Current and novel bronchodilators in respiratory disease.

REVIEW URRENT C OPINION

Current and novel bronchodilators in respiratory disease Domenico Spina

Purpose of review b2-Agonists and muscarinic antagonists are widely used to treat asthma and chronic obstructive pulmonary disease (COPD), and a number of novel drug targets are being investigated for potential clinical utility. This review will summarize current developments in the field. Recent findings The clinical effectiveness of a number of once a day inhaled b2-agonists and muscarinic antagonists is a major advance providing sustained bronchodilation in asthma and COPD. The identification of novel targets (e.g. bitter taste receptor TASR2), the demonstration of clinical effectiveness of others [e.g. phosphodiesterase (PDE)3/4] and exploring the potential of inverse agonists/biased agonists are evidence of continuing interest in the development of novel bronchodilators. Summary Novel long-acting b2-agonists (e.g. indacaterol, vilanterol, olodaterol and carmoterol) and muscarinic antagonists (e.g. tiotropium, aclidinium, glycopyrronium and umeclidinium bromide) document sustained bronchodilation and their combination provides additional benefits over monotherapy. Not surprisingly, inhaled long-acting b2-agonist and long-acting muscarinic antagonists remain the drugs of choice for maintenance bronchodilation. However, there is a continued interest in developing novel bronchodilators illustrated by the clinical effectiveness of long acting mixed PDE3/4 inhibitors, vasointestinal peptide adenylyl cyclase agonists and inverse agonists/biased agonists for the b2-adrenoceptor, and the identification of intracellular (e.g. Rho kinase, exchange proteins activated by cyclic AMP) and cell surface (e.g. TAS2R, natriuretic peptide receptor) targets. Keywords asthma, bronchodilation, COPD, long-acting b2-agonist, long-acting muscarinic antagonist

INTRODUCTION

b2-AGONISTS

b2-Agonists, muscarinic antagonists and, to a lesser degree, xanthines including theophylline are used for the treatment of respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). For inhaled drug classes, they are increasingly used in combination for the treatment of COPD [1 ,2]. The clinical effectiveness of inhaled short-acting bronchodilators (e.g. salbutamol, terbutaline) as reliever medication is without question but the introduction of longer acting b2-agonists and muscarinic antagonists has led to significant improvements in the management of these respiratory conditions. This review will focus on inhaled bronchodilators and draw attention towards other targets being evaluated for the development of novel bronchodilators (Table 1) [3 ,4,5 ,6–11,12 , 13,14,15 ,16,17 ,18 ].

b2-Agonists reduce airflow limitation by improving airway diameter as a consequence of a direct action on airway smooth muscle. b2-Adrenoceptors are located throughout the airways, principally found on airway smooth muscle but also on a variety of pulmonary cells including epithelium, submucosal

&&

&

&

&&

&

&

&

Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, School of Biomedical Science, King’s College London, London, UK Correspondence to Domenico Spina, PhD, Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, School of Biomedical Science, King’s College London, 150 Stamford Street, London SE1 9NH, UK. Tel: +44 207 848 4341; fax: +44 207 848 4500; e-mail: [email protected] Curr Opin Pulm Med 2014, 20:73–86 DOI:10.1097/MCP.0000000000000012

1070-5287 ß 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

www.co-pulmonarymedicine.com

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Asthma

KEY POINTS Long-acting bronchodilators have improved the treatment of asthma and COPD.

their duration of action: short-acting b2-agonists (SABAs), including salbutamol, terbutaline and fenoterol, have pharmacodynamic half-lives between 2 and 6 h [1 ]; long-acting b2-agonists (LABAs), including salmeterol and formoterol, require twice daily treatment [1 ]; and ultra-LABAs (e.g. indacaterol) require once a day dosing [19]. Other longacting b2-agonists that are currently being developed as once a day treatment include vilanterol [20 ], olodaterol [21], carmoterol [22], abediterol [23 ] and milveterol [24 ]. Reversible binding of these agonists to the b2-adrenoceptor causes the activation of the canonical Gas-protein–cyclic AMP pathway, and hence relaxation of airway smooth muscle (Fig. 1) [25–28, 29 ,30–32]. Activation of b2-adrenoceptors, which serve as guanosine exchange factors, leads to the replacement of guanosine diphosphate (GDP) for guanosine triphosphate (GTP) on the Gas subunit of trimeric G protein. The subsequent dissociation &&

Combination LABA/inhaled glucocorticosteroid and LABA/LAMA as once a day formulation will be the norm for the maintenance treatment of asthma and COPD, respectively.

&&

&&

Novel bronchodilator targets have been identified and are at various stages of clinical development, which may provide alternatives for the treatment of these respiratory diseases.

glands and mast cells, although to what extent activation of b2-adrenoceptors on non-airway smooth muscle cells contributes to reducing airway obstruction remains a subject of debate [1 ,2]. b2-Agonists can be broadly classified according to &&

&

&

&

Table 1. Summary of potential novel targets limited to in-vitro and in-vivo studies in humans Endogenous stimuli

Drug

Protein target

Comment

Authors

PL-3994

NPR-A, NPR-B, NPR-C

ANP, BNP and CNP, respectively

PL-3994 (NPR-A, NPR-C selective agonist) stimulates cyclic GMP. Relaxation of human precision-cut lung slice Ro 25-1553 caused rapid bronchodilation in asthma patients; 4–6 h duration (600 mg)

[3 ]

Ro 25-1553

VPAC2-R

VIP

L-9026885

EP4-R

Prostaglandin E2

Relaxation of precontracted human bronchial preparations. More potent than salbutamol and salmeterol, anti-inflammatory

Y-27632

ROCK

rhoA

Relaxation of human airways, anti-inflammatory

[6]

NS1619

KCa1.1

No in-vitro relaxant effect

[7–9]

Bimakalim, BRL38227

Kir6

Ca2þ, PKA, b2receptor coupling ATP

No bronchodilator effect following inhaled bimakalim; oral BRL 38227 caused bronchodilation at the expense of headache

[10,11]

RPL554

PDE

Cyclic AMP

RPL554 caused relaxation of human bronchial smooth muscle; bronchodilator in asthma patients and in COPD, anti-inflammatory

[12 ,13,14]

TASR2 agonists

TASR2

Bitter tastants

Chloroquine, quinine cause relaxation of human airway smooth muscle

[15 ]

8-pCPT-2-O-MecAMP, Sp-8-pCPT2’-O-Me-cAMPS

Epac1/2

Cyclic AMP

Epac activators cause relaxation of airway smooth muscle, antiproliferative

[16,17 ]

R837 (imiquimod)

TLR7

Single-strand viral RNA

Relaxation of human airway smooth muscle via release of nitric oxide from airway sensory neurones

[18 ]

&

[4] [5 ] &

&

&

&&

&

AMP, adenosine monophosphate; ANP, atrial natriuretic peptide; ATP, adenosine triphosphate; BNP, brain natriuretic peptide; BRL38227, levcromakalim; CNP, C-type natriuretic peptide; EP4-R, E prostanoid receptor 4; GMP, guanosine monophosphate; L-9026885, [(1E,3R)-4,4-difluoro-3-hydroxy-4-phenyl-1-buten-1-ul]-1[6(2H-tetrazol-5R-yl)hexl]-2-pyrrolidone; NPR, natriuretic peptide receptor; NS1619, (1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2Hbenzimidazol-2-one; PL-3994, hept-cyclo(Cys-His-Phe-D-Ala-Gly-Arg-D-Nle-Asp-Arg-Ser-Cys)-Tyr-Arg-mimetic]-Nh2; Ro 25-1553, Ac-His-Ser-Asp-Ala-Val-Phe-Thr-GluAsn-Tyr-Thr-Lys-Leu-Arg-Lys-Gln-Nle-Ala-Ala-Lys-Lys-Tyr-Leu-Asn-Asp-Leu-Lys-Lys-Gly-Gly-Thr-NH2 (cyclo21-25); ROCK, rhoA kinase; RPL554, 9,10-dimethoxy-2(2,4,6trimethylphenylimino)-3-(n-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one; 8-pCPT-2-O-Me-cAMP, 8-(4-chlorophenylthio)-20 -Omethyladenosine-30 ,50 -cyclic monophosphate; Sp-8-pCPT-20 -O-Me-cAMPS; 8-(4-chlorophenylthio)-20 -O-methyladenosine-30 ,50 -cyclic monophosphorothioate, Sp isomer; TASR2, bitter taste receptor; TLR, toll-like receptor; VIP, vasointestinal peptide; VPAC, vasointestinal peptide adenylyl cyclase receptor; Y-27632, N-(4pyridyl)-4-(1-aminethyl)cyclohexanecarboxamide.

