Pfizer ($PFE) and Allergan ($AGN) are coming down to the wire on a merger that would be the biggest pharma deal ever. The all-stock transaction would be worth up to $150 billion, at a price of $370 to $380 per share, according to media reports, though analysts have estimated a per-share price of up to $400. Bloomberg says an announcement could come as soon as Monday, though CNBC's sources peg the due date as the Monday after Thanksgiving. The two sides are "in the final stages" of negotiations, CNBC reports. More from FiercePharma