At present, the genetic drug compatibility or genotype tests are regularly being carried out for cancer patients before undergoing chemotherapy.
FORTY-six-year-old Girija Kumar was detected with breast cancer a few months ago. Her doctor advised her to start chemotherapy. Her doctor was a bit anxious as she had already undergone one round of failed chemotherapy.
The doctor then thought of conducting a drug-compatibility test (genotype test) on Girija. The test would help detect whether the targeted drugs prescribed along with chemotherapy would suit her body or cause any side-effects. After undergoing the test, the doctor found out that certain target drugs, given along with the chemotherapy, were not suiting her metabolism. Hence, the doctor put her on medicines that would work on her and cause no side-effects.
At present, the genetic drug compatibility or genotype tests are regularly being carried out for cancer patients before undergoing chemotherapy. However, these tests are now available for other diseases as well. For instance, nearly 4.2 per cent of people in India suffer from Irritable Bowel Syndrome (a chronic problem in bowel habits). A quarter of these don’t respond to the drugs prescribed to them. In fact, the drugs could have been accumulating and generating toxicity in their body. With the help of genenotype testing doctors can find out whether certain drugs will be suitable for the person.
“We give the patients certain target drugs along with chemotherapy, which are expensive. Each dose would cost about Rs 1 lakh and a patient has to take eight such doses. Therefore, we need to justify the usage of any drugs and the toxicity of the target agents by doing genotype tests,” explained Dr Niti Narang, consultant medical oncologist, Bangalore Institute of Oncology.
Still in its nascent stage, a couple of biotech labs in the country have ventured into this field. Sandeep Saxena, CEO of Pune-based Acton Biotech, said that there were a few drugs like azathioprine, methotrexate and warfarin that are commonly used in many disorders. “Some patients benefit from these drugs while others suffer from severe side effects. In fact, warfarin is the drug that is responsible for a very large percentage of ICU admissions,” he noted.
Apart from cancer, the tests are done for hematology, cardiovascular, nephrology, urology and gastroenterology. Although, the lab has collection centres in 12 cities, it soon plans to open one in the City.
Similarly, Delhi-based OncQuest Laboratories Ltd has tied up with several hospitals in the City to conduct genetic drug compatibility tests for Acute Lymphoblastic Leukemia, Irritable Bowel Syndrome (Crohn’s Disease), organ transplants and certain types of cancer.
OncQuest managing director Aditya Burman said, “The technology is highly specific and sensitive with accuracy is close to 100 per cent. The goal is to see that the patients can be treated in a proper manner and reduce adverse reaction of drugs on them.”
Although still in its infancy, genotype test definitely throws open the possibility of customised medicines and gives an option to people suffering from these diseases.
How it works
Dr Sarjana Dutt from OncQuest Labs explained that there are four genetic variations that affected the Thiopurine Methyltransferance (TPMT) enzyme levels of a person. The genotype test checks the response of Thiopurine drugs (used for the treatment) in patients with reduced TMPT enzymes.
“We extract the DNA from the patient’s blood sample. We then conduct the genotyping test, which diagnoses and pin-points which genetic variation the patient has,” she said. The test also helps in checking the accumulation of the drugs in the patient’s body, which can lead to toxicity in the body. Such patients will require a lower dosage, Dr Sarjana said.
(Published in Deccan Herald on 23rd November, 2009)