Inclusion Criteria:
* Healthy premenopausal female 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 (12-lead ECG), and clinical laboratory tests without any clinically significant abnormalities.
* Age of 18 to 35 years (inclusive).
* Body mass index (BMI) of 18.5 to 29.9 kg/m2 (inclusive).
* Signed and dated written informed consent in accordance with International Conference on Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial.
* Female subjects who meet any of the following criteria starting from at least 30 days before the first administration of BI 425809 and until 30 days after trial completion:
* Use of adequate contraception, e.g. non-hormonal intrauterine device plus condom.
* Sexually abstinent.
* A vasectomised sexual partner (vasectomy at least 1 year prior to enrolment).
* Surgically sterilised (including hysterectomy).
Exclusion Criteria:
Subjects will not be allowed to participate, if any of the following general criteria apply:
* Any finding in the medical examination (including BP, PR or 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 millimetre(s) 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.
* 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.
