Paving the Path to Precision: Leveraging Pharmacogenomic Screening to Optimize Treatment in a Greek Internal Medicine Clinic

Introduction

Pharmacogenomic testing (PGt) is increasingly incorporated in clinical practice, with multiple tests available to guide drug administration. The application of PGt in routine clinical care varies considerably across healthcare systems. This study focused on assessing the impact of routine PGt implementation at a high patient volume Internal Medicine clinic in Greece.

Methods

142 patients (98 females, 44 males; ranging 24-91 years) were enrolled in a pilot PGt screening program approved by the “Attikon” University Hospital Research Committee, assessing CYP2C9, CYP2C19, SLCO1B1, and VKORC1 gene variants. Inclusion criteria comprised age >18 years, and the capacity for autonomous decision making.

Results

In 139/142 (98%) cases a pharmacogenetically informative variant was identified. In 33/142 cases, official recommendations were available for the optimization of drug selection and dosing for medications used during their hospitalization. Of these, in 4 cases, recommendations were available for >1 of the prescribed drugs. Overall, recommendations related to 3 major drug classes: alimentary tract (17 cases), cardiovascular (12 cases), and nervous system (4 cases). These included omeprazole (8), pantoprazole (6), lansoprazole (3), atorvastatin (8), rosuvastatin (2), clopidogrel (1), simvastatin (1), escitalopram (2), and amitriptyline/perphenazine (2). In 22/33 cases they involved CYP2C19, while in 11/33 cases they related to SLCO1B1 variants. The strength of these recommendations according to PharmGKB varied across ‘strong’ (4), ‘moderate’ (19), and ‘optional’ (10).

Conclusion

In summary, genotyping of CYP2C9, CYP2C19, SLCO1B1, and VKORC1 led to actionable findings for 98% of the patient population. In 24% of cases recommendations for optimization of currently administered treatments were available – 12% of which were marked as ‘strong’. This study provides insights into the distribution of clinically relevant pharmacogenomic variants within the Greek population and highlights the potential clinical utility of integrating targeted PGt into routine care in Internal Medicine clinics. Knowledge of patient-specific allele frequency data, combined with frequently used medications, may inform evidence-based establishment of new policies.