Discovery and development of direct Xa inhibitors Xa was identified as a promising target for the development of new anticoagulants in the early 1980s. In 1987 the first factor Xa inhibitor, the naturally occurring compound antistasin, was isolated from the salivary glands of the Mexican leech "Haementeria officinalis". Antistasin is a polypeptide and a potent Xa inhibitor. In 1990 another naturally occurring Xa inhibitor was isolated, tick anticoagulant peptide (TAP) from extracts of the tick "Ornithodoros moubata". TAP and antistasin were used to estimate factor Xa as a drug target. Blood coagulation is a complex process by which the blood forms clots. It is an essential part
Venoms in medicine pharmacology) or target directed assays to identify their biological target and mechanism of action (reverse pharmacology). In this way, toxic venomous poisons may be a starting point for a therapeutic drug. Venoms are naturally occurring substances that organisms evolved to deploy against other organisms, in defense or attack. They are often mixtures of proteins that act together or singly to attack their specific targets within the organism against which they are used, generally with high specificity and generally easily accessible through the vascular system. This has made venoms a subject of study for people who work in drug discovery. With