Later-stage clinical trials

A sample-size estimation must be based on a specific objective in a clinical trial s study protocol. By the time sample-size estimation becomes particularly meaningful, i.e., in later-stage clinical trials designed to demonstrate efficacy, it is a very good idea to have a single objective (the primary objective) and a single... 

AG337, also known as nolatrexed, and as the hydrochloride, Thymitaq) advanced into human testing and had progressed into later-stage clinical trials as an antitumor agent by 1996 (67). 

Finally, it is also important to consider comedication that is likely to be used in the patient population of interest for the later-stage clinical trials. 

On this basis, a large number of piperazinylphenyl derivatives, such as PNU-97665 [52], PNU-100592 (eperezolid) [53], and their morpholino and thiomorpholino analogues PNU-100766 (linezolid) [53] and PNU-10048 [54], were synthesized. These compounds are either on the market or in the later stages of clinical trials for the treatment of infections caused by strains resistant to conventional antibacterials. See Fig. 4 for the corresponding structures. 

The result of this different (informal) standard of review is driving initial research into the public not-for-profit sector, with commercial drug companies tending to become involved in later stages (phases 2 and 3) of development. The process effectively provides greater flexibility early in the development process while carefully controlling more extensive and intensive clinical trials. 

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