LB 01.4 - EMA601, a Novel Humanised Fab Inhibits Platelet Glycoprotein VI with Unprecedented Potency and Protects Mice from Arterial Thrombosis and Ischemic Stroke

Sunday, June 23, 2024

10:15 – 10:30 ICT

Room: Plenary Hall

Presenting Author(s)

Stefano Navarro, PhD

postdoctoral researcher
Universitätklinikum Würzburg
Würzburg, Bayern, Germany

Co-Author(s)

IT

Ivan Talucci

Phd candidate
University Hospital Würzburg
Wuerzburg, Bayern, Germany
Vanessa Göb

Postdoc
5Institute for Experimental Biomedicine, University Hospital Würzburg
Würzburg, Bayern, Germany
SH

Stefanie Hartmann

Laboratory technician
University Hospital Würzburg
Wuerzburg, Bayern, Germany
SB

Sarah Beck

Postdoc
Universitätklinikum Würzburg
Würzburg, Bayern, Germany
VO

Valerie Orth

Management, research & development
Emfret Analytics
Wuerzburg, Bayern, Germany
GS

Guido Stoll

Professor
University Hospital Wuerzburg
Wuerzburg, Bayern, Germany
HM

Hans M. Maric

Group leader
University of Wuerzburg
Wuerzburg, Bayern, Germany
DS

David Stegner

PI
Institute for Experimental Biomedicine, University Hospital Würzburg
Würzburg, Bayern, Germany
BN

Bernhard Nieswandt

Director of Institute of Experimental Biomedicine
University Hospital Würzburg
Würzburg, Bayern, Germany

Background: Glycoprotein VI (GPVI) is a platelet collagen/fibrin(ogen) receptor and an emerging pharmacological target for the treatment of thrombotic and thrombo-inflammatory diseases, notably ischemic stroke. A first anti-human (h)GPVI antibody Fab-fragment (ACT017/glenzocimab, KD: 4.1 nM) recently passed a clinical phase 1b/2a study in acute ischemic stroke patients and was found to be well tolerated, safe and potentially beneficial.

Aims: The development of a novel humanised anti-GPVI antibody Fab-fragment (EMA601; KD: 0.195 nM) that inhibits hGPVI function with unprecedented potency in vitro and in vivo.

Methods: Fab-fragments of the mouse anti-human GPVI IgG Emf6.1 were tested for functional GPVI inhibition in human platelets and in hGPVI expressing (hGP6tg/tg) mouse platelets. The in vivo effect of Emf6.1Fab was assessed in a tail bleeding assay, an arterial thrombosis model and the transient middle cerebral artery occlusion (tMCAO) model of ischemic stroke. Using CDR grafting, a humanised version of Emf6.1Fab (EMA601) was generated. Emf6.1Fab/EMA601 interaction with hGPVI was mapped in array format and kinetics and quantified by bio-layer interferometry.

Results: Emf6.1Fab (KD: 0.427 nM) blocked GPVI function in human and hGP6tg/tg mouse platelets in multiple assays in vitro at concentrations ≥5 µg/mL. Emf6.1Fab (4 mg/kg)-treated hGP6tg/tg mice showed potent hGPVI inhibition ex vivo and were profoundly protected from arterial thrombosis as well as from cerebral infarct growth after tMCAO, whereas tail-bleeding times remained unaffected. Emf6.1Fab binds to a so far undescribed membrane proximal epitope in GPVI. The humanised variant EMA601 displayed further increased affinity for hGPVI (KD: 0.195 nM) and fully inhibited the receptor at 0.5 µg/mL, corresponding to a >50-fold potency compared to ACT017.

Conclusion(s): EMA601 is a conceptually novel and promising anti-platelet agent to efficiently prevent or treat arterial thrombosis and thrombo-inflammatory pathologies in humans at risk.