Personalized Medicine

Authored By: Akhila Satchidanandam

In earlier times, when allopathy was still at the base line in India, our ancestors had actually long been practicing personalized medication. For instance, if a person was suffering from stomach ache, the first thing the “country-doctor” would do is to first examine the tummy by pressing and feeling to diagnose the reason for it and then prescribe medicine derived from herbs mostly that would not have any side-effects. So, personalized medication is an age old practice in India, still being followed in the villages.

The personalized medicine that we are talking about today though, is an extension called pharmacogenomics. It does not only aim at diagnosing the reason for the disease symptomatically but also its molecular basis. That makes it easier for a pharmacologist to design or tailor a drug that would best treat the individual’s ailment.

The genetic makeup of one person is not entirely identical to that of another person. What causes a particular condition or ailment in a person could be due to a variation of a gene or mutation acquired later in life. If we were to compare two different patients with diabetes, chances are that, they have acquired the disease due to mutation in two different genes involved in glucose metabolism. Doctors reflexively administer insulin, incidentally ending up treating the symptoms and not the condition. The difference being, treating the condition would in most cases not mean medication for a life time whereas if a doctor goes with treating the symptoms especially of a gene based disease, treatment means for a life time.

There are surplus examples of how chemotherapy has drastic side effects on some individuals while it has been promising for others. Pharmacogenomics is especially applicable for cancer patients, the reason being that there are many genes responsible for causing cancer and chemotherapy involves administration of a group of drugs that varies with the clinicians who treats the patient.

Besides the genetic disorders, gene variation from person to person can also cause difference in response to a drug. Drugs that may have similar response may also differ in their way and rate of metabolism post action. What is an elixir to one person can be allergic to another person. Such observations lead to the idea of individualized medicine.

In addition to treating diseases, before a baby is born, pharmacogenomics can help couples know if their child would be predisposed to any disease by sequencing the parents’ genome. This can help doctors and parents to be prepared for treating the child well in advance.

Psychiatric disorders and pathogenic diseases may not require genome sequencing since they usually do not have a genetic basis. However, one can still study the patient’s genetic make up to identify if a commonly used drug for the particular disease would be effective.

To begin with, the entire genome of the individual has to be sequenced following which the sequence would be scanned for genetic variation if any attributing to the disease. The human genome having been mapped, has now opened new frontiers for pharmacogenomics – genome has become more accessible and with the advent of genotyping tools, time consumption has largely reduced.

The initial step would be to isolate the coding region (functional part of the DNA) of the DNA followed by sequencing it. The nucleotide sequence is then compared with a control i.e with coding region sequenced from a normal person. Sequences of gene variants found in the normal samples are eliminated from the patient’s sample. The remaining variants are the probable disease causing mutations.

Well, the hitches at this point are training the practitioners and the cost involved in sequencing the genome. Since nobody is a real expert in individualized medicine yet, the question of who trains who comes in. The second drawback is that the cost of sequencing a patient’s genome may cost somewhere between $100 and $500.

Individualized medicine thus hits the bull’s eye rather than missing the aim. Besides, it opens up new horizons in the research frontiers as well. The future of personalized medicine however lies in finding ways to cut the cost involved. Pharmaceutical companies though are working towards it, it is bound to take time for the under-developed and developing countries to acquire the privilege.