For me the interesting question that I would like to see explained more to my satisfaction is, given the FDA response, why did EXEL choose to focus first on the 306 study instead of putting their energy and $ into the larger, more expensive survival study that they knew they would have to do anyway? Resources are now tight for EXEL, and to run even 307 to completion is likely to need more money which would be painful at the current share price.
I agree, I think EXEL would be better off just focusing resources on a trial with an OS endpoint. I've mentioned before that I don't think the FDA will approve cabozantinib unless they see OS data, and I think a rejection of the SPA for '306 affirms that view.