Recombinant clotting factors have been the mainstay treatments for hemophilia, but there are a growing number of companies developing hemophilia drugs using novel mechanisms of action. Those companies will get a look at the competition later this month at the International Society on Thrombosis and Haemostasis (ISTH) conference as they vie for patients with unmet needs, including those with antibodies that inhibit the clotting factors and as treatments that can be used for prophylaxis.