Abstract: The inhibitors, obtainable from tissue or secretions of leeches typically of the order Rhynchobdellida, has the following terminal sequence: NH.sub.2 -Lys-Leu-Leu-Pro-Cys-Lys-Glu-Y-His-Gln-Gly-Ile-Pro-Asn-Pro-Arg- wherein Y represents any amino acid sequence; or a pharmaceutically acceptable salt, derivative or bioprecursor of said sequence, or an analogue or homologue thereof. Because of their extreme potency in the nanomolar range, they can be used to treat a number of diseases where protein cross-linking is important. They can be used for the treatment of Crohn's disease, tumor implantation, atherosclerosis, thrombotic microangiophathy, fibrous growths of the skin, acne, scar formation, membranous glomerulonephrits, cataracts, or infection with microfilarial nematodes. In particular, they can be used to reduce the stability of thrombi so that they are more susceptible to lysis by thrombolytic agents.

Abstract: The invention provides an antidote to blood anticoagulants comprising Factor VIII or fragments of Factor VIII which retain its activity or a substance which increases its concentration in blood.