74


Volume 20 Number 1 January 2014


Bronchodilators in respiratory disease Spina

Potential bronchodilators • • • • •

Muscarinic antagonists • Inverse agonist

Mixed PDE inhibitors VPAC, NPR, EP4, TAS2R agonist Potassium channel openers Epac selective activators ROCK inhibitors

α

γ

β

GTP

β2–agonists β2-antagonist • Inverse agonists? • Biased ligands? • β-arrestin and/or ERK antagonist?

α

GTP

GTP GDP PKA

M3-receptor

β2-adrenoceptor

GRK Gαs–AC pathway

β–arrestin pathway

Gαq/11–PLC pathway Cyclic AMP RhoGEF Ca2+–CM

RhoA

MLC20

ROCK

Contraction MLCP

MLCK

MLC20

Relaxation

PKC

PDE

ASM Relaxation PKA • Decrease Ca2+i • Inhibition of RhoA • Telokin phosphorylation • MYPT1 activation • MLCK phosphorylation

• • • •

Receptor internalization Raf/MEK/ERK Ask1/MKK4/JNK3 PDE4, RhoA, PI3K, p38 MAPK

RTK Cytokine–R Chemokine–R

?

Inflammation BHR

Epac • Decrease MLC20 • Inhibition of RhoA via Rac and/ or Rap1

• Loss in bronchoprotection

FIGURE 1. Illustration of the potential mechanism of clinically effective bronchodilators (b2-agonists and muscarinic antagonists) and potentially novel targets including ion channels, other G-protein-coupled receptors and intracellular proteins (Table 1). It has been proposed that regular treatment with b2-agonists might promote b-arrestin and/or ERK dependent pathways in the lung to cause inflammation and bronchial hyperresponsiveness (BHR). Nadolol might interfere with this process to promote anti-inflammatory/anti-BHR action [31,32]. AC, adenylyl cyclase; ASM, airway smooth muscle; ATP, adenosine triphosphate; cAMP, cyclic adenosine monophosphate; CM, calmodulin; Epac, exchange proteins activated by cyclic AMP; ERK, extracellular receptor kinase; GDP, guanosine diphosphate; GEF, guanosine exchange factor; GRK, G protein receptor kinase; GTP, guanosine triphosphate; JNK, janus kinase; MAPK, mitogen activated protein kinase; MLC20, myosin light chain; MLCK, myosin light chain kinase; MLCP, myosin light chain phosphatase; MYPT1, myosin phosphatasetargeting substrate-1; P3IK, phosphoinositide 3-kinase; PKC, protein kinase C; PLC, phospholipase C; RhoGEF, rhoA guanosine exchange factor; ROCK, rhoA kinase; RTK, receptor tyrosine kinase.

allows Gas-GTP to bind to transmembrane spanning adenylyl cyclase and Gbg to a myriad of signalling proteins (e.g. GRK2, PLCb, PI3K) [25]. The hydrolysis of GTP to GDP by the endogenous GTPase activity of Gas leads to the reassembly of the trimeric G protein for subsequent activation. Conversion of ATP to cyclic AMP by adenylyl cyclase results in the stimulation of protein kinase A (PKA) and Epac (exchange proteins activated by cyclic AMP) dependent pathways leading to dephosphorylation of myosin light chain (MLC20) and airway smooth muscle relaxation [26,27]. Other mechanisms for relaxation have also

been proposed including the opening of potassium channels to induce hyperpolarization, although the importance of this mechanism has been questioned in human airways [7,28] (Fig. 1). Activation of the b2-adrenoceptor can also lead to the phosphorylation of the cytoplasmic tail of the receptor by G protein receptor kinase (GRK) and/or PKA leading to the binding of b-arrestin, which can interdict Gas –adenylyl cyclase signalling, promote receptor internalization/recycling and serve as a platform to recruit a variety of intracellular signalling proteins (eg Raf/MEK/ERK) [29 ,30,33–36]


&


75


Asthma Table 2. Potency and operational efficacy of b-adrenoceptor ligands for three signalling pathways in HEK-293 cells overexpressing human b2-adrenoceptor in vitro

Cyclic AMP

b-Arrestin-2 recruitment

ERK1/2 activation

Cyclic AMP

b-Arrestin-2 recruitment

ERK1/2 activation

Bias (arrestin : cyclic AMP) relative to isoproterenol

9.8 (100)

8.1 (100)

10.8 (100)

19490

30

61659

1

pEC50 (% Emax) Drug Isoproterenol

t

a

6591 Salbutamol Salmeterol

8.7 (106) 9.1 (114)

6.4 (42) 8.1 (59)

10 (97) 9.6 (104)

1.6

81a

0.69a

14

1.1

120 b

a

a

1a

88.5

282

3.34 Formoterol

a

3019

2.53 0.72a

63

8.93

a

3.84a

a

5.53a

0.3 18

Propranolol

ND

ND

(10.5 )

ND

ND

ND

Carvedilol

ND

(21b)

7.6 (26)

ND

ND

0.5

ERK, extracellular receptor kinase. ND, no detectable response. Data selected from Kahsai et al. [33] and aRajagopal et al. [34]. pEC50 ¼ log EC50. Values in parentheses indicate the magnitude of the response (% Emax). Note that the instrinsic activity of salmeterol against cyclic AMP generation is near maximal because of overexpression of the receptor in HEK-293 cells. b potency could not be determined because of the low response. t ¼ operational efficacy as proposed by Black and Leff [35] to describe the efficiency of coupling between the agonist–receptor complex and effector response based on the relationship: E/Em ¼ [A]t/([A]t þ ([A] þ KD)) and t ¼ [RT]/KE where RT is the total concentration of receptors and KE is the concentration of agonist– receptor complex at half of the maximum effector response (Em). The b-adrenoceptor antagonist carvedilol does not stimulate G protein–cyclic AMP, recruits b-arrestin-2 and activates ERK1/2 evidence of biased agonism, but is also an example of an inverse agonist [36]. In contrast, bias relative to epinephrine was quantified for a range of b2-agonists [34], but to compare different publications, bias was calculated relative to isoprenaline and expressed arithmetically as the reciprocal of the antilog of the bias factor (b).

(Fig. 1) (Table 2). This can give rise to a number of cellular responses including cell chemotaxis, apoptosis, proliferation, regulation of protein synthesis and metastasis [29 ,30]. It is clear that ligands can induce different conformational states in G-protein-coupled receptors resulting in the phenomenon of biased agonism [33,37 ]. For example, b2-agonists including salbutamol and salmeterol display different efficacy for Gas-stimulated cyclic AMP generation, b-arrestin-2 translocation to the receptor and activation of ERK (Table 2), which may be related to the different ways these agonists stabilize the receptor. Similarly, relative to epinephrine, both formoterol and salmeterol are weakly biased towards b-arrestin [34] (Table 2), and to what extent this affects the clinical effectiveness and safety of these drugs is not known at present. In contrast, carvedilol, propranolol and nadolol do not cause Gas-stimulated cyclic AMP generation but behave as inverse agonists with negative efficacy for cyclic AMP production. However, carvedilol and propranolol are partial agonists for the activation of ERK1/2 but via different mechanisms. Nadolol differs from carvedilol and propranolol and does not activate ERK1/2 signalling [33,36] and is another illustration of the flexibility of receptors in adopting ligand-dependent conformational states that can exert distinct functional effects of varying efficacy (Table 2). The potential functional consequence of differences in the effect of these ligands on the &

&&

76


b2-receptor signalling pathway in airway inflammation will be described later. To what extent the clinical effectiveness of b2-agonists is determined by their different efficacy for these distinct signalling pathways at native b2-adrenoceptors on human airway smooth muscle cells and whether biased agonists ‘selective’ for the canonical Ga–cyclic AMP-dependent pathway would be clinically more effective than currently used b2-agonists remain to be determined [31].

