Its market cap is less than $400M; if it could capture only 10% of the Botox market, it's value to big pharma, PFE included, is more than 10 times that. It doesn't have the money or the ability to market RT002 on its own, especially against big pharma, so a buyout could easily be made at a very attractive price to existing shareholders.
Today's gain, while biotech was retreating, and reversing RVNC's trend would seem to suggest that the market thinks a takeout is possible, if not probable.