I suppose a single person and a scientist working in cahoots. The one acting under the concept of "this will take a while and some money-but its worth the investment" and the other being "It might not be completely ethical , but its for science" and of course they'd both assume that they'll either be making a profit or that no one will ever find out what they're doing and thus the legality of the whole thing would never really be called into question.

It would probably make sense to start off with one experiment (bribed,willing or unwilling) and then if the serum works/doesn't work/works but not in the intended way but doesn't screw everything to high heaven the would make it more public and let people volunteer.