The purpose of this study is to evaluate the safety and tolerability of single and multiple subcutaneous (SC) doses of MBX 4291 in adults with obesity.

This is a Phase 1, double-blind, placebo-controlled first-in-human study to evaluate the single ascending doses (SAD) and multiple ascending doses (MAD) of MBX 4291 in participants with obesity, who are otherwise generally healthy. Approximately 124 patients aged 18 to 65 years old will be enrolled.

Inclusion Criteria:

• Age of >18 to ≤65 years at the time of signing the informed consent.
• Has a BMI of ≥30 to <50 kg/m2 at screening and baseline.
• Weight-stable, i.e., no more than ±5% change in body weight for at least 3 months prior to screening and between screening and baseline.

Exclusion Criteria:

• History of, or currently active, significant illness or medical disorders that in the opinion of the investigator may preclude participants from participating in the study.
• History of currently active pancreatitis, type I and type II diabetes.
• Secondary causes of obesity, including but not limited to hypothalamic, monogenic, syndromic, or endocrine causes.
• A personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2.