Mechanism of sustained bronchodilation The chemical evolution of b2-agonists to once daily administration is seen as a major advance in the bronchodilator treatment of respiratory disease and various mechanisms have been proposed to account for the pharmacodynamics of LABAs. Radioligand binding studies performed under physiological conditions revealed that the association or dissociation rate constants for various b2-agonists cannot explain the property of onset of action and long-effect duration. For example, the bronchodilator onset of action of salmeterol is slower compared with other LABAs, yet the association rate constant on human recombinant b2-adrenoceptors is fast and highlights a discordance between receptor binding kinetics and clinical effect [38 ]. Similarly, the long duration of action of these agonists is also not explained by slow dissociation &&




half-life from the receptor, which in general occurs within minutes (Table 3) [20 ,21,38 ,39–41]. There is an exception to this rule in the case of olodaterol (t1/2 ¼ 17 h) [39]; however, the magnitude of this value has been questioned on the grounds that the binding studies were not undertaken under physiological conditions (e.g. physiological Naþ concentration, presence of GTP) to maintain the receptor in a predominantly low affinity state as might be anticipated in living cells [38 ]. Similarly, although the dissociation of vilanterol from the high affinity state of the b2-adrenoceptor is relatively long (47 min), this would still be insufficient to account for sustained bronchodilation with once a day treatment [20 ]. Hence, factors such as efficacy and retention within specific domains of cell membranes are likely to account for long duration of action rather than receptor kinetics. For example, although indacaterol is equally hydrophobic as salmeterol, this agonist documents a two-fold difference in preference for partitioning in lipid rafts that has been suggested to contribute towards the longer clinical duration of action of indacaterol over salmeterol [42]. Furthermore, the efficacy of indacaterol is also an order of magnitude greater than salmeterol and is likely to be a factor concerning duration of action (Table 3). Another characteristic feature of LABAs is persistent ‘retention’ by cells and tissues in vitro long after termination of drug exposure. The contraction of airway smooth muscle by endogenously released acetylcholine following the activation of parasympathetic postganglionic nerve terminals is functionally antagonized by LABAs. This action is reversed by b-adrenoceptor antagonists because of competition with LABAs for b2-receptor binding sites. However, the functional antagonism resumes upon removal of the antagonist. Ligands like salmeterol, indacaterol and vilanterol demonstrate ‘re-assertion behaviour’, although this feature is lost for both formoterol and carmoterol in vitro [20 ,43]. Hence, the long duration of action of LABAs observed clinically is a consequence of efficacy and retention within the vicinity of receptor sites via: binding to an ‘exosite’ as in the case of salmeterol and possibly vilanterol [44]; preferential retention in lipid domains coupled with very high efficacy (e.g. formoterol) [42,45]; and ‘re-binding’ of ligands (e.g. moderate-to-high efficacy ligands, olodaterol, indacaterol and carmoterol) [46,47]. &&

&&

&&

&&

&&

b-Receptor polymorphisms Single nucleotide polymorphisms and haplotypes have been described for the b2-adrenoceptor

and their functional consequence on receptor expression and sensitivity to desensitization has been investigated in vitro, and not surprisingly their role in disease morbidity and clinical effectiveness is the subject of considerable debate [48 ]. Of the numerous receptor polymorphisms that have been identified, the Arg16 ! Gly16 and Ile164 ! Thr164 alleles have been more widely investigated. The Gly16 and Thr164 alleles correspond to receptors with greater susceptibility to desensitization and reduced signalling in vitro, respectively [48 ]. Only the Thr164 receptor polymorphism was associated with reduced lung function and increased risk of COPD, and neither this nor the Gly16 or Glu27 polymorphism was associated with increased risk of asthma [49,50]. Various studies have implied allele specific differences in treatment responsiveness [48 ]; however, a number of large well controlled clinical trials have shown that there is no evidence of differences in improvement in baseline lung function, exacerbation rate and symptom free days following monotherapy or combination LABA/glucocorticosteroids treatment in Arg16 versus Gly16 genotypes [50–52]. Similarly, there was no difference in improvement in lung function in individuals with the Arg16 genotype treated with salmeterol or tiotropium bromide in combination with steroid [53]. This suggests that earlier studies reporting deterioration in lung function following regular b2-agonist therapy, although paradoxically in the Arg16 and not the Gly16 genotype, was not observed with LABAs [48 ]. The Salmeterol Multicentre Asthma Research Trial (SMART) investigating the safety of salmeterol was halted because of safety concerns in African-American patients; however, there was no evidence of a difference in asthma control between races [50], although there was some discrepancy concerning the lack of bronchoprotection afforded by salmeterol in African-Americans with the Arg16 genotype [50,52]. Similarly, airway responsiveness in combination with LABA/glucocorticosteroids treatment was not different in patients with b2-adrenoceptor haplotypes that included the Gly16, Glu27 and Ile164 alleles [50]. Therefore, it is unlikely that b2-receptor polymorphisms play a major role in asthma morbidity and/or responsiveness to b2-adrenoceptor agonists. &

&

&

&

Loss of bronchoprotection Regular treatment with SABAs has been linked to increasing morbidity and, controversially, mortality in asthma. Similarly, a number of studies have shown that regular treatment with SABAs and LABAs is associated with a loss in bronchoprotection to direct and indirect acting stimuli [54,55 ].


&


77


78


HO

HN

OH

OH

O

HO

HN

Indacaterol

H

O

Formoterol

HO

OH

Vilanterol

HO

OH

Salmeterol

HO

OH

Salbutamol

HO

HO

OH

Isoproterenol

OH

OH

H N

H N

OH

H N

H N

H N

H N

O

O

O

O

Cl

Cl

7.37

7.83

9.06L 10.4H 9.44GppnHp

9.70

6.65

6.89

Kinetic

pKDa

Table 3. Affinity, potency and efficacy of a range of b2-agonists

0.20

0.21

3GppNHp

3L 47H

0.91

0.17

0.23

Dissociation t1/2 (min)

9.03

9.59

10.37

10.1

7.34

8.34

pEC50b (cyclic AMP)

46

58

10GppNHp

2L 21H

3.5

5.9

29

tc

16

150

2400

3000

27

0.24

b2/b1 selectivity

3.88 0.75 (3.26)

1.57 0.36 (1.06)

4.01 0.80 (4.13)

3.07 0.4 (3.61)

0.01 0.30 (0.24)

0.25 0.28 (0.24)

cLog Pd

150–300 mg od

12–24 mg t.i.d.

25–100 mg od

50–100 mg t.i.d.

100 mg up to q.i.d.

Clinical dosing

Asthma



HO

HN


HN

OH

O

OH

OH

H N

H N

O

O

9.39L 11H 8.07GppNHp

8.32

Kinetic pKDa

32L 1068H

1.51


9.965

10.19

pEC50b (cyclic AMP)

5L 1.1H 11GppNHp

75

tc

65

53

b2/b1 selectivity

1.17 0.4 (1.93)

2.34 0.85 (2.49)

cLog Pd

2–20 mg od

2–4 mg od

Clinical dosing

b.i.d., twice daily; od, once a day; t.i.d., three times daily; q.i.d., four times daily. && && a Kinetic pKD calculated for isoprenaline, salbutamol, salmeterol, formoterol, indacaterol, carmoterol [38 ] and vilanterol [20 ] under physiological conditions and olodaterol [39] under nonphysiological conditions. In && the case of vilanterol [20 ] and olodaterol [39] low (L) and high (H) affinity estimates obtained in the absence or presence of the nonhydrolyzable GTP analog GppNHp are shown. For olodaterol, binding pKD in the && && && presence of GppNHp is quoted. Corresponding dissociation half-life of the agonist–receptor complex are shown [20 ,38 ,39] and b2/b1 selectivity ratios obtained from the literature [21,38 ]. && b Average potency values obtained from a number of studies that measured cyclic AMP in response to agonist stimulation in cells overexpressing human b2-adrenoceptor in vitro [20 ,21,40,41]. c t, an estimate of occupational efficacy at 50% Em for cyclic AMP by re-arrangement of the operational model (t ¼ 1 þKD/EC50). d cLog P values calculated using ACD/Chemsketch and Chemaxon (parenthesis), respectively.

