GLP-1 Receptor Agonists Post-Bariatric Surgery (GRABS) Pilot Trial
Severe Obesity · Obesity · BMI Greater Than 30
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Phase 2 / Phase 3
- Age range
- 25 years - 65 years
- Sex eligible
- All sexes
- Healthy volunteers
- Not accepted
- Participants
- 30 Estimated
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
The goal of this pilot clinical trial is to determine the effectiveness of Tirzepatide in patients with persistent obesity (BMI \> 30) 12 months after bariatric surgery (Roux-en-Y Gastric Bypass). The investigators also aim to determine the frequency of side effects with Tirzepatide in this patient population. Patients who take tirzepatide 12 months after bariatric surgery will be compared to patients who continue with the current standard of care for patients who have previously undergone Gastric Bypass Surgery.
Read the full description
Obesity affects nearly half of the U.S. population, impacting health outcomes including diabetes, cardiovascular risk, longevity, and quality of life. While bariatric surgery such as gastric bypass stands as the most effective intervention, 65% of individuals experience persistent obesity when undergoing surgical weight loss alone. Given the wide-ranging impact of obesity on health outcomes, a critical need exists to explore the efficacy of adjuvant weight loss therapies after gastric bypass surgery. Tirzepatide (TRZ), a type of glucagon-like peptide-1 receptor agonist, shows remarkable effectiveness in medical obesity with 25% weight loss after sustained therapy. However, nearly two-thirds of patients taking medications like TRZ have mild to moderate gastrointestinal (GI) symptoms, including nausea, vomiting, and abdominal pain. These medication side-effects could be a consequence of gastroparesis via vagal stimulation of the stomach, and may represent a major driver of weight loss. Limited data exist regarding use of these newer agents, such as TRZ, in patients who have undergone gastric bypass, which disrupts vagal nerves responsible for managing food transit and gastric emptying. This is a major and timely scientific gap in understanding whether gastric bypass surgery might mitigate these GI symptoms while allowing for enhanced weight loss with adjuvant TRZ use in the post-operative period. The investigators propose a pilot, phase II, open-label trial enrolling patients twelve months after gastric bypass with a nadir Body Mass Index ≥ 30 kg/m2. Study subjects will be randomized to either 24 weeks of TRZ or post-surgery standard of care. Subjects randomized to the standard of care arm will crossover to receive the intervention drug after 24 weeks of observation. Our proposal consists of two aims. First, the investigators will determine the impact of adjuvant TRZ administration on weight, total fat mass, and lean body mass in patients with a history of gastric bypass (Aim 1). Second, the investigators aim to investigate the frequency and severity of GI discomfort associated with TRZ utilizing a validated patient reported outcome questionnaire, and they will investigate the impact of TRZ on GI motility in patients with prior Gastric Bypass (Aim 2).
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Inclusion Criteria:
1. Subject must be able to understand and provide informed consent.
2. BMI ≥ 30 12 months after bariatric surgery.
3. Age \> 25 and \< 65
4. Patients undergoing primary Roux-en-Y Gastric Bypass
Exclusion Criteria:
1. Inability or unwillingness of a subject to give written informed consent or comply with the study protocol.
2. Diagnosis of type I Diabetes
3. Revisional bariatric surgery (prior adjustable gastric band, sleeve gastric, vertical banded gastroplasty).
4. Use of medications for type 2 diabetes treatment other than metformin
5. Hemoglobin A1c \> 8.5 in last 3 months.
6. Patient-reported Tobacco, e-cigarette, or smoked marijuana use within 12 months As this would preclude patients from undergoing bariatric surgery.
7. Personal history of pancreatitis as determined by history.
8. Personal or family history of medullary thyroid cancer by history or multiple endocrine neoplasia syndrome type 2
9. Pregnancy by urine testing, current lactation, or plans to become pregnant during the study period.
10. Use of systemic glucocorticoids in the past 28 days
11. Myocardial infarction, unstable angina, stroke, or heart failure (NYHA class II) within 1 year by history.
12. History of solid organ transplant.
13. History of physician-diagnosed malignancy (other than excised non-melanoma skin cancer) in the past 5 years.
14. Current uncontrolled hypertension (systolic \>150, diastolic \>90) or untreated hyperthyroidism.
15. Current, diagnosed, or self-reported drug or alcohol abuse that, in the opinion of the investigator, would interfere with the subject's ability to comply with study requirements.
