Portola Pharmaceuticals Inc. will get an undisclosed amount of cash in a deal with Bristol-Myers Squibb Co. and Pfizer Inc. to test its experimental treatment to reverse the effect of blood-thinning Factor Xa inhibitor drugs, the company said Thursday. The antidote, called PRT-4445, is supposed to reverse the anticoagulation work of so-called Factor Xa inhibitors, including Eliquis from Bristol-Myers Squibb (NYSE: BMY) and Pfizer (NYSE: PFE) and South San Francisco-based Portola's betrixaban. Anticoagulants…