A clinical trial endpoint is a measure that allows the FDA to determine whether the null hypothesis of a clinical trial should be accepted or rejected. In a clinical trial, the null hypothesis states that there is no statistically significant difference between two treatments or strategies being compared with respect to the endpoint measure chosen. Clinical trial endpoints can be classified as primary or secondary.

Primary endpoints measure outcomes that will answer the most important question being asked by a trial, such as whether a new treatment is better at preventing disease-related death than the standard therapy. In this case, the primary endpoint would be based on the occurrence of disease-related deaths during the duration of the trial. The size of a trial is determined by the power needed to detect a difference in this primary endpoint.

Secondary endpoints ask other relevant questions about the same study; for example, whether there is also a reduction in disease measures other than death, or whether the new treatment reduces the overall cost of treating patients.

If primary endpoints are met, the stock has a tendency to move higher. If primary endpoints are not met, the stock has a tendency to move lower. Secondary endpoints usually have much less an influence on stock price as do primary endpoints.

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