The primary objective of the study is to determine the effects of KAI-9531 subcutaneous (SC) injection once weekly compared to placebo on percent change in body weight.

Inclusion Criteria:

• BMI ≥30 kg/m^2 or BMI ≥27 kg/m^2 and previously diagnosed with at least 1 of the following:

  1. hypertension,
  2. dyslipidemia,
  3. obstructive sleep apnea, or
  4. cardiovascular (CV) disease.

• History of at least 1 self-reported unsuccessful effort to lose weight with diet and exercise within the prior 6 months.

Exclusion Criteria:

• Current diagnosis or history of diabetes mellitus.
• Started medications within 3 months prior to Screening that may cause significant weight gain, including, but not limited to, tricyclic antidepressants, atypical antipsychotics, and mood stabilizers.
• Unstable weight defined as self-reported change in body weight exceeding 5% within 3 months prior to Screening.
• Family or personal history of multiple endocrine neoplasia Type 2 or medullary thyroid cancer.
• Uncontrolled hypertension or unstable cardiovascular disease.
• History of chronic or acute pancreatitis.
• Known clinically significant gastric-emptying abnormality or chronic treatment with medications that directly affect gastrointestinal motility.
• History of suicide attempt.
• History of significant active or unstable Major Depressive Disorder (MDD) or other severe psychiatric disorder.
• Received treatment with semaglutide, tirzepatide, GLP-1 receptor agonist, GLP-1/glucose-dependent insulinotropic polypeptide (GIP), or glucagon receptor agonist within 3 months prior to Screening.

Note: Additional inclusion/exclusion criteria may apply, per protocol.