Kinetic binding assays for the analysis of protein-ligand interactions

The importance of binding kinetics in terms of residence time and on-rate in drug discovery has been broadly accepted in the past few years. Furthermore, evidence has accumulated that the optimal binding mechanism of a drug to its target molecule is related to physiological efficacy as well as selectivity and thus drug safety. Homogeneous fluorescence-based binding assays have been shown to enable high throughput kinetics requiring only small amounts of protein and can be developed to elucidate even complex mechanisms of molecular recognition. A generalized approach is proposed that combines high quality kinetic and equilibrium data in an Integrated Global Fit analysis yielding the most probable binding mechanism.

On-rate based optimization of structure-kinetic relationship--surfing the kinetic map

In the lead discovery process residence time has become an important parameter for the identification and characterization of the most efficacious compounds in vivo. To enable the success of compound optimization by medicinal chemistry toward a desired residence time the understanding of structure-kinetic relationship (SKR) is essential. This article reviews various approaches to monitor SKR and suggests using the on-rate as the key monitoring parameter. The literature is reviewed and examples of compound series with low variability as well as with significant changes in on-rates are highlighted. Furthermore, findings of kinetic on-rate changes are presented and potential underlying rationales are discussed.

Tiotropium Respimat(®) Soft Mist™ inhaler: a review of its use in chronic obstructive pulmonary disease

The long-acting anticholinergic agent tiotropium bromide (Spiriva(®)) is available as a solution for inhalation via Respimat(®) Soft Mist™ Inhaler in the EU and various other countries for the treatment of chronic obstructive pulmonary disease (COPD). With the Respimat(®) Soft Mist™ Inhaler there is improved lung deposition of drug (allowing a reduced dosage compared with tiotropium HandiHaler(®)), the delivered drug dose is independent of inspiratory effort and the prolonged duration of the aerosol cloud should make the co-ordination of actuation and inhalation easier. In patients with COPD, tiotropium Respimat(®) improved lung function, COPD exacerbations, health-related quality of life and dyspnoea and was at least as effective as tiotropium HandiHaler(®). Tiotropium Respimat(®) was generally well tolerated in patients with COPD, with anticholinergic adverse events among the most commonly reported adverse events. In the TIOSPIR trial, tiotropium Respimat(®) was noninferior to tiotropium HandiHaler(®) in terms of all-cause mortality, and the risk of cardiovascular mortality or major adverse cardiovascular events did not significantly differ between the two treatment groups. In conclusion, tiotropium Respimat(®) Soft Mist™ Inhaler is a useful option for the treatment of patients with COPD.

Safety of inhaled glycopyrronium in patients with COPD: a comprehensive analysis of clinical studies and post-marketing data

Background

Chronic use of inhaled anticholinergics by patients with chronic obstructive pulmonary disease (COPD) has raised long-term safety concerns, particularly cardiovascular. Glycopyrronium is a once-daily anticholinergic with greater receptor selectivity than previously available agents.

Methods

We assessed the safety of inhaled glycopyrronium using data pooled from two analysis sets, involving six clinical studies and over 4,000 patients with COPD who received one of the following treatments: glycopyrronium 50μg, placebo (both delivered via the Breezhaler^® device), or tiotropium 18 μg (delivered via the HandiHaler^® device). Data were pooled from studies that varied in their duration and severity of COPD of the patients (ie, ≤12 weeks duration with patients having moderate or severe COPD; and >1 year duration with patients having severe and very severe COPD). Safety comparisons were made for glycopyrronium vs tiotropium or placebo. Poisson regression was used to assess the relative risk for either active drug or placebo (and between drugs where placebo was not available) for assessing the incidence of safety events. During post-marketing surveillance (PMS), safety was assessed by obtaining reports from various sources, and disproportionality scores were computed using EMPIRICA™. In particular, the cardiac safety of glycopyrronium during the post-marketing phase was evaluated.

Results

The overall incidence of adverse events and deaths was similar across groups, while the incidence of serious adverse events was numerically higher in placebo. Furthermore, glycopyrronium did not result in an increased risk of cerebro-cardiovascular events vs placebo. There were no new safety reports during the PMS phase that suggested an increased risk compared to results from the clinical studies. Moreover, the cardiac safety of glycopyrronium during the PMS phase was also consistent with the clinical data.

