Design of phase II oncology trials evaluating combinations of experimental agents

We consider the design of phase II trials evaluating combinations of experimental therapies. In the modern era, many immunotherapy and targeted therapy regimens are being developed as combination regimens, including combinations consisting only of experimental agents. In some clinical or drug development scenarios, it may be difficult to isolate the effect of the individual agents composing a combination of this type, which makes the evaluation of the combination challenging. One such scenario arises when none of the agents making up the experimental combination have demonstrated single-agent activity in the clinical setting of interest. One solution to this problem is to use a randomized comparative trial in which the combination of interest is compared with 1 or both of its component agents, but some modifications to more traditional randomized comparative phase II trials must be made because all arms in such a trial would be experimental. In this manuscript, we present sensible modifications to randomized phase II trial designs that can be used in 2 common drug development scenarios of this type and provide a detailed discussion of the practical aspects of designing these trials. We also include 2 worked examples to further illustrate how to design such a trial.