Annu Rev Physiol 71:333–359
Brake AJ, Wagenbach MJ, Julius D (1994) New structural motif for ligand-gated ion channels defined by an ionotropic ATP receptor. Nature 371(6497):519–523
Cockayne DA, Hamilton SG, Zhu QM, Dunn PM, Zhong Y, Novakovic S, Malmberg AB, Cain G, Berson A, Kassotakis L, Hedley L, Lachnit WG, Burnstock G, McMahon SB, Ford AP (2000) Urinary bladder hyporeflexia and reduced pain-related behaviour in P2X3-deficient mice. Nature 407(6807):1011–1015
Kwong K, Kollarik M, Nassenstein C, Ru F, Undem BJ (2008) P2X2 receptors differentiate placodal vs. neural crest C-fiber phenotypes innervating guinea pig lungs and esophagus. Am J Physiol 295(5):L858–L865
Cockayne DA, Dunn PM, Zhong Y, Rong W, Hamilton SG, Knight GE, Ruan HZ, Ma B, Yip P, Nunn P, McMahon SB, Burnstock G, Ford AP (2005) P2X2 knockout mice and P2X2/P2X3 double knockout mice reveal a role for the P2X2 receptor subunit in mediating multiple sensory effects of ATP. J Physiol 567(Pt 2):621–639
Finger TE, Danilova V, Barrows J, Bartel DL, Vigers AJ, Stone L, Hellekant G, Kinnamon SC (2005) ATP signaling is crucial for communication from taste buds to gustatory nerves. Science 310(5753):1495–1499
Pelleg A, Hurt CM (1996) Mechanism of action of ATP on canine pulmonary vagal C fibre nerve terminals. J Physiol 490(Pt 1):265–275
Kwong K, Hong JL, Morton RF, Lee LY (1998) Role of pulmonary C fibers in adenosine-induced respiratory inhibition in anesthetized rats. J Appl Physiol 84(2):417–424
Burki NK, Dale WJ, Lee LY (2005) Intravenous adenosine and dyspnea in humans. J Appl Physiol 98(1):180–185
Chou YL, Mori N, Canning BJ (2018) Opposing effects of bronchopulmonary C-fiber subtypes on cough in guinea pigs. Am J Physiol 314(3):R489–R498
Chuaychoo B, Lee MG, Kollarik M, Pullmann R Jr, Undem BJ (2006) Evidence for both adenosine A1 and A2A receptors activating single vagal sensory C-fibres in guinea pig lungs. J Physiol 575(Pt 2):481–490
Undem BJ, Chuaychoo B, Lee MG, Weinreich D, Myers AC, Kollarik M (2004) Subtypes of vagal afferent C-fibres in guinea-pig lungs. J Physiol 556(Pt 3):905–917
Nassenstein C, Taylor-Clark TE, Myers AC, Ru F, Nandigama R, Bettner W, Undem BJ (2010) Phenotypic distinctions between neural crest and placodal derived vagal C-fibres in mouse lungs. J Physiol 588(Pt 23):4769–4783
Wang J, Kollarik M, Ru F, Sun H, McNeil B, Dong X, Stephens G, Korolevich S, Brohawn P, Kolbeck R, Undem B (2017) Distinct and common expression of receptors for inflammatory mediators in vagal nodose versus jugular capsaicin-sensitive/TRPV1-positive neurons detected by low input RNA sequencing. PLoS ONE 12(10):e0185985
Kollarik M, Ru F, Undem BJ (2019) Phenotypic distinctions between the nodose and jugular TRPV1-positive vagal sensory neurons in the cynomolgus monkey. NeuroReport 30(8):533–537
Canning BJ, Mazzone SB, Meeker SN, Mori N, Reynolds SM, Undem BJ (2004) Identification of the tracheal and laryngeal afferent neurones mediating cough in anaesthetized guinea-pigs. J Physiol 557(Pt 2):543–558
Muroi Y, Ru F, Chou YL, Carr MJ, Undem BJ, Canning BJ (2013) Selective inhibition of vagal afferent nerve pathways regulating cough using Nav 1.7 shRNA silencing in guinea pig nodose ganglia. Am J Physiol 304(11):R1017–R1023
Kamei J, Takahashi Y, Yoshikawa Y, Saitoh A (2005) Involvement of P2X receptor subtypes in ATP-induced enhancement of the cough reflex sensitivity. Eur J Pharmacol 528(1–3):158–161
Kamei J, Takahashi Y (2006) Involvement of ionotropic purinergic receptors in the histamine-induced enhancement of the cough reflex sensitivity in guinea pigs. Eur J Pharmacol 547(1–3):160–164
