Pretty much. Evidence-based medicine doesn't take its cues from Cave Johnson and just spitball stuff when people's lives are at stake. Plenty of promising drugs have horrible side effects, and it takes a lot of careful work to make sure they can be used safely to treat people. Thalidomide would be an excellent example of such a drug, which can cause excessive clotting and severe birth defects but also treats leprosy and certain cancers.

https://en.wikipedia.org/wiki/Thalidomide