Trial timelines have grown longer and success rates have stayed stubbornly low, even as the past decade brought new trial formats, new endpoints, new regulation, and rising competitive pressure. That raises an uncomfortable question: have trials become more complex than they need to be? The Boston Consulting Group set out to answer it with a large-scale analysis of protocols and other data from over 16,000 trials. Using a machine learning algorithm, they measured key features of these trials, such as the number of endpoints and the number of inclusion-exclusion criteria, then used regression analysis to combine them into a new metric, the Trial Complexity Score, which correlates with overall clinical trial duration. Across clinical phases and therapeutic areas, the score rose substantially over time, suggesting that trials are indeed becoming more complex. The authors discuss the drivers of that rise, necessary or helpful (‘good’) complexity versus unnecessary (‘bad’) complexity, and how sponsors can reduce complexity where appropriate.
Analyzing Trial Complexity Scores by therapy area (TA) shows increases across all TAs.
- Oncology has historically had the most complex trials, including in major indications such as prostate, colorectal, breast and lung cancer. Between 2014 and 2020, the average complexity of oncology trials was increasing steadily, but has leveled off since 2020. The authors believe this may be due to the impact of COVID-19 on trial planning.
- Immunology and neurology/CNS trials have historically had average trial complexity, with Crohn’s disease, multiple sclerosis and stroke contributing to more complex trials, and spikes being driven by changes in sponsors and modalities. Cardiovascular trials have seen large increases in complexity up until 2021, driven by a surge in endpoints as wearable devices became widely adopted.
- Endocrinology has historically had the lowest complexity, but this has been steadily rising over the last few years, driven by moving from lower complexity indications such as diabetes, to higher complexity indications such as NASH. As with cardiology, there is a rise in digital endpoints as a contributory factor.
In and of itself, trial complexity, as defined by the score, is neither good nor bad. There are often legitimate reasons for higher complexity trials, such as the need to address specific unmet medical needs, to ensure rigorous trial design, to address regulatory requirements, or the desire to explore novel scientific objectives. However, in some cases complexity may be unnecessary, for example when measuring similar or the same endpoints in different ways, or having an excessive number of exploratory endpoints.
Whatever the reason for trial complexity, it can be associated with increased burdens on patients and investigators, higher costs, and, as this analysis demonstrates, longer timelines to bring medicines to patients. However, the analysis also shows that clinical trial complexity is not inevitable, as low-complexity trials exist in every disease area, and for all major indications the spectrum of trial complexities is extremely wide. It is therefore worth examining carefully whether complexity can be reduced in a given trial.
Effective strategies to lower trial complexity usually start with systematic evaluation of complexity at the protocol or synopsis review stages. Often, trial design does not take into account the impact on patient and investigator burden, and does not always focus sharply on what is sufficient for approval and competitive market access. Throughout the design process, complexity should be reviewed regularly to ensure it remains under control. In governance forums, trial complexity can be a useful dimension to support decision making about planned trials.
In conclusion, the Boston Consulting Group’s analysis demonstrates that clinical trial complexity has increased across all phases and most therapy areas. This has many consequences, specifically longer timelines to bring medicines to patients, a higher likelihood of protocol changes, higher patient and investigator burdens, increased chances of errors and biases, alongside potential replication challenges. Going forward, sponsors will need to decide if the increases in trial complexity are truly required (e.g. to demonstrate an important outcome or endpoint), whether the consequences of greater complexities are worth it, and how to navigate the cost/speed-versus-complexity trade-off.
How Simplified Trial Processes Can Increase Participation
Participation in trials often falls short of expectations because of complicated enrollment processes, overwhelming procedures, and logistical barriers. Simplified medical trials make the process more accessible and patient-friendly. They encourage participation and also improve retention, which produces reliable, meaningful data.
Simplification begins with understanding the perspective of potential participants. What challenges do they face, and how can these be reduced? Trials that prioritize accessibility, communication, and convenience give people a reason to trust the study and stay with it.
