Genetic testing to help us choose the right medical regimen

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From the onset of World War II until the end of the Vietnam war, we enjoyed the golden age of antibiotics. The ability of antibiotics to kill infections is the reason why our life span grew by about 8 years during that era.  We even believed that infectious diseases would be eradicated soon.  While not a microbial disease, the advent of AIDS (a viral disease) disabused us of this notion.

Now (for the past decade or so),  we have been  researching what genetic variants exist among us, so we can determine which patients can benefit from our therapies, which may have side-effects, and, perhaps, even lead to tailor-make our drug therapy.  Some companies (among them Pfizer and Abbott) have been co-developing gene tests and potential therapies in concert to be able to discern which patients would be perfectly attuned to the proposed treatment.   Genentech had already done so in the late 1990s for one of its drug regimes.  A new report describing a developing gene therapy for renal cell carcinoma (under the direction of Dr. Dent of MCV, in concert with MCV and University of Alabama researchers) also employs such techniques.

Now, a group of scientists (from various institutions in Cologne [Germany] , Nieuwegein and Maastricht [Netherlands] under the direction of Dr. Taubert has performed such studies for the popular drug, Plavix (clopidogrel), which is the world’s second best selling drug ($9.5 billion annual turnover).  Plavix’ mode of operation requires the body to convert it to an active metabolite; as such it has radically different effectiveness in humans, dependent upon that conversion capability (which seems to involve paraoxonase-1 enzyme).  The group did not find clopidogrel’s usefulness related to the gene variant CYP2C19, as others have claimed.

The research study examined subjects with coronary artery disease, who also received a stent (a device used to “prop” open blocked arterial passages), and required the drug to preclude thromboses (blood clots).  They found that variant QQ192 demonstrated a higher risk than those with RR192, which was associated with higher paraoxonase levels (and lower active drug levels).  This accounted for some 75% of the variability in response to the drug.

The next step could be to develop a genetic test or a concentration test to provide the best patient results.

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