If leron turns out to be much more effective than expected then it is fairly common to see “interim” analyses and could easily be conducted at a third and two-thirds the expected trial number of patients enrolled.

<<The job of reviewing these analyses would fall to a committee of outside experts on what is known as an independent data and safety monitoring board, or DSMB. Though they generally go unseen, DSMBs are among the most important and powerful forces in medical research. They are allowed to analyze the data from a trial while it’s ongoing, even as drug companies, doctors, and patients are kept from knowing who is getting the medicine and who is getting placebo. These boards have two jobs: to make sure that patients aren’t being harmed by the experimental drug, and to ensure that it’s not already clear beyond a doubt that a medicine is effective.

Those decisions bring moments of triumph, despair, and, occasionally, confusion.

When Merck decided to withdraw the painkiller Vioxx in 2004, it was because a DSMB had recommended stopping a study of the drug when it became clear the medicine increased the risk of heart attacks and strokes. In 2014, when a study of the cancer immunotherapy Opdivo first proved that drug extended survival in melanoma, it was because a DSMB had found the result incontrovertible and recommended stopping the study.>>