NEW YORK (AP) — Novartis AG said Thursday it bought for the right to develop and sell elinogrel, an experimental blood thinner being developed by Portola Pharmaceuticals Inc., in a deal that could total $575 million plus royalty payments. Elinogrel is in midstage clinical testing. Portola said the drug may offer advantages compared to Plavix, the second-best selling drug in the world, by reducing the risk of bleeding and ischemia, or reductions in blood supply. The Swiss drugmaker agreed to pay Portola $75 million upfront for elinogrel, which is designed to help prevent heart attacks and strokes by blocking a receptor on blood platelets. Novartis will pay for late-stage tests of elinogrel and could pay $500 million to Portola if the drug passes through development and regulatory goals and reaches sales targets. Portola, a privately held company based in San Francisco, also will get royalties on worldwide sales if the drug is approved, and will have the option to co-market the drug to U.S. hospitals and specialty markets. Plavix is marketed by Sanofi-Aventis and Bristol-Myers Squibb Co.