Novel medications for asthma: a look at the future

Small Airway Absorption and Microdosimetry of Inhaled Corticosteroid Particles after Deposition

PURPOSE

To predict the cellular-level epithelial absorbed dose from deposited inhaled corticosteroid (ICS) particles in a model of an expanding and contracting small airway segment for different particle forms.

METHODS

A computational fluid dynamics (CFD)-based model of drug dissolution, absorption and clearance occurring in the surface liquid of a representative small airway generation (G13) was developed and used to evaluate epithelial dose for the same deposited drug mass of conventional microparticles, nanoaggregates and a true nanoaerosol. The ICS medications considered were budesonide (BD) and fluticasone propionate (FP). Within G13, total epithelial absorption efficiency (AE) and dose uniformity (microdosimetry) were evaluated.

RESULTS

Conventional microparticles resulted in very poor AE of FP (0.37%) and highly nonuniform epithelial absorption, such that <5% of cells received drug. Nanoaggregates improved AE of FP by a factor of 57-fold and improved dose delivery to reach approximately 40% of epithelial cells. True nanoaerosol resulted in near 100% AE for both drugs and more uniform drug delivery to all cells.

CONCLUSIONS

Current ICS therapies are absorbed by respiratory epithelial cells in a highly nonuniform manner that may partially explain poor clinical performance in the small airways. Both nanoaggregates and nanoaerosols can significantly improve ICS absorption efficiency and uniformity.

The future in paediatric respirology

The authors were given the charge of providing a vision of the future in paediatric respirology. Themes selected for being ripe for this visionary analysis include bronchopulmonary dysplasia (BPD), asthma, cystic fibrosis (CF), lung infections, obstructive sleep disordered breathing (OSDB) and pulmonary diagnostics and monitoring. A profound reduction or elimination of BPD is seen. Given the strong genetic component of this disease, genetic biomarkers will likely be identified that will permit much earlier recognition of BPD susceptibility and potentially the ability to modify disease course by altering gene expression. The ultimate prevention of BPD will be to prevent prematurity, but recognition of both the genetic basis of BPD and the inflammatory background should lead to improved prevention and therapy. A clear understanding and definition of asthma phenotypes will lead to more specific and targeted therapy, earlier detection and prevention, better monitoring of severity and adherence to therapy, lower mortality and decreased inappropriate diagnosis of asthma. The greatest opportunities in asthma care will likely come through tools to improve adherence to effective therapy. Also, areas are identified where better therapies are needed such as in patients with severe mucus hypersecretion (secretory hyperresponsiveness) especially in those with life-threatening asthma. The future of CF is easier to foresee with early successes seen in clinical trials. After the expected ability to correct the CF transmembrane regulator, care will need to change and additional research will be needed. Additionally, the face of CF is changing with more adults than children presently having the disease. This will necessitate changes to our approach to treating this disease in a fortunately aging population. If we are going to affect the worldwide lung health of children, we will need to address respiratory infections particularly pneumonia, tuberculosis and HIV-associated infections. Preventive, diagnostic and treatment strategies will shape the future face of these problems. The availability of inexpensive, readily available, and rapid molecular techniques to identify true infection (including HIV and tuberculosis) may permit earlier use of effective therapy while preventing the inappropriate use of antibiotics for common viral diseases. Sleep medicine will continue to be an important aspect of paediatric pulmonology. The evaluation of OSDB cannot rely on full-night attended polysomnography due to limited access. Identifying reliable markers of end organ dysfunction in children with OSDB may permit more rapid identification of patients in need of intervention like CPAP and assisted breathing. In addition, management options, as an alternative to adenotonsilectomy, are listed with a call for further research. Pulmonary diagnostics and monitoring will see the development and refinement of tools like the lung clearance index and the analysis of exhaled gases, volatiles and dissolved biomarkers of inflammation as techniques that might help clinicians identify both the initiation of inflammation while it is more amenable to therapy, and to identify more readily the early changes associated with chronic lung diseases in children. The authors hope that these visionary articles will generate comments, arguments, inspiration, and perhaps even motivate funding agencies.

Purinergic regulation of neutrophil chemotaxis

Chemotaxis allows polymorphonuclear neutrophils (PMN) to rapidly reach infected and inflamed sites. However, excessive influx of PMN damages host tissues. Better knowledge of the mechanisms that control PMN chemotaxis may lead to improved treatments of inflammatory diseases. Recent findings suggest that ATP and adenosine are involved in PMN chemotaxis. Therefore, these purinergic signaling processes may be suitable targets for novel therapeutic approaches to ameliorate host tissue damage.