Most useful research model is Mice . You can GM model for the same. 

It must be doubtful if  this is is achivable at all . If you use 4 drugs can they ALL synergise each with the other ?   Such that ANY three would not suffice but 4 would ?remember response depends on dose for each drug  so that there would be a near infinite number of combinations to test

Monte Carlo simulations would be required but even this approach would be tested to the limit, perhaps tested to destruction !!