Compound/Combination Selection Core

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The pathogenesis of CF and COPD lung disease is multi-factorial, but includes a common disease-initiating step: the reduction of mucociliary clearance (MCC). Based on studies shaping the foundation of the tPPG Projects I and II, it has been observed that normal mucus clearance requires adequate hydration of the airway surface (see Program Overview). However, both CF and COPD patients exhibit an increase in airway mucus concentration (% solids), as a result of reduced airway hydration, due to CFTR dysfunction (1), mucin hypersecretion (2), or a combination of the two. The result is the appearance of airway-adherent mucus plaques and the slowing of both cilial- and cough-dependent mucus clearance, leading to chronic airway infections. Therefore, developing therapies to enhance the clearance of mucus from the airways is likely to benefit patients with CF/COPD. The primary goal of Core E is to support all the Projects of the tPPG by identifying the most effective therapeutic agents to enhance the dis-adherence and transportability of mucus. As part of this tPPG project, we have identified a number of classes of candidate therapeutic agents, which are predicted to alter the properties of mucus, facilitating its clearance. These classes and examples of potential agents are summarized in Table 1. Because the viscoelasticity of mucus is concentration dependant, agents which increase the hydration state of mucus (called hydrators) will be studied (3). This will include osmolytes (such as hypertonic saline and mannitol) as well as modifiers of ENaC-mediated fluid reabsorption, including: ENaC blockers (Parion P552 and PI 527) and modifiers of ENaC activity (QUB and SPLUNK). As an alternative approach to reduce mucus concentration, we will also evaluate the use of macrolides, which have been shown to reduce mucus expression (4). As well as Azithromycin, we will test a series of novel macrolide agents from Cempra and Gilead which are optimized to improve their activity (see Letters of Support). In addition to lowering the concentration of mucus, we will also seek to identify agents which reduce its viscoelasticity and adhesivity, by altering mucin-mucin and mucin-protein interactions. Di-sulfhydryl reducing agents are predicted to decrease the viscoelasticity of mucus by decreasing the head-to-tail chaining of mucin monomers. In addition to existing reducing agents (e.g. N-acetylcysteine and DTT) we will also test novel reducing agents such as Gamma-interferon-inducible lysosomal thiol reductase (GILT) from Dr. Peter Cresswell (Yale) and a variety of novel recombinant- DTTs (DTT-Rs) from Parion which increase the efficiency and duration of action (see Program Introduction). Surfactants and detergents that disrupt protein-protein interactions within the mucus layer are envisaged to decrease the cohesive properties of mucus (5-6). There are a number of other putative mucus-altering agents (e.g. Ca2+ chelators (7), dextran (8), heparin (9), bicarbonate (10)) that we will study to identify novel therapeutics for restoring/ stimulating MCC. Core E consists of three distinct functional divisions that will identify effective agents for potential use in a human clinical trial. The overall strategy of this Core and its interactions with each tPPG Project is shown in Figure 1. The general concept is to screen a large number of test agents using in vitro mucus screening methodologies and identify the most effective agent(s) to be studied in subsequent cell culture and mouse studies. The primary goal of the mucus rheology and hydration core service is to provide Project I & II investigators with a comprehensive analysis of all agents of interest and establish the dose-effect relationship on changes in (1) mucus viscoelasticity - a measure of the "flowability" the mucus, and (2) the hydration of the airway. Once the most effective candidate agents are identified, the effect of each of these agents on stimulating and restoring mucus transport in human airway epithelial cultures will be studied in the next core service. Finally, in the third core component, the most effective agents from the previous studies will be tested in a mouse model for obstructive airway diseases during a single and multiple dose testing regimens. The goal is to evaluate drug efficacy and toxicity, as assessed by histopathology, morphometric measurements, biochemical analysis and inflammatory cell count. Once identified, these agents (or class of agents) will be the focus of a human trial in Project III.