Study of the Mechanisms of Asthma (MAST)

The purpose of this study is to identify the causes of asthma that were not previously suspected, to better understand the effects of inhaled steroids on asthma and to identify new way to treat asthma. In order to take advantage of the most current scientific expertise, we (scientists at UCSF) plan to work together with Genentech Inc. We believe that working with Genentech will provide the best chance of developing new treatments for asthma.

Asthma is a common airway disease with persistent unmet needs on terms of treatment. Although many asthmatics enjoy good control of their disease by using regularly scheduled corticosteroid treatment, a significant minority do not achieve optimal control with steroids and suffer asthma exacerbations which can be severe and even fatal. Asthma pathophysiology is complex and involves multiple cell types and multiple signaling mechanisms. One approach to this complexity has been to study responses of isolated airway cells to experimental conditions which model asthmatic inflammation; another has been genetic manipulations of candidate mediators of asthma in inbred mice. These studies have yielded important insights about possible mechanisms of asthma in humans, but the relevance of these mechanisms to human disease has not always been proven, and it is possible that unsuspected mechanism have not yet been revealed by these approaches. In the studies proposed here we will take an experimental approach which takes advantage of the distinct clinical phenotype of human asthma, the ability to measure steroid response in asthma, the relative ease of collecting airway cells and tissues by bronchoscopy, and the availability of new technologies such as high density microarrays which have probes for all genes in the genome or proteomics which can identify all proteins present in a biologic sample. Using this approach, we will identify differential expression of genes and proteins in airway cells and tissues in asthma that can then be explored further in cell and animal model systems to determine their potential as drug targets in asthma. We further believe that our approach will identify previously unsuspected mechanisms of action of corticosteroids in airway cells and tissues in asthma. Presently, relatively little is known about why some asthmatics respond well and some poorly to steroids and closing this gap in knowledge will help identify candidate genes and proteins to target in order to address unmet therapeutic needs in asthmatics with steroid resistant asthma.

Asthmatics, who are already on inhaled corticosteroids who will be put on standardized dose of inhaled corticosteroids

The primary outcome measure for this study is the scaled mean value of three gene expression markers of IL-13 in the airway: PERIOSTIN, calcium-activated chloride channel regulator 1 (CLCA1), and plasminogen activator inhibitor-2 (SERPINB2). First, for each of the three interleukin-13 (IL-13) signature genes, the log (base-2) transformed relative expression value for each subject is measured using real-time polymerase chair reaction (PCR) and normalized with the geometric mean of 5 housekeeping genes. Next, these values are centered (by subtracting the mean for that gene) and scaled (by dividing by the standard deviation for that gene) so that each gene makes an equal, assay-independent contribution to the Th2 phenotype. Then, for each subject, the arithmetic mean of the three centered & scaled genes is calculated, producing the "three-gene-mean" metric.

Healthy Control: Visit 2 (at 1 week); Steroid Naive Asthmatics: Visit 2 (at 1 week); Steroid Treated Asthmatics: Visit 5 (at 9 weeks)

Inclusion Criteria: Group C: Male and female subjects between the ages of 18 and 70 years History of asthma Continuous treatment with inhaled corticosteroids for at least the 6-week Hyperreactivity to methacholine (provocative concentration of methacholine causing a 20% drop in forced expiratory volume in 1 second (PC20 FEV1) Methacholine ≤ 16.0 mg/mL). Exclusion Criteria: History of asthma No use of oral or inhaled corticosteroids for the treatment of asthma in the past 6 weeks Hyperreactivity to methacholine (PC20 FEV1 Methacholine ≤ 8.0 mg/mL). At least one of the following symptoms, beta agonist use, or FEV1 criteria: Asthma symptoms on at least two days per week; OR Beta agonist use on at least two days per week; OR Forced expiratory volume in 1 second (FEV1) < 85% predicted Subjects must be non-smokers (patients who have never smoked or patients who have not smoked for 1 year and have a total pack-year smoking history < 15 packs).

Solberg OD, Ostrin EJ, Love MI, Peng JC, Bhakta NR, Hou L, Nguyen C, Solon M, Nguyen C, Barczak AJ, Zlock LT, Blagev DP, Finkbeiner WE, Ansel KM, Arron JR, Erle DJ, Woodruff PG. Airway epithelial miRNA expression is altered in asthma. Am J Respir Crit Care Med. 2012 Nov 15;186(10):965-74. doi: 10.1164/rccm.201201-0027OC. Epub 2012 Sep 6.