Emerging drugs for the treatment of chronic obstructive pulmonary disease

Green access to chiral Vince lactam in a buffer-free aqueous system using a newly identified substrate-tolerant (−)-γ-lactamase

A novel (−)-γ-lactamase with high catalytic efficiency, strong substrate tolerance and environmental friendliness was identified for green access to chiral Vince lactam.

Stabilization of porcine pancreatic elastase crystals by glutaraldehyde cross-linking

Elastase is a serine protease from the chymotrypsin family of enzymes with the ability to degrade elastin, an important component of connective tissues. Excessive elastin proteolysis leads to a number of pathological diseases. Porcine pancreatic elastase (PPE) is often used for drug development as a model for human leukocyte elastase (HLE), with which it shares high sequence identity. Crystals of PPE were grown overnight using sodium sulfate and sodium acetate at acidic pH. Cross-linking the crystals with glutaraldehyde was needed to resist the soaking procedure with a diethyl N-(methyl)pyridinyl-substituted oxo-β-lactam inhibitor. Crystals of PPE bound to the inhibitor belonged to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 51.0, b = 58.3, c = 74.9 Å, and diffracted to 1.8 Å resolution using an in-house X-ray source.

CBD binding domain fused γ-lactamase from Sulfolobus solfataricus is an efficient catalyst for (-) γ-lactam production

Background

γ-lactamase is used for the resolution of γ-lactam which is utilized in the synthesizing of abacavir and peramivir. In some cases, enzymatic method is the most utilized method because of its high efficiency and productivity. The cellulose binding domain (CBD) of cellulose is often used as the bio-specific affinity matrix for enzyme immobilization. Cellulose is cheap and it has excellent chemical and physical properties. Meanwhile, binding between cellulose and CBD is tight and the desorption rarely happened.

Results

We prepared two fusion constructs of the γ-lactamase gene gla, which was from Sulfolobus solfataricus P2. These two constructs had Cbd (cellulose binding domain from Clostridium thermocellum) fused at amino or carboxyl terminus of the γ-lactamase. These two constructs were heterogeneously expressed in E. coli rosetta (DE3) as two fusion proteins. Both of them were immobilized well on Avicel (microcrystalline cellulose matrix). The apparent kinetic parameters revealed that carboxyl terminus fused protein (Gla-linker-Cbd) was a better catalyst. The V_max and k_cat value of Avicel immobilized Gla-linker-Cbd were 381 U mg^-1 and 4.7 × 10⁵ s^-1 respectively. And the values of the free Gla-linker-Cbd were 151 U mg^-1 and 1.8 × 10⁵ s^-1 respectively. These data indicated that the catalytic efficiency of the enzyme was upgraded after immobilization. The immobilized Gla-linker-Cbd had a 10-degree temperature optimum dropping from 80°C to 70°C but it was stable when incubated at 60°C for 48 h. It remained stable in catalyzing 20-batch reactions. After optimization, the immobilized enzyme concentration in transformation was set as 200 mg/mL. We found out that there was inhibition that occurred to the immobilized enzyme when substrate concentration exceeded 60 mM. Finally a 10 mL-volume transformation was conducted, in which 0.6 M substrate was hydrolyzed and the resolution was completed within 9 h with a 99.5% ee value.

Conclusions

Cellulose is the most abundant and renewable material on the Earth. The absorption between Cbd domain and cellulose is a bio-green process. The cellulose immobilized fusion Gla exhibited good catalytic characters, therefore we think the cellulose immobilized Gla is a promising catalyst for the industrial preparation of (-) - γ-lactam.

Blood specimen biomarkers of inflammation, matrix degradation, angiogenesis, and cardiac involvement: a future useful tool in assessing clinical outcomes of COPD patients in clinical practice?