O

Olodaterol

O

Carmoterol

Table 3 (Continued)



79


Asthma

Regular treatment with salmeterol did not cause bronchodilator tolerance as assessed by improvement in forced expiratory volume in 1 s (FEV1) in response to this bronchodilator; however, there was a significant loss in bronchoprotection against methacholine challenge from 3.3 doubling doses on day 0, decreasing to 1 doubling dose after 8 weeks regular treatment [56], and a similar observation has been observed for formoterol [57]. This loss in bronchoprotection is also observed in studies that examined the ability of salbutamol to reverse acute bronchospasm in response to methacholine in individuals regularly receiving LABAs, in an attempt to replicate circumstances in which asthma patients might undergo an exacerbation of their asthma during maintenance LABAs, who require rescue medication. An approximate two-fold loss in ‘rescue’ bronchodilator potency is observed under these conditions [58–60]. It is generally considered that b2-adrenoceptor desensitization is responsible for this loss of bronchoprotection despite the fact that bronchodilation per se is unaltered presumably because of the very significant b2-receptor reserve on human airway smooth muscle [61] and the rapid rate at which Class A receptors like b2-adrenoceptors recycle to the cell surface [62]. Moreover, glucocorticosteroids can reverse b2-adrenoceptor desensitization in vitro, but do not appear to protect against this loss in bronchoprotection [54,55 ]. Furthermore, there is no difference in the loss of bronchoprotection following regular LABA/glucocorticosteroid treatment in individuals with Arg16 or Gly16 genotype, the latter being associated with a greater probability of receptor desensitization [63]. A potential mechanism to account for this loss in bronchoprotection might involve non Gas –cyclic AMP-dependent pathways. Genetic ablation of b-arrestin-2 led to the inhibition of eosinophil recruitment and reduction in T helper 2 (Th2)-like cytokine levels presumably reflecting the importance of this protein for Th2 cell chemotaxis to the lung via G-protein-coupled chemokine receptor signalling mechanisms and chemokine release from pulmonary cells [64]. Bronchial hyperresponsiveness (BHR) was also inhibited but was not due to impairment in airway smooth muscle contraction per se, suggesting interdict of an upstream process in knockout mice (e.g. increased epithelium thickness, loss in airway surface tension) [64]. The expression of b-arrestin-2 in cells within the lung (e.g. epithelium and/or airway smooth muscle) was sufficient to drive antigen-induced BHR [65]. Regular treatment with b2-agonists could lead to the recruitment of b-arrestin and subsequent activation of intracellular signalling cascades [e.g. &

80


MAPK-dependent pathways, phosphodiesterase 4 (PDE4)], which could drive inflammatory processes [29 ,30,66,67], increase BHR and reduce the clinical effectiveness of b2-agonists [32]. It remains to be established whether the development of an allergic inflammatory phenotype in mice following regular b2-agonist exposure is via a b-arrestin and/or ERKdependent process or via the canonical Gas –cAMP pathway as many of these indices of the allergic inflammatory response are also suppressed in PDE4B gene knockout mice, implicating signalling pathways downstream of cyclic AMP [68]. Intriguingly, genetic ablation of the b2-adrenoceptor also suppressed the development of allergic inflammation, and increased epithelium mucin content and BHR in mice [69], which was mimicked by chemical depletion of endogenous catecholamines or in mice lacking the ability to synthesize epinephrine [70 ]. A major conclusion drawn from this study is that constitutive b2-adrenoceptor activity does not promote the asthma phenotype in allergic mice but requires ligand-induced activation of the b2-adrenoceptor [70 ]. Moreover, the allergic phenotype could be re-capitulated following chronic treatment with formoterol in mice unable to synthesize epinephrine [70 ]. The finding that formoterol demonstrates bias towards the b-arrestin pathway relative to epinephrine (Table 1) suggests that signalling via this pathway could account for these findings. The allergic inflammatory phenotype in mice is also pre-empted to varying degrees of effectiveness following chronic treatment with inverse agonists (nadolol ¼ ICI-118551 > carvedilol), but not the partial agonist alprenolol [69,71,72]. It has been suggested that the beneficial action of nadolol may not be due to inverse agonism per se, but possibly by impairing b2-adrenoceptor signalling via b-arrestin and/or ERK signalling [69,70 ,71,72] (Table 2) (Fig. 1). The clinical relevance of these findings is being explored with an open-label trial reporting a decrease in BHR following chronic treatment with nadolol [73,74], although there appeared to be no beneficial effect on this variable following chronic treatment with propranolol in asthma patients concurrently treated with glucocorticosteroids and muscarinic antagonist [75 ]. These different clinical outcomes would be consistent with the hypothesis that nadolol and not propranolol impairs ERK signalling pathways, and therefore nadolol would be anticipated to exert a beneficial action compared with propranolol [31]. &

&

&

&

&

&

MUSCARINIC ANTAGONISTS Tiotropium bromide is clinically effective in the management of COPD by improving baseline Volume 20 Number 1 January 2014



FEV1, reducing the frequency of exacerbations, and increasing the quality of life [76]. Consequently, other long-acting muscarinic antagonist (LAMAs) including glycopyrronium bromide [77 ], aclidinium bromide [78 ] and umeclidinium bromide [79 ,80 ] are under clinical development (Table 4) [81 ,82,83,84 ]. This drug class is not used in the treatment of asthma, although tiotropium bromide causes bronchodilation of a similar magnitude to salmeterol and is clinically effective in difficult to control asthma [53,85 ,86]. There are five muscarinic receptor subtypes and their expression on airway smooth muscle cells (M3-receptor) and submucosal glands (M1-receptor) forms the basis for the beneficial action of this drug class in COPD, by virtue of antagonism of airway smooth muscle contraction and submucosal gland secretion by endogenously released acetylcholine, but with potential for side-effects via antagonism of cardiac M2-receptors. LAMAs are characterized as nonselective antagonists with similar affinities between muscarinic receptor subtypes but tend to dissociate more quickly from the M2-receptor versus M3-receptor (Table 4). The association rate constants are the same order of magnitude for all LAMAs, and therefore receptor kinetics does not explain the faster clinical onset of action of glycopyrronium bromide compared with tiotropium bromide despite being similarly effective in terms of improvement in lung function and exacerbation rate [77 ]. Aclidinium bromide (twice daily) [78 ] and umeclidinium bromide [79 ] are also characterized by slow onset of action. The potentially quicker dissociation rate from the M2-receptor might confer an advantage allowing lung vagal prejunctional M2-autoreceptors and cardiac M2-receptors to remain functionally active thereby improving the benefit/risk ratio. Many studies have reported lengthy dissociation times for LAMAs from the M3-receptor that is proposed to explain once a day treatment and prolonged improvement in baseline lung function (Table 4). However, the calculated dissociation half-life for LAMAs appears to be dependent upon the binding conditions used in these assays (e.g. absence of Naþ ions under non-physiological conditions) [81 ]. For example, a comparison of binding characteristics under physiological versus non-physiological conditions reveals an order of magnitude overestimation of the dissociation half-life of muscarinic antagonists from the receptor under the latter condition [81 ] (Table 4). Similarly, receptor kinetics does not explain why aclidinium bromide with a similar dissociation half-life as tiotropium bromide (under non-physiological conditions) requires twice daily treatment to achieve comparable bronchodilator activity as &

