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Updated May 2026 · ClinicalTrials.gov

RECRUITINGPhase 2INTERVENTIONAL

Metformin for Pulmonary Hypertension HFpEF

Phase II Trial of Metformin for Pulmonary Hypertension in Heart Failure With Preserved Ejection Fraction

Metformin for Pulmonary Hypertension HFpEF (NCT03629340) is a Phase 2 interventional studying Pulmonary Hypertension and Heart Failure, sponsored by University of California, San Francisco. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

Important: This information is not medical advice. Talk to your doctor about whether a clinical trial is right for you.

About This Trial

The main objective of this study is to determine the clinical efficacy of metformin versus placebo and the therapeutic response with regards to functional capacity and hemodynamics in PH-HFpEF.

What Stage of Research Is This?

Phase 2 trials evaluate whether a treatment actually works against Pulmonary Hypertension and continue monitoring side effects. Phase 2 enrolls larger groups (typically 100–300 patients) and produces the first real efficacy signal. A successful Phase 2 readout is what unlocks the much larger Phase 3 confirmatory trials needed for FDA approval.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

With a target enrollment of 10 participants, this is a small study — typical of early-phase research, rare-disease trials, or pilot studies designed to generate preliminary signal before a larger study is launched.

Who May Be Eligible (Plain English)

Who May Qualify: 2\. PH-HFpEF Confirmed diagnosis by RHC within the past 6 months: Mean Pulmonary Arterial Pressure (mPAP) ≥ 25 mm Hg AND Pulmonary artery wedge pressure (PAWP) ≥ 15 mm Hg AND Transpulmonary Gradient (TPG) ≥ 12 mm Hg OR Exercise measurements Mean Pulmonary Arterial Pressure (mPAP) ≥ 30 mm Hg AND Pulmonary artery wedge pressure (PAWP) ≥ 20 mm Hg AND PA calculation (change in mPAP/change in cardiac output) = ≥3 mmHg/L/min 3\. Three or more features of metabolic syndrome defined as: Body Mass Index (BMI) ≥ 30 kg/m² Systolic blood pressure (BP) ≥ 130 mm Hg and/or diastolic BP ≥ 85 mm Hg Elevated waist circumference \> 102 cm in men and \> 88 cm in women Fasting triglyceride (TG) level over 150 mg/dl High-density lipoprotein \<40 mg/dL in men or \< 50 mg/dL in women Who Should NOT Join This Trial: 1. Age less than 18 years; 2. Uncontrolled systemic hypertension based on repeated measurement of sitting systolic blood pressure \>170 mm Hg or sitting diastolic blood pressure \>95 mm Hg at Screening; 3. Systemic sitting blood pressure \< 110 mmHg systolic or \< 60 mm Hg diastolic at Screening; 4. Hemoglobin A1C \> 10; 5. Currently taking metformin or history of intolerance to metformin or contraindication to taking metformin; 6. Known type 1 diabetes 7. Positive urine pregnancy test or breastfeeding 8. Ejection Fraction \< 50% 9. Dementia; ...See full criteria on ClinicalTrials.gov Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language
Inclusion Criteria: 2\. PH-HFpEF Confirmed diagnosis by RHC within the past 6 months: Mean Pulmonary Arterial Pressure (mPAP) ≥ 25 mm Hg AND Pulmonary artery wedge pressure (PAWP) ≥ 15 mm Hg AND Transpulmonary Gradient (TPG) ≥ 12 mm Hg OR Exercise measurements Mean Pulmonary Arterial Pressure (mPAP) ≥ 30 mm Hg AND Pulmonary artery wedge pressure (PAWP) ≥ 20 mm Hg AND PA calculation (change in mPAP/change in cardiac output) = ≥3 mmHg/L/min 3\. Three or more features of metabolic syndrome defined as: Body Mass Index (BMI) ≥ 30 kg/m² Systolic blood pressure (BP) ≥ 130 mm Hg and/or diastolic BP ≥ 85 mm Hg Elevated waist circumference \> 102 cm in men and \> 88 cm in women Fasting triglyceride (TG) level over 150 mg/dl High-density lipoprotein \<40 mg/dL in men or \< 50 mg/dL in women Exclusion Criteria: 1. Age less than 18 years; 2. Uncontrolled systemic hypertension based on repeated measurement of sitting systolic blood pressure \>170 mm Hg or sitting diastolic blood pressure \>95 mm Hg at Screening; 3. Systemic sitting blood pressure \< 110 mmHg systolic or \< 60 mm Hg diastolic at Screening; 4. Hemoglobin A1C \> 10; 5. Currently taking metformin or history of intolerance to metformin or contraindication to taking metformin; 6. Known type 1 diabetes 7. Positive urine pregnancy test or breastfeeding 8. Ejection Fraction \< 50% 9. Dementia; 11\. End-stage malignancy; 12. Major cardiovascular event or procedure within 6 weeks prior to enrollment; 13. Severe valvular disease; 14. Other severe acute or chronic medical, psychiatric or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the subject inappropriate for entry into this study or would prevent completion of the study; 15. Current Smoker; 16. Hemoglobin \<9 g/dL; 17. Estimated glomerular filtration rate (eGFR) \<30 mL/min/1.73 m2; 18. Receipt of an investigational product or device, or participation in a drug research study within a period of 15 days 19. \<3 months of stable dose of PDE5i

Treatments Being Tested

DRUG

Metformin

500 mg PO BID x 1 week then increase to 1000 mg PO BID x 11 weeks

DRUG

Placebo oral capsule

Placebo capsule that is of identical size, shape, and color to experimental drug capsule PO (by mouth) BID (two times each day) for 12 weeks

Locations (2)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

UCSF Medical Center
San Francisco, California, United States
University of Pittsburgh Medical Center
Pittsburgh, Pennsylvania, United States

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT03629340), the sponsor (University of California, San Francisco), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT03629340 clinical trial studying?

The main objective of this study is to determine the clinical efficacy of metformin versus placebo and the therapeutic response with regards to functional capacity and hemodynamics in PH-HFpEF. The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.

Who can participate in NCT03629340?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT03629340?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT03629340. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT03629340. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-05-08 · Data from ClinicalTrials.gov.