Study design and endpoints in graft-versus-host disease.

The design of clinical trials for prevention or treatment of acute or chronic graft-versus-host disease poses many challenges. These challenges include the selection of primary and secondary endpoints that demonstrate clinical benefit, and the identification of measures indicating success both for individual patients and groups. Assessment of response in treatment trials should ideally encompass the prior trajectory of change before treatment. The criteria, timing and duration of response should be specified, and the potential effects of concomitant treatment and complications other than GVHD should be taken into account in assessing outcomes. A crucial element in clinical trial design is the pre-specification of the hypothesis to be tested in quantitative terms. Potential barriers to enrollment should be carefully considered in order to ensure timely completion of the trial.