Why 80% of Clinical Trials Can't Find Enough Patients
Up to 80% of clinical trials fail to enroll enough patients on time. Many never finish at all. The search for participants is one of the greatest bottlenecks in drug development, and it affects every one of us waiting for new treatments.
This video from Clarity Clinical Solutions lays out why recruitment is so hard, and what the industry is doing about it.
How bad the enrollment problem really is
The numbers are stark:
- 80% of trials fail to enroll enough patients on time
- 30% of phase 3 trials are delayed by slow recruitment
- 50% of trial sites enroll zero or one patient
- The average trial extends its enrollment period by nearly six months, adding millions in costs
When trials cannot find patients, everyone loses. Each day of delay in phase 3 costs sponsors half a million to a million dollars. Between 10 and 15% of initiated trials are terminated early because they cannot enroll. All that investment is lost, and patients who could have benefited never get the chance.
Barrier 1: strict eligibility criteria
The single biggest reason patients cannot join trials is strict eligibility criteria. Protocols exclude patients with any other medical condition, any other medication, or any lab value outside the normal range. But 80% of patients have at least one comorbidity.
For every one patient enrolled, 10 to 15 are screened, and 70 to 80% fail eligibility criteria. An analysis of 250 phase 3 trials found that 30 to 40% of exclusion criteria could be removed without compromising safety.
Barrier 2: patients don't know trials exist
Most patients simply do not know clinical trials exist. Only 25% of cancer patients are told about trials by their doctor. ClinicalTrials.gov has over 500,000 trials listed, but the search interface is not designed for patients.
Community physicians, who see 85% of patients, either do not know about ongoing trials or do not have time to discuss them. Social media and targeted ads are emerging as tools, but most sponsors still use outdated methods like newspaper ads.
Barrier 3: the physical burden
The physical burden of participation is enormous. The average patient travels 50 to 100 miles to reach a trial site. Rural patients may travel 200 miles.
A typical phase 3 trial requires 10 to 20 site visits over 6 to 24 months. Each visit means time off work, childcare, and transportation costs. For 50% of patients, site travel is the primary reason for declining. The average patient spends $600 to $1,200 per month out of pocket to participate.
Barrier 4: mistrust of medical research
Mistrust of medical research is a deep and justified barrier. The Tuskegee syphilis study, where Black men were denied treatment without consent, is the most notorious example. The National Library of Medicine's Native Voices exhibit documents the study and its legacy (NLM: Native Voices — Tuskegee Study Timeline).
A 2023 survey found that 55% of Black Americans and 45% of Hispanic Americans say they would not trust a clinical trial. Common fears include being treated like a guinea pig and getting a placebo. Building trust requires community engagement, not one-time recruitment drives.
Barrier 5: trials designed for researchers, not patients
Clinical trials are designed for researchers, not for patients. Rigid visit windows of plus or minus three days mean a patient who misses a window may be withdrawn. Frequent procedures, blood draws, biopsies, and ECGs add to the burden. Some visits require eight hours at the clinic.
Lengthy consent forms of 20-plus pages assume college-level reading, but 50% of U.S. adults read at or below eighth grade level. Language and health literacy are major barriers. 22% of the U.S. population speaks a language other than English at home, yet trial materials are rarely available in other languages. Culturally tailored materials are rare, even though health beliefs vary by culture.
Barrier 6: competition for the same patients
In hot therapeutic areas, multiple trials compete for the same patients. In oncology, over 5,000 trials are actively recruiting for the same few cancer types. A patient with metastatic breast cancer may be eligible for 20 different trials.
The first trial to launch enrolls fastest. Later ones compete for the remaining pool. In 2023 there were over 8,000 oncology trials but only about 600,000 patients available. Simple math: not enough patients.
Barrier 7: socioeconomic factors
Socioeconomic factors strongly predict participation. Low-income patients are significantly less likely to participate because out-of-pocket costs are prohibitive. Patients without insurance are rarely referred. Trial sites are in academic medical centers, not community clinics. And education level strongly correlates with participation.
Clinical trials systematically exclude the poor. The NIH Revitalization Act mandated inclusion of women and minorities, but trials still fail to reflect diversity (ClinicalTrials.gov: Learn About Clinical Studies).
What's being done: the solutions
Decentralized and hybrid trials. Telemedicine visits allow patients to participate from home. Direct-to-patient drug delivery ships medications to the patient's door. Wearables replace in-clinic measurements. Mobile nurses visit patients at home for blood draws. Decentralized trials grew 400% during COVID-19, and the FDA now supports this approach.
AI matching and patient navigation. Machine learning scans electronic health records to identify eligible patients in real time. Patient navigators guide patients through every step.
Plain language registries make trial information accessible.
Community partnerships with churches and local clinics increase enrollment from diverse populations by two to three times.
The bottom line
80% of trials fail to enroll on time. The barriers are stacked: narrow criteria, low awareness, travel burden, mistrust, rigid schedules, language, competition, and socioeconomic factors. The cost is high in delays, failed trials, and lost opportunities.
But solutions exist: decentralized trials, AI matching, patient navigators, and community partnerships. Recruitment is not just about filling trial slots. It is about ensuring that every patient who could benefit from research actually has access to it.
This article is based on the Clarity Clinical Solutions video "Why 80% of Clinical Trials Can't Find Enough Patients." Watch it here: Why 80% of Clinical Trials Can't Find Enough Patients
References
- Clarity Clinical Solutions — "Why 80% of Clinical Trials Can't Find Enough Patients" (video, source of the enrollment statistics and barrier analysis). https://www.youtube.com/watch?v=5YD7u-d92Lo
- National Library of Medicine — Native Voices: The Tuskegee Study timeline (context on why mistrust persists). https://www.nlm.nih.gov/nativevoices/timeline/543.html
- ClinicalTrials.gov — the official registry where patients can learn about and find studies. https://clinicaltrials.gov/