Thromb Haemost 2021; 121(11): 1395-1399
DOI: 10.1055/a-1481-3039
Review Article

Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT): Targeting Pathomechanisms with Bruton Tyrosine Kinase Inhibitors

1  Institute for Cardiovascular Prevention (IPEK), LMU Munich, Munich, Germany
2  DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, Munich, Germany
,
Reinhard Lorenz
1  Institute for Cardiovascular Prevention (IPEK), LMU Munich, Munich, Germany
,
1  Institute for Cardiovascular Prevention (IPEK), LMU Munich, Munich, Germany
2  DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, Munich, Germany
,
1  Institute for Cardiovascular Prevention (IPEK), LMU Munich, Munich, Germany
2  DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, Munich, Germany
3  Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Centre, Maastricht, The Netherlands
4  Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
› Author Affiliations
Funding This work was supported by the Deutsche Forschungsgemeinschaft (SFB1123-A1/A2/A10).

Abstract

A series of cases with rare thromboembolic incidents including cerebral sinus vein thrombosis (some of them fatal) and concomitant thrombocytopenia occurring shortly after vaccination with the coronavirus disease 2019 (COVID-19) vaccine AZD1222 (Vaxzevria) have caused significant concern and led to its temporary suspension in many countries. Immediate laboratory efforts in four of these patients have identified a tentative pathomechanism underlying this syndrome termed initially vaccine-induced prothrombotic immune thrombocytopenia (VIPIT) and renamed recently vaccine-induced immune thrombotic thrombocytopenia (VITT). It encompasses the presence of platelet-activating antibodies to platelet factor-4/heparin complexes, possibly emulated by polyanionic constituents of AZD1222, and thus resembles heparin-induced thrombocytopenia (HIT). Because these immune complexes bind and activate platelets via Fcγ receptor IIA (FcγRIIA), high-dose intravenous immunoglobulin G has been suggested for treatment of VITT in addition to non-heparin anticoagulants. Here we propose inhibitors of Bruton tyrosine kinase (Btk) approved for B cell malignancies (e.g., ibrutinib) as another therapeutic option in VITT, as they are expected to pleiotropically target multiple pathways downstream of FcγRIIA-mediated Btk activation, for example, as demonstrated for the effective inhibition of platelet aggregation, dense granule secretion, P-selectin expression and platelet-neutrophil aggregate formation stimulated by FcγRIIA cross-linking. Moreover, C-type lectin-like receptor CLEC-2- and GPIb-mediated platelet activation, the interactions and activation of monocytes and the release of neutrophil extracellular traps, as encountered in HIT, could be attenuated by Btk inhibitors. As a paradigm for emergency repurposing of approved drugs in COVID-19, off-label use of Btk inhibitors in a low-dose range not affecting haemostatic functions could thus be considered a sufficiently safe option to treat VITT.

Note

After acceptance of this review, two articles have been published which describe further cases of vaccine-induced thrombotic thrombocytopenia (VITT). See below:


1. Greinacher A, Thiele T, Warkentin TE, et al. Thrombotic thrombocytopenia after ChadOx1 nCoV-19 vaccination. N Engl J Med 2021;384(22):2092–2101


2. Schultz NH, Sørvoll IH, Michelsen AE, et al. Thrombosis and thrombocytopenia after ChadOx1 nCoV-19 vaccination. N Engl J Med 2021;384(22):2124–2130


* The review process for this paper was fully handled by Gregory Y. H. Lip, Editor-in-Chief.




Publication History

Received: 06 April 2021

Accepted: 09 April 2021

Publication Date:
13 April 2021 (online)

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