Genotype Stratified Pharmacokinetic Study of Montelukast

Leukotriene receptor antagonists (LTRAs) are frequently prescribed to reduce the symptoms associated with asthma. Singulair (montelukast), manufactured by Merck, is a popular LTRA, however its effectiveness varies greatly between individuals. We are interested in understanding why the effectiveness of Singulair varies so greatly. For an oral drug such as Singulair to be effective, the body must efficiently absorb it. We have found that blood levels of Singulair vary greatly between individuals, and we think that this variability is responsible for variability in response. Drug absorption occurs primarily in the intestine. Due to differences in the chemical properties of drugs, some drugs can be absorbed easily while other drugs require help from special proteins produced by the cells that line the intestine. These proteins, or transporters act like revolving doors to allow drugs to move from the intestine to the bloodstream. The activity of a transporter can be influenced by individual genetic variability. We think that adsorption of Singulair requires help from a transport protein called OATP2B1. We have found that a single common genetic change in this protein is associated with low plasma concentration of montelukast. In this proposal we will determine plasma levels of montelukast in individuals with two copies of this genetic change. We predict that these individuals will have roughly half the plasma level of montelukast as individuals with no copies of this genetic change. Eventually, what we learn from this work will allow doctors to quickly test individuals with asthma to determine how well they will absorb Singulair and possibly other LTRAs. Knowing this will allow the doctor to adjust the drug treatment on an individual basis to maximize benefit in the treatment of asthma.