A Review of Pharmacogenetics of Anticoagulant Therapy

Variances in the patients’ outcomes have been a well-documented challenge in anticoagulant therapy. A clinical encounter with a thromboembolic or a hemorrhagic event, due to subtherapeutic or adverse effects of an anticoagulant, is often managed by switching the anticoagulant agent into another, which is more specific and direct-acting. This management approach is usually associated with a financial burden. Additionally, the certainty of achieving better efficacy and safety profile is still questionable. Genetic variants affecting the protein sites that are involved in the anticoagulant pharmacokinetic and pharmacodynamics interactions have been suggested to contribute to the variability in the response to anticoagulant therapy. The current work reviewed the studies investigating the response variability associated with the anticoagulant therapy (heparins, rivaroxaban, apixaban, and dabigatran) and the potential pharmacogenes contributing to such response variability. Several genetic polymorphisms were reported as potential contributors to variances in response to anticoagulant therapy and were associated with adverse events. A link has been proposed for heparin resistance with single nucleotide polymorphisms (SNPs) of the anti-thrombin-encoding gene ( SERPINC1 ) as well as heparin-induced thrombocytopenia with human leukocyte antigen (HLA) variant allele ( HLA-DRB3*01:01 ). Several investigations also remarked variations in the serum drug level of direct oral anticoagulants (DOACs) that are associated with SNPs in the proteins contributing to the pharmacokinetics of the anticoagulant agent. Several studies discerned significant associations between SNPs in the ABCB1 gene and elevations in the serum levels of rivaroxaban, apixaban, and dabigatran. Moreover, carriers of the variant genotype of the SNP (rs776746) in the cytochrome P450 3A5 enzyme-encoding gene ( CYP3A5 ) had significantly higher drug levels when compared with the non-carriers. In contrast, some SNPs were reported to impart a protective phenotype to the carrier. The SNP (rs2244613) in the carboxylesterase-encoding gene ( CES1 ) has been significantly associated with a decline in dabigatran trough levels and a lower risk of hemorrhage. Further investigations are essential to elucidate the extent of pharmacogenetics-based alterations in the drug levels as well as the subsequent clinical outcomes of anticoagulant therapy.