The main objective of this trial is to investigate the effect of fluconazole, under steady state conditions on the pharmacokinetics of BI 425809 (Reference Treatment R: BI 425809 alone; Test Treatment T: BI 425809 given under steady state conditions of fluconazole).

Inclusion Criteria:

• Healthy male subjects according to the assessment of the investigator, as based on a complete medical history including a physical examination, vital signs (blood pressure (BP), pulse rate (PR)), 12-lead Electrocardiogram (ECG), and clinical laboratory tests
• Age of 18 to 55 years (inclusive)
• Body mass index (BMI) of 18.5 to 29.9 Kilograms/Square Meter (kg/m2) (inclusive)
• Signed and dated written informed consent prior to admission to the study, in accordance with Good Clinical Practice (GCP) and local legislation

Exclusion Criteria:

• Any finding in the medical examination (including blood pressure (BP), pulse rate (PR) or Electrocardiogram (ECG)) deviating from normal and assessed as clinically relevant by the investigator
• Repeated measurement of systolic blood pressure outside the range of 90 to 140 millimetres of mercury (mmHg), diastolic blood pressure outside the range of 50 to 90 mmHg, or pulse rate outside the range of 45 to 90 beats per minute (bpm)
• Any laboratory value outside the reference range that the investigator considers to be of clinical relevance
• Any evidence of a concomitant disease assessed as clinically relevant by the investigator
• Relevant gastrointestinal, hepatic, renal, respiratory, cardiovascular, metabolic, immunological or hormonal disorders
• Cholecystectomy or other surgery of the gastrointestinal tract that could interfere with the pharmacokinetics of the trial medication (except appendectomy or simple hernia repair)
• Diseases of the central nervous system (including but not limited to any kind of seizures or stroke), and other relevant neurological or psychiatric disorders
• History of relevant orthostatic hypotension, fainting spells, or blackouts Further exclusion criteria apply.

Clinical studies sponsored by Boehringer Ingelheim, phases I to IV, interventional and non-interventional, are in scope for sharing of the raw clinical study data and clinical study documents, except for the following exclusions:

1. studies in products where Boehringer Ingelheim is not the license holder;
2. studies regarding pharmaceutical formulations and associated analytical methods, and studies pertinent to pharmacokinetics using human biomaterials;
3. studies conducted in a single center or targeting rare diseases (because of limitations with anonymization).

For more details refer to: https://www.clinicalstudies.boehringer-ingelheim.com/msw/datasharing

Treated set (TS): The TS included all subjects who were entered and treated with at least one dose of study drug.

BI 425809 (BI) in period 1: From drug administration of BI in period 1 on Day 1 until 11 days (d) thereafter. Fluconazole alone in period 2: From the first Fluconazole administration in period 2 until BI administration in period 2, up to 4d. BI 425809+Fluconazole in period 2: From drug administration of BI in period 2 until 14 days (d) thereafter.

Safety analyses were based on the treated set (TS). The TS included all subjects who were entered and treated with at least one dose of study drug.

The objective of this trial was to evaluate the pharmacokinetics of BI 425809 under steady state conditions of fluconazole. BI 425809 was administered after the fifth of the 13 daily doses of fluconazole. The steady state analysis of fluconazole was assessed from the time of BI 425809 dosing up to 215 h thereafter in order to achieve the objective.