Portola Pharmaceuticals, a South San Francisco biotech company developing cardiovascular and vascular disease therapies, has raised $20 million in debt financing from Hercules Technology Growth Capital.

Portola is already backed by venture firms Abingworth, Alta Partners, ATV, Frazier Healthcare Ventures, MPM Capital, Prospect Ventures and Sutter Hill Ventures.

The company said it has two drug candidates in clinical development: 1) an oral Factor Xa inhibitor in a Phase II trial for the prevention of Deep Vein Thrombosis in patients undergoing knee surgery, and 2) a direct acting, orally available ADP receptor antagonist in multiple Phase I trials.