ObesityPhase 2NCT04684589
Effect of PDE5 Inhibition on Adipose Metabolism in Humans
A Phase 2 study testing Tadalafil 20 MG in people with Obesity, run by Vanderbilt University Medical Center at 1 site in United States.
Trial summary
This is a randomized, double-blinded, placebo-controlled study of the effects of PDE5 inhibition with tadalafil on adipose tissue in obese individuals. Adipose metabolism will be measured using magnetic resonance imaging (MRI) scans and by aspirating a small amount of adipose to measure gene expression. Read more about this study
- Who is it for?
- Ages 19 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Obesity
- What is being tested?
- Tadalafil 20 MG
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 99 participants
- Where
- 1 siteUnited States
- Study dates
- 16 Mar 2021to 24 Jun 2025
- Phase
- Phase 2
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 19 to 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Adults
- Obesity (BMI ≥ 30 kg/m2)
Who cannot join
- Age <19 or > 50
- BMI < 30 kg/m2
- Systolic blood pressure (SBP) < 100, > 150 mmHg
- Current anti-hypertensive medication use, including diuretics
- Current use of organic nitrates
- Current use of PDE-5 inhibitors (sildenafil, tadalafil, vardenafil)
Show all 22Show fewer
- History of reaction to PDE-5 inhibitors
- Known HIV infection
- Use of medications that strongly alter CYP3A4 activity
- History of myocardial infarction, angina, uncontrolled cardiac arrhythmia, stroke, transient ischemic attack, or seizure
- Known non-arteritic ischemic optic retinopathy (NAIOR)
- History of hearing loss
- Estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 by the modified diet in renal disease (MDRD) equation
- Hepatic transaminase (AST and ALT) levels greater than three times the upper limit of normal
- Known pregnancy or breastfeeding or those unwilling to avoid pregnancy during the course of the study
- History of priapism
- Use in excess of four alcoholic drinks daily
- History of diabetes mellitus or use of anti-diabetic medications
- Known anemia (men, Hct < 38% and women, Hct <36%)
- Menopause
- Weight > 300 pounds
- Individuals with circadian rhythm disorders, shift workers, or those who travel across time zones frequently
Trial locations and contacts
1 site in 1 country.
United States1 site
Vanderbilt University Medical Center
Nashville, Tennessee, 37203
About this study
This is a randomized, double-blinded, placebo-controlled study of the effects of PDE5 inhibition with tadalafil on adipose tissue in obese individuals. Adipose metabolism will be measured using magnetic resonance imaging (MRI) scans and by aspirating a small amount of adipose to measure gene expression.
Read the detailed description
The purpose of this study is to test whether tadalafil causes subcutaneous adipose tissue to have a "beige" phenotype. Participants will be randomized to either placebo or tadalafil for 12 weeks. Investigators will study adipose metabolism using MRI scans and aspiration of subcutaneous adipose from the abdomen. In addition to MRI scans at room temperature, the investigators will use a cooling protocol to test the combined effects of tadalafil and on adipose metabolism. Investigators will also measure the effects of the drug on body composition. In addition to the study visits, participants will wear an activity tracker (Fitbit) and log their dietary intake several times using an online tool. There will be a small amount of radiation exposure. Participants will be compensated for participation in this study.
- Conditions
- Obesity
- Being tested
- Tadalafil 20 MG, Placebo
- Medical subject headings
- Obesity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Tadalafil 20 MGDrug
Also called CIALIS
Tadalafil is an FDA approved, clinically-available drug that inhibits the enzyme phosphodiesterase type 5A (PDE5). Subjects who are randomized to this arm will be provided with 20mg of Tadalafil to take every day for 12 weeks, beginning at their baseline visit.
PlaceboDrug
Subjects in this arm will be provided with 20mg Placebo to take every day for 12 weeks, beginning at their baseline visit.
| Study group | Role | What they receive |
|---|---|---|
| Tadalafil | Active comparator | Subjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the Tadalafil arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of Tadalafil (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the active comparator subjects will undergo the following visit protocol: screening visit, baseline visit, an interim visit (10 weeks post-baseline), and a 12-week visit. Receives: Drug: Tadalafil 20 MG |
| Placebo | Placebo comparator | Subjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the placebo arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of a placebo pill (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the placebo comparator subjects will undergo the following visit protocol: screening visit, baseline, an interim visit (10 weeks post-baseline), and a 12-week visit. Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Thermoneutral FSF of WAT at the Level of the Umbilicus at 12 Weeks.
Measured by fat signal fraction (FSF) at Week 12. FSF is the percent of MRI signal derived from lipids within a voxel. Lower FSF values indicate greater lipid consumption and correspond to brown adipose tissue (BAT), whereas higher FSF values indicate lipid storage and correspond to white adipose tissue (WAT).
Measured: 12 weeks
Thermoneutral Subcutaneous Adipose Tissue Expression of UCP1 (Normalized Expression Units) at 12 Weeks.
Measured by mRNA expression of subcutaneous adipose tissue obtained via biopsy at 12 weeks. Higher expression of UCP1 indicates increased thermogenic (beige/brown) adipose activity; lower expression indicates a white adipose phenotype associated with reduced energy expenditure.
