G6b-B antibody-based cis-acting platelet receptor inhibitors (CAPRIs) as a new family of anti-thrombotic therapeutics
Posted on: 3 June 2024 , updated on: 5 June 2024
Preprint posted on 14 May 2024
The CAPRI sun rises: new bispecific antiplatelet agents for targeted inhibition of signalling through GPVI or CD32A
Selected by Simon ClearyCategories: cell biology, immunology, pharmacology and toxicology
Background
A medicine that prevents thrombosis without increasing bleeding risk is the ‘holy grail’ of platelet research. Excitingly, researchers have now identified multiple platelet receptors that are important for thrombosis, but only seem to play supporting roles in haemostasis.
One pro-thrombotic platelet receptor is the collagen receptor glycoprotein VI (GPVI). Platelets come in to contact with collagen when blood vessels are damaged by atherosclerosis, and the GPVI-mediated platelet responses that ensue contribute to thrombotic strokes. Promisingly, a recent trial indicates that glenzocimab, an antibody fragment that blocks GPVI binding to collagen, might decrease mortality without increasing bleeding risk when given in combination with alteplase following ischaemic stroke (1).
Another platelet-expressed receptor involved in thrombotic responses is FcγRIIA (FCGR2A, also referred to as CD32A), a low affinity immunoglobulin Fcγ receptor that mediates responses to IgG antibodies. CD32A drives the devastating thrombosis and bleeding experienced by people affected by antibody responses that cause antiphospholipid syndrome (APS), heparin-induced thrombocytopaenia (HIT) or vaccine-induced thrombotic thrombocytopenia (VITT).
Both GPVI and CD32A signal through immunoreceptor tyrosine-based activation motifs (ITAMs) to trigger platelet activation. Physiologically, ITAMs are counteracted by inhibitory phosphatases under the control of receptors containing immunoreceptor tyrosine-based inhibitory motifs (ITIMs). One ITIM-containing receptor, G6B (also known as G6b-B and MPIG6B), is exclusively expressed on megakaryocytes and platelets. It has been speculated that the natural function of G6B might be enhanced to suppress harmful platelet responses (2), but achieving this is not easy because the ITIM domains of G6B need to be positioned immediately adjacent to target ITAMs for effective inhibition mediated by SHP-1 or SHP-2 tyrosine phosphatases.
Key findings
Bispecific single chain variable fragments (scFvs) are fusion proteins built from fragments of two different antibodies that are used in the form of bispecific T cell engagers (BiTEs) to treat forms of leukaemia. BiTEs act by bringing T-cell receptors onto cancer cell-expressed antigens to promote T cell-mediated anticancer immune responses.
In this preprint (3), Mazharian and colleagues tested an alternative use for bispecific scFvs – using them to bring G6B together with GPVI or CD32A on the surfaces of platelets (Figure 1). The authors named these bispecific agents cis-acting platelet receptor inhibitors (CAPRIs). Structural modelling indicated that CAPRIs were sufficiently small to bring ITIMs close enough to ITAMs to enable targeted inhibition. CAPRIs elicited their intended cell signalling effects as well as agonist-specific inhibition in functional assays. Excitingly, the G6B-CD32A CAPRI displayed protective effects in models using human blood, endothelial cells and antibodies to reproduce APS, HIT and VITT pathophysiology in vitro.
Figure 1: Proposed mechanism of action of cis-acting platelet receptor inhibitors (CAPRIs).
Why this work is interesting
We live in an era of modular pharmacology. Drug hunters around the world are designing agents that bind multiple different targets to make molecular glues, proteolysis targeting chimeras (PROTACs), bispecific T cell engagers (BiTEs), and antibody products that can be bispecific, trispecific or even tetraspecific. This preprint caught my eye because it describes pioneering work applying modular therapeutic development approaches to platelets. To my knowledge, only one bispecific antibody is actively under investigation that intentionally targets platelets (HMB-001, bringing the clotting factor FVIIa together with TLT-1 on the surface of activated platelets to treat inherited bleeding disorders (4)), and only one study has used PROTACs for targeted protein degradation in platelets (5).
I also find the concept of alleviating disease by increasing inhibition an attractive approach. Rational design of a therapeutic to selectively increase activity of a protein used to be near-impossible. This study is a nice example of how expertise in cell signalling can be combined with modular, recombinant approaches to expand possibilities for development of therapeutics.
