Selective Nonsteroidal Glucocorticoid Receptor Modulators for the Inhaled Treatment of Pulmonary Diseases.

A class of potent, nonsteroidal, selective indazole ether-based glucocorticoid receptor modulators (SGRMs) was developed for the inhaled treatment of respiratory diseases. Starting from an orally available compound with demonstrated anti-inflammatory activity in rat, a soft-drug strategy was implemented to ensure rapid elimination of drug candidates to minimize systemic GR activation. The first clinical candidate 1b (AZD5423) displayed a potent inhibition of lung edema in a rat model of allergic airway inflammation following dry powder inhalation combined with a moderate systemic GR-effect, assessed as thymic involution. Further optimization of inhaled drug properties provided a second, equally potent, candidate, 15m (AZD7594), that demonstrated an improved therapeutic ratio over the benchmark inhaled corticosteroid 3 (fluticasone propionate) and prolonged the inhibition of lung edema, indicating potential for once-daily treatment.

The discovery of a selective and potent A2a agonist with extended lung retention.

Although the anti-inflammatory role of the A2a receptor is well established, controversy remains with regard to the therapeutic value for A2a agonists in treatment of inflammatory lung diseases, also as a result of unwanted A2a-mediated cardiovascular effects. In this paper, we describe the discovery and characterization of a new, potent and selective A2a agonist (compound 2) with prolonged lung retention and limited systemic exposure following local administration. To support the lead optimization chemistry program with compound selection and profiling, multiple in vitro and in vivo assays were used, characterizing compound properties, pharmacodynamics (PD), and drug concentrations. Particularly, pharmacokinetic-PD modeling was applied to quantify the effects on the cardiovascular system, and an investigative toxicology study in rats was performed to explore potential myocardial toxicities. Compound 2, in comparison to a reference A2a agonist, UK-432,097, demonstrated higher solubility, lower lipophilicity, lower plasma protein binding, high rat lung retention (28% remaining after 24 h), and was efficacious in a lung inflammatory rat model following intratracheal dosing. Despite these properties, compound 2 did not provide a sufficient therapeutic index, that is, separation of local anti-inflammatory efficacy in the lung from systemic side effects in the cardiovascular system. The plasma concentration that resulted in induction of hypotension (half maximal effective concentration; EC50 0.5 nmol/L) correlated to the in vitro A2a potency (rIC50 0.6 nmol/L). Histopathological lesions in the heart were observed at a dose level which is threefold above the efficacious dose level in the inflammatory rat lung model. In conclusion, compound 2 is a highly potent and selective A2a agonist with significant lung retention after intratracheal administration. Despite its local anti-inflammatory efficacy in rat lung, small margins to the cardiovascular effects suggested limited therapeutic value of this compound for treatment of inflammatory lung disease by the inhaled route.

Sensitivity of disease parameters to flexible budesonide/formoterol treatment in an allergic rat model.

RATIONALE: Clinical studies show that flexible dosing (maintenance and symptom-driven dose adjustments) of budesonide and formoterol (BUD/FORM) improves control of asthma exacerbations as compared to fixed maintenance dosing protocols (maintenance therapy) even when the latter utilize higher BUD/FORM doses. This suggests that dose-response relationships for certain pathobiologic mechanisms in asthma shift over time. Here, we have conducted animal studies to address this issue. OBJECTIVES: (1) To test in an animal asthma-like model whether it is possible to achieve the same or greater pharmacological control over bronchoconstriction and airway/lung inflammation, and with less total drug used, by flexible BUD/FORM dosing (upward adjustment of doses) in association with allergen challenges. (2) To determine whether the benefit requires adjustment of both drug components. METHODS: Rats sensitized on days 0 and 7 were challenged intratracheally with ovalbumin on days 14 and 21. On days 13-21, rats were treated intratracheally with fixed maintenance or flexible BUD/FORM combinations. On day 22, rats were challenged with methacholine and lungs were harvested for analysis. RESULTS: A flexible BUD/FORM dosing regimen (using 3.3 times less total drug than the fixed maintenance high dose regimen), delivered the same or greater reductions of excised lung gas volume (a measure of gas trapped in lung by bronchoconstriction) and lung weight (a measure of inflammatory oedema). When either BUD or FORM alone was increased on days of challenge, the benefit of the flexible dose upward adjustment was lost. CONCLUSIONS: Flexible dosing of the BUD/FORM combination improves the pharmacological inhibition of allergen-induced bronchoconstriction and an inflammatory oedema in an allergic asthma-like rat model.