16. Screening creatinine elevation with EGFR \< 60 at time of randomization.
17. Tobacco use in last 12 months
18. Pregnancy
19. Prisoners
20. Unable or unwilling to follow-up
21. Unable to understand English/Spanish
Treatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- No masking
Tirzepatide Group
Participants in the TRZ cohort will initiate a standardized dose titration as described in the package insert. Participants will begin TRZ at 2.5 mg for four weeks and then increase by 2.5 mg every 4 weeks to a maximum dose of 15 mg. If subjects experience intolerable GI symptoms, they will be allowed to decrease to a lower dose by 2.5 mg for 2 weeks, at which point another attempt at an increased dose will be trialed. Should patients not tolerate a higher dose a second time, they will have the dose again lowered by 2.5 mg and kept at the lower dose for the remainder of the study, except for patients who do not tolerate two attempts at 5 mg. For patients who fail to titrate to at least 5 mg TRZ, a third attempt at an increased dose will be attempted 4 weeks after the second decrease in dose. These patients will then remain on 5 mg for the remainder of the intervention period. All participants receiving TRZ will be pooled in terms of outcomes measures.
Drug: Tirzepatide
Control - Standard of care Post-Gastric Bypass Surgery
Patients randomized to the control arm will receive the standard of care for weight maintenance after gastric bypass including dietary guidance provided by the Vanderbilt Surgical Weight Loss handbook for 24 weeks. After 24 weeks, particiapnts in the control arm will crossover to the Tirzepatide arm and receive 24 weeks of TRZ following the same titration.
Other: Standard of Care post-gastric bypass
Tirzepatide DRUG
Tirzepatide will be initiated 12 or 18 months (12 months + 24 weeks) after patients undergo Roux-en-Y Gastric Bypass. Patients will be started on the lowest dose of 2.5 mg and the dose increased every 6 weeks following an adaptive maximum dose titration protocol. Patients will then complete a final 4 weeks of the study drug.
Standard of Care post-gastric bypass OTHER
Patients randomized to the control arm will receive the standard of care for weight maintenance after gastric bypass including dietary guidance provided by the Vanderbilt Surgical Weight Loss handbook. This includes recommendations for 64 oz of fluids per day, ≥60 grams of protein/day, and daily bariatric multivitamins. Patients will continue to have access to dedicated bariatric dietitians, advanced practice providers, and surgeons on an ad hoc basis per patients' request.
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Weight loss
Time frame: baseline to 24 weeks
Percent total weight change baseline to 24 weeks
Gastrointestinal symptoms
Time frame: baseline to 24 weeks
Mixed-model adjusted mean difference at Week 24
Secondary measures
Change in body composition
Time frame: baseline to 24 weeks
Changes in fat mass
Acetaminophen Area Under the Curve
Time frame: baseline to 24 weeks
Changes in acetaminophen area under the curve in the intervention arm
Lean body mass
Time frame: baseline to 24 weeks
Utilizing DXA, we will determine changes in lean body mass in both arms
Other measures
weight regain after TRZ discontinuation
Time frame: weeks 24 to 48
Degree of weight regain in intervention arm after discontinuation of TRZ
Obesity remission
Time frame: baseline to 24 weeks
incidence of obesity remission (BMI \< 30)
Remission of pre-existing comorbidities
Time frame: baseline to 24 weeks.
Incidence of remission of Type 2 Diabetes, Hyperlipidemia, Hypertension
change in anthropometric measurements
Time frame: baseline to 24 weeks
Changes in clinical obtained anthropometric measurements including waist circumference and waist-to-hip ratio
changes in body composition
Time frame: baseline to 24 weeks.
Changes in DXA-proven body composition including lean body mass and ratio of lean body mass to fat mass
Change in PAGI-SYM sub-scale scores
Time frame: baseline to 24 weeks
1\. heartburn/regurgitation, 2. nausea/vomiting, 3. postprandial fullness, 4. bloating, 5. upper and lower abdominal pain
change in PAGI-SYM scores in the TRZ arm
Time frame: baseline to week 24 and week 24 to week 28 (after TRZ discontinuation)
Determining evolution of PAGI-SYM scores across treatment in both arms and after discontinuation of TRZ in the intervetion arm.
Difference in acetaminophen AUC between groups
Time frame: baseline to 24 weeks
difference in acetaminophen AUC between Intervention and control groups
Changes in response to mixed meal tolerance test
Time frame: baseline to 24 weeks
change in intervention arm mixed meal AUC for Glucose, Insulin, and GLP-1
Medication adherence
Time frame: baseline to 24 weeks
Incidence of missed doses, patient-driven drug discontinuation, patient withdrawal in intervention arm
Adverse events and healthcare resource utilization
Time frame: baseline to 48 weeks
Incidence of adverse events including emergency department visits, hospitalizations, and reoperations
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (1)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
1 locations
Vanderbilt University Medical CenterNashville, Tennessee, United StatesStatus unknown
Study team and timeline
- Lead sponsor
- Vanderbilt University Medical Center
- Study start
- Oct 30, 2024 Actual
- Primary completion
- Oct 10, 2026 Actual
- Study completion
- Apr 30, 2027 Estimated
- First posted
- Dec 8, 2023 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
No central contact is listed. Check the locations and the official record.
Official study title
GLP-1 Receptor Agonists Post-Bariatric Surgery (GRABS) Pilot Trial
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 11, 2026 · Last registry update: Nov 10, 2026