Effects of thrombopoietin receptor agonists on procoagulant state in patients with immune thrombocytopenia.

Thrombopoietin receptor agonists (TPO-RA) have recently been introduced for the treatment of immune thrombocytopenia (ITP), an anti-platelet-antibodies autoimmune disease. The observation of a low frequency of bleeding episodes despite their thrombocytopenia suggests the existence of a compensatory mechanism. This study aimed to evaluate the effect of TPO-RA treatment on platelet function and on the procoagulant state in ITP patients before (ITP-bR) and after responding (ITP-aR) to treatment. Plasma- and microparticle (MP)-associated procoagulant capacity from ITP patients was similar before and after responding to the TPO-RA regimen but higher than the healthy control values. High MP-associated procoagulant activity did not seem to be due to increased platelet activation, since platelet stimulation by agonists was reduced in ITP-bR and ITP-aR patients. It could be related to increased platelet apoptosis, evaluated in terms of surface phosphatidylserine (PS), observed in both ITP groups. In summary, TPO-RA treatment increased platelet count but did not ameliorate their function and did not change plasma- and MP-associated procoagulant state of ITP patient responders to this therapy.