Isis Pharmaceuticals' ISIS-FXI shows positive Phase 2 data Isis Pharmaceuticals announced positive top-line data from a Phase 2 comparator-controlled study evaluating the incidence of venous thrombolic events in patients treated with ISIS-FXIRx undergoing total knee replacement surgery, or total knee arthroplasty. ISIS-FXIRx inhibits the production of Factor XI, a coagulation factor that plays a key role in thrombosis. Patients treated with 300 mg of ISIS-FXIRx experienced a seven-fold lower incidence of VTEs compared to patients treated with enoxaparin. Patients treated with 200 mg of ISIS-FXIRx had comparable incidence of VTEs compared to patients treated with enoxaparin. .