BACKGROUND: For genetic polymorphisms known to alter drug effect or safety, 
regulatory authorities can tap into population genomic databases and other 
sources of allele and genotype distribution data to make a more informed 
decision about the anticipated impact of such variants on the main ethnic groups 
in a country's population.
OBJECTIVE: The aim of this short communication is to describe how the Singapore 
Health Sciences Authority (HSA) made use of allele and genotype distributions in 
the main ethnic groups in Singapore (Chinese, Malay, Indian) and population 
genetic tools to compare with North American Caucasians and Japanese.
METHODS: Published papers and publicly accessible genomic databases were 
searched up to August 2009 to obtain allele and genotype frequencies for 
UGT1A1*6 and *28, two common variants of UGT1A1, a gene that encodes for a key 
enzyme in the pathway of irinotecan metabolism. These variants are associated 
with greater risk of serious toxicity.
RESULTS: In Singapore, the combined prevalence of three high-risk genotypes, 
UGT1A1*6/*6, *6/*28 and *28/*28, is 9.7% in Chinese, 5.0% in Malays and 18.7% in 
Indians, compared with 11.5% in North American Caucasians and 8.1% in Japanese. 
Indians are at an elevated risk of irinotecan-induced neutropenia associated 
with UGT1A1*28 compared with Chinese and Japanese, and at an even higher risk 
compared with North American Caucasians. On the other hand, Chinese and Japanese 
are at an elevated risk of irinotecan-induced neutropenia associated with 
UGT1A1*6 relative to Indians in Singapore or North American Caucasians. 
Population genotype data were the basis for the HSA to request revision of the 
package insert from manufacturers of irinotecan products. Moreover, the data 
provided the impetus for the HSA to publicize the availability of UGT1A1 genetic 
testing at the National Cancer Centre.
CONCLUSION: With the growing volume of genomic data and pharmacogenomic 
associations, a regulatory authority is now able to more readily utilize 
population genetic information and tools to supplement evaluations of drug 
products pertinent to the country's ethnic demography.