Phase I study of eptifibatide in patients with sickle cell anaemia.

The alphaIIbbeta3 antagonist eptifibatide is an effective treatment for patients with acute coronary syndromes (ACS). Platelet reactivity and CD40 ligand (CD40L) may play a role in the pathophysiology of sickle cell anaemia (SCA) similar to that in ACS, suggesting that inhibition of platelet aggregation and CD40L release by eptifibatide may benefit patients with SCA. Following eptifibatide infusion, safety and pharmacodynamic data were obtained from four SCA patients in their non-crisis, steady states. Eptifibatide was well tolerated, with no adverse changes in the haematological, biochemical or coagulation parameters studied. Eptifibatide did not increase plasma levels of platelet factor 4 or beta-thromboglobulin, P-selectin exposure or platelet:leucocyte aggregate formation. Moreover, decreases in platelet aggregation and soluble CD40L (sCD40L) levels achieved in SCA patients were comparable to those observed in the treatment of ACS. Finally, indicators of inflammation, macrophage inflammatory protein-1alpha, tumour necrosis factor-alpha and myoglobin were reduced following eptifibatide infusion, while vasodilation correlatives, matrix metalloproteinases (MMP-2 and MMP-9) and leptin were increased. Based on these phase I results, eptifibatide may benefit SCA patients by inhibiting platelet aggregation, decreasing sCD40L levels and favourably altering plasma levels of inflammatory mediators.

Biologically active CD40 ligand is elevated in sickle cell anemia: potential role for platelet-mediated inflammation.

OBJECTIVE: After activation, platelets expose CD40 ligand (CD40L) on their surface, then subsequently release the inflammatory mediator as a soluble fragment (sCD40L). Because sickle cell anemia (SCA) is noted for both platelet activation and chronic inflammation, we asked whether platelet-released CD40L potentially plays a role in SCA. METHODS AND RESULTS: ELISAs demonstrate that SCA patient plasma contains 30-fold more sCD40L than control plasma. Correspondingly, platelets from these patients contain less than half the CD40L found in control platelets. Platelets from patients in painful crises are further depleted of CD40L, with even higher plasma levels, suggesting a correlation to the patient's clinical state. In addition, elevated sCD40L correlates with increased tissue factor in SCA plasma. Blockage of the CD40L receptor CD40 reduces SCA plasma-induced production of tissue factor and endothelial intercellular adhesion molecule-1 (ICAM-1). Finally, sCD40L activity in SCA plasma is confirmed by its induction of B-cell proliferation. CONCLUSIONS: Platelet-derived sCD40L is elevated in SCA, further elevated in crises, and biologically active. The participation of sCD40L in SCA plasma-induced production of B cells, tissue factor, and ICAM-1 suggests that CD40L may contribute to the chronic inflammation and increased thrombotic activity known to occur in SCA.