Quantifying the usefulness of PD biomarkers in Phase 2 screening trials of oncology drugs.

This paper develops a framework for evaluating the usefulness of a PD biomarker as a primary endpoint in a Phase 2 screening trial of an oncology drug. We judge the contribution of the PD biomarker by assessing its impact on the efficiency of the drug development process. 'Efficiency' is defined as the probability that an active drug is found to be effective in Phase 3 divided by the sum of the expected number of events in Phase 3 and the pre-Phase 2 drug development costs appropriately normalized. We show that 20 Phase 2 trials of different experimental treatments can provide a reasonable answer as to whether a PD biomarker makes a positive or negative contribution to the drug development process.