Background/Purpose: Timely recruitment of patients into interventional trials is necessary for their successful completion. The aim of this study was to evaluate recruitment rates of interventional trials in RA with clinical centers in the United States (US).

Methods: We searched the ClinicalTrials.gov registry in May 2017 to identify trials in RA. Inclusion criteria were: phase 3 trials, starting enrollment in 2005 to 2016, adult RA patients, at least one center in the US, an intervention to modify RA activity, and a clinical evaluation (DAS28, ACR20, or other) as the primary endpoint. Exclusion factors were: if patients with other diseases were included, trials carried out only in specific RA subgroups, trials terminated early, trials which had not completed enrollment, and trials with insufficient data to calculate the recruitment rate. The recruitment rate was defined as the average number of patients enrolled per center per month during the recruitment period, with the recruitment period defined as the time between enrollment start date and date of enrollment of the last patient. As the registry only provides the “Primary Completion Date”, this was used as the proxy for date of enrollment of the last patient. Recruitment rate and other trial characteristics were compared in two calendar year periods (2005-2010 and 2011-2016) using the Wilcoxon rank sum test and chi-square test. Negative binomial regression was used to evaluate the relationship between the percent of US centers and recruitment rate.

Results: 179 trials were identified using our search strategy. 111 trials were excluded: 35 included other diseases, 24 did not complete recruitment (6 were terminated because low enrollment or sponsor decision), 40 did not use a clinical evaluation primary endpoint, and 12 started enrollment before 2005 or after 2016. Besides, 1 trial was excluded due to inconsistency on reported data. The ACR20 criteria was the most widely used outcome measure (70%). Most trials evaluated efficacy of biological therapies (97%), and only 2 evaluated efficacy of non-biological drugs. 8 trials (12%) assessed the efficacy of biosimilars. All trials but one were industry sponsored. Number of recruitment centers increased more than 25% in the second period (117 [77–154] vs 148 [111–186]; P = 0.058). Conversely, percent of US centers slightly decreased in the same period (35% vs 31%; P = 0.492). The recruitment rate per center per month was lower in the most recent time period (0.11 [0.08–0.16] vs 0.08 [0.05–0.11]; P = 0.02). Percentage of US centers was not related to recruitment rate (P = 0.295) in regression analysis.

Conclusion: The recruitment rate per center has decreased in recent years, accompanied by a non-significant rise in the number of centers per trial. While US-based trials remain feasible, understanding the reasons for declining enrollment trends is needed to improve the efficiency and performance of RA trials.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/recruitment-of-ra-trials-in-the-modern-era-are-united-states-based-trials-still-feasible/