endpoints, clinical trial outcomes, & surrogate endpoints 

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Clinical outcomes are a critical aspect of a successful clinical trial. Clinical outcomes include how an individual feels, how an individual functions, and how long an individual survives relative to an untreated group or relative to a group that receives an existing treatment, the standard of care. Clinical outcomes are measured through a clinical outcome assessment or COA. COAs are performed by physicians or other healthcare professionals, such as a physical therapist, to determine the health status of the patient.
Endpoints are events or outcomes that show whether a treatment has a benefit on a disease for a patient. The success of a clinical trial depends on the treatment achieving its stated endpoints. Endpoints are a very big deal for successful development of a new drug. Clinical outcomes generally serve as the endpoints for a clinical trial. Perhaps not surprisingly, biomarkers and clinical outcomes often correlate, perhaps even correlate quite strongly. Despite correlation of these two items, biomarkers are generally not accepted as endpoints. There are exceptions, however.
Surrogate endpoints are biomarkers that have been very well established to correlated with clinical outcomes to the extent that the biomarker has become accepted by regulatory authorities to serve as a trial endpoint. Surrogate endpoints are often also called surrogate markers, a nod to the fact that they are biomarkers and not endpoints in the sense of a traditional clinical outcome. An advantage of using a surrogate endpoint in a clinical trial is that the timeframe of the trial can be greatly decreased. Let’s demonstrate this idea with a classic example of a surrogate endpoint.
LDL cholesterol is a biomarker. LDL cholesterol is also an accepted surrogate endpoint for lowering the risk of adverse cardiovascular events - things like heart attacks. Running a clinical trial and studying the incidence of heart attacks would take a long time. Running a clinical trial with an endpoint of lowering cholesterol, however, requires much less time. Therefore, a potential drug can achieve a shorter path to approval by reducing LDL cholesterol in patients compared to the longer period required to demonstrate a lower incidence of cardiovascular events in trial subject. The pathway to approval may literally be shortened by years.