This study is a phase I, randomized, double-blind, placebo-controlled, single-center, to evaluate the safety, tolerability, and pharmacokinetics (PK) of GLPG3667 after an oral single dose (SD) of GLPG3667 (part 1) and after oral multiple doses (MD) for 13 days of GLPG3667 (part 2) in healthy male subjects.

Inclusion Criteria:

• Male between 18 and 55 years of age (extremes included), on the date of signing the informed consent form (ICF).
• A body mass index (BMI) between 18.0 and 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, 12-lead electrocardiogram (ECG), and fasting clinical laboratory safety tests, available at screening and prior to randomization. Hemoglobin, neutrophil, lymphocyte, and platelet counts must be above the lower limit of normal range. Total bilirubin, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) must be below the upper limit of normal. 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 not clinically significant in the opinion of the investigator.

This list only contains the key inclusion criteria.

Exclusion Criteria:

• Known hypersensitivity to investigational product (IP) ingredients or history of a significant allergic reaction to IP ingredients as determined by the investigator.
• Positive serology for hepatitis B virus surface antigen (HBsAg) or hepatitis C virus (HCV) or history of hepatitis from any cause with the exception of hepatitis A that has resolved at least 3 months prior to first dosing of the IP.

This list only contains the key exclusion criteria.