Systematic review of interventional sickle cell trials registered in ClinicalTrials.gov

Background/Aims: The registry ClinicalTrials.gov was created to provide investigators and patients an accessible database of relevant clinical trials. Methods: To understand the state of sickle cell disease clinical trials, a comprehensive review of all 174 closed, interventional sickle cell trials registered at ClinicalTrials.gov was completed in January 2015. Results: The majority of registered sickle cell disease clinical trials listed an academic center as the primary sponsor and were an early phase trial. The primary outcome for sickle cell disease trials focused on pain (23%), bone marrow transplant (BMT) (13%), hydroxyurea (8%), iron overload (8%), and pulmonary hypertension (8%). A total of 52 trials were listed as terminated or withdrawn, including 25 (14% of all trials) terminated for failure to enroll participants. At the time of this review, only 19 trials uploaded results and 29 trials uploaded a manuscript in the ClinicalTrials.gov database. A systematic review of pubmed.gov revealed that only 35% of sickle cell studies completed prior to 2014 resulted in an identified manuscript. In comparison, of 80 thalassemia trials registered in ClinicalTrials.gov, four acknowledged failure to enroll participants as a reason for trial termination or withdrawal, and 48 trials (60%) completed prior to 2014 resulted in a currently identified manuscript. Conclusion: ClinicalTrials.gov can be an important database for investigators and patients with sickle cell disease to understand the current available research trials. To enhance the validity of the website, investigators must update their trial results and upload trial manuscripts into the database. This study, for the first time, quantifies outcomes of sickle cell disease trials and provides support to the belief that barriers exist to successful completion, publication, and dissemination of sickle cell trial results.