There is a process in place that’s meant to capture a certain number of potential problems. I didn’t make that process. The people who are making drugs safe designed the process. There is never zero risk of a treatment behaving badly, of course but when a drug gets fast tracked and doesn’t go through the regular approval process, it just hasn’t been proven to be safe by the regular standard of what experts deem safe.
It’s not very complicated.
trials ok => drug most likely ok
trials not done => we don’t really know.