&

&

&

&&

&

&

&

&

&

&

tiotropium bromide [78 ]. However, aclidinium bromide is an ester that is rapidly metabolized within minutes by plasma esterases and characterized by a pH-dependent instability in aqueous solution (hours) that might explain why twice daily dosing is required, with obvious advantages for limiting systemic side-effects. Hence, onset of action and long duration of action is likely to be influenced by retention within the vicinity of receptor sites either via interaction with nonreceptor proteins, lipid membranes or rebinding as described for LABAs, rather than differences in receptor affinity and kinetics [47]. LAMAs including tiotropium, aclidinium and glycopyrronium bromide are inverse agonists with similar intrinsic activity as documented by their ability to inhibit the activation of the AP-1 gene in M3-receptor overexpressing Chinese hamster ovary cells; this is therefore unlikely to account for their long duration of action [87]. However, this mechanism could account for the anti-inflammatory effect of muscarinic antagonists reported in various in-vitro studies [88], although the clinical relevance is not firmly established. Clinical studies have reported the beneficial effect of combined use of LABAs and LAMAs for a number of variables including bronchodilation, rate of exacerbation, dyspnoea and symptom control [80 ,89 –91 ]. Additional bronchodilation can be achieved particularly if some patients are not dosed optimally on monotherapy, and combination therapy offers the opportunity of reducing the dose of each bronchodilator but not at the expense of clinical effectiveness and potential to reduce the risk of adverse side-effects with high dose monotherapy. Another approach has been the development of a dual acting muscarinic antagonist, b2-agonist (MABA) for once a day treatment as exemplified by GSK961081 [92 ], which offers the advantage of a molecule with a single pharmacokinetic profile and potential benefits concerning formulation of one as opposed to two separate molecules. This treatment could offer greater simplicity for patients undergoing triple therapy with combination LABA/ LAMA/inhaled corticosteroid in COPD. &

&

&

&

&&

&&

NOVEL BRONCHODILATORS The development of novel bronchodilators is motivated by safety concerns of currently used inhaled drugs, the potential for loss in bronchoprotection of the b2-agonist class, and lack of disease modifying properties of inhaled bronchodilators. A number of clinical studies have reported bronchodilation/ bronchoprotection by new drug classes (Table 1) including RPL554, a ‘bifunctional’ molecule that



81


82


+

O

O

OH

+

O

O

S

S

OH

OH

O

O

N

+

Glycopyrronium bromide

O

N

Tiotropium bromide

N

Ipratropium bromide

M1 M2 M3 M4 M5

M1 M2 M3 M4 M5

M1 M2 M3 M4 M5

9.5 8.7 9.5 9.1 9.2

10.2 10.1, (9.1, 10.3) 10.2, (9.4,10.7) 10.1 9.8

(8.78) (9.97)

Kinetic pKD 9.40) 9.53) 9.58) 9.65) 9.07)

9.6, (10.09) 8.7, (9.7) 9.6 (10.0, 10.3) 9.1, (10.3) 8.9, (9.7)

10.3, (9.88,10.8) 10.0, (9.88, 10.7) 10.4, (9.7, 11.0, 11.1) 10.2, (9.5, 11.02) 9.97, (9.74, 9.96)

(8.88, (8.95, (8.91, (8.72, (8.49,

Affinity estimates, pKi

Table 4. Affinity and dissociation half-life of a range of muscarinic antagonists

13.9, (120) 1.1 (22.2) 11.4 (173–366) 3.1 12.6

35.9, (630) 10.8, (39–906) 46.2, (273–1620) 30.1 77

(6) (1.8, 4.8) (13.2, 28.2)


1 5 1 2 3.4

1.1 1.7 1 1.3 5.5

1.3 1 1 1.2 2.9

M3/Mx selectivity

a

0.38 0.53 (1.4)

0.79 0.63 (1.8)

2.21 0.51 (1.8)

cLog Pb

50 mg

18 mg

40 mg (t.i.d.–q.i.d.)

Clinical dosing (od)

Asthma



N

+

O

O HO

S


+

HO

S

M1 M2 M3 M4 M5

M1 M2 M3 M4 M5

(9.79) (10.5)

(9.46) (9.49)

Kinetic pKD

(9.8) (9.8) (10.2) (10.3) (9.9)

(10, 10.8) (9.8, 10.7) (9.8, 10.7) (9.7, 10.8) 9.8, 10.3)

Affinity estimates, pKi

(9.4) (82.2)

(108, 281) (642, 1754)


1.54 0.56 (0.68)

1.44 0.6 (0.45)

cLog Pb

62.5–500 mg

400 mg (b.i.d)

Clinical dosing (od)

]. Values in parenthesis represent parameter estimates

&&

2.7 2.5 1 0.8 2.2

0.8 1.1 1 1.2 2.1

M3/Mx selectivity

a

b.i.d., twice daily; t.i.d., three times daily; q.i.d., four times daily. Kinetic pKD, dissociation half-life and pKi determined under physiological conditions [81 & determined under nonphysiological conditions for ipratropium [82,83], glycopyrronium [82], aclidinium [83] and umeclidinium [84 ] bromide. a average values across the different studies. b cLog P values based on the base only calculated using ACD/Chemsketch and Chemaxon (parenthesis), respectively.

N

O

Umeclidinium bromide

O

Aclidinium bromide

Table 4 (Continued)



83


Asthma

provides long-lasting bronchodilation and antiinflammatory activity via inhibition of PDE3/4. Other drugs classes that could exert this dual activity include E prostanoid receptor 4 agonists, rhoA kinase inhibitors and Epac activators (Table 1). Other bronchodilator targets have met with limited clinical success (e.g. potassium channel openers) whereas others are currently in early preclinical investigation (e.g. natriuretic peptide receptor agonists). The discovery of biter taste receptors (TASR2) on airway smooth muscle might also offer the possibility of developing novel bronchodilators [15 ], although whether nonbitter tasting bronchodilator molecules can be developed remains to be established. &

CONCLUSION b2-agonists and muscarinic antagonists are clinically effective and their combination has provided additional benefit in patients with COPD. However, both drug classes are not disease modifying and therefore treatment with an appropriate antiinflammatory agent is necessary. Numerous bronchodilator targets are being evaluated and their potential as well tolerated and effective bronchodilators combined with anti-inflammatory activity could represent a new type of treatment for these respiratory diseases. Acknowledgements The author is a consultant for Verona Pharma plc but it is not relevant to this article. Conflicts of interest There are no conflicts of interest.

REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Cazzola M, Page CP, Calzetta L, et al. Pharmacology and therapeutics of bronchodilators. Pharmacol Rev 2012; 64:450–504. An excellent review of the pharmacology of bronchodilator drugs used for the treatment of asthma and COPD. 2. Barnes PJ. Biochemical basis of asthma therapy. J Biol Chem 2011; 242:31– 50. 3. Edelson JD, Makhlina M, Silvester KR, et al. In vitro and in vivo pharmaco& logical profile of PL-3994, a novel cyclic peptide (Hept-cyclo(Cys-His-Phe-dAla-Gly-Arg-d-Nle-Asp-Arg-Ile-Ser-Cys)-Tyr-[Arg mimetic]-NH(2)) natriuretic peptide receptor: an agonist that is resistant to neutral endopeptidase and acts as a bronchodilator. Pulm Pharmacol Ther 2013; 26:229– 238. The article describing the pharmacology of PL-3994, a cyclo natriuretic peptide that demonstrates bronchodilation of human airways by elevating cyclic GMP. 4. Linden A, Hansson L, Andersson A, et al. Bronchodilation by an inhaled VPAC(2) receptor agonist in patients with stable asthma. Thorax 2003; 58: 217–221.

