Onyx Pharmaceuticals (Nasdaq: ONXX) hedged its bet when it purchased privately held Proteolix less than a year ago paying $276 million upfront, with contingencies for another $575 million if Proteolix's pipeline panned out. Turns out, the contingencies may not have been necessary: This morning Onyx announced positive phase 2b results for its recently acquired multiple myeloma drug, carfilzomib.

Of the patients taking carfilzomib, 24% responded to the drug, and their response lasted a median of 7.4 months. What's most impressive is that these are very sick patients, having relapsed after a median of five prior lines of therapy, including drugs such as Johnson & Johnson (NYSE: JNJ) and Takeda's Velcade and Celgene's (Nasdaq: CELG) Revlimid.

Onyx thinks the data should be enough to garner an accelerated approval from the Food and Drug Administration considering the lack of options for these patients. However, even with the strong data, there are no guarantees when asking for approval using phase 2 data with no control arm -- all patients in the study got carfilzomib so there's nothing to compare to. Genzyme (Nasdaq: GENZ) had a tough time expanding approval of its cancer drug Clolar because of a lack of a control arm.

But Onyx doesn't have much to lose -- other than the cost of the FDA application -- by taking this route. If the FDA doesn't give carfilzomib an accelerated approval, Onyx already has a phase 3 trial in progress testing the drug in combination with Revlimid. That trial does have a control group and should say for certain whether carfilzomib works.

Nothing is for certain in biotech. But companies with a backup plan -- extra clinical trials and payments based on the success of what a company acquired -- are exactly what investors should be looking for. Onyx seems to have both; only time will tell if it needs them.

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