Evaluation of excised lung gas volume measurements in animals with genetic or induced emphysema.

Emphysema, a leading cause of respiratory disability and mortality in humans, is characterized by destruction of alveolar walls and enlargement of airspaces. Animal studies are critical in understanding the pathogenesis of emphysema. However, current measurements of airspace enlargement and emphysema in small laboratory animals are labor intensive and may not be sensitive enough for measuring alterations in lung function and structure at the early stages of emphysema. In this study, we have investigated the excised lung gas volume (ELGV) measurement as a potential index for determining airspace enlargement in pallid mice with developing emphysema, in tight-skin mice with developed emphysema, or in Wistar rats with emphysema induced by an intratracheal instillation of pancreatic elastase. Our results showed that values of both ELGV per lung and per gram lung tissue were significantly increased in all three emphysema models, compared to control. The ELGV values were correlated well with morphometric evaluation of emphysema. Variations in transpulmonary pressures caused by different termination procedures were critical factors influencing the ELGV values. The present study demonstrates that ELGV measurement is a simple and sensitive method to monitor the development of emphysema.

Effects of budesonide and N-acetylcysteine on acute lung hyperinflation, inflammation and injury in rats.

Leukocyte activation and production of inflammatory mediators and reactive oxygen species are important in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury. The present study investigated acute lung hyperinflation, edema, and lung inflammation 4 h after an intratracheal instillation of LPS (0.5, 2.5, 5, 10, 50, 100, 500, 1000, and 5000 microg/ml/kg). Effects of budesonide, an inhaled anti-inflammatory corticosteroids, and N-acetylcysteine (NAC), an antioxidant, were evaluated in Wistar rats receiving either low (2.5 microg/ml/kg) or high (50 microg/ml/kg) concentrations of LPS. This study demonstrates that LPS in a concentration-dependent pattern induces acute lung hyperinflation measured by excised lung gas volume (25-45% above control), lung injury indicated by increased lung weight (10-60%), and lung inflammation characterized by the infiltration of leukocytes (40-14000%) and neutrophils (80-17000%) and the production of cytokines (up to 2700%) and chemokines (up to 350%) in bronchoalveolar lavage fluid (BALF). Pretreatment with NAC partially prevented tumor necrosis factor alpha (TNFalpha) production induced by the low concentration of LPS, while pretreatment with budesonide totally prevented the increased production of TNFalpha, interleukin (IL)-1beta, IL-6, and monocyte chemoattractive protein (MCP)-1 after LPS challenge at both low and high concentrations. Budesonide failed to prevent BALF levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant 1 (GRO/CINC-1) as well as lung hyperinflation induced by both low and high concentrations of LPS. Pretreatment with budesonide totally prevented the formation of lung edema at the low concentration of LPS and had partial effects on acute lung injury and leukocyte influx at the high concentrations. Thus, our data indicate that therapeutic effects of budesonide and NAC are dependent upon the severity of the disease.

Lung inflammatory responses and hyperinflation induced by an intratracheal exposure to lipopolysaccharide in rats.

Exposure of the respiratory tract to lipopolysaccharide (LPS) induces acute local inflammation and tissue injury associated with the various deliveries of LPS. To determine potential association of local inflammatory responses with respiratory tract dysfunction, infiltration of inflammatory cells, production of inflammatory mediators, lung hyperinflation and edema were measured in Wister rats 2, 4, and 24 h after an intratracheal administration of LPS at different doses (5, 50, 500 and 5000 microg/ml/kg). Lung hyperinflation determined by an increased excised lung gas volume was significantly increased 2 and 4 h after LPS instillation and lung edema occurred from 2 h onward. Peak BAL levels of TNFalpha appeared at 2 h, MCP-1 at 4 h, and IL-6 at 2 and 4 h, while BAL levels of IL-1beta were increased during 24 h after the intratracheal instillation of LPS. Neutrophilia in BAL fluid was noted from 2 h post-challenge. Our results demonstrate a clear dose-related change in the lung weight at 4 and 24 h, in the BAL levels of MCP-1 at 4 h, and IL-6 and IL-1beta at 2 and 4 h. It seems important to understand polymorphisms of LPS-induced lung hyperinflation and inflammation. Lung hyperinflation and inflammation may be independent during the development of acute lung injury.