Who runs the most US clinical trials?
Sponsors, conditions, and phases ranked across 175,638 US clinical trials, drawn straight from the NIH ClinicalTrials.gov registry and refreshed from the public source.
The rankings in one line
National Cancer Institute (NCI) runs the most US trials (3,257), Breast Cancer is the most-studied condition (1,251 trials), and Phase 2 leads the active pipeline.
- 3,257
- top sponsor: National Cancer Institute (NCI)
- 1,251
- most-studied: Breast Cancer
- 31,395
- Phase 2 trials (largest phase)
- 14%
- recruiting now (24,857)
Counts reflect the public ClinicalTrials.gov registry as last mirrored by PlainTrial. Sponsor and phase are reported by each study's sponsor. Reference information, not medical advice.
Most active sponsors, most studied conditions, and phase distribution across U.S. clinical trials drawn from ClinicalTrials.gov. According to ClinicalTrials.gov, the National Institutes of Health public registry maintained by the U.S. National Library of Medicine catalogs more than 500,000 clinical studies across over 220 countries since 1997, with the U.S. Food and Drug Administration Amendments Act (FDAAA) of 2007 requiring registration for most studies of FDA-regulated products. Rankings refreshed monthly from the public registry; see our methodology.
These rankings aggregate clinical trial activity from ClinicalTrials.gov across three dimensions: sponsor pipeline depth, condition research volume, and trial phase distribution. Sponsor rankings reflect the total number of studies registered across the registry's history, older sponsors with mature pipelines often dominate the top spots, while emerging biotechs may rank lower despite high recent activity.
Most-studied conditions reflect the breadth of research investment across disease areas. Oncology subtypes typically lead because cancer research draws diverse sponsorship from pharma, NIH, academic centers, and cooperative groups. Common chronic conditions (diabetes, hypertension, depression) follow because of their prevalence and the recurring need for combination-therapy and head-to-head studies. Recruiting-only rankings show which sponsors are most actively enrolling right now, which is more relevant to patients seeking trial participation than total-pipeline counts.
Trial phase distribution shows the overall maturity of US clinical research, Phase 1 safety studies, Phase 2 dose-finding and efficacy work, and Phase 3 pivotal trials that support FDA submission. The mix tells you about the state of the development pipeline at any moment: a Phase-3-heavy snapshot suggests imminent approvals; a Phase-1-heavy snapshot suggests an active innovation pipeline.
Most Active Sponsors
| # | Sponsor | Trials |
|---|---|---|
| 1 | National Cancer Institute (NCI) | 3,257 |
| 2 | Mayo Clinic | 2,844 |
| 3 | M.D. Anderson Cancer Center | 2,692 |
| 4 | Massachusetts General Hospital | 2,032 |
| 5 | National Institute of Allergy and Infectious Diseases (NIAID) | 2,006 |
| 6 | Memorial Sloan Kettering Cancer Center | 1,884 |
| 7 | Pfizer | 1,845 |
| 8 | Stanford University | 1,744 |
| 9 | Duke University | 1,725 |
| 10 | University of California, San Francisco | 1,713 |
| 11 | VA Office of Research and Development | 1,668 |
| 12 | Washington University School of Medicine | 1,502 |
| 13 | Yale University | 1,492 |
| 14 | Johns Hopkins University | 1,448 |
| 15 | University of Pennsylvania | 1,423 |
| 16 | Novartis Pharmaceuticals | 1,375 |
| 17 | GlaxoSmithKline | 1,345 |
| 18 | Eli Lilly and Company | 1,341 |
| 19 | University of Michigan | 1,327 |
| 20 | AstraZeneca | 1,285 |
Most Studied Conditions
| # | Condition | Trials |
|---|---|---|
| 1 | Breast Cancer | 1,251 |
| 2 | Healthy | 1,096 |
| 3 | Obesity | 1,057 |
| 4 | Prostate Cancer | 749 |
| 5 | Depression | 687 |
| 6 | Cancer | 621 |
| 7 | HIV Infections | 615 |
| 8 | Hypertension | 472 |
| 9 | Stroke | 456 |
| 10 | Non-Small Cell Lung Cancer | 450 |
| 11 | Multiple Myeloma | 441 |
| 12 | Lung Cancer | 430 |
| 13 | Heart Failure | 399 |
| 14 | Colorectal Cancer | 382 |
| 15 | Asthma | 378 |
| 16 | Pain | 377 |
| 17 | Anxiety | 367 |
| 18 | Diabetes Mellitus, Type 2 | 351 |
| 19 | Diabetes | 342 |
| 20 | Ovarian Cancer | 338 |
Sponsors with Most Recruiting Trials
Trials by Phase
| Phase | Trials |
|---|---|
| Not Applicable | 86,577 |
| Phase 2 | 31,395 |
| Phase 1 | 30,052 |
| Phase 3 | 15,530 |
| Phase 4 | 9,318 |
| Early Phase 1 | 2,766 |
Reading the US Clinical-Trial Rankings
These rankings draw on 175,638 US clinical trials indexed on ClinicalTrials.gov, registered by 15,751 distinct sponsors across 28,964 condition areas. The single most active sponsor is National Cancer Institute (NCI) with 3,257 registered studies, a position that reflects decades of accumulated pipeline rather than current-year activity, which is why a mature academic center or large cooperative group often outranks a fast-growing biotech. Sponsor totals count every study a sponsor has ever registered, so they read as a measure of institutional research footprint, not of how many trials are open today.
On the condition side, Breast Cancer leads with 1,251 indexed trials, and oncology subtypes dominate the upper ranks because cancer research draws diverse sponsorship from pharma, the NIH, academic medical centers, and cooperative groups at once. The phase distribution tells a parallel story: Phase 2 is the largest reported phase at 31,395 trials, ahead of Phase 3 at 15,530, which is typical of a healthy pipeline where many candidates are still establishing efficacy before the larger, costlier pivotal studies.
Across the registry, 24,857 trials, about 14% of the indexed total, are currently listed as recruiting, which is the figure most relevant to patients looking for participation options. All counts are derived directly from the public ClinicalTrials.gov dataset maintained by the National Library of Medicine and are reproduced here for reference. Inclusion of a sponsor or condition in a ranking is neither an endorsement nor a recommendation; verify current status on ClinicalTrials.gov and consult a qualified healthcare provider before acting on anything you see here.
What to do with these rankings
Rankings show where research is concentrated, use them as a starting point, then drill into what's open now.
- 24,857 trials are recruiting right now, filter them by condition or state. Find recruiting trials
- Breast Cancer leads with 1,251 trials, see its phase mix and sponsors. Breast Cancer trials
- Compare research activity across all 52 states and territories. Trials by state
Sponsor totals span the full registry history and reflect institutional footprint, not current-year activity.
Read our methodology - how these rankings are sourced, computed, and refreshed.
Source: ClinicalTrials.gov (NIH/NLM) ClinicalTrials.gov AACT registry · 2026 Sponsor, condition, and phase rankings derived from ClinicalTrials.gov. Sponsor totals span the full registry history; phase is sponsor-reported.
Every figure on PlainTrial is rendered directly from the ClinicalTrials.gov registry, no number is typed in by an editor. This hub surfaces the top sponsors, conditions, and recruiting trials, live from the dataset. See our editorial standards & corrections policy, the methodology behind these numbers, the data changelog, or report a data error.