&&

84


5. Benyahia C, Gomez I, Kanyinda L, et al. PGE(2) receptor (EP(4)) agonists: & potent dilators of human bronchi and future asthma therapy? Pulm Pharmacol Ther 2012; 25:115–118. A research article demontrating the potential of targeting EP4-receptors for the development of novel bronchodilators for the treatment of asthma. 6. Yoshii A, Iizuka K, Dobashi K, et al. Relaxation of contracted rabbit tracheal and human bronchial smooth muscle by Y-27632 through inhibition of Ca2þ sensitization. Am J Respir Cell Mol Biol 1999; 20:1190–1200. 7. Corompt E, Bessard G, Lantuejoul S, et al. Inhibitory effects of large Ca2þactivated Kþ channel blockers on beta-adrenergic- and NO-donor-mediated relaxations of human and guinea-pig airway smooth muscles. Naunyn Schmiedebergs Arch Pharmacol 1998; 357:77–86. 8. Muller-Schweinitzer E, Fozard JR. SCA 40: studies of the relaxant effects on cryopreserved human airway and vascular smooth muscle. Br J Pharmacol 1997; 120:1241–1248. 9. Janssen LJ. Ionic mechanisms and Ca(2þ) regulation in airway smooth muscle contraction: do the data contradict dogma? Am J Physiol Lung Cell Mol Physiol 2002; 282:L1161–L1178. 10. Faurschou P, Mikkelsen KL, Steffensen I, et al. The lack of bronchodilator effect and the short-term safety of cumulative single doses of an inhaled potassium channel opener (bimakalim) in adult patients with mild to moderate bronchial asthma. Pulm Pharmacol 1994; 7:293–297. 11. Kidney JC, Fuller RW, Worsdell YM, et al. Effect of an oral potassium channel activator, BRL 38227, on airway function and responsiveness in asthmatic patients: comparison with oral salbutamol. Thorax 1993; 48:130–133. 12. Calzetta L, Spina D, Page C, et al. The effect of the mixed phosphodiesterase & 3/4 inhibitor Rpl554 on human isolated bronchial smooth muscle tone. J Pharmacol Exp Ther 2013; 346:414–423. In-vitro study describing synergism with combination mixed PDE3/4 inhibitor and muscarnic antagonist for the relaxation of human airway smooth muscle. 13. Franciosi LG, Zuiker R, Kamerling IM, et al. RPL554 a dual PDE3/4 inhibitor is well tolerated and maintains bronchodilator activity when administered by inhalation to mild to moderate allergic asthmatics on 6 consecutive days. Am J Respir Crit Care Med 2013; 187:A3875. 14. Cazzola M, Calzetta L, Segreti A, et al. Safety and bronchodilator effects of nebulized RPL554 a novel dueal PDE3/4 inhibitor in COPD. Am J Respir Crit Care Med 2013; 187:A1497. 15. Liggett SB. Bitter taste receptors on airway smooth muscle as targets for & novel bronchodilators. Expert Opin Ther Targets 2013; 17:721–731. An excellent review summarizing our current understanding of the role of bitter tastants and their receptors in mediating airway smooth muscle relaxation and the potential of developing a new class of bronchodilator. 16. Grandoch M, Roscioni SS, Schmidt M. The role of Epac proteins, novel cAMP mediators, in the regulation of immune, lung and neuronal function. Br J Pharmacol 2010; 159:265–284. 17. Dekkers BGJ, Racke´ K, Schmidt M. Distinct PKA and Epac compartmenta&& lization in airway function and plasticity. Pharmacol Ther 2013; 137:248– 265. An excellent review of the biology of Epac of relevance to lung biology and discussing the role of Epac in mediating airway smooth muscle relaxation and anticellular activity. 18. Drake MG, Scott GD, Proskocil BJ, et al. Toll-like receptor 7 rapidly relaxes & human airways. Am J Respir Crit Care Med 2013; 188:664–672. Publication demonstrating the relaxation of human airway smooth muscle because of the release of nitric oxide from airway sensory nerves that express toll-like receptor 7. 19. Baur FO, Beattie D, Beer D, et al. The identification of indacaterol as an ultralong-acting inhaled b2-adrenoceptor agonist. J Med Chem 2010; 53: 3675–3684. 20. Slack RJ, Barrett VJ, Morrison VS, et al. In vitro pharmacological character&& ization of vilanterol, a novel long-acting b2-adrenoceptor agonist with 24-hour duration of action. J Pharmacol Exp Ther 2012; 344:218–230. In-vitro studies evaluating the pharmacology of the novel LABA vilanterol in comparison with other LABAs. Receptor kinetics, in-vitro relaxation, duration of action and reassertion studies were conducted. Data shows that receptor kinetics is unlikely to account for once a day sustained bronchodilation. 21. Bouyssou T, Hoenke C, Rudolf K, et al. Discovery of olodaterol, a novel inhaled b2-adrenoceptor agonist with a 24 h bronchodilatory efficacy. Bioorg Med Chem Lett 2010; 20:1410–1414. 22. Voss HP, Donnell D, Bast A. Atypical molecular pharmacology of a new longacting beta 2-adrenoceptor agonist, TA 2005. Eur J Pharmacol 1992; 227:403–409. 23. Aparici M, Gomez-Angelats M, Vilella D, et al. Pharmacological characteriza& tion of abediterol, a novel inhaled b2-adrenoceptor agonist with long duration of action and a favorable safety profile in preclinical models. J Pharmacol Exp Ther 2012; 342:497–509. An example of a long-acting hydroxyquinolin-2-one, which demonstrates greater binding affinity (IC50), potency and similar intrinsic activity compared with formoterol and indacaterol and sustained bronchodilation of similar duration to indacaterol. 24. Jacobsen JR, Choi SK, Combs J, et al. A multivalent approach to the discovery & of long-acting b2-adrenoceptor agonists for the treatment of asthma and COPD. Bioorg Med Chem Lett 2012; 22:1213–1218. Description of the synthesis and pharmacology of milveterol, a potent bronchodilator with long effect duration in vivo.



Bronchodilators in respiratory disease Spina 25. Lin Y, Smrcka AV. Understanding molecular recognition by G protein bg subunits on the path to pharmacological targeting. Mol Pharmacol 2011; 80:551–557. 26. Roscioni SS, Maarsingh H, Elzinga CRS, et al. Epac as a novel effector of airway smooth muscle relaxation. J Cell Mol Med 2011; 15:1551–1563. 27. Zieba BJ, Artamonov MV, Jin L, et al. The cAMP-responsive Rap1 guanine nucleotide exchange factor, Epac, induces smooth muscle relaxation by down-regulation of rhoA activity. J Biol Chem 2011; 286:16681–16692. 28. Janssen LJ, Tazzeo T, Zuo J. Enhanced myosin phosphatase and Ca(2þ)uptake mediate adrenergic relaxation of airway smooth muscle. Am J Respir Cell Mol Biol 2004; 30:548–554. 29. Reiter E, Ahn S, Shukla AK, et al. Molecular mechanism of b-arrestin-biased & agonism at seven-transmembrane receptors. Ann Rev Pharmacol Toxicol 2012; 52:179–197. This review discusses the current understanding of biased angonism and the mechanism by which biased ligands can alter the balance between between Gprotein-dependent and b-arrestin-dependent signal transduction. 30. Rajagopal S, Rajagopal K, Lefkowitz RJ. Teaching old receptors new tricks: biasing seven-transmembrane receptors. Nat Rev Drug Discov 2010; 9: 373–386. 31. Walker JKL, Penn RB, Hanania NA, et al. New perspectives regarding b2adrenoceptor ligands in the treatment of asthma. Br J Pharmacol 2011; 163: 18–28. 32. Dickey BF, Walker JKL, Hanania NA, et al. b-Adrenoceptor inverse agonists in asthma. Curr Opin Pharmacol 2010; 10:254–259. 33. Kahsai AW, Xiao K, Rajagopal S, et al. Multiple ligand-specific conformations of the b2-adrenergic receptor. Nat Chem Biol 2011; 7:692–700. 34. Rajagopal S, Ahn S, Rominger DH, et al. Quantifying ligand bias at seventransmembrane receptors. Mol Pharmacol 2011; 80:367–377. 35. Black JW, Leff P. Operational models of pharmacological agonism. Proc R Soc Lond B Biol Sci 1983; 220:141–162. 36. Wisler JW, DeWire SM, Whalen EJ, et al. A unique mechanism of betablocker action: carvedilol stimulates beta-arrestin signaling. Proc Natl Acad Sci U S A 2007; 104:16657–16662. 37. Liu JJ, Horst R, Katritch V, et al. Biased signaling pathways in beta2&& adrenergic receptor characterized by 19F-NMR. Science 2012; 335: 1106–1110. The detection of two conformational states of the b2-adrenoceptor using nuclear magnetic resonance techniques reveals conformational changes in helices VI and VII for G protein and b-arrestin biased molecules, respectively. 38. Sykes DA, Charlton SJ. Slow receptor dissociation is not a key factor in the && duration of action of inhaled long-acting b2-adrenoceptor agonists. Br J Pharmacol 2012; 165:2672–2683. Excellent article undertaken to re-evaluate receptor binding kinetics of a number of clinical relevant b2-agonists under physiological conditions to mimic the environment of receptor and G protein in living cells. Under these conditions, it is clear that receptor kinetics cannot explain the sustained bronchodilation observed with once a day LABA. Several possibilities including retention within the tissue environment, rebinding and high efficacy are more likely explanations. 39. Casarosa P, Kollak I, Kiechle T, et al. Functional and biochemical rationales for the 24-h-long duration of action of olodaterol. J Pharmacol Exp Ther 2011; 337:600–609. 40. Battram C. In vitro and in vivo pharmacological characterization of 5-[(R)-2(5,6-diethyl-indan-2-ylamino)-1-hydroxy-ethyl]-8-hydroxy-1H-quinolin-2-one (Indacaterol), a novel inhaled beta2 adrenoceptor agonist with a 24-h duration of action. J Pharmacol Exp Ther 2006; 317:762–770. 41. Rosethorne EM, Turner RJ, Fairhurst RA, et al. Efficacy is a contributing factor to the clinical onset of bronchodilation of inhaled beta(2)-adrenoceptor agonists. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:255– 263. 42. Lombardi D, Cuenoud B, Kra¨mer SD. Lipid membrane interactions of indacaterol and salmeterol: do they influence their pharmacological properties? Eur J Pharm Sci 2009; 38:533–547. 43. Patel S, Summerhill S, Stanley M, et al. The reassertion profiles of long acting beta2-adrenoceptor agonists in the guinea pig isolated trachea and human recombinant beta2-adrenoceptor. Pulm Pharmacol Ther 2011; 24:247–255. 44. Coleman RA. On the mechanism of the persistent action of salmeterol: what is the current position? Br J Pharmacol 2009; 158:180–182. 45. Anderson GP, Linden A, Rabe KF. Why are long-acting beta-adrenoceptor agonists long-acting? Eur Respir J 1994; 7:569–578. 46. Szczuka A, Wennerberg M, Packeu A, et al. Molecular mechanisms for the persistent bronchodilatory effect of the b2-adrenoceptor agonist salmeterol. Br J Pharmacol 2009; 158:183–194. 47. Vauquelin G, Charlton SJ. Long-lasting target binding and rebinding as mechanisms to prolong in vivo drug action. Br J Pharmacol 2010; 161: 488–508. 48. Ortega VE, Wechsler ME. Asthma pharmacogenetics. Curr Opin Allergy Clin & Immunol 2013; 4:399–409. A review of the pharmacogenetics of asthma highlighting the current understanding of the effect of polymorphisms for drug targets for the treatment of this disease. 49. Thomsen M, Nordestgaard BG, Sethi AA, et al. b2-adrenergic receptor polymorphisms, asthma and COPD: two large population-based studies. Eur Respir J 2011; 39:558–566.

