CEOs don't get canned for tactical errors -- e.g., paid $3B for take-over target when they could have gotten it for $1B.
They DO, however, get canned for strategic blunders -- e.g., paid $1B for take-over target worth $0.
MRK's c-suite isn't interested in high-beta biotech equity investments. They're interested in fostering a relationship that will position them to be the take-over partner when the drugs are pretty much known quantities.