Today the New York Times published an article titled Genes Show Limited Value in Predicting Diseases.

For over six years, technology has allowed researchers to examine the genomes of healthy people and compare them to the DNA sequences of patients. These comparisons should have help researchers identify DNA that is associated with particular diseases. Unfortunately, it has not worked out so easily, as the article explains:

. . . it has been disappointing in that the kind of genetic variation it detects has turned out to explain surprisingly little of the genetic links to most diseases.
. . .
This would be bleak news for those who argue that the common variants detected so far, even if they explain only a small percentage of the risk, will nonetheless identify the biological pathways through which a disease emerges, and hence point to drugs that may correct the errant pathways. If hundreds of rare variants are involved in a disease, they may implicate too much of the body's biochemistry to be useful. [boldface added]

Research into IBD, specifically Crohn's disease, appears to fit this pattern. In June 2008, scientists announced a "big haul of Crohn's Genes"--32 genetic variations to Crohn's disease had been found, tripling the number of genes previously associated with the disease. At the time of the announcement, the lead researcher, Jeffrey Barrett from the Wellcome Trust Centre for Human Genetics at the University of Oxford, went on to say:

"These explain only about a fifth of the genetic risk [of Crohn's disease], which implies that there may be hundreds of genes implicated in the disease, each increasing susceptibility by a small amount"

With so many genes involved with a disease, the prospects of developing drugs based on this knowledge dims.

"In pointing at everything," Dr. Goldstein writes in the [New England] journal [of Medicine], "genetics would point at nothing."

source: New York Times: Genes Show Limited Value in Predicting Diseases

Bottom line: The development of drug treatments based on genetic research into inflammatory bowel disease appears to be many years in the future--much slower than initially thought.