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CYP2C19 polymorphism is associated with pretreatment drug response prediction, metabolism, and disposition. Pakistan consists of a population comprising of various ethnic groups residing in different regions of the country each claiming diverse ethnic origins. The identification of CYP450 genotypic composition of these populations is therefore necessary to avoid adverse drug reactions in these individuals. The main objective of the study was to investigate the prevalence of CYP2C19*2 and CYP2C19*17 alleles in these ethnic groups. The study was conducted on one thousand and twenty-eight (n = 1028) healthy volunteers from nine ethnic groups of Pakistan namely Brusho (n = 28), Hazara (n = 102), Kalash (n = 64), Pathan (n = 170), Punjabi (n = 218), Saraiki (n = 59), Brahui (n = 118), Parsi (n = 90), and Sindhi (n = 179). DNA was extracted from leukocytes and analyzed by allele specific amplification polymerase chain reaction (ASA-PCR). Multi allelic polymorphism of CYP2C19 led to four distinct phenotypes identified as extensive metabolizer (EM), poor metabolizer (PM), intermediate metabolizer (IM), and ultra-rapid metabolizer (UM). Over all, the percentage of predicted poor metabolizer allele was 29.0% compared to UM allele (23.70%). Among the studied groups, Saraiki and Brahui showed highest percentage of PM allele (40%, 36%) whereas Parsi and Hazara had highest percentage of UM allele (37% and 30% respectively). In conclusion, the high allele frequency of PM (CYP2C19*2 and *17) in Pakistani population led to the recommendation of a pre-treatment test to monitor drug response and dosage (personalized medicine) to avoid post-treatment adverse drug reactions.

Favourable genotypes of IFNL3 polymorphism CC for rs12979860 and TT for rs8099917 are strongly associated with the interferon/ribavirin treatment outcome in hepatitis C virus (HCV) patients with genotypes 1 and 4. Contrarily, conflicting results have been reported for patients with HCV genotypes 2 and 3. Therefore, we sought to investigate the association between IFNL3 with sustained virological response (SVR) after treatment to ascertain the predictive value of IFNL3 single-nucleotide polymorphisms (SNPs) in HCV patients with genotype 3. For this purpose, we genotyped five IFNL3 SNPs, rs12980275, rs12979860, rs9109886, rs8099917 and rs7248668, in HCV patients with genotype 3 and assessed its association with SVR, individually and in haplotype. Interestingly, we report that the IFNL3 SNPs we genotyped have shown no association with SVR following treatment, either individually or in haplotype, indicating that genotyping IFNL3 SNPs have limited predictive value in HCV patients with genotype 3. Therefore, we propose that IFNL3 genotyping can be excluded from a patient's pre-treatment workup for subsequent treatment choice. This will greatly reduce the economic burden for HCV patients with genotype 3 in resource-limited regions, especially South Asia where genotype 3 is predominant.