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Phase 1 clinical drug trials do not pose risk to most healthy participants

About one-third of healthy volunteers who participated in phase 1 drug trials experienced no adverse events, and among those who did, they were rarely ever serious adverse events, according to recently published data in BMJ.

“A key ethical concern about non-oncology phase 1 trials rests on the idea that they pose high risks of serious harm to healthy participants who cannot receive clinical benefit from the study drugs. This study… largely ally these concerns and provide context and quantification of the risks of phase 1 studies. Overall, there were three serious adverse events for every 1,000 participants, with several occurring with placebo, and others judged unrelated to the study drug or a study procedure,” Ezekiel J. Emanuel, MD, PhD, chair of the department of medical ethics and health policy at Perelman School of Medicine, University of Pennsylvania, and colleagues, wrote.   

To assess the risks and adverse events associated with phase 1 clinical trials, Emanuel and colleagues evaluated data from participants of non-oncology phase 1 research studies conducted by Pfizer, between 2004 and 2011. In total, 394 different studies were analyzed, which included 11,028 healthy participants.

Results demonstrated that 63.7% of participants experienced at least one adverse event. Most of the reported adverse events, 84.6%, were mild. Only 1% of experienced adverse events were severe, and 0.31% were serious. No life-threatening events or deaths were reported.

Almost one-quarter, 24.1%, of reported adverse events were found to be unrelated to the study drug.

Neuropsychiatric and infectious disease trials had the greatest proportion of reported adverse events. Among all trials, headache, drowsiness and diarrhea were the most common adverse events reported.

The researchers noted that the study findings may not cross over to other types of phase 1 trials, specifically those with biological agents, and further research may be needed to access the safety of those trials.

 “The findings provide good support for the general safety of phase 1 trials. Some have claimed that these trials pose high risks of harm to participants. But these findings show such claims to be essentially without empirical validity,” Emanuel said in a press release. – by Casey Hower

Disclosure: Emanuel reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.