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible; this airflow limitation is both progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gasses. COPD is undoubtedly an umbrella term, and it seems unlikely that all patients with COPD have the same underlying disease processes; thus, there is a need for differential treatment of different subgroups. A potential solution is to find modifiable biomarkers that can assist in drug development and distinguish subgroups of COPD. With the exception of lung function tests, there are currently no well-validated biomarkers or surrogate endpoints that can be used to establish the efficacy of a drug for COPD. This article discusses biomarkers of inflammation (fibrinogen, C-reactive protein, pulmonary and activation-regulated chemokine/CC-chemokine ligand-18, serum surfactant protein D, interleukin (IL)-6, IL-8 and tumor necrosis factor α, complement factor C5a), angiogenesis factors as a part of the pathogenetic aspect in this disease (vascular endothelial growth factor, angiogenin, and IL-8), and matrix degradation biomarkers. Troponin and natriuretic peptides are presented as biomarkers of cardiac involvement in the light of COPD comorbidities. Trials based on research on known clinical variables such as FEV1, BODE, and 6MWT in combination with biomarkers from lung and blood specimens will probably clarify part of the prognosis and natural history of the disease. This will also represent an additional step in COPD phenotyping and new treatment possibilities.

Pathobiologic mechanisms of chronic obstructive pulmonary disease

COPD is a worldwide public health problem that reduces the quality of life. The exact pathways by which CS and other environmental toxins produce COPD are not known. Currently, the leading candidates are (1) the protease-antiprotease hypothesis, (2) the Dutch hypothesis, (3) the British hypothesis, and the (4) autoimmunity hypothesis. Given the heterogeneity of the disease (and phenotypes), it is probably unrealistic that one pathway will fully explain COPD pathophysiology.

Neutrophil elastase inhibitors

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) constitutes a worldwide health problem. There is currently an urgent and unmet need for the development of small molecule therapeutics capable of blocking and/or reversing the progression of the disorder. Recent studies have greatly illuminated our understanding of the multiple pathogenic processes associated with COPD. Of paramount importance is the key role played by proteases, oxidative stress, apoptosis and inflammation. Insights gained from these studies have made possible the exploration of new therapeutic approaches.

AREAS COVERED

An overview of major developments in COPD research with emphasis on low-molecular mass neutrophil elastase inhibitors is described in this review.

EXPERT OPINION

Great strides have been made toward our understanding of the biochemical and cellular events associated with COPD. However, our knowledge regarding the inter-relationships among the multiple pathogenic mechanisms and their mediators involved is still limited. The problem is further compounded by the unavailability of suitable validated biomarkers for assessing the efficacy of potential therapeutic interventions. The complexity of COPD suggests that effective therapeutic interventions may require the administration of more than one agent such as a human neutrophil elastase or MMP-12 inhibitor with an anti-inflammatory agent such as a PDE4 inhibitor or a dual function agent capable of disrupting the cycle of proteolysis, apoptosis, inflammation and oxidative stress.

Targeting non-malignant disorders with tyrosine kinase inhibitors

Receptor and non-receptor tyrosine kinases are involved in multiple proliferative signalling pathways. Imatinib, one of the first tyrosine kinase inhibitors (TKIs) to be approved, revolutionized the treatment of chronic myelogenous leukaemia, and other TKIs with different spectra of kinase inhibition are used to treat renal cell carcinoma, non-small-cell lung cancer and colon cancer. Studies also support the potential use of TKIs as anti-proliferative agents in non-malignant disorders such as cardiac hypertrophy, and in benign-proliferative disorders including pulmonary hypertension, lung fibrosis, rheumatoid disorders, atherosclerosis, in-stent restenosis and glomerulonephritis. In this Review, we provide an overview of the most recent developments--both experimental as well as clinical--regarding the therapeutic potential of TKIs in non-malignant disorders.

Dual function inhibitors of relevance to chronic obstructive pulmonary disease

The general strategy and rationale underlying the design of COPD therapeutics that possess protease inhibitory activity and are also capable of releasing a species that attenuates inflammation by inhibiting caspase-1, are described. The synthesis and in vitro biochemical evaluation of a dual function molecule that sequentially inhibits HNE and caspase-1 in a time-dependent manner is reported.

Effects of structure on inhibitory activity in a series of mechanism-based inhibitors of human neutrophil elastase

A structurally-diverse series of carboxylate derivatives based on the 1,2,5-thiadiazolidin-one 1,1 dioxide scaffold were synthesized and used to probe the S' subsites of human neutrophil elastase (HNE) and neutrophil proteinase 3 (Pr 3). Several compounds are potent inhibitors of HNE but devoid of inhibitory activity toward Pr 3, suggesting that the S' subsites of HNE exhibit significant plasticity and can, unlike Pr 3, tolerate various large hydrophobic groups. The results provide a promising framework for the design of highly selective inhibitors of the two enzymes.

