This was a Phase I, open-label, single-sequence crossover study conducted in healthy male participants at the Boehringer Ingelheim Human Pharmacology Center, Biberach, Germany (Clinicaltrials.gov identifier, NCT02783040). The study consisted of 2 treatment periods in a fixed sequence. In period 1, participants received a single dose of a probe-drug cocktail containing midazolam (2 mg), warfarin (10 mg), and omeprazole (20 mg) on day 1 and a single dose of digoxin (0.25 mg) on day 2. Period 1 was followed by a wash-out period of ≥5 days. In period 2, participants received BI 425809 25 mg once daily on days 1 to 14, a single dose of the probe-drug cocktail on day 10, and a single dose of digoxin on day 11. On days 1 and 2 of period 1 and days 10 and 11 of period 2, participants fasted overnight for at least 10 hours before dosing and for 4 hours afterward. All participants attended an end-of-trial visit 11 to 16 days after the last administration of BI 425809.