Probably the biggest break Pfizer will get in the next decade. Why is this on hackernews? That shouldn't be surprising to anyone, but rather a pretty normal thing to do if you have stocks: selling high.
In principle the CEO could have post-/preponed the press announcement knowing that his sale is due. I don't know if that alone makes the sale legally dubious, but there are some ethical considerations here. If he postponed the press release, could it be that he expects the markets to overreact, i.e., are the actual findings not as good as the release makes them sound? If he preponed the release, did he potentially release unsound information to improve his own valuation? It would be better for him if he could prove that there was no involvement from his side into the schedule.