The first time someone did a human heart transplant that wasn't 100 percent guaranteed to work. Sadly she died and we have later down the years perfected it. My sister is a heart transplant recipiant and if it wasn't for them trying it 20 years prior it wouldn't have happened. Plus you look at the patients rights, which he/she ultimately has rights, but what in the case of minors. They are technically under the custody of their parents or guardians and an 11 year old can't make a decision between life and death procedures. And what if the patient is unable to communicate that they do or don't want the operation/medicine. Then do we just let people die because their loved ones don't know what they want. They want what is best I would hope. I agree that we humans shouldn't be the first to test on, but when you think about it no matter how close our biology is to another species theres still a chance it could fail for us do to minor changes in our biology.
While I support medical research and want it to be taken as far as possible, that should extend only as far as the patient willingly allows. Admittedly, this can leave unexplored and unpracticed research territory, but it preserves the dignity and rights of the patient. I believe the patient has every right to willingly put the research before his own welfare, but until he does so, the patient's welfare is of default importance.