Modulation of fibrin clot lysis and potential future clinical implications

The formation of a blood clot is vital for the prevention of blood loss following vessel injury. The haemostatic system allows the closing of damaged blood vessels, retention of blood in a fluid state and removal of clots after the restoration of vascular integrity. Blood clots are formed of a network of fibrin fibres with platelets, red and white blood cells embedded within. Imbalances and alterations in coagulation factors and the multitude elements of the coagulation cascade can impact fibrin clot properties. Fibrin clot susceptibility to lysis has implications in both bleeding and thrombotic disorders. Formation of an intravascular obstructive thrombus can result in end organ damage, and treatment is aimed at reperfusion to regain blood flow to the affected vessels followed by prophylactic therapy to prevent re-occlusion. Conversely, in trauma or surgical associated bleeding, or that resulting from some haematological disorders, limiting fibrin clot lysis to stabilise the clot is a key aim of therapy. Considering the potential future therapeutic benefits of targeting the fibrin network, I hypothesised that fibrinogen-specific Affimer proteins represent a tool to modulate the fibrinolytic process. The aim of this work was to investigate the use of these synthetic proteins in altering fibrin clot structure/lysis, with the long term view that they may constitute new therapeutic agents for the treatment of thrombotic and/or bleeding disorders. The objectives of my work were to i) identify fibrinogen-specific Affimer proteins, ii) investigate the effects of fibrinogen-specific Affimers on fibrinolysis, and iii) characterise the mechanistic pathways for Affimer-mediated modulation of clot lysis. My work describes the isolation of fibrinogen-binding Affimer proteins that modulate fibrin clot lysis. Particular focus was on an anti-fibrinolytic Affimer that reduced plasmin generation in a fibrin-specific manner. Elucidation of this Affimer’s mechanism of action and potential therapeutic relevance of this Affimer protein was explored.