Pharmacogenomics of Rivaroxaban: Association of CYP3A4, CYP3A5, CYP2J2, ABCB1, and ABCG2 Variants with Bleeding and Thrombotic Outcomes in Real-World Clinical Practice

Aim: To evaluate associations between polymorphisms in CYP3A4 (*1B, *22), CYP3A5 (*3), CYP2J2 (*7, rs11572325), ABCB1 (c.1236C>T, c.2677G>T/A, c.3435C>T, rs4148738) and ABCG2 (c.421C>A) and the occurrence of bleeding or occlusive events in patients receiving rivaroxaban in real-world clinical practice. Methods: A nested case-control study, divided into two substudies (bleeding and thromboembolic events), was conducted within a prospective cohort of 385 adults receiving rivaroxaban at University Hospital Centre Zagreb (September 2021–September 2024). Bleeding events were classified per ISTH criteria, and genotyping was performed using TaqMan real-time PCR. Cases and controls were balanced using entropy balancing, and associations were estimated with Bayesian logistic regression under a skeptical prior N(0, 0.355); LASSO regression was used to identify clinical and genetic predictors of outcomes. Results: In total, 71 patients (18.4%) experienced bleeding events, most frequently gastrointestinal (47.9%), while 314 patients served as controls. No pharmacogenomic variant showed a clear association with bleeding risk (raw and balanced odds ratios 0.80–1.35; 95% credible intervals crossing 1.0). LASSO regression identified age (OR 2.00 per decade), gastrointestinal comorbidity (OR 8.77), and eGFR as the dominant predictors of bleeding. Twenty-one patients experienced occlusive events (15 venous, 6 arterial); however, the low event count precluded meaningful pharmacogenomic analysis. Conclusions: Individual pharmacogenomic variants in CYP3A4, CYP3A5, CYP2J2, ABCB1, and ABCG2 together with pharmacogenetic-based phenotypes were not associated with clinically relevant bleeding in rivaroxaban-treated patients. Traditional clinical risk factors, particularly advanced age and gastrointestinal comorbidity, remain the dominant determinants of adverse outcomes. Routine pharmacogenomic testing to guide rivaroxaban dosing is not currently supported.