The company hinted earlier this year that they might request the p value figure from the DSMB, and if it's below 0.05 but misses the interim alpha, then refile the BLA based on 9902B being a second statistically significant randomized trial in overall survival. To me, that's the only logical reason for the supposed interim alpha to be in the 0.01 range. Otherwise, why not make it higher, like 0.02 or 0.025? If Provenge has a clinical benefit, then it should easily beat 0.025 or 0.03 at the final look with a large trial of over 500 patients and 360 death events. They can't keep so many personnel around doing nothing, they don't have an infinite supply of cash, and there are other competing treatments coming down the pike, like a new AZN drug and possibly Avastin and GVAX.
If this is the usual situation and the DSMB definitely won't give them any additional info beyond the continue, stop for efficacy, or stop for futility scenarios, then might as well designate the interim p value to be somewhere between 0.005 and 0.01.