Pharmacogenetics and Pharmacogenomics

In addition to the complex interactions that drug compounds can have with molecules in the body, there are other reasons why some patients experience different responses to drugs. Two people that appear to have the same disease may actually have different diseases that may not respond to the same drug treatment. Modern genomic analysis methods, such as microarray gene expression profiling, can distinguish two diseases that, by all other clinical and diagnostic methods, appear to be identical.

An example is diffuse large B-cell lymphoma (DLBCL), the most common form of non-Hodgkin's lymphoma, a cancer of the white blood cells. About 40 percent of patients can be cured by the standard chemotherapy for DLBCL, but 60 percent respond poorly and eventually die. Using microarray technology to gather and compare the gene expression patterns of cancer cells from many different DLBCL patients, molecular biologists have discovered that DLBCL actually comprises two distinct disease forms. Patients with one form are treatable with the standard chemotherapy, while those with the other form are not. Using this kind of genomic information, doctors can now diagnose patients more accurately and put them on the most appropriate drug-therapy regime. Similar genomic diagnoses based on gene expression profiles are being developed for important diseases such as breast cancer and Alzheimer's disease.