Measured: 12 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Dec 2020
- Study start16 Mar 2021
- Primary completion20 Jun 2025
- Study completion24 Jun 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for ObesityStudies of the same condition, open and under way.
- More trials run by Vanderbilt University Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Half of participants to get tadalafil and half to get placebo.
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 99 participants (actual)
Sponsor and investigators
- Lead sponsor
- Vanderbilt University Medical Center
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Evan Brittain, Vanderbilt University Medical Center
- Investigators
- Evan Brittain, MD, MSci, Principal investigator, VUMC
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04684589
- Sponsor's protocol ID
- 202420
- Status last verified
- Jul 2026
- First submitted
- 16 Dec 2020
- Last updated
- 30 Jul 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 30 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of PDE5 Inhibition on Adipose Metabolism in Humans
- ClinicalTrials.gov ID
- NCT04684589
- Acronym / sponsor ID
- 202420
- Conditions
- Obesity
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 99 participants (actual)
- Lead sponsor
- Vanderbilt University Medical CenterUniversity, hospital or other
- Study start
- 16 Mar 2021 (actual)
- Primary completion
- 20 Jun 2025 (actual)
- Study completion
- 24 Jun 2025 (actual)
- First posted
- 24 Dec 2020 (actual)
- Results
- Posted 30 Jul 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This is a randomized, double-blinded, placebo-controlled study of the effects of PDE5 inhibition with tadalafil on adipose tissue in obese individuals. Adipose metabolism will be measured using magnetic resonance imaging (MRI) scans and by aspirating a small amount of adipose to measure gene expression.
Detailed description
The purpose of this study is to test whether tadalafil causes subcutaneous adipose tissue to have a "beige" phenotype. Participants will be randomized to either placebo or tadalafil for 12 weeks. Investigators will study adipose metabolism using MRI scans and aspiration of subcutaneous adipose from the abdomen. In addition to MRI scans at room temperature, the investigators will use a cooling protocol to test the combined effects of tadalafil and on adipose metabolism. Investigators will also measure the effects of the drug on body composition. In addition to the study visits, participants will wear an activity tracker (Fitbit) and log their dietary intake several times using an online tool. There will be a small amount of radiation exposure. Participants will be compensated for participation in this study.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
- Model description
- Half of participants to get tadalafil and half to get placebo.
| Arm | Type | Receives |
|---|---|---|
| Tadalafil | Active comparator | Drug: Tadalafil 20 MGSubjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the Tadalafil arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of Tadalafil (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the active comparator subjects will undergo the following visit protocol: screening visit, baseline visit, an interim visit (10 weeks post-baseline), and a 12-week visit. |
| Placebo | Placebo comparator | Drug: PlaceboSubjects will be randomized to one of two arms. 50 obese adult subjects will be randomized to the placebo arm following the screening visit. Beginning at their baseline visit, they will receive an oral daily dose of a placebo pill (20mg) that they will take for 12 weeks (through their completion of the study). After randomization has occurred, the placebo comparator subjects will undergo the following visit protocol: screening visit, baseline, an interim visit (10 weeks post-baseline), and a 12-week visit. |
Who may qualify
- Ages
- 19 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (2 listed)
- Adults
- Obesity (BMI ≥ 30 kg/m2)
Key exclusion criteria (22 listed)
- Age <19 or > 50
- BMI < 30 kg/m2
- Systolic blood pressure (SBP) < 100, > 150 mmHg
- Current anti-hypertensive medication use, including diuretics
- Current use of organic nitrates
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Tadalafil 20 MGAlso: CIALISTadalafil is an FDA approved, clinically-available drug that inhibits the enzyme phosphodiesterase type 5A (PDE5). Subjects who are randomized to this arm will be provided with 20mg of Tadalafil to take every day for 12 weeks, beginning at their baseline visit. | Drug | Tadalafil |
| PlaceboSubjects in this arm will be provided with 20mg Placebo to take every day for 12 weeks, beginning at their baseline visit. | Drug | Placebo |
Primary outcome
Thermoneutral FSF of WAT at the Level of the Umbilicus at 12 Weeks.
Time frame: 12 weeks
Measured by fat signal fraction (FSF) at Week 12. FSF is the percent of MRI signal derived from lipids within a voxel. Lower FSF values indicate greater lipid consumption and correspond to brown adipose tissue (BAT), whereas higher FSF values indicate lipid storage and correspond to white adipose tissue (WAT).
Thermoneutral Subcutaneous Adipose Tissue Expression of UCP1 (Normalized Expression Units) at 12 Weeks.
Time frame: 12 weeks
Measured by mRNA expression of subcutaneous adipose tissue obtained via biopsy at 12 weeks. Higher expression of UCP1 indicates increased thermogenic (beige/brown) adipose activity; lower expression indicates a white adipose phenotype associated with reduced energy expenditure.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 30 Jul 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Evan Brittain, MD, MSci principal investigator
VUMC
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Tadalafil 20 MG in people with Obesity, run by Vanderbilt University Medical Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 22 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 30 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 30 Jul 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Thermoneutral FSF of WAT at the Level of the Umbilicus at 12 Weeks. (time frame: 12 weeks). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 Jul 2026.