Garceau D, Chauret N (2019) BLU-5937: a selective P2X3 antagonist with potent anti-tussive effect and no taste alteration. Pulm Pharmacol Ther 56:56–62
Abdulqawi R, Dockry R, Holt K et al (2015) P2X3 receptor antagonist (AF-219) in refractory chronic cough: a randomised, double-blind, placebo-controlled phase-2 study. Lancet 385:1198–1205
Smith JA, Kitt MM, Morice AH, Birring SS, McGarvey LP, Sher MR, Li YP, Wu WC, Xu ZJ, Muccino DR, Ford AP, Protocol 012 Investigators (2020) Gefapixant, a P2X3 receptor antagonist, for the treatment of refractory or unexplained chronic cough: a randomised, double-blind, controlled, parallel-group, phase 2b trial. Lancet Respir Med S2213–2600(19):30471
Vandenbeuch A, Larson ED, Anderson CB, Smith SA, Ford AP, Finger TE, Kinnamon SC (2015) Postsynaptic P2X3-containing receptors in gustatory nerve fibres mediate responses to all taste qualities in mice. J Physiol 593(5):1113–1125
Niimi A, Ishihara H, Hida H, et al (2019) Phase 2a randomised, double-blind, placebo-controlled crossover study of a novel P2X3 receptor antagonist S-600918 in patients with refractory cough [abstract] Eur Respir J 54: Suppl 63, RCT452
Morice AH, Smith J, McGarvey L et al (2020) Safety and efficacy of BAY 1817080, a P2X3 receptor antagonist, in patients with refractory chronic cough (RCC)[abstract]. Am J Respir Crit Care Med 201:A7648
Smith JA, Kitt MM, Butera P et al (2020) Gefapixant in two randomised dose-escalation studies in chronic cough. Eur Respir J. https://doi.org/10.1183/13993003.01615-2019
Muccino D, Morice AH, Birring S et al (2019) Rationale and design of two Phase 3 randomized controlled trials (COUGH-1 and COUGH-2) of gefapixant, a P2X3 receptor antagonist, in refractory and unexplained chronic cough [abstract]. Am J Respir Crit Care Med 199:A4700
Birring SS, Prudon B, Aj C et al (2003) Development of a symptom specific health status measure for patients with chronic cough: leicester cough questionnaire (LCQ). Thorax 58:339–343
Garceau D, Chauret N, Harvey L (2020) Abstracts from the 7th American cough conference. BLU-5937, A highly selective P2X3 homotrimeric receptor antagonist, exhibits excellent pharmacokinetic and safety profile including improved taste safety profile in healthy subjects. Lung 198:35–41
Niimi A, Ishihara H, Hida H et al (2020) Phase 2a randomized, double-blind, placebo-controlled, crossover study of a P2X3 receptor antagonist S-600918: effects on health-related quality of life in patients with refractory chronic cough [abstract]. Am J Respir Crit Care Med 201:A7647
Eccles R (2020) The powerful placebo effect in cough: relevance to treatment and clinical trials. Lung 198:13–21
Birrell MA, Belvisi MG, Grace M et al (2009) TRPA1 agonists evoke coughing in guinea pig and human volunteers. Am J Respir Crit Care Med 180:1042–1047
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PVD and LPM have served as consultants for Merck, Bellus Health, Bayer and Shionogi. BJC has served as a consultant for Merck and Bellus Health. LPM has participated as a clinical trialist for Merck, Bellus Health, Bayer and Shionogi.
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Dicpinigaitis, P.V., McGarvey, L.P. & Canning, B.J. P2X3-Receptor Antagonists as Potential Antitussives: Summary of Current Clinical Trials in Chronic Cough. Lung 198, 609–616 (2020). https://doi.org/10.1007/s00408-020-00377-8
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DOI: https://doi.org/10.1007/s00408-020-00377-8