Screening chemical libraries for the development of oral treatments for bleeding disorders.

Hemophilia is a rare bleeding disorder due to factor VIII (FVIII) or FIX deficiency involved in hemophilia A (HA) or HB, respectively. Treatment has long relied on invasive IV infusions of the missing factor for prophylaxis or bleeding treatments. Despite significant progress in patient care, there is still no oral procoagulant drug available for people with hemophilia. Such an oral procoagulant could provide benefits to other inherited and acquired bleeding disorders, as well as anticoagulant-induced bleeding. To find chemical compounds that could become potential future orally administered procoagulants, we designed a hierarchical high-throughput screening protocol combining 2 successive screening filters: a miniaturized fibrin formation assay, followed by a thrombin generation assay, both on severe HA plasma. We screened 3 chemical collections totaling > 2300 chemical compounds; we identified adapalene, a commercialized antiacneic compound (Differin), which is strongly hydrophobic. To design a drug that could be orally administered, we developed a series of chemical analogs of adapalene, and 3 of them, with similar procoagulant activities in FVIII-deficient plasma, showed improved solubilities. The mechanism of action was thoroughly investigated by a series of thrombin generation and enzymatic assays. These studies conclude that the procoagulant activity of the chemical compounds in FVIII-deficient plasma is due to the activation of FXII.