CYP3A4, CYP3A5, and CYP4F2 Polymorphisms and Bleeding Risk in Ticagrelor-Based Dual Antiplatelet Therapy

Background and Objectives: Ticagrelor reduces ischemic events in acute coronary syndrome (ACS) but increases bleeding risk. Clinical predictors of bleeding are well established; the contribution of cytochrome P450 polymorphisms involved in ticagrelor metabolism remains uncertain, with conflicting reports in the literature. We examined the association of CYP3A4* 22 (rs 35599367), CYP3A5* 3 (rs 776746), and CYP4F2 (rs3093135) with bleeding in a Serbian ACS cohort. Materials and Methods: This prospective, single- center observational study enrolled 105 consecutive ACS patients undergoing percutaneous coronary intervention (PCI) or medical management after coronary angiography and receiving dual antiplatelet therapy (DAPT) with acetylsalicylic acid and ticagrelor at the University Clinical Center Niš between January 2024 and the end of May 2025. Bleeding events occurring during the index hospitalization and the six-month follow-up were classified according to the Bleeding Academic Research Consortium (BARC) criteria. Genotyping used TaqMan assays. Associations with bleeding were assessed using Firth's penalized logistic regression, with multivariable adjustment for age and renal function. Severity-stratified analyses and gradient-boosted machine learning (XGBoost with SHAP) were performed as exploratory analyses. Results: Thirteen patients (12.4%) experienced bleeding (nine minor [BARC 1/2], four major [BARC 3/5]). Age ≥ 75 years (univariable OR 7.62, p = 0.001) and eGFR < 60 mL/min/1. 73 m ² (OR 3.68, p = 0.006) were the strongest predictors. CYP3A5 *1 carrier status was univariably associated with bleeding (OR 4.16, p = 0.043) but did not remain significant after adjustment for age and renal function, and *1 carriers were significantly older and more likely to have impaired renal function. No genotype was associated with major (BARC 3/5) bleeding. The apparent effect was concentrated in minor bleeding (BARC 1/2 rate: 30.8% versus 5.5%), with no major events among *1 carriers. CYP 3 A 4* 22 (OR 1.37, p = 0.109) and CYP 4 F 2 (OR 1.17, p = 0.111) showed no association. Machine-learning analyses confirmed eGFR and age as the dominant predictors. Conclusions: In this Serbian ACS cohort, clinical factors-particularly advanced age and impaired renal function-dominated the prediction of bleeding risk. The CYP3A5 signal was largely explained by baseline imbalances in age and renal function. CYP 3 A 4* 22 and CYP 4 F 2 polymorphisms did not contribute additional predictive information. Preemptive genotyping for these variants is unlikely to materially improve bleeding-risk assessment beyond standard clinical evaluation in patients of this type.