Conclusion

The overall safety profile of glycopyrronium was similar to its comparators indicating no increase in the overall risk for any of the investigated safety end points.

Pharmacological interaction between LABAs and LAMAs in the airways: optimizing synergy

Nowadays there is solid clinical information for combining β2-agonists and anti-muscarinic agents, although the nature (additive or synergistic) of the net clinical result obtained by co-administration of these two classes of bronchodilators is not completely elucidated from a pharmacological point of view. Recent preclinical studies demonstrated that combining a long-acting β2-agonist (LABA) with a long-acting anti-muscarinic agent (LAMA) provides synergistic benefit on airway smooth muscle relaxation, which may have major implications for the use of LABA/LAMA combinations in the treatment COPD. Indeed, the LABA/LAMA synergism has been proved also in patients with moderate-to-severe COPD. Nevertheless, there is still a strong medical need for dose-finding clinical trials designed to identify the most favourable doses of LABA/LAMA combinations able to induce a real synergism. We strongly believe that the Bliss Independence theory represents an effective model for investigating the cross-talk between β2-adrenoreceptor and the muscarinic pathways leading to the synergistic interaction between β2-agonists and anti-muscarinic agents. In any case, the possibility of eliciting a synergistic bronchodilator effect when combining a LABA and a LAMA suggests that the therapeutic approach proposed by GOLD recommendations to only use LABA/LAMA combination in more severe COPD patients who are not controlled by a single bronchodilator should be reconsidered. We support the possibility of an early intervention with low doses of LABA/LAMA combination to optimize bronchodilation and reduce the risk of adverse events that characterize both LABAs and LAMAs, especially when administered at the full doses currently approved for the treatment of COPD.

Pharmacology of novel treatments for COPD: are fixed dose combination LABA/LAMA synergistic?

Bronchodilators are mainstay for the symptomatic treatment of chronic obstructive pulmonary disease (COPD) and the introduction of long-acting bronchodilators has led to an improvement in the maintenance treatment of this disease. Various clinical trials have evaluated the effects of fixed dose long-acting β2-agonists (LABA)/long-acting anti-muscarinics (LAMA) combinations and documented greater improvements in spirometry but such improvements do not always translate to greater improvements in symptom scores or reduction in the rates of exacerbation compared with a single component drug. An analysis of whether this significantly greater change in spirometry with combination therapy is additive or synergistic was undertaken and is the subject of this review. Bronchodilators are not disease modifiers and whilst glucocorticosteroids have been shown to reduce rates of exacerbation in moderate to severe COPD, the increase risk of pneumonia and bone fractures is a motivation enough to warrant developing novel anti-inflammatory and disease-modifying drugs and with the expectation of positive outcomes.

Pharmacologic rationale, efficacy and safety of the fixed-dose co-formulation of indacaterol and glycopyrronium

Chronic obstructive pulmonary disease (COPD) is a widespread respiratory disorder, usually characterized by progressive and poorly reversible airflow limitation. Inhaled long-acting bronchodilators, namely LABA (long-acting β2-adrenergic agonists) and LAMA (long-acting muscarinic receptor antagonists) are the mainstay of COPD treatment. Because the symptoms of many patients with COPD do not satisfactorily improve by using a single, either LABA or LAMA bronchodilator, the synergism of action resulting from the combination of the different bronchodilating mechanisms activated by LABA and LAMA, respectively, can significantly contribute to a better disease control. Based on these clinical and pharmacological considerations, several LABA/LAMA fixed-dose combinations have been developed and experimentally evaluated. Within such a context, the drug co-formulation containing indacaterol and glycopyrronium is probably the LABA/LAMA association which has been most extensively studied during the last few years.

Profile of inhaled glycopyrronium bromide as monotherapy and in fixed-dose combination with indacaterol maleate for the treatment of COPD

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality. The cornerstone of pharmacological treatment for COPD is bronchodilation. Inhaled glycopyrronium bromide is a long-acting muscarinic antagonist developed as a maintenance treatment for patients with COPD. Phase III trials have shown that glycopyrronium produces rapid and sustained bronchodilation with an efficacy similar to tiotropium and is well tolerated, with a low incidence of muscarinic side effects in patients with moderate to severe COPD. A combination of glycopyrronium bromide with indacaterol maleate (QVA149) has recently been approved as a once-daily maintenance therapy in adult patients with COPD. Phase III trials (the IGNITE program) with QVA149 have demonstrated significant improvements in lung function versus placebo, glycopyrronium, and tiotropium in patients with moderate to severe COPD, with no safety concerns of note. Hence QVA149 is a safe treatment option for moderate to severe COPD patients in whom long-acting muscarinic antagonist monotherapy is inadequate.

