Some reflections on the crucial role of trial data monitoring committees ( #DMCs) at this time when we try to find out, via clinical trials, which treatments are effective for the treatment of COVID-19 1/9

Trusted with reviewing accruing trial data, it will be the DMC’s role to monitor for ongoing safety in the COVID-19 trials and review the data for signals for benefit (or harm) 2/9

It will be the DMC who will advise whether a trial should stop early if they believe there is evidence that one trial treatment is clearly better, or worse, than the other (or if there are major concerns about side effects). 3/9

DMC deliberations are never easy - you only ever have incomplete data to review as the trial is, by definition, still ongoing - and data can oscillate in the early stages due to the effects of small numbers. 4/9

DMC deliberations can be particularly difficult in critical care trials where the mortality rate can be high and thus observed differences in treatments can have profound implications 5/9

Knowing when to stop early and when to keep going is rarely clear cut. Having highly experienced DMC members is invaluable in these situations. 6/9

A good DMC should always include both clinical and statistical experts and DMC members should be independent of the trial team. 7/9

Wishing all DMC members wisdom as they undertake their invaluable roles at this time 8/9

Finally, the DAMOCLES project provides an evidence-based review of how to set-up and run a DMC well. This includes the development of a DMC charter to inform the DMC operation 9/9 https://www.thelancet.com/pdfs/journals/lancet/PIIS0140673605179653.pdf