First rule of any scientific endeavour is to test the null hypothesis. The FDA also uses the null hypothesis. As it relates to biotechs, there are two versions of it that go hand in hand:
1) a drug X for a condition Y at a dosage Z is not safe until proven otherwise.
2) a drug X for a condition Y at a dosage Z is not efficacious until proven otherwise.
Objective data is required to address the two hypotheses. Without data, it is merely a hunch or a gut feeling. Nothing wrong with that, but it doesn't get drug approvals or address safety and efficacy concerns.