Treatment of chronic obstructive pulmonary disease by dual bronchodilation with coformulation of indacaterol/glycopyrronium

Bronchodilators are the cornerstone of the treatment of chronic obstructive pulmonary disease (COPD). In particular, the most commonly used drugs are inhaled long-acting agents, including long-acting β2-adrenergic agonists (LABAs) and long-acting muscarinic receptor antagonists (LAMAs). The combination of a LABA with a LAMA, i.e. of molecules characterized by different mechanisms of action, results in a synergistic enhancement of their clinical and functional effects. Therefore, this combined treatment can be implemented in a number of cases in which disease control is not adequately achieved by a single active agent such as a LABA or a LAMA. Several LABA/LAMA fixed-dose combinations, mainly made up of newly developed compounds, are currently in advanced phases of experimental evaluation. Within such a context, the aim of this review is to outline the pharmacological basis of dual bronchodilation as well as to discuss the results of the main trials carried out using the drug combination consisting of indacaterol and glycopyrronium, a LABA and a LAMA recently introduced in the treatment of COPD.

Modified T4 Lysozyme Fusion Proteins Facilitate G Protein-Coupled Receptor Crystallogenesis

G protein-coupled receptors (GPCRs) mediate the majority of cellular responses to hormones and neurotransmitters. Most GPCR crystal structures have been obtained using a fusion protein strategy where the flexible third intracellular loop is replaced by T4 lysozyme (T4L). However, wild-type T4L may not be ideally suited for all GPCRs because of its size and the inherent flexibility between the N- and C-terminal subdomains. Here we report two modified T4L variants, designed to address flexibility and size, that can be used to optimize crystal quality or promote alternative packing interactions. These variants were tested on the M3 muscarinic receptor (M3). The original M3-T4L fusion protein produced twinned crystals that yielded a 3.4 Å structure from a 70 crystal data set. We replaced T4L with the modified T4L variants. Both T4L variants yielded M3 muscarinic receptor crystals with alternate lattices that were not twinned, including one that was solved at 2.8 Å resolution.

Current and novel bronchodilators in respiratory disease

PURPOSE OF REVIEW

β2-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 β2-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 β2-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 β2-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 β2-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.

Is there a rationale and role for long-acting anticholinergic bronchodilators in asthma?

Despite current guidelines and the range of available treatments, over a half of patients with asthma continue to suffer from poor symptomatic control and remain at risk of future worsening. Although a number of non-pharmacological measures are crucial for good clinical management of asthma, new therapeutic controller medications will have a role in the future management of the disease. Several long-acting anticholinergic bronchodilators are under investigation or are available for the treatment of respiratory diseases, including tiotropium bromide, aclidinium bromide, glycopyrronium bromide, glycopyrrolate and umeclidinium bromide, although none is yet licensed for the treatment of asthma. A recent Phase III investigation demonstrated that the once-daily long-acting anticholinergic bronchodilator tiotropium bromide improves lung function and reduces the risk of exacerbation in patients with symptomatic asthma, despite the use of inhaled corticosteroids (ICS) and long-acting β₂-agonists (LABAs). This has prompted the question of what the rationale is for long-acting anticholinergic bronchodilators in asthma. Bronchial smooth muscle contraction is the primary cause of reversible airway narrowing in asthma, and the baseline level of contraction is predominantly set by the level of ‘cholinergic tone’. Patients with asthma have increased bronchial smooth muscle tone and mucus hypersecretion, possibly as a result of elevated cholinergic activity, which anticholinergic compounds are known to reduce. Further, anticholinergic compounds may also have anti-inflammatory properties. Thus, evidence suggests that long-acting anticholinergic bronchodilators might offer benefits for the maintenance of asthma control, such as in patients failing to gain control on ICS and a LABA, or those with frequent exacerbations.

