A Study to Evaluate the Effects of a Single and Multiple Oral Doses of GLPG3121 in Adult, Healthy, Male Subjects

Inclusion Criteria: * Able and willing to comply with the protocol requirements and signing the Informed Consent Form (ICF) as approved by the Independent Ethical Committee (IEC)/Institutional Review Board (IRB), prior to any screening evaluations. * Male between 18 to 55 years of age (extremes included), on the date of signing the ICF. * A Body Mass Index (BMI) between 18.0 to 30.0 kg/m2, inclusive. * Judged to be in good health by the investigator based upon the results of a medical history, physical examination, vital signs, (triplicate) 12-lead electrocardiogram (ECG), and fasting clinical laboratory safety tests, available at screening and prior to randomization. Hemoglobin, neutrophil, lymphocyte, and platelet counts must not be below the lower limit of normal range. Bilirubin, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) must be no greater than 1.5x the upper limit of normal range (ULN). Other clinical laboratory safety test results must be within the reference ranges or test results that are outside the reference ranges need to be considered nonclinically significant in the opinion of the investigator. Exclusion Criteria: * Known hypersensitivity to investigational medicinal product (IMP) ingredients or history of a significant allergic reaction to IMP ingredients as determined by the investigator. * Known contraindication or hypersensitivity to interferon-α (IFN-α) or any component of Intron-A® (Note: this criterion is only applicable to subjects in the MAD part). * Having any illness, judged by the investigator as clinically significant, in the 3 months prior to first dosing of the IMP. * Presence or sequelae of gastrointestinal, liver, kidney (creatinine clearance ≤80 mL/min using the Cockcroft-Gault formula: if calculated result is ≤80 mL/min a 24-hours urine collection to assess creatinine clearance can be done) or other conditions known to interfere with the absorption, distribution, metabolism, or excretion of drugs. * History of malignancy within the past 5 years prior to screening with the exception of excised and curatively treated non-metastatic basal cell carcinoma or squamous cell carcinoma of the skin.