The purpose of this trial is to assess the safety, tolerability, and PK of 3 doses of GRT6019 in healthy male participants.

This Phase I trial will be a multiple dose trial in healthy male participants with administration of GRT6019 in 3 cohorts.

For each participant, the trial consists of a Screening Period of up to 28 days, a 4 week Treatment Period (including a 2-week clinic stay and 2 weeks in an outpatient setting), and a 5 week Follow-up Period.

There are 8 participants planned per cohort to ensure sufficient sample size for a reliable estimate of PK parameters.

Main Inclusion Criteria:

1. Participant must be male, 18 to 55 years of age (inclusive) at the time of signing the informed consent form and affiliated to the social security system.
2. Participant must be capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.
3. Participant must sign the informed consent form before any trial-related assessments.
4. The participant is in good health as determined by the medical history, physical examination, 12-lead ECG, vital signs (heart rate, respiratory rate, systolic and diastolic blood pressure [BP]), body temperature, and clinical laboratory parameters (clinical chemistry, hematology, coagulation, and urinalysis) without clinically relevant (per investigator judgement) deviations from reference ranges unless further specified in the exclusion criteria. The population of this clinical trial is healthy volunteer participants.

Main Exclusion Criteria:

1. Any disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding that contraindicates the use of an investigational drug, comparator, rescue medication, or any ingredients therein, or may affect the interpretation of the results, or may render the participant at high risk from treatment complications/ participation in the study unsafe
2. Major surgical procedure, within 3 months prior to ICF signing, or anticipation of need for a major surgical procedure during the trial
3. Clinically significant history or evidence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, neurological, or immunological disorder(s)
4. Regularly uses any medication, including herbal remedies or over-the-counter medication within 2 weeks before screening into this trial and anticipated use during the trial
5. Concurrent enrollment in another clinical trial, unless it is an observational (non interventional) clinical trial or during the follow-up period of an interventional trial
6. Recent participation in another clinical trial with an IMP administered within 30 days before Day 1 or within 5 times the elimination half-life of the IMP, whichever is longer