ABCG2 and atrial fibrillation: In Japanese AF cohorts, CYP3A5*3 (rs776746) and ABCG2 421A/A have been linked to higher concentration-to-dose ratios, whereas common ABCB1 variants (1236C>T, 2677G>T/A, 3435C>T) generally showed null or inconsistent PK effects [10,11].