You have just pointed out the problem with all effectiveness trials. If you used the current threshold you can still do the same thing, you just need to test more non-toxic drugs.<p>A better approach would be to not have any effectiveness trials at all and just collect good data on all patients using the drug. If a drug really worked it would become obvious the more patients used the drug, while if it was worthless this would also become obvious. A new drug would start out unknown with only the most desperate trying it and overtime we would learn more and more about its effects and side-effects.<p>This bayesian approach was not possible in the past, but with modern technology it is now. We would get better drugs with better known side-effects at far lower costs.