Improving Access with Streamlined Processes
Accessibility is one of the most significant factors in patient participation. Many potential participants aren’t able to join trials because they live far from study sites, have mobility challenges, or can’t take time off work. Simplified processes directly address these barriers with a more inclusive approach to research.
Technology expands access through remote consultations, virtual check-ins, and online consent forms so participants can take part without the need for frequent travel. This particularly benefits people in rural areas or those with limited transportation options. Virtual participation removes geographic location as a limiting factor.
Trials improve accessibility by simplifying how information is presented. Complex medical jargon and lengthy consent documents can intimidate potential participants, while clear, concise explanations and visual aids help individuals understand what is involved.
Financial and logistical support further remove barriers. Travel expense reimbursements, home visits, or flexible appointments make participation feasible for more people. These small changes increase participation because the study has been designed around participants’ lives.
Simplified Medical Trials Build Trust and Confidence
Successful clinical trials are based on trust. People will take part and stay in a study when they feel confident in the safety, transparency, and purpose of the research. Simplified medical trials build this trust by focusing on clarity and participant well-being.
Educational materials play an important role in building confidence. Plain language helps participants fully understand the study’s goals, potential risks, and expected outcomes. Informed participants develop a sense of ownership and commitment to the trial, and understanding earlier spares everyone the cost of a withdrawal later.
Open communication channels strengthen trust. Researchers can create a supportive environment and reduce dropout rates by giving participants regular trial progress updates, access to medical staff, and prompt responses to their concerns.
Safety is another factor. Streamlined protocols prioritize participant well-being, reduce the risk of complications, and reinforce confidence in the process. Trials that have a clear focus on participant health and safety build long-term trust in the research community.
Patient Participation Through Simplified Recruitment
Recruitment is the first challenge in the clinical trial process. Traditional methods are time-consuming and frustrating for both participants and researchers. Simpler approaches are changing how trials reach and inform potential participants.
Digital tools help here. Online platforms allow potential participants to complete pre-screening questionnaires and eligibility checks from home, saving time and effort, and make it easier to reach diverse populations, increasing the generalizability of trial results. Eligibility is only part of the picture, though. A person can meet every criterion and still be unready for what participation asks of them, and tools that help them see that early save the site a later withdrawal.
Personalized recruitment strategies add another layer of effectiveness. Tailored campaigns that address the specific needs, preferences, and concerns of potential participants create a stronger connection. Testimonials from past participants or information about how the trial’s findings will directly benefit patients can motivate individuals to enroll.
Making Trials Convenient and Patient-Focused
Convenience is one of the most important aspects of increasing patient participation. Patients juggle work, family, and other commitments, and don’t have much time to dedicate to a trial. A simplified trial process makes a difference for these individuals.
Remote monitoring tools and wearable devices are ways that convenience can be integrated into trials. These tools allow participants to provide data from home and reduce the need for frequent clinic visits. A wearable device can track vital signs or medication adherence and send data directly to researchers. This saves time and reduces the burden on participants.
Flexible scheduling is another factor. Trials that allow participants to choose appointment times or complete certain tasks at their convenience demonstrate respect for their commitments. Home-based services like sample collection or telemedicine consultations further ease the burden of participation.
Streamlined data collection increases convenience. Participants feel less overwhelmed when the amount of paperwork and redundant forms is reduced or eliminated. The focus on simplicity creates a positive experience that encourages both enrollment and retention.
Patient feedback helps improve convenience. A commitment to continuous improvement inspires trust and participation and is demonstrated by listening to patients’ experiences and adapting trial processes accordingly.
Complexity you cannot remove from the protocol can still be made understandable to the person deciding whether to join. See what trialport does for sponsors and CROs.
About the author
Keith Berelowitz has spent more than twenty years watching clinical trials work on paper and struggle in real life. He has helped run studies, advises sponsors and CROs on how they engage with people, and chairs a UK research ethics committee, where consent forms and participant information sheets cross his desk every month. That vantage point led to one conclusion: most trial problems are not failures of science. They are failures of understanding at the moment a person decides.
He founded trialport, a clinical trial navigation and decision-support platform, so that understanding a study comes before anyone is asked to join one. Understanding comes first. Decisions follow.