Developments in drugs for the treatment of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) affects more than 600 million adults worldwide and accounts for 3 million deaths annually. Approximately 50% of the cases are directly attributable to cigarette smoking; the rest are accounted for by different risk factors, including childhood infections, genetic defects, environmental pollution and biomass exposure. The mainstay of current drug treatment is bronchodilation. Anti-inflammatory drugs are reserved for patients with moderate-to-severe disease. In this article, we will review the current paradigm of COPD pathogenesis and discuss some promising molecular targets that may be modified in the future to improve health outcomes of patients with COPD.

Synthesis, stability, biochemical and pharmacokinetic properties of a new potent and selective 4-oxo-β-lactam inhibitor of human leukocyte elastase

The 4-oxo-β-lactams (azetidine-2,4-diones) are potent acylating agents of the human leukocyte elastase (HLE), a neutrophil serine protease that plays a key role in several inflammatory diseases. A novel 4-oxo-β-lactam containing a N-(4-(phenylsulphonylmethyl)phenyl) group, 3, was designed as a potential mechanism-based inhibitor capable of undergoing elimination of phenylsulphinate upon Ser-195 acylation. Compound 3 was found to be a potent slow-tight binding inhibitor of HLE, presenting a remarkable second-order rate constant of 1.46 x 10⁶ M⁻¹s⁻¹ and displaying selectivity over the proteinase 3 and cathepsin G. However, liberation of phenylsulphinate was not observed in the hydrolysis of 3 in both pH 7.4 phosphate buffer and human plasma. The C(max) values of 1207 μg/total blood, 179 μg/g spleen and 106 μg/g lung were determined by HPLC, following a single 30 mg/kg dose of 3 given intraperitoneally to NMRI mice, suggesting that the inhibitor distributes well into tissues. Although being a powerful selective inhibitor of HLE, 4-oxo-β-lactam 3 has a limited stability, being susceptible to off-target reactions (plasma and liver enzymes).

Review: Surfactant protein D: A lung specific biomarker in COPD?

A major impediment in the development of novel drugs for chronic obstructive pulmonary disease (COPD) has been the scarcity of a well-validated, robust, and easily obtainable intermediate end point such as serum biomarkers. To date the best serum biomarkers in COPD have been non-speci“c pro-in”ammatory molecules synthesized largely by extra-pulmonary organs. In COPD, an ideal biomarker would be one that (1) was produced mostly in the lungs (and was reliably measurable in the peripheral circulation using commercially available kits), (2) changed with the clinical status of patients or with relevant exposures; and (3) had inherent functional attributes that suggested a possible causal role in the pathogenesis of the disease. In this paper, we review one promising systemic biomarker that ful“lls some of these criteria, surfactant protein D (SPD).

Chemical toxicology: reactive intermediates and their role in pharmacology and toxicology

Reactive intermediates formed during the metabolism of drugs have been investigated extensively over the past decades. Today, interest in reactive intermediates in drug discovery is focused on minimising bioactivation in hopes of reducing the risk of causing so-called idiosyncratic toxicity. These efforts are justified based on the 'hapten hypothesis', namely, that on binding to protein, reactive intermediates may elicit an immune response to the modified protein, leading to a cascade of events that ultimately manifests as a toxic outcome. However, the pharmacological action of certain drugs depends on reactive intermediates that modify critical amino acid residues of proteins, typically enzymes, thereby altering their activity. Thus, the notion that reactive intermediates are inherently dangerous is unjustified. When a reactive intermediate is necessary for the desired pharmacological effect of a drug, the selectivity it displays towards the target protein is crucial, as off-target binding may produce unwanted toxicities. On the other hand, reactive intermediates may play no role in toxicity. This review provides a balanced perspective, primarily focusing on the proposed role of reactive intermediates in drug toxicity, while also highlighting examples in which they are involved in causing the desired pharmacology. It is hoped that this knowledge can help scientists involved in drug discovery and development in their challenging task of producing safe and effective drugs.