Most Hong Kong-Chinese have at least one genetic variant that could affect the effectiveness of drug treatments, research showed.

The study, conducted by the University of Hong Kong medical school, is the first and largest study of its kind among Hong Kong-Chinese, highlighting the potential of personalized medicine.

After studying drug prescription data of 7.5 million people in Hong Kong in 2019 provided by the Hospital Authority, as well as the genetic data of more than 1,000 Hongkongers, the research team identified 531 rare and harmful variants in 108 genes associated with drugs.

Among the variants, 96 have never been reported in any genetic databases, the researchers said.

The team also found that 93.6 percent of the Hongkongers carried at least one of the 531 rare genetic variants.

They also analyzed 133 genetic variants known to affect responses for 36 types of drugs and found that 99.6 percent of Hongkongers have at least one variant, with a median of four.

The researchers stressed the importance of personalized medicine based on patients' genes, adding that this could determine the rate of drug metabolism.

For example, patients with a high metabolism may find the drug less effective than expected because it would be quickly broken down in their bodies and lose its function, they said.

"By contrast, drugs remain active for longer in patients with slow metabolism. The blood concentration of drugs in these patients may reach toxic levels, causing undesired adverse drug reactions," the researchers said.

Currently, genetic tests targeting drug response will only be conducted when adverse drug reactions have already occurred or high-risk medications are prescribed, meaning patients could be harmed before remedial action is taken, the researchers said.

According to data from health authorities, more than one million Hongkongers were prescribed drugs that can be affected by genetic variants in 2019, accounting for one-seventh of the local Chinese population.

Drugs that are most susceptible to genetic variation include lipid-lowering drug simvastatin, anti-inflammatory drug and pain reliever ibuprofen and clopidogrel used to reduce the risk of heart disease and stroke, the researchers said.

They suggested genetic tests be done before patients are prescribed medicines to minimize the risk of adverse reactions and achieve higher drug efficacy.

Study boosts potential of personalized drugs