Portola Pharmaceuticals, a South San Francisco, Calif., biotech aiming to develop treatments for blood clots and other heart-related problems, raised $70 million in a third round of financing dominated by late-stage and public-market investors.

Among new investors in the round were Brookside Capital; AllianceBernstein; Teachers’ Private Capital, the private investment arm of Ontario Teachers’ Pension Plan; Goldman Sachs, T. Rowe Price, IBTM and CIDC. They were joined by existing investors Abingworth, Alta Partners, Advanced Technology Ventures, Frazier
Healthcare Ventures
, MPM Capital, Prospect Ventures and Sutter Hill Ventures.

Portola plans to use the funding for additional clinical trials of its two leading drug candidates, both experimental blood thinners targeting different blood proteins that promote coagulation. PRT054021, an oral molecule that inhibits Factor Xa, showed promising signs in a recent mid-stage human test, and will advance into further clinical trials. Meanwhile, PRT060128, which prevents blood platelets from aggregating, has completed early trials and should move into mid-stage testing by the second half of 2007. Should they receive regulatory approval, both compounds would compete with blood thinners already on the market.

Portola aims to go public and may do so as early as next year, the company’s chief financial officer, Mardi Dier, told VentureWire (subscription required).