I disagree with your statement that their cancer drug was not included, I suspect that drug was a large part of the valuation. They have done very successful prelim studies and I suspect a large drug company wants the patent. After trials are complete and the results are positive, a billion dollar valuation would be peanuts and the players know that.
Pretty sure it said "current" valuation which doesn't include future development. So the valuation is minimum value, now add in the future development possibilities.