This study will assess the safety of the investigational drug CRB-913 and how it is processed in the body. The study has two parts: Part 1 will measure drug levels in healthy adults after taking CRB-913 tablets, and Part 2 will compare three doses of CRB-913 with placebo to evaluate safety, effects on body weight, and drug levels in the blood. Part 2 is blinded, meaning participants, study doctors, and the sponsor will not know which treatment is given. Participants in Part 2 will take study treatment for 12 weeks and will be followed for 28 days after treatment ends.