Outline of Therapeutic Interventions With Muscarinic Receptor-Mediated Transmission

Muscarinc receptor-mediated signaling takes part in many physiological functions ranging from complex higher nervous activity to vegetative responses. Specificity of action of the natural muscarinic agonist acetylcholine is effected by action on five muscarinic receptor subtypes with particular tissue and cellular localization, and coupling preference with different G-proteins and their signaling pathways. In addition to physiological roles it is also implicated in pathologic events like promotion of carcinoma cells growth, early pathogenesis of neurodegenerative diseases in the central nervous system like Alzheimer´s disease and Parkinson´s disease, schizophrenia, intoxications resulting in drug addiction, or overactive bladder in the periphery. All of these disturbances demonstrate involvement of specific muscarinic receptor subtypes and point to the importance to develop selective pharmacotherapeutic interventions. Because of the high homology of the orthosteric binding site of muscarinic receptor subtypes there is virtually no subtype selective agonist that binds to this site. Activation of specific receptor subtypes may be achieved by developing allosteric modulators of acetylcholine binding, since ectopic binding domains on the receptor are less conserved compared to the orthosteric site. Potentiation of the effects of acetylcholine by allosteric modulators would be beneficial in cases where acetylcholine release is reduced due to pathological conditions. When presynaptic function is severly compromised, the utilization of ectopic agonists can be a thinkable solution.

Inhalation of glycopyrronium inhibits cigarette smoke-induced acute lung inflammation in a murine model of COPD

Glycopyrronium bromide (GB) is a muscarinic receptor antagonist that has been used as a long-acting bronchodilator in chronic obstructive pulmonary disease (COPD) patients. The aim of this study was to investigate the anti-inflammatory activity of inhaled GB in a cigarette smoke-induced acute lung inflammation mouse model. We found that aerosol pre-treatment with GB suppresses the accumulation of neutrophils and macrophages in the bronchoalveolar lavage fluid (BALF) in cigarette smoke (CS)-exposed mice. GB at doses of 300 and 600 μg/ml significantly inhibited the CS-induced increases in the mRNA and protein expression levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1 and transforming growth factor (TGF)-β1 in lung tissues and the BALF. Moreover, GB at a dose of 600 μg/ml significantly inhibited the CS-induced changes in glutathione (GSH) and myeloperoxidase (MPO) activities in the BALF, decreased the CS-induced expression of matrix metalloproteinases (MMP)-9, and increased the CS-induced expression of tissue inhibitor of metalloproteinases (TIMP)-1, as determined through the immunohistochemical staining of lung tissue. Our results demonstrate the beneficial effects of inhaled GB on the inflammatory reaction in COPD.

Once-daily glycopyrronium via the Breezhaler® device for the treatment of COPD: pharmacological and clinical profile

In the management of chronic obstructive pulmonary disease (COPD), there is an unmet medical need for effective bronchodilator treatments that not only have a fast onset of action, but also a long duration of action and are delivered using a simple, easy-to-use device. Long-acting muscarinic antagonists such as glycopyrronium and tiotropium, along with long-acting beta-2 agonists such as indacaterol, formoterol and salmeterol are the pillars of pharmacological therapy for the long-term management of patients with COPD. Glycopyrronium, the quaternary ammonium ion of glycopyrronium bromide, acts as a competitive antagonist by selectively binding to the muscarinic receptors in the bronchial smooth musculature, thus inhibiting acetylcholine-mediated bronchoconstriction. Glycopyrronium is an inhaled once-daily long-acting muscarinic antagonist recently approved for the maintenance treatment of patients with COPD. Glycopyrronium is administered by a single-dose, dry-powder inhaler, the Breezhaler® device, designed specifically to have a low internal resistance, be easy to use and confirm efficient drug delivery in patients with a wide range of COPD severities, irrespective of the age. Glycopyrronium has been shown to provide rapid and sustained improvements in lung function, dyspnea, health status, exercise endurance and exacerbation risk and an acceptable safety and tolerability profile.

The Novartis view on emerging drugs and novel targets for the treatment of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a debilitating lung disease characterized by airflow limitation and chronic inflammation in the lungs. The mainstay of drug therapy for COPD is represented by long-acting bronchodilators, an important aspect of Novartis' development program. Novel once-daily dosing bronchodilators, such as the long-acting muscarinic antagonist (LAMA) glycopyrronium and the LAMA/long-acting β2-agonist (LABA) fixed-dose combination QVA149, have been shown to provide significant benefits to patients with COPD in terms of improvement in lung function, exercise tolerance, health-related quality of life, symptoms and reduction in the rate of exacerbations. Despite the benefits provided by these new treatment options, prevention of disease progression and control of exacerbations in certain patient phenotypes remain key challenges in the treatment of COPD. In order to address these needs and gain new insights into the complexity of COPD, Novartis is, in addition to bronchodilator-only therapies, developing LABA/inhaled corticosteroids (ICS) combinations to target inflammation, such as QMF149, as well as non-steroid based anti-inflammatory agents against key novel targets. These commitments are central to the Novartis' final goal of improving the standard of care in respiratory medicine and offering a better quality of life to patients with COPD.

