The hazards of endpoints.

of development, we would plant seeds from each variety and spray the sprouting plants with pesticide. We would drop from further development those varieties that seem adversely affected. In the next phase, we would plant seeds from those varieties still under consideration and pull up the stalks 8 weeks later to weigh the ears. Small ear varieties would be discarded. In the next phase, 14 weeks after planting, we assess the sugar content of the kernels, discarding those with low concentrations. Then, we would consider hardiness and so on. We’d probably end up with lousy corn and we’d wonder if we had discarded a better overall variety along the way. One problem with this approach to choosing corn varieties is that we would have failed to address the relationships among the various effects. Another is that we would have failed to observe the effects of all the variables at maturity. But the biggest problem is the staccato learning process. Each experiment was a discrete unit rather than one part of a continual learning process in which the answers to relevant questions got stronger over time. In the clinical development of cancer drugs, we consider toxicity early on, then antitumor effect (or immunologic effect or other biomarker effect), and then clinical effect. We fail to assess and relate these effects over the patients’ follow-up, and we fail to associate them with the primary clinical endpoint in a longitudinal fashion. We must address the entire patient, including the patient’s course of disease over time. Especially important are tumor burden and factors that may be related to tumor burden. In the immunology setting, this includes measures such as T-cell proliferation. There are obstacles to building better drug and vaccine development. One is the notion that early endpoints should play a role in clinical trials only if they are surrogates for the primary endpoint. Another is the notion that we can use markers only if they