• Part I: Safety and tolerability of BI 706321 is the percentage of subjects with drug-related adverse events [ Time Frame: Up to 22 Days ]
• Part II: AUC0-tz (area under the concentration-time curve of BI 706321 in plasma over the time interval from 0 to the last quantifiable data point) [ Time Frame: Up to 22 Days ]
• Part II: Cmax (maximum measured concentration of BI 706321 in plasma) [ Time Frame: Up to 22 Days ]

• Part I: AUC0-∞ (area under the concentration-time curve of BI 706321 in plasma over the time interval from 0 extrapolated to infinity) [ Time Frame: Up to 22 Days ]
• Part I: Cmax (maximum measured concentration of BI 706321 in plasma) [ Time Frame: Up to 22 Days ]
• Part I: tmax (time from dosing to the maximum measured concentration of BI 706321 in plasma) [ Time Frame: Up to 22 Days ]
• Part II: AUC0-∞ (area under the concentration-time curve of BI 706321 in plasma over the time interval from 0 extrapolated to infinity) [ Time Frame: Up to 22 Days ]

• AUC0-∞ (area under the concentration-time curve of BI 706321 in plasma over the time interval from 0 extrapolated to infinity) [ Time Frame: Up to 22 Days ]
• Cmax (maximum measured concentration of BI 706321 in plasma) [ Time Frame: Up to 22 Days ]
• tmax (time from dosing to the maximum measured concentration of BI 706321 in plasma) [ Time Frame: Up to 22 Days ]

The main objectives are:

• Part I: To investigate safety, tolerability, and pharmacokinetics (PK) of BI 706321 in healthy male subjects following oral administration of single rising doses.
• Part II: The relative bioavailability of BI 706321 after administration of tablets and capsules under fasted conditions will be compared with each other and the effect of food on the tablet bioavailability will be investigated.

• Drug: BI 706321
  Capsule or Oral Solution
• Drug: Placebo
  Capsule or Oral solution

• Experimental: BI 706321
  Intervention: Drug: BI 706321
• Placebo Comparator: Placebo
  Intervention: Drug: Placebo

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 (BP, PR, oral body temperature), 12-lead ECG, and clinical laboratory tests
• Age of 18 to 45 years (inclusive) in Part I and of 18 to 55 years (inclusive) in Part II
• BMI of 18.5 to 29.9 kg/m2 (inclusive)
• Signed and dated written informed consent prior to admission to the study, in accordance with GCP and local legislation

Exclusion Criteria:

• Any finding in the medical examination (including Blood Pressure (BP), (PR), oral body temperature 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 mmHg, diastolic blood pressure outside the range of 50 to 90 mmHg, or pulse rate outside the range of 50 to 90 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
• Chronic or relevant acute infections
• History of relevant allergy or hypersensitivity (including allergy to the trial medication or its excipients)
• Use of drugs within 30 days of planned administration of trial medication that might reasonably influence the results of the trial (including drugs that cause QT/QTc interval prolongation)
• Intake of an investigational drug in another clinical trial within 60 days of planned administration of investigational drug in the current trial, or concurrent participation in another clinical trial in which investigational drug is administered
• Smoker (more than 10 cigarettes or 3 cigars or 3 pipes per day)
• Inability to refrain from smoking on specified trial days
• Alcohol abuse (consumption of more than 24 g per day)
• Drug abuse or positive drug screening
• Blood donation of more than 100 mL within 30 days of planned administration of trial medication or intended blood donation during the trial
• Intention to perform excessive physical activities within one week prior to the administration of trial medication or during the trial
• Inability to comply with the dietary regimen of the trial site
• A marked baseline prolongation of QT/QTc interval (such as QTc intervals that are repeatedly greater than 450 ms) or any other relevant ECG finding at screening
• A history of additional risk factors for Torsade de Pointes (such as heart failure, hypokalaemia, or family history of Long QT Syndrome)
• Subject is assessed as unsuitable for inclusion by the investigator, for instance, because the subject is not considered able to understand and comply with study requirements, or has a condition that would not allow safe participation in the study
• Male subjects with WOCBP partner who are unwilling to use male contraception (condom or sexual abstinence) from time point of administration of trial medication until 30 days thereafter. Sperm donation is not allowed from the time point of drug administration until 30 days thereafter.
• ALT (alanine transaminase), AST (aspartate transaminase), or creatinine exceed upper limit of normal range at screening, confirmed by a repeat test
• During COVID-19 pandemic: laboratory test indicative of an ongoing SARS-CoV-2 infection