Clinical Pharmacogenomic Variants Among the Saudi Population and Their Impact on Drug Response: A Review of Saudi-Based Evidence

Pharmacogenomic implementation depends on the validity of gene-drug relationships within specific ethnic groups. However, the Saudi Arabian population, which had distinctive characteristics and high rates of marriage between relatives, remains underrepresented in global dosing algorithms. This systematic review and meta-analysis synthesized quantitative evidence from 16 studies encompassing 4,111 Saudi Arabian participants to examine the clinical impact of pharmacogenomic variants on drug efficacy, toxicity, and dosing requirements. The quality of the studies was assessed using the ROBINS-I tool, and the certainty of the evidence was graded according to the GRADE framework. The primary meta-analysis revealed a high-certainty association between <i>VKORC1</i> and <i>CYP2C9</i> variants and warfarin sensitivity, with variant carriers requiring a substantially lower maintenance dose (pooled mean difference: -20.68 mg/week; 95% confidence interval [CI]: -35.66 to -5.70). Trial sequential analysis confirmed that the required information size for this association was surpassed, establishing definitive evidence for genotype-guided anticoagulation. Regarding findings from individual studies and single gene-drug pairs, <i>CYP2C19</i> loss-of-function alleles were strongly associated with clopidogrel non-response in the primary study on this topic (odds ratio: 3.43), and the <i>CYP3A5</i> genotype was identified as a critical determinant of tacrolimus trough levels with a large effect size (Hedges' <i>g</i> = 1.59). Significant statistical heterogeneity was observed, particularly within warfarin studies (<i>I2</i> > 90%), which subgroup analysis suggested that geographical differences between the Eastern and Central provinces contributed to this variation. These findings indicate that the standard dosing regimens are suboptimal for a significant proportion of the Saudi population. These findings support the immediate integration of <i>VKORC1</i> and <i>CYP2C9</i> genotyping into local anticoagulation guidelines. They also highlight the need for large-scale pragmatic trials to confirm the effectiveness of genotype-guided strategies in antiplatelet and immunosuppressive therapies.