"Big trials are expensive, so you can either avoid diseases with big trials or try to argue for ways to make them smaller (through surrogate endpoints, perhaps, or with fewer arms in the dosing groups). But those shortcuts will invariably give you (and the regulators evaluating your drugs) less useful data to work with"
Derek Lowe, In the pipeline.

https://www.science.org/content/blog-post/better-trials-someday