Why Site Selection Can Make or Break a Clinical Trial

The right sites do more than recruit patients—they determine whether a protocol can succeed in the real world.

A clinical trial can have a compelling scientific hypothesis, a carefully designed protocol and adequate funding—and still struggle to deliver.

One of the most consequential decisions occurs before the first participant is enrolled: selecting the right investigative sites.

Site selection is sometimes viewed primarily as an operational start-up activity. In reality, it is a strategic decision that can influence recruitment, participant retention, protocol compliance, data quality, study timelines and overall trial performance.

For sponsors and Contract Research Organizations (CROs), the question should therefore not simply be:

"Which sites are interested in our study?"

It should be:

"Which sites can realistically deliver this study, for this patient population, under this protocol?"

That distinction matters.

 

Site Selection Begins With Feasibility

Clinical trial feasibility assesses whether a proposed study can realistically be conducted within the intended countries, institutions and patient populations.

At the site level, feasibility commonly considers factors such as:

• Availability of the target patient population
• Investigator experience
• Previous clinical trial performance
• Competing studies
• Standard-of-care pathways
• Site infrastructure and facilities
• Availability of appropriately trained staff
• Recruitment potential
• Participant retention capability
• Pharmacy and laboratory capabilities
• Regulatory and ethics requirements
• Contracting and budget timelines
• Protocol complexity and operational burden

The objective is not simply to identify sites capable of signing a clinical trial agreement.

It is to identify sites capable of executing the protocol successfully.

 

The Recruitment Question: Are the Patients Really There?

One of the most important—and difficult—questions during feasibility is whether the site has access to enough eligible participants.

A site may treat hundreds of patients with a particular disease each year. That does not necessarily mean hundreds will qualify for the trial.

Consider what happens when protocol criteria are applied:

Total disease population

↓

Patients meeting the disease definition

↓

Patients within the required disease stage/severity

↓

Patients meeting inclusion criteria

↓

Patients without exclusion criteria

↓

Patients not enrolled in competing studies

↓

Patients willing and able to participate

↓

Realistically recruitable participants

The final population may be considerably smaller than the initial estimate.

This is why relying exclusively on investigator estimates can create unrealistic recruitment projections.

A strong feasibility process interrogates the assumptions behind those numbers.

Where appropriate, sponsors and CROs may complement feasibility questionnaires with epidemiological data, historical site performance, referral patterns, electronic health data, disease registries and other relevant evidence.

 

Why Recruitment Performance Matters

Recruitment remains a persistent challenge in clinical research.

An analysis of registered randomized trials found that a substantial proportion were discontinued, with poor recruitment representing the most frequently reported reason for discontinuation.

The implications extend beyond delayed timelines.

When recruitment underperforms, sponsors may need to:

• Activate additional sites
• Expand into additional countries
• Extend recruitment periods
• Amend operational plans
• Increase monitoring and site-management resources
• Reforecast budgets
• Reconsider development timelines

Site selection therefore has both scientific and commercial consequences.

Selecting more sites is not necessarily the solution.

Selecting the right sites is.

 

Investigator Experience Matters—but It Isn't Everything

An experienced Principal Investigator can be extremely valuable.

Previous therapeutic-area experience, knowledge of Good Clinical Practice (GCP), familiarity with investigational products and established research processes can contribute significantly to successful execution.

However, investigator credentials should not be evaluated in isolation.

The wider site team matters just as much.

A high-performing research site often depends on:

• Principal and Sub-Investigators
• Clinical Research Coordinators (CRCs)
• Research nurses
• Pharmacists
• Laboratory personnel
• Regulatory coordinators
• Data-entry personnel
• Administrative and contract teams

An internationally recognized investigator without sufficient operational support may struggle to deliver a complex protocol.

Conversely, a well-organized research team with realistic recruitment potential, experienced CRCs and responsive site processes may become one of a study's strongest performers.

Site capability is a team characteristic—not merely an investigator credential.

 

Protocol Complexity Must Be Tested Against Site Reality

A protocol can appear entirely manageable during development but become challenging when introduced into routine clinical practice.

Consider a study requiring:

• Frequent participant visits
• Narrow visit windows
• Multiple laboratory assessments
• Complex imaging
• Pharmacokinetic sampling
• Electronic patient-reported outcomes
• Investigational product preparation
• Long-term follow-up
• Multiple specialist assessments

Can the site actually deliver all of these consistently?

If the protocol requires a six-hour pharmacokinetic sampling schedule, does the research unit have adequate staffing and facilities?

If specialized imaging is required, is it available within the protocol-defined window?

If participants must attend frequent visits, is travel likely to affect recruitment or retention?

If a rare disease is being studied, does the investigator directly manage eligible patients—or depend upon external referrals?

These are not minor logistical questions.

They determine whether the theoretical protocol can become an operationally viable study.

 

Competing Trials Can Change the Recruitment Landscape

A site may have the right investigators and the right patient population but still be unsuitable because several competing studies are recruiting the same patients.

Competition can arise from trials involving:

• The same indication
• Similar mechanisms of action
• Comparable eligibility criteria
• The same line of therapy
• Overlapping investigators
• Similar recruitment periods

Feasibility therefore needs to capture not only the site's current workload but also its anticipated trial pipeline.

A site that appears highly attractive today may have substantially different recruitment capacity six months later when the study actually opens.

 

Start-Up Performance Matters Too

A site cannot recruit participants until it is activated.

Site selection should therefore consider expected start-up performance, including:

• Ethics/IRB review timelines
• Regulatory documentation
• Site contracting
• Budget negotiation
• Essential document collection
• Institutional approvals
• Investigator availability
• Site initiation readiness

This becomes especially important in multinational studies, where regulatory, ethics, contracting and institutional processes vary between countries and sites.

