I 100% believe clinical studies are important but in my experience, I have learned that a lot of mistakes happen. Either it is human study or animal study. Frankly, animal study more often than human, may be because no animal can sue. But that’s sad and disheartening. Biggest disadvantage is losing a life whether it is human or animal. In one of the previous post of mine, I had mention how the study I was working on all of sudden got cancelled because scientist overdosed male monkey since he messed up on the calculations of dosage. This one small mistake of a scientist cost a living being to give up his life. I believe that rather than animal study, it is better to test directly on humans since scientist will be more careful and attentive. But I know it is not possible and some studies or drugs or devices have to be tested on animal and then on human. The obvious advantage is we get brand new drug or device, or revised and better version of it.