PHASE II TRIAL

the second stage of the evaluation of a new drug in humans; these trials evaluate drug efficacy, involve more participants (often several hundred) and typically last longer than Phase I studies. Phase II trials may be divided into Phase IIa (pilot trials in patients with the disease to be treated) and phase IIb (well-controlled efficacy trials). Typically Phase II trials are done only if Phase I trials have shown the drug to be safe, but sometimes Phase I and Phase II studies are combined.