Shares of Caribou Biosciences Inc. CRBU ran up 21.3% toward a three-month high in premarket trading Thursday, after the genome-editing biopharmaceutical company said drug giant Pfizer Inc. has made a $25 million equity investment in the company. Pfizer shares slipped 0.1% ahead of the open. Under terms of the investment, Pfizer bought 4.69 million Caribou shares, or about 7.6% of the shares outstanding. Pfizer paid $5.33 for each share purchased, representing a 30.6% premium to Wednesday’s closing price of $4.08. Caribou said it will use the proceeds from the investment to fund its CB-011 immune cloaked allogeneic CAR-T…