Matching a nausea-inducing placebo would not be convincing in my view. The only way to address this sort of problem is to do a dose response study. With varying doses everyone will get some nausea but because nausea is very unpredictable in severity nobody will know what dose they are having. If the drug works it should show a dose dependent response. More people should improve on a bigger dose up to a certain limit. The real problem with cyclophosphamide is that there is no longer any convincing theoretical basis for using it and it is such an unpleasant drug in terms of unwanted effects (especially bladder cancer) that I personally would advise strongly against any further testing.