I went to two sources about the timing of the story for December 8th. Primenews dated the story at 5:02 or 17:02 Eastern and Yahoo News (not Finance, but news.yahoo.com) has the story timed in at 8:02 or 20:02 Eastern.
This news was not released Friday morning as you suspected. My guess is it came out after the extended hours closed.
I am surprised that this news is not part of the stock news for any of the three. It strikes me as odd since news.yahoo.com and finance.yahoo.com are the same.
It may be that they recognized VRTX's first in class technologies in target/drug molecule imaging, computational drug design, and maturity in management and as a pharmaceutical company, etc. etc... Such intellectual properties will generate future revenues.
Watch the price movement of ALNY. It has more than doubled since mid-July. The most advanced drug candidate it has is in early Phase 1, and yet, it is in Russell 2000.