Portola falls on betrixaban Phase III miss

Portola Pharmaceuticals Inc. (NASDAQ:PTLA) sank $8.35 (29%) to $20.27 on Thursday after its oral Factor Xa inhibitor betrixaban ( PRT054021) failed to show superiority to standard of care enoxaparin in the Phase III APEX trial to prevent venous thromboembolism (VTE) in acutely medically ill patients.

APEX's design required that significant superiority be shown in a first cohort of patients with elevated D-dimer levels, a biomarker for high-risk patients seen in about 62% of the study's overall population, in order to evaluate two larger cohorts sequentially. In the first cohort, relative risk of clotting events was a non-significant 0.806 (p<0.054), as calculated by dividing the frequency of clotting events with betrixaban by the frequency with enoxaparin. ...