Testing MBX 4291 for safety and body effects in adults with obesity

A Randomized, Double-blind, Placebo-controlled First-in-human Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single and Multiple Ascending Doses of MBX 4291 in Adult Participants With Obesity

Phase 1 Interventional MBX Biosciences · NCT07142707

This Phase 1 trial will test whether single and multiple under-the-skin (subcutaneous) doses of MBX 4291 are safe and well tolerated in adults with obesity.

Quick facts

PhasePhase 1
Study typeInterventional
Enrollment124 (estimated)
Ages18 Years to 65 Years
SexAll
SponsorMBX Biosciences Industry-sponsored
Locations2 sites (Lexington, Kentucky and 1 other locations)
Trial IDNCT07142707 on ClinicalTrials.gov

What this trial studies

This is a first-in-human, double-blind, placebo-controlled Phase 1 study using single ascending dose (SAD) and multiple ascending dose (MAD) designs to characterize safety, tolerability, pharmacokinetics, and pharmacodynamics of MBX 4291. About 124 adults aged 18–65 with BMI 30 to <50 kg/m2 who are otherwise generally healthy will be enrolled. Participants will receive subcutaneous doses of MBX 4291 or placebo and undergo scheduled safety and laboratory monitoring as well as PK/PD sampling. The study excludes people with diabetes, active pancreatitis, secondary causes of obesity, and certain thyroid cancer risk factors.

Who should consider this trial

Good fit: Adults 18–65 years old with a BMI between 30 and <50 kg/m2 who have been weight-stable and do not have diabetes or other excluded medical conditions are ideal candidates.

Not a fit: People with type 1 or type 2 diabetes, active pancreatitis, secondary or syndromic causes of obesity, a personal or family history of medullary thyroid carcinoma or MEN2, children, older adults above 65, or those with significant active illnesses are unlikely to be eligible or to benefit from this Phase 1 safety-focused trial.

Why it matters

Potential benefit: If successful, MBX 4291 could become a new medication option to help manage body weight.

How similar studies have performed: MBX 4291 is first-in-human and untested in people specifically, although other classes of weight-loss medications have shown effectiveness in prior trials.

Eligibility criteria

Show full inclusion / exclusion criteria
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.

Where this trial is running

Lexington, Kentucky and 1 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions ObesityBody WeightBody Mass IndexOverweightNutrition Disorders
Last reviewed 2026-06-10 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.