We are designing a trial to know about comparative efficacy of various interventions that were previously used for some other indications. What phase of clinical trial is it?
From your question, what I understand is that you are going to compare a new new treatment strategy, never used for this indication, with established treatment strategies. Here the question of Ethics comes in; any patient in whom this treatment was given and it failed can sue you, I think and rightly so.
What I would suggest is that select few patients in whom other treatments have failed and try your new treatment, as a pilot study to establish its efficacy (ie if you believe it has rationale). Then if it is successful, you can consider comparative trials.
You can give off the cuff innovative treatments and succeed; but be clear about the difference between "Clinical Research" and "Innovative treatment".