Update on the clinical trial landscape: analysis of ClinicalTrials.gov registration data, 2000-2020.

BACKGROUND: The clinical trial landscape has evolved over the last two decades, shaped by advances in therapeutics and drug development and innovation in trial design and methods. The tracking of such changes became possible with trial registration, providing the public with a window into the massive clinical research enterprise. The ClinicalTrials.gov website was launched in 2000 by the NIH National Library of Medicine and is the largest clinical trial registry worldwide. The purpose of this analysis is to describe the composition and methodologic features of clinical trials as registered on ClinicalTrials.gov and to identify trends over time. METHODS: We analyzed data from the publicly available Clinical Trials Transformation Initiative Aggregate Analysis of ClinicalTrials.gov (AACT) database, focusing on trials (interventional studies) started between 1 January 2000 through 31 December 2020. Characteristics of design (e.g., phase, randomization, use of masking, number of treatment groups, sample size), eligibility criteria (age groups, gender), interventions, conditions, and funders (primary sponsor) were tabulated over time, by year trial started. RESULTS: There were 274,043 registered interventional studies (trials) included in the analysis. Most trials were reported as randomized (65%); single site (60%); parallel-group (56%); funded by other sources (e.g., individuals, universities, and community-based organizations) (65%); and involving drug interventions (55%). Notable trends include an increase in the proportion of registered trials without FDA-defined phases ("Phase N/A") over time, a decrease in proportion of trials that involve drugs or report treatment as a primary purpose, declining sample size and time to complete trials, and an increase in proportion of trials reporting results among completed trials. The proportion of missing registration fields has also decreased over time and more trials make protocols and other documents available. There is a current need to expand the registration fields in ClinicalTrials.gov to adapt to the evolving trial designs and reduce the number of trials categorized as "other." Observed trends may be explained by changes in trial regulations as well as expanding and evolving trial designs, interventions, and outcome types. CONCLUSIONS: Clinical trial registration has transformed how trial information is accessed, disseminated, and used. As clinical trials evolve and regulations change, trial registries, including ClinicalTrials.gov, will continue to provide a means to access and follow trials over time, thus informing future trial design and highlighting the value of this tremendous resource.

Assessment of Trends in the Design, Accrual, and Completion of Trials Registered in ClinicalTrials.gov by Sponsor Type, 2000-2019.

Importance: ClinicalTrials.gov is a valuable resource that can be used to trace the state and nature of trials. Since its launch in 2000, more than 345 000 trials have been registered. Little is known about the characteristics and trends in clinical trials over time and how they differ by sponsor type. Objective: To assess trends in clinical trials registered in ClinicalTrials.gov over time and by sponsor type. Design, Setting, and Participants: This cross-sectional study included clinical trials (interventional studies) registered in ClinicalTrials.gov from January 1, 2000, through December 31, 2019. The trials were grouped by lead sponsor: National Institutes of Health (NIH) and other US government agencies, industry, and other sources (foundations, universities, hospitals, clinics, and others). A static version of the Clinical Trials Transformation Initiative Aggregate Analysis of ClinicalTrials.gov database was downloaded on January 1, 2020, for analysis. Main Outcomes and Measures: ClinicalTrials.gov registration fields, including overall status, phase, intervention, number of sites, use of masking and randomization, sample size, and time to study completion by start year and lead sponsor (organization that provided funding or support for a clinical study). Results: A total of 245 999 clinical trials (interventional studies) were started between 2000 and 2019, of which 135 144 (54.9%) were completed. Among completed trials, 5113 (3.8%) were sponsored by the NIH or a US government agency, 48 668 (36.0%) by industry, and 81 363 (60.2%) by other sources. Most trials were single center (61.3%), randomized (65.6%), and phase 1 to 2 (35.5%) or did not have a US Food and Drug Administration-defined phase (38.4%), with fewer drug trials being conducted over time. Sample sizes were small (median, 60; interquartile range [IQR], 30-160) and diminished over time. Trial median completion times varied by lead sponsor: 3.4 years (IQR, 1.9-5.0 years) for NIH- and US government-sponsored trials, 1.2 years (IQR, 0.5-2.4 years) for industry trials, and 2.1 years (IQR, 1.1-3.7) for trials sponsored by other sources. Conclusions and Relevance: The findings suggest that the composition and design of trials changed from 2000 to 2019 and differed substantially by sponsor type. Increased funding toward larger randomized clinical trials may be warranted to inform clinical decision-making and guide future research.