Effect of Five Therapeutic Strategies on the Coagulation Defect Induced By the Thrombomodulin C.1611C>a Mutation

• Published in: Blood 2015-12, Vol.126 (23), p.2287-2287
• Main Authors: Dargaud, Yesim G., Jourdy, Yohann, Le Quellec, Sandra, Hemker, Coen, Lindhout, Theo, Castoldi, Elisabetta, Negrier, Claude
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V126.23.2287.2287

A novel autosomal dominant bleeding disorder characterized by trauma- and surgery-induced severe bleeding despite normal coagulation factor levels, platelet functional tests and fibrinolysis was recently described by two independent groups (1, 2). The genetic cause of this bleeding disorder was identified as a nonsense mutation in the THBD gene (c.1611C>A,p.Cys537Stop), resulting in very highlevels of soluble thrombomodulin (TM) in plasma. Extremely elevated plasma TM levelsenhance APC generation and down-regulate factor (F)Va, FVIIIa and thrombin generation (TG). This rare bleeding disorder is caused by a gain-of-function mutation in an anticoagulant factor. The clinical management of bleeding episodes in patients with this disorder remains challenging. The aim of this in-vitro study was to evaluate the ability of five haemostatic agents to restore the coagulation capacity of patients with TMc.1611C>A mutation. We compared the in-vitro efficacy of five haemostatic agents to restore thrombin generation in plasma of a patient affected by the disease. The addition of APCC in patient's plasma showed a dose dependent improvement of TG. A full normalization of ETP (1698nM.min) and peak thrombin (270nM) was observed with the lowest concentration of FEIBA. There was over-correction of TG at higher concentrations of FEIBA, which may represent a risk of thrombosis. In contrast, the haemostatic effect of PCC evaluated in the same experimental conditions showed no significant modification of TG with any concentration of PCC tested. No improvement of TG was observed with any concentration of rFVIIa added. In our patient, life-threatening hemorrhage could be stopped by the combined administration of platelet concentrates and fresh frozen plasma (2). This can be explained by considering that platelets contain and release at the site of injury, a form of FV which is partially activated and resistant to APC-mediated inactivation and therefore relatively insensitive to the anticoagulant effects of soluble TM. Since soluble TM and APC target not only FVa generation but also FVIIIa generation, and since platelets do not contain FVIII, we speculated that using FVIII concentrates in combination with platelet concentrates might be clinically even more effective in preventing bleeding in the patient. Our in vitro results showed a partial correction of TG with increasing concentrations of rFVIII concentrate. After addition of control platelets (50 - 100-150 x109/L) to the patient