Assessment of Radiolabeled rhAnnexin V-128 in Infective Endocarditis (AnnIE)

Intraluminal thrombi adherent to cardiac valves or atria share a common pathophysiology involving the aggregation of activated platelets with phosphatidylserine (PS) expression on the outer layer of the thrombus. They also share common complications, i.e. damages to the underlying myocardium and embolic risk related to thrombus fragmentation. The diagnostic work-up, currently relying on morphologic imaging alone (mainly echography), lacks sensitivity and does not allow to differentiate between active (renewal and growth activity) and quiescent (scarred) thrombus. It is therefore highly desirable to develop a new approach able to non-invasively provide insight on the biological activity of thrombi and to detect embolic events in a single exam.

Annexin V is a 36 kDa endogenous glycoprotein which binds PS with nanomolar affinity. Radiolabeled Annexin V has been shown to provide molecular imaging of PS expressed by apoptotic cells or activated platelets. The ability of the imaging agent to bind mural thrombus has been established in vivo in a murine model of abdominal aortic aneurysm and ex vivo in human. It has been also shown that radiolabeled Annexin V allowed in vivo detection of vegetations and secondary pulmonary emboli with high sensitivity in various animal models of infective endocarditis.

A radiolabeling kit of annexin V complying with GMP requirements has been developed (rhAnnexine V-128, Advanced Accelerator Applications - Atreus) and is currently available. AnniE is a single centre, proof of concept, interventional, open, non-randomized study aiming at evaluating the sensitivity of 99mTc-Annexin V-128 in the detection thrombus in comparison with reference imaging in patients presenting with either: 1/ infective endocarditis or 2/ atrial thrombus. The safety of the 99mTc-Annexin V-128 will be assessed in a first phase (10 first patients enrolled). Data in relation with safety of the imaging agent will be reviewed by an independent Data and Safety Monitoring Board (DSMB); in case of positive answer, the study will continue with a second phase. The data gathered in all patients (n=120) will be used to determine outcome measures.