Just do stats all the way down.
There are 6 possibilities:
1- stop early, effective
2- stop early, ineffective
3- passed all trials, effective
4- passed all trials, ineffective
5- failed trials, effective
6- failed trials, ineffective
Assign a utility value (lives saved, risks, cost,...) and a probability to each situation and do the maths.
P(1) = P(3) + P(5)
P(2) = P(4) + P(6)
So, if (P(3) + P(5))U(1) + (P(4) + P(6))U(2) > P(3)U(3) + P(4)U(4) + P(5)U(5) + P(6)U(6) it is better to stop early.
The risk of fraud can be taken into account.