Some clinical trials aren’t designed to answer scientific questions. They’re designed to market drugs. In our recently published research, my team and I analyzed over 34,000 industry-funded trials and found that hundreds of studies across seven medical fields were likely designed to promote a drug to physicians rather than to generate scientific data. For some fields, nearly 1% of clinical trials were for marketing purposes.

Known as seeding trials, these studies prioritize marketing over science while disguising their commercial purpose as legitimate research. Pharmaceutical companies use them to familiarize physicians with new products under the guise of data collection. Participants sign consent forms, believing they are contributing to medical knowledge.

In reality, patients are absorbing risks that serve corporate interests rather than resolving genuine uncertainty about the therapeutic potential of a drug.

The term seeding trial first entered the medical literature in 1994, when then-commissioner of the Food and Drug Administration David Kessler and his colleagues described such studies as attempts to entice doctors to prescribe new drugs through trials that appear to serve little scientific purpose.

Three decades later, the problem of seeding trials persists.

How seeding trials work

While the structure of a seeding trial looks similar to legitimate clinical trials on the surface, the objectives are different.

In a typical clinical trial, researchers recruit patients across clinics and hospitals to test whether a treatment is safe and effective.

In contrast, the pharmaceutical company behind a seeding trial enrolls large numbers of physicians at many sites, each seeing only a few patients. The goal is exposure: getting doctors to prescribe the drug, not generating robust data. Doctors may be selected based on their prescribing volume rather than their research credentials.

In a legitimate trial, the number of study sites reflects the number of patients needed to answer a scientific question. In a seeding trial, the number of sites reflects the number of doctors the company wants to reach.

Seeding trials often target drugs already on the market and operate as Phase 4, or postmarketing, studies. These types of studies are typically conducted after a drug has been approved to monitor its long-term safety or effectiveness. This trial stage receives less regulatory scrutiny than trials for initial drug approval, and the aims of the study may have limited relevance to actual patient care. For example, a seeding trial might measure whether patients prefer the taste of a new formulation or how quickly a drug dissolves in the stomach, rather than whether it actually improves health outcomes.

Legitimate trials also have independent oversight, with committees of scientists and ethicists who monitor the study’s progress and can halt it if patients are being harmed.

In a seeding trial, this oversight is often minimal. The sponsor of the study – typically the pharmaceutical company funding the research – maintains heavy control over the trial’s design and conduct.

Cases that exposed seeding trials

Seeding trials had attracted little public attention until litigation in the 1990s forced open the internal files of two major pharmaceutical companies, revealing that studies presented as science had been designed as marketing campaigns.

The most notorious example is Merck’s ADVANTAGE trial for the painkiller Vioxx (rofecoxib), which was first approved in 1999. The company presented the study, which ran from 1999 to 2001, as scientific research, but internal documents revealed that its primary purpose was to encourage physicians to prescribe Vioxx to their patients.

Meanwhile, Merck was accused of downplaying the significant cardiovascular risks associated with the drug. The consequences were severe: Approximately 30,000 lawsuits and nearly $5 billion in compensation followed Vioxx’s withdrawal from the market.

Parke-Davis’ STEPS trial for the painkiller Neurontin (gabapentin) – first approved in 1993 for epilepsy – followed a similar pattern of disguising marketing as research. Internal documents showed that the trial, which ran from 1996 to 1998, aimed to disseminate marketing messages through the medical literature and encourage clinicians to prescribe the drug off-label for conditions it was not approved for, such as neuropathic pain and bipolar disorder.

Unlike Vioxx, gabapentin was never withdrawn. The trial’s commercial legacy outlasted its scientific one.

These cases came to light only because litigation forced the release of internal company documents. Without that exposure, they would have remained indistinguishable from ordinary research.

How common are seeding trials?

My team and I study how pharmaceutical firms innovate and respond to regulations. To estimate the prevalence of seeding trials, we analyzed nearly 34,400 industry-funded Phase 3 and Phase 4 studies that posted results on ClinicalTrials.gov between 1998 and 2024. The trials covered seven therapeutic areas where researchers had previously documented seeding trials, including major depressive disorder, epilepsy, Type 2 diabetes and rheumatoid arthritis.

We screened these trials for criteria that prior research has identified as hallmarks of a seeded trial, such as low patient-to-site ratios and limited independent oversight.

Ultimately, we identified 204 trials – 0.59% – that had characteristics consistent with marketing-driven study design. The prevalence of these probable seeding trials in different disciplines ranged from 0.15% in osteoarthritis to 0.98% in rheumatoid arthritis.

These figures might understate the true scope of marketing-driven research. The criteria we used capture only the most identifiable cases of studies driven by marketing purposes. Definitively identifying seeding trials requires access to internal sponsor documents revealing the intent of the study, and those documents surface only through litigation or whistleblowers.

Many trials occupy an ambiguous middle ground, generating useful data while simultaneously serving promotional objectives. Without systematic surveillance, the full extent of marketing-driven studies remains unknown.

The criteria to identify seeding trials also require careful interpretation. A low patient-to-site ratio, for instance, can reflect the practical difficulties of enrolling patients in studies of drugs already on the market, such as trials testing new drug combinations or new uses for an existing treatment. These markers are best understood as signals of possible marketing intent warranting closer scrutiny, not proof of marketing intent.

Whether the prevalence of seeding trials has shifted with the expansion of transparency requirements over the past decade cannot be determined from existing registry data.

What can be done

Seeding trials may be uncommon, but they are not accidental. They reflect structural incentives in a system where the companies that fund research also stand to gain from its results. Strengthening transparency in clinical trial registration, funding disclosure and oversight would help ensure that clinical research serves patients first.

Along with other researchers, we’ve proposed reforms that cluster around two areas. The first is standardized reporting that discloses trial funding, investigator payments, enrollment criteria and the rationale for site selection. The second is independent oversight, such as committees funded through pooled industry levies, which are fees collected from pharmaceutical companies to finance independent monitoring. Random audits with publicly available results are one form of such oversight.

Some infrastructure for tracking financial relationships between industry and physicians is already in place. In the U.S., the Open Payments database allows public tracking of industry payments to physicians. But regulatory variability across countries creates openings for companies to conduct marketing-driven trials in jurisdictions with weaker oversight, particularly in low- and middle-income countries.

Clinicians can protect themselves and their patients by screening for a set of red flags before agreeing to participate in or cite a trial in their research. These include unusually low patient-to-site ratios, selecting investigators based on prescribing volume, sponsor-dominated oversight and study endpoints of limited clinical relevance. Consent forms are among the few documents patients see before enrolling, and clearer disclosure of the commercial and scientific purpose of a study is among the reforms we have called for.

For patients, clinicians and regulators alike, the question to ask of any trial is the same: Whom does it really serve?

Sukhun Kang does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.