Industry Insight from Paul Meade, M. Sc, MPH
When we visit a doctor and receive a prescription for a medication to treat our illness, we assume that this drug will work. But can we be sure? Well, most of the time the medicine you receive will do the job as prescribed. You might get an unexpected side effect from the medication, or even an expected one that is commonly found to occur with a particular drug–but they generally do the job.
We are learning more and more that some drugs just don’t seem to work for certain people in the population. We have learned recently that a popular drug to fight colon and lung cancer, bevacizumab (Avastin), is being considered for withdrawal from using it for breast cancer, despite some cancer patients responding to it. Why do some people respond to a drug and others don’t? The answer may be found in biomarkers.
Our genome, with its 3 billion base pairs and tens of thousands of genes, is basically the code for the many different ways people interact with their environment, from the food we eat to the drugs we take. And despite an amazing commonality among everyone’s respective genetic makeup, we all have enough differences to account for a variable response to many elements in our environment. Some people are more susceptible to air and water pollution, some are more prone to certain diseases, some are allergic to specific foods, and some respond to certain drugs.
Scientists have been diligently searching for those biomarkers that identify the genetic factors that may account for these idiosyncratic responses, or at the very least, predict who is likely to respond a certain way given their genetic biomarkers. So as it is with Avastin, some breast cancer patients have a set of biomarkers that predict a likely response to the treatment, while some patients do not have these biomarkers and are unlikely to respond as expected. Should the drug be prohibited for use in breast cancer patients? Well, of course, for those who are unlikely to respond, it’s a no-brainer. But stop it for everyone? It’s the proverbial baby and the bath water situation!
So how do you know which drug is right for you? Apart from obtaining a full genome sequencing of your DNA and mapping all known polymorphisms into a predictive health map, you will simply have to wait while scientists slowly unravel the mysteries of our genome and, bit by bit, gain some insight into the people who are likely to respond to a drug. Will it take some time? It sure will. Will we get there eventually? We sure will.
And when that day comes, you can rest assured that when a doctor gives you a prescription for a drug to cure your illness, it will have a very high probability to work as expected. That is personalized medicine, and it’s definitely on the horizon. Until that time, it’s an educated guess by some very bright clinicians looking carefully at the results of exhaustive clinical studies. But hang in there–it’s getting better than it was 100 years ago. At least we are not blood-letting and using leeches as routine procedures in doctors’ offices these days.