Amgen ( AMGN) has a cancer-killing virus in clinical development, known as Onco-Vex, which is modified to also stimulate a patient's immune system against the tumor. Last year, Amgen terminated a phase III study of Onco-Vex in head-and-neck cancer although a separate phase III study in melanoma continues. Lastly, the Reolysin data do seem overdue based on comments and promises made by CEO Brad Thompson to Wall Street investors during various investor meetings. This raises worries that the company is sitting on results or trying to "massage" the data in order to find something positive to report. If the first stage of the Reolysin phase III study is successful -- meaning Reolysin plus chemo demonstrates a "meaningful benefit" in PFS over chemo alone -- Oncolytics says it will advance to stage two and enroll another 100 to 400 additional head-and-neck cancer patients. Stage two of the study will determine if Reolysin plus chemo can demonstrate a survival benefit over chemo alone. How is "meaningful benefit" defined in stage one of the Reolysin phase III study? Oncolytics hasn't disclosed that except to say that it's looking for a PFS benefit that "predicts probability of success" in stage two of the study. That sounds like a rather fungible efficacy threshold so be careful when evaluating the stage one data upon its release. Oncolytics may decide to move ahead into stage two of the phase III study even if the stage-one benefit is equivocal. The company wouldn't be the first to do so and won't be the last. I laid out a strong bull case for Sarepta Therapeutics ( SRPT) and its Duchenne muscular dystrophy (DMD) drug eteplirsen in this July 24 article describing the positive results from the small phase II study as well as in this follow-up Mailbag column on July 27. My colleague Nate Sadeghi, however, thinks I'm overlooking some important risks to the Sarepta story. He likes the stock but advises more caution. Sadeghi raises valid concerns and you should definitely read what he has to say, if you haven't already. One point where I continue to disagree with him is over the scenario by which FDA would grant accelerated approval to eteplirsen based on positive results from the phase II study, even if it comes from just a handful of patients. Sadeghi insists the phase II study is too small; no way FDA will be comfortable enough with the eteplirsen data to approve Sarepta without running a larger phase III trial.