50. Bleecker ER, Postma DS, Lawrance RM, et al. Effect of ADRB2 polymorphisms on response to long acting beta2-agonist therapy: a pharmacogenetic analysis of two randomised studies. Lancet 2007; 370:2118–2125. 51. Bleecker ER, Nelson HS, Kraft M, et al. b2-receptor polymorphisms in patients receiving salmeterol with or without fluticasone propionate. Am J Respir Crit Care Med 2010; 181:676–687. 52. Wechsler ME, Kunselman SJ, Chinchilli VM, et al. Effect of beta2-adrenergic receptor polymorphism on response to longacting beta2 agonist in asthma (LARGE trial): a genotype-stratified, randomised, placebo-controlled, crossover trial. Lancet 2009; 374:1754–1764. 53. Bateman ED, Kornmann O, Schmidt P, et al. Tiotropium is noninferior to salmeterol in maintaining improved lung function in B16-Arg/Arg patients with asthma. J Allergy Clin Immunol 2011; 128:315–322. 54. Page CP, Spina D. Beta2-agonists and bronchial hyperresponsiveness. Clin Rev Allergy Immunol 2006; 31:143–162. 55. Cockcroft DW, Sears MR. Are inhaled longacting b2 agonists detrimental to & asthma? Lancet Respir Med 2013; 1:339–346. Excellent review summarizing recent data concerning the safety of regular use of LABA in asthma and concluded that monotherapy should be avoided, and that the black box warning for LABA/inhaled corticosteroid should be lifted. 56. Cheung D, Timmers MC, Zwinderman AH, et al. Long-term effects of a longacting beta2-adrenoceptor agonist, salmeterol, on airway hyperresponsiveness in patients with mild asthma. N Engl J Med 1992; 327:1198–1203. 57. Lipworth B, Tan S, Devlin M, et al. Effects of treatment with formoterol on bronchoprotection against methacholine. Am J Med 1998; 104:431–438. 58. Haney S, Hancox RJ. Rapid onset of tolerance to beta-agonist bronchodilation. Respir Med 2005; 99:566–571. 59. Haney S, Hancox RJ. Tolerance to bronchodilation during treatment with longacting beta-agonists, a randomised controlled trial. Respir Res 2005; 6:107. 60. Wraight JM, Hancox RJ, Herbison GP, et al. Bronchodilator tolerance: the impact of increasing bronchoconstriction. Eur Respir J 2003; 21:810–815. 61. Giembycz MA. An estimation of beta 2-adrenoceptor reserve on human bronchial smooth muscle for some sympathomimetic bronchodilators. Br J Pharmacol 2009; 158:287–299. 62. Oakley RH, Laporte SA, Holt JA, et al. Differential affinities of visual arrestin, beta arrestin1, and beta arrestin2 for G protein-coupled receptors delineate two major classes of receptors. J Biol Chem 2000; 275:17201–17210. 63. Lee DK, Currie GP, Hall IP, et al. The arginine-16 beta2-adrenoceptor polymorphism predisposes to bronchoprotective subsensitivity in patients treated with formoterol and salmeterol. Br J Clin Pharmacol 2004; 57:68–75. 64. Walker JKL, Fong AM, Lawson BL, et al. b-Arrestin-2 regulates the development of allergic asthma. J Clin Investig 2003; 112:566–574. 65. Hollingsworth JW, Theriot BS, Li Z, et al. Both hematopoietic-derived and non-hematopoietic-derived b-arrestin-2 regulates murine allergic airway disease. Am J Respir Cell Mol Biol 2010; 43:269–275. 66. Shenoy SK, Lefkowitz RJ. b-arrestin-mediated receptor trafficking and signal transduction. Trends Pharmacol Sci 2011; 32:521–533. 67. Houslay MD. Arrestin times for developing antipsychotics and beta-blockers. Sci Signal 2009; 2:1–5. 68. Jin SL, Goya S, Nakae S, et al. Phosphodiesterase 4B is essential for T(H)2cell function and development of airway hyperresponsiveness in allergic asthma. J Allergy Clin Immunol 2010; 126:1252–1259. 69. Nguyen LP, Lin R, Parra S, et al. Beta2-adrenoceptor signaling is required for the development of an asthma phenotype in a murine model. Proc Natl Acad Sci U S A 2009; 106:2435–2440. 70. Thanawala VJ, Forkuo GS, Al-Sawalha N, et al. b2-Adrenoceptor agonists are & required for development of the asthma phenotype in a murine model. Am J Respir Cell Mol Biol 2013; 48:220–229. Genetic ablation of the enzyme required for the synthesis of epinephrine or pharmacological depletion of endogenous catecholamines with reserpine preempted the development of allergic lung inflammation. This suggests that activation of the b2-adrenoceptor is required to promote the allergic phenotype in mice. Indeed, chronic treatment with formoterol in epinephrine deficient mice recapitulated the allergic phenotype, potentially mimicking the increased morbidity seen with regular treatment with b2-agonists in asthma. 71. Callaerts-Vegh Z, Evans KL, Dudekula N, et al. Effects of acute and chronic administration of beta-adrenoceptor ligands on airway function in a murine model of asthma. Proc Natl Acad Sci U S A 2004; 101:4948–4953. 72. Nguyen LP, Omoluabi O, Parra S, et al. Chronic exposure to beta-blockers attenuates inflammation and mucin content in a murine asthma model. Am J Respir Cell Mol Biol 2008; 38:256–262. 73. Hanania NA, Singh S, El-Wali R, et al. The safety and effects of the betablocker, nadolol, in mild asthma: an open-label pilot study. Pulm Pharmacol Ther 2008; 21:134–141. 74. Hanania NA, Mannava B, Franklin AE, et al. Response to salbutamol in patients with mild asthma treated with nadolol. Eur Respir J 2010; 36: 963–965. 75. Short PM, Williamson PA, Anderson WJ, et al. Randomized placebo-con& trolled trial to evaluate chronic dosing effects of propranolol in asthma. Am J Respir Crit Care Med 2013; 187:1308–1314. Clinical trial demonstrating a lack of effect of chronic treatment with propranolol on BHR to methacholine, quality-of-life scores and airway inflammation as monitored by exhaled nitric oxide in mild-to-moderate asthma patients treated with muscarinic antagonist and inhaled glucocorticosteroid.



