Phase IV Trials: Interventional and Non-interventional Studies

Phase IV trials, studies conducted in the post-marketing scenario, are usually performed with a large number of patients and heterogeneous populations. They can be used to increase the generalizability of findings from phase III trials, to evaluate uncommon adverse events, and sometimes to assess cost-effectiveness. In oncology, phase IV trials also encompass the concept of “compassionate use”, where patients are given access to new therapies when enrollment in clinical trials is not feasible. Recently, regulatory agencies have started requesting phase IV studies for approved drugs; however, only 25% of marketed drugs go beyond mandatory phase III trials. Several study designs have been described for phase IV trials, but this is still a sparsely regulated area.