New oral anticoagulants under development that target factor IIa and factor Xa. Participating proteins are depicted by their zymogen symbols for simplicity. Factor X and its activation to Xa, and Factor II and its activation to IIa are more fully illustrated, because these two proteases are targets of the therapeutic agents in the shaded boxes. Bold arrows from the shaded boxes point to the proteases that those agents inhibit, and an agent with a line through it has been withdrawn from development.