85


Asthma 76. Tashkin DP, Celli BR, Senn S, et al. A 4 year trial of tiotropium in chronic obstructive pulmonary disease. N Engl J Med 2007; 359:1543–1554. 77. Kerwin E, Hebert J, Gallagher N, et al. Efficacy and safety of NVA237 versus & placebo and tiotropium in patients with COPD: the GLOW2 study. Eur Respir J 2012; 40:1106–1114. A clinical study evaluating the clinical effectiveness of glycopyrronium bromide in COPD. Glycopyrronium bromide provided significant improvements in lung function, dyspnoea, health status, exacerbations and rescue medication use versus placebo, and was comparable with tiotropium bromide. 78. Beier J, Kirsten A-M, MrUˆz R, et al. Efficacy and safety of aclidinium bromide & compared with placebo and tiotropium in patients with moderate-to-severe chronic obstructive pulmonary disease: results from a 6-week, randomized, controlled phase IIIb study. COPD 2013; 10:511–522. Clinical study showing a similar degree of bronchodilator activity between aclidinium bromide and tiotropium in COPD. 79. Decramer M, Maltais F, Feldman G, et al. Bronchodilation of umeclidinium, a & new long-acting muscarinic antagonist, in COPD patients. Respir Physiol Neurobiol 2013; 185:393–399. A clinical study evaluating the dose–response effect for once a day treatment with umeclidinium bromide in COPD. 80. Donohue JF, Maleki-Yazdi MR, Kilbride S, et al. Efficacy and safety of once& daily umeclidinium/vilanterol 62.5/25 mcg in COPD. Respir Med 2013; 107:1538–1546. Clinical study demonstrating significantly greater changes in baseline FEV1 with once a day combination umeclidinium bromide and vilanterol compared with either drug alone. Although numerically greater, there was no significant difference in other outcome variables including quality-of-life scores, transition dyspnoea index and time to first exacerbation between combination versus monotherapy. 81. Sykes DA, Dowling MR, Leighton-Davies J, et al. The influence of && receptor kinetics on the onset and duration of action and the therapeutic index of NVA237 and tiotropium. J Pharmacol Exp Ther 2012; 343:520– 528. Excellent article comparing receptor kinetics of glycopyrronium and tiotropium bromide that demonstrates the importance of undertaking binding studies under physiological conditions. The dissociation half-life of tiotropium bromide is overestimated by at least 10-fold when nonphysiological conditions are employed. Receptor kinetics is therefore not an explanation of the sustained bronchodilation seen with LAMA and ultra-LAMAs. 82. Casarosa P, Bouyssou T, Germeyer S, et al. Preclinical evaluation of longacting muscarinic antagonists: comparison of tiotropium and investigational drugs. J Pharmacol Exp Ther 2009; 330:660–668. 83. Gavalda A, Miralpeix M, Ramos I, et al. Characterization of aclidinium bromide, a novel inhaled muscarinic antagonist, with long duration of action and a favorable pharmacological profile. J Pharmacol Exp Ther 2009; 331:740– 751.

86


84. Salmon M, Luttmann MA, Foley JJ, et al. Pharmacological characterization of GSK573719 (umeclidinium): a novel, long-acting, inhaled antagonist of the muscarinic cholinergic receptors for treatment of pulmonary diseases. J Pharmacol Exp Ther 2013; 345:260–270. Research article summarizing the binding characteristics against human recombinant M2 and M3-receptors, and in-vitro and in-vivo pharmacology of the LAMA, umeclidinium bromide. 85. Kerstjens HAM, Engel M, Dahl R, et al. Tiotropium in asthma poorly controlled & with standard combination therapy. N Engl J Med 2012; 367:1198–1207. Randomized clinical trials demonstrating the beneficial effect of tiotropium bromide in patients with poorly controlled asthma and in whom were concurrently prescribed inhaled glucocorticoids and LABAs. The time to the first severe exacerbation was significantly delayed with the addition of tiotropium bromide and was associated with modest sustained bronchodilation. 86. Peters SP, Kunselman SJ, Icitovic N, et al. Tiotropium bromide step-up therapy for adults with uncontrolled asthma. N Engl J Med 2010; 363:1715–1726. 87. Casarosa P, Kiechle T, Sieger P, et al. The constitutive activity of the human muscarinic M3 receptor unmasks differences in the pharmacology of anticholinergics. J Pharmacol Exp Ther 2009; 333:201–209. 88. Bateman ED, Rennard S, Barnes PJ, et al. Alternative mechanisms for tiotropium. Pulm Pharmacol Ther 2009; 22:533–542. 89. Mahler DA, D’Urzo A, Bateman ED, et al. Concurrent use of indacaterol plus & tiotropium in patients with COPD provides superior bronchodilation compared with tiotropium alone: a randomised, double-blind comparison. Thorax 2012; 67:781–788. Clinical trial comparing tiotropium monotherapy with indacaterol and tiotropium, and showing greater improvements in bronchodilation and lung deflation with combination therapy in moderate-to-more severe COPD. 90. Compton C, McBryan D, Bucchioni E, et al. The Novartis view on emerging & drugs and novel targets for the treatment of chronic obstructive pulmonary disease. Pulm Pharmacol Ther 2013; 26:562–573. A review of the clinical effectiveness of glycopyrronium bromide and indacaterol combination compared with monotherapy showing improved bronchodilator effectiveness of combination treatment compared with monotherapy. 91. Wedzicha JA, Decramer M, Ficker JH, et al. Analysis of chronic obstructive & pulmonary disease exacerbations with the dual bronchodilator QVA149 compared with glycopyrronium and tiotropium (SPARK): a randomised, double-blind, parallel-group study. Lancet Respir Med 2013; 1:199–209. Clinical trial demonstrating the superiority of combination indacaterol/glycopyrronium compared with glycopyrronium or tiotropium bromide alone against baseline FEV1, rate of exacerbation and quality-of-life scores in individuals with severe (GOLD stages III–IV) COPD. 92. Wielders PLML, Ludwig-Sengpiel A, Locantore N, et al. A new class of & bronchodilator improves lung function in COPD: a trial with GSK961081. Eur Respir J 2013; 42:972–981. Clinical study documenting dose–response effect for sustained bronchodilation with once a day MABA in patients with COPD. &



A Novel in vivo System to Test Bronchodilators.

Effect of bronchodilators on respiratory resistance in infants and young children with bronchiolitis and wheezy bronchitis.

Novel methods for diagnosis of respiratory disease.

Beware of nebulized bronchodilators.

Discovery of a novel nidovirus in cattle with respiratory disease.

Aerosol bronchodilators.

Prediction of acute respiratory disease in current and former smokers with and without COPD.

Aerosolized bronchodilators.

Inhaled bronchodilators and the risk of tachyarrhythmias.

Acute respiratory distress syndrome following cardiovascular surgery: current concepts and novel therapeutic approaches.

Current patterns of acute respiratory disease in the United States Navy and Marine Corps.

Editorial: Bronchodilators, new and old.

Beta-adrenergic bronchodilators.

Asthma. Bronchodilators: new developments.

Recurrent respiratory papillomatosis: current and future perspectives.

Long-acting bronchodilators in patients with chronic obstructive pulmonary disease: still more to know.

Prophylactic use of bronchodilators.

The role of anticholinergic bronchodilators in adult asthma and chronic obstructive pulmonary disease.

Implementing Precision Antimicrobial Therapy for the Treatment of Bovine Respiratory Disease: Current Limitations and Perspectives.

Ocular hazards of nebulized bronchodilators.

Bronchodilators use in patients with COPD.

Homelessness and respiratory disease.

Bronchodilators in patients with chronic obstructive pulmonary disease on mechanical ventilation. Utilization of metered-dose inhalers.

APOE-modulated Aβ-induced neuroinflammation in Alzheimer's disease: current landscape, novel data, and future perspective.