Interim Clinical Trial Data: Who Can See What, and When?

It has long been a basic principle of randomized clinical trials addressing serious outcomes and/or major public health issues that interim data should be inaccessible to investigators and to industry sponsors, with interim data reviewed on a regular basis by an independent data monitoring committee (DMC). Challenges to this principle may arise when sponsors and/or regulators perceive a need to review interim data while the trial remains ongoing-for example, when a trial is being considered for accelerated approval. In this paper we propose approaches that could minimize the extent of interim data that is made available to others while the trial continues.