For sponsors, a theoretically high-recruiting site that takes many months to activate may ultimately contribute fewer participants than a moderately recruiting site that can start substantially earlier.

Feasibility therefore needs to consider time-to-activation alongside expected recruitment rate.

 

Site Selection Is Increasingly Data-Informed

Historically, site selection often relied heavily on existing investigator networks and feasibility questionnaires.

Relationships remain important, but modern clinical development increasingly allows decisions to be supplemented by data.

Depending on the study and available data sources, site intelligence may incorporate:

• Historical trial performance
• Previous enrollment rates
• Screen-failure patterns
• Site activation timelines
• Protocol deviation history
• Therapeutic-area experience
• Investigator publication history
• Epidemiological information
• Claims or electronic health data
• Patient referral pathways
• Geographic accessibility

The objective is not to replace clinical judgment with an algorithm.

It is to combine data with operational intelligence and local expertise.

 

Patient-Centricity Should Begin at Site Selection

Site selection is also a patient-access decision.

A highly experienced research centre may still be poorly positioned if participation requires patients to travel unreasonable distances or repeatedly miss work, arrange childcare or navigate complex transportation.

Patient-centric feasibility should therefore consider:

• Geographic accessibility
• Visit frequency
• Travel burden
• Duration of study visits
• Accessibility requirements
• Local patient pathways
• Language considerations
• Cultural factors
• Availability of decentralized or hybrid trial options

The Declaration of Helsinki emphasizes the protection of the rights, interests and well-being of research participants.

Participant considerations should therefore influence trial planning from the beginning—not only after recruitment problems emerge.

 

Quality Must Never Be Sacrificed for Recruitment

A site promising high enrollment is attractive.

But recruitment alone does not define a high-performing site.

Sites must also be capable of:

• Obtaining valid informed consent
• Following the protocol
• Protecting participants
• Reporting safety information appropriately
• Maintaining essential documentation
• Ensuring investigational product accountability
• Entering reliable and timely data
• Responding effectively to queries
• Supporting monitoring and oversight

ICH E6(R3) reinforces a proportionate, risk-based approach to quality, emphasizing factors that are critical to participant protection and the reliability of trial results.

The best site is therefore not necessarily the one promising the largest enrollment number.

It is the site most likely to deliver appropriate recruitment, participant protection and reliable data consistently throughout the study.

 

Site Selection in Multicountry Clinical Trials

The challenge becomes even greater when studies span multiple countries.

Country and site strategy may need to account for:

Regulatory environment: How efficiently can the study obtain required approvals?

Patient population: Is the target population sufficiently represented?

Standard of care: Does local clinical practice align with the protocol?

Site infrastructure: Can study-specific procedures be performed reliably?

Language: Will documents, participant materials or site communications require localization?

Contracts and budgets: What are realistic negotiation timelines?

Recruitment: How does the indication's epidemiology differ across regions?

Operational support: Are experienced CRAs, CRCs and site-management professionals available locally?

This is why global trial execution requires a combination of centralized governance and strong local knowledge.

 

From Site Selection to Site Partnership

There is another important shift occurring in clinical research.

High-performing sites should not simply be treated as vendors activated for individual studies.

Strong sponsor-CRO-site relationships can create long-term value through better communication, greater understanding of operational expectations and earlier identification of potential challenges.

Sites also possess knowledge that sponsors and CROs may not have.

Investigators and CRCs understand local patient pathways, referral networks, standard clinical practice and the practical realities of implementing a protocol.

Engaging sites early can therefore help identify operational problems before they become study-wide problems.

 

What Does Successful Site Selection Look Like?

Successful site selection sits at the intersection of four dimensions:

Patient Access
Can the site identify and retain the right participants?

Operational Capability
Can the team actually execute the protocol?

Quality
Can the site protect participants and generate reliable data?

Deliverability
Can it activate and recruit within realistic timelines?

A strong site-selection strategy evaluates all four.

Because ultimately:

The goal is not to activate the greatest number of sites. It is to activate the right sites.

 

The Agile Clinical Trendz Perspective

At Agile Clinical Trendz, we view site feasibility and selection as strategic components of clinical development—not simply administrative steps before activation.

Effective site operations require collaboration across feasibility, study start-up, regulatory activities, contracting, monitoring, site management and recruitment planning.

This becomes particularly important in multicountry studies, where local regulatory pathways, patient populations and site practices must be integrated within a consistent global study strategy.

Our approach is built around a simple principle:

Understand the protocol. Understand the patient pathway. Understand the site. Then build the operational strategy around all three.

Because when the right investigators, the right sites and the right patients come together, clinical research moves forward more efficiently—and with greater potential to generate meaningful evidence.

 

References

1. Kasenda B, von Elm E, You J, et al. Prevalence, characteristics, and publication of discontinued randomized trials. JAMA. 2014;311(10):1045–1051. doi:10.1001/jama.2014.1361.
2. International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Harmonised Guideline E6(R3): Guideline for Good Clinical Practice. Final guideline; 2025.
3. World Medical Association. World Medical Association Declaration of Helsinki: Ethical Principles for Medical Research Involving Human Participants. JAMA. 2025;333(1):71–74. doi:10.1001/jama.2024.21972.
4. U.S. Food and Drug Administration. E6(R3) Good Clinical Practice (GCP). FDA; 2025.
5. European Medicines Agency. Clinical Trials Regulation (EU) No 536/2014 and Clinical Trials Information System (CTIS). EMA.
6. Huang GD, Bull J, Johnston McKee K, et al. Clinical trials recruitment planning: A proposed framework from the Clinical Trials Transformation Initiative. Contemp Clin Trials. 2018;66:74–79. doi:10.1016/j.cct.2018.01.003.