Those who actually know something about PFE know that it's not being held back by anyone. Fund managers keep dumping their stock, the billions of shares bought in the '80s & '90s, same as they have been doing since 1999.
That selling is what is "holding PFE back". Name the hedgies & arbs you imagine can so manipulate a stock with 8.1 billion shares outstanding. The arbs were gone after the WYE deal was sealed.