OBJECTIVES : Missing or incomplete reporting of clinical trial results has significant scientific and ethical consequences. When some or all studies conducted by a sponsor for a specific drug and condition are not publicly available, the body of public evidence is distorted. Our aim was to assess the extent to which results information for selected sets of trials registered on ClinicalTrials.gov with the same sponsor, drug intervention, and condition were available publicly in ClinicalTrials.gov and/or PubMed.

METHODS : We examined ClinicalTrials.gov records for industry-sponsored, phase 2-4 trials of drugs or biologics, with at least one U.S. study location, completed or terminated between 2007-2009. We grouped trials into a “sponsor-drug-condition” trial set when the listed sponsor, drug, and condition for each trial appeared to be identical. Using a convenience sample of the first 96 sponsor-drug-condition trial sets identified, we assessed whether there were results posted on ClinicalTrials.gov and/or publications identified in PubMed as of July 25, 2017.

RESULTS : We identified 329 clinical trials representing 45 sponsors, 86 drug products, and 78 conditions (e.g., Abbott’s adalimumab for Crohn’s disease). Trial results were publicly available for 255 (78%) of 329 trials, with 79 (24%) only available from ClinicalTrials.gov, 63 (19%) from PubMed only, and 113 (34%) from both sources, but results were not available from either source for 74 (22%) of trials. Overall, 58 (60%) of the 96 sponsor-drug-condition trial sets had results available for all trials, including 10 trial sets with results only in ClinicalTrials.gov; 25 (26%) trial sets had results available for some trials, including 5 trial sets with results only in ClinicalTrials.gov; and 13 (14%) trial sets had no results available for any trials.

CONCLUSIONS : Our findings demonstrate the importance of the ClinicalTrials.gov database in enhancing the public availability of clinical trial results, but gaps in results reporting must still be ameliorated.