Objective To quantify the proportion of trials for unsuccessfully licensed drugs that are not published.Design A systematic assessment of the availability of published research reports for publicly registered trials testing drugs stalling in clinical development ("stalled drugs") and drugs receiving regulatory licensure in the same time period ("licensed drugs").Data sources Searches of clinicaltrials.gov, Google Scholar, PubMed, Embase, and electronic query of contacts in registries to identify trials and assess publication status.
Eligibility criteria
ResultsThe unadjusted publication proportion for registered trials of licensed drugs was 75% (72/96) versus 37% (30/81) for stalled drugs. The adjusted hazard ratio for publication was 2.7 (95% confidence interval 1.7 to 4.3) in favour of licensed drug trials. Higher publication rates for licensed drug trials were observed regardless of disease type, sponsorship, trial phase, and geography. The rate of non-publication of stalled drug trials was significantly higher for studies that did not complete enrolment compared with licensed drug trials. A total of 20 135 patients participated in trials of stalled drugs that were never published.
ConclusionsMuch of the information collected in unsuccessful drug trials is inaccessible to the broader research and practice communities. These findings provide an evidence base and rationale for policy reforms aimed at promoting transparency, ethics, and accountability in clinical research.