Symptom variability in COPD: a narrative review

Chronic obstructive pulmonary disease (COPD) has traditionally been considered an inexorably progressive disease, associated with a constant increase of symptoms that occur as the forced expiratory volume in 1 second (FEV1) worsens, only intermittently interrupted by exacerbations. However, this paradigm has been challenged in recent decades by the available evidence. Recent studies have pointed out that COPD-related symptoms are not consistently perceived by patients in the same way, showing not only seasonal variation, but also changes in symptom perception during a week or even within a single day. According to the available data, patients experience the biggest increase in respiratory symptoms during the first hours of the early morning, followed by the nighttime. This variation over time is of considerable importance, since it impacts on daily life activities and health-related quality of life, as measured by a recently developed ad hoc questionnaire. Additionally, recent clinical trials have suggested that the use of rapid-onset long-acting bronchodilators may have an impact on morning symptoms, despite their current use as maintenance treatment for a determined period. Although this hypothesis is to be validated in future long-term clinical trials comparing fast-onset versus slow-onset inhaled drugs in COPD, it may bring forward a new concept of long-term bronchodilator therapy. At the present time, the two available long-acting, fast-onset bronchodilators used in the treatment of COPD are formoterol and the recently marketed indacaterol. Newer drugs have also been shown to have a rapid onset of action in preclinical studies. Health care professionals caring for COPD patients should consider this variation in the perception of symptoms during their clinical interview as a potential new target in the long-term treatment plan.

Pharmacotherapies for COPD

This review article summarizes the main treatments for chronic obstructive pulmonary disease, their mechanisms, and the key evidence from trials supporting their use. Drug classes covered were short acting beta agonists (SABA), short acting muscarinic antagonists (SAMA), long acting beta agonists (LABA), long acting antimuscarinics (LAMA), inhaled corticosteroids (ICS), LABA/ICS combinations, specific phosphodiesterase (PDE4) inhibitors, non-specific PDE inhibitors, mucolytics, and oxygen. Non-specific therapies, such as opiates for relief of dyspnoea and therapies for smoking cessation, are also covered briefly. For each class of drug, mechanisms of action are described, key clinical trial results are reported, and available agents compared. Finally, the place of each drug in therapy is compared between current worldwide guidelines.

Profile of glycopyrronium for once-daily treatment of moderate-to-severe COPD

Bronchodilators are central in the symptomatic management of chronic obstructive pulmonary disease (COPD). Long-acting muscarinic antagonists (LAMAs) and long-acting β(2)-agonists (LABAs) are the main classes of long-acting bronchodilators. To date, tiotropium is the only once-daily LAMA available for the treatment of COPD. Glycopyrronium is a novel LAMA, currently in development for COPD. Phase II studies have shown that glycopyrronium 50 μg once daily provides clinically significant 24-hour bronchodilation with a rapid onset of action, which is faster than that of tiotropium, and a favorable safety and tolerability profile. The Phase III GLycopyrronium bromide in COPD airWays (GLOW) program has now confirmed the long-term efficacy and tolerability of glycopyrronium 50 μg once daily. The three studies included in this program have further shown that the effect of glycopyrronium versus placebo is similar to that of tiotropium in reducing dyspnea and the risk of exacerbations, as well as improving lung function, exercise tolerance, and health status in patients with COPD. The safety profile of glycopyrronium is also similar to that of tiotropium in terms of overall incidence of adverse events and muscarinic side effects. Glycopyrronium could be an alternative choice to tiotropium, and like tiotropium, has the potential to be used as a monotherapy or combination therapy. Phase II studies have shown that a fixed-dose combination of glycopyrronium and the 24-hour LABA indacaterol, produces rapid and sustained bronchodilation compared with indacaterol monotherapy in patients with COPD. Phase III studies are currently ongoing to assess the long-term efficacy and safety of this combination.