CD32A is interesting to me as a target because of its implication in multiple antibody-mediated diseases and the lack of evidence that it plays an important role in either immunity or haemostasis, with mice entirely lacking an equivalent receptor (conflict of interest disclosure: I have worked on CD32A in the context of responses to alloantibodies (6)). Notably, the CD32A antibody used in this preprint was developed into a humanised, effector-dead therapeutic candidate (VIB9600, formerly MEDI9600). A phase I clinical trial was registered for VIB9600, but this trial was terminated at some point during a series of spinouts and acquisitions (from Medimmune to Viela Bio, Horizon Therapeutics and then Amgen), making it hard to tell whether this therapeutic is still under investigation. It is therefore exciting to see CD32A revisited as a target for therapeutics with a novel approach.
Questions I would like to ask the authors about their work
- Is there an assay that could test whether the G6B-GPVI CAPRI accelerates alteplase-mediated dissolution of an established thrombus or makes the platelets released during thrombolysis less likely to cause further harm? Superiority of a CAPRI relative to glenzocimab with this type of test would be very encouraging.
- Demonstrating that the G6B-CD32A CAPRI has greater efficacy in the APS, HIT or VITT models compared to a therapeutic in current use (e.g. high-dose intravenous immunoglobulins) would be interesting. Do you have plans/enough patient IgGs to do this?
- I imagine that this is difficult to test, but is it possible that the greater extent of inhibition of platelet adhesion by G6B-GPVI CAPRIs relative to glenzocimab might end up increasing bleeding risk?
- I was concerned that CAPRIs might cross-link and agglutinate different platelets (becoming ‘TAPRIs’?), so it was good to read assurance that this does not seem to happen in the discussion. CD32A is expressed on leukocytes as well as on platelets. Did you look at whether the G6B-CD32A CAPRI causes platelet-leukocyte complexes to form in the whole blood assays?
References
- Mazighi M, et al. Safety and efficacy of platelet glycoprotein VI inhibition in acute ischaemic stroke (ACTIMIS): a randomised, double-blind, placebo-controlled, phase 1b/2a trial. The Lancet Neurology. 2024;23(2):157–167.
- Soriano Jerez EM, Gibbins JM, Hughes CE. Targeting platelet inhibition receptors for novel therapies: PECAM-1 and G6b-B. Platelets. 2021;32(6):761–769.
- Mazharian A, et al. G6b-B antibody-based cis-acting platelet receptor inhibitors (CAPRIs) as a new family of anti-thrombotic therapeutics. bioRxiv. 2024;2024.05.10.593500.
- Gandhi PS, et al. A bispecific antibody approach for the potential prophylactic treatment of inherited bleeding disorders. Nat Cardiovasc Res. 2024;3(2):166–185.
- Trory JS, et al. Chemical degradation of BTK/TEC as a novel approach to inhibit platelet function. Blood advances. [published online ahead of print: November 7, 2022]. https://doi.org/10.1182/BLOODADVANCES.2022008466.
- Cleary SJ, et al. IgG hexamers initiate complement-dependent acute lung injury. J Clin Invest. 2024;e178351.
doi: https://doi.org/10.1242/prelights.37541
Read preprintSign up to customise the site to your preferences and to receive alerts
Register hereAlso in the cell biology category:
Motor Clustering Enhances Kinesin-driven Vesicle Transport
Sharvari Pitke
Cellular signalling protrusions enable dynamic distant contacts in spinal cord neurogenesis
Ankita Walvekar
Green synthesized silver nanoparticles from Moringa: Potential for preventative treatment of SARS-CoV-2 contaminated water
Safieh Shah, Benjamin Dominik Maier
Also in the immunology category:
Alzheimer’s Disease Patient Brain Extracts Induce Multiple Pathologies in Vascularized Neuroimmune Organoids for Disease Modeling and Drug Discovery
Manuel Lessi
Global coordination of protrusive forces in migrating immune cells
yohalie kalukula
Integrin conformation-dependent neutrophil slowing obstructs the capillaries of the pre-metastatic lung in a model of breast cancer
Simon Cleary
Also in the pharmacology and toxicology category:
G6b-B antibody-based cis-acting platelet receptor inhibitors (CAPRIs) as a new family of anti-thrombotic therapeutics
Simon Cleary
Pervasive sublethal effects of agrochemicals as contributing factors to insect decline
Roberto Amadio
Mixed Alkyl/Aryl Phosphonates Identify Metabolic Serine Hydrolases as Antimalarial Targets
Zhang-He Goh
preListscell biology category:
in theNovember in preprints – the CellBio edition
This is the first community-driven preList! A group of preLighters, with expertise in different areas of cell biology, have worked together to create this preprint reading lists for researchers with an interest in cell biology. Categories include: 1) cancer cell biology 2) cell cycle and division 3) cell migration and cytoskeleton 4) cell organelles and organisation 5) cell signalling and mechanosensing 6) genetics/gene expression
List by | Felipe Del Valle Batalla et al. |
BSCB-Biochemical Society 2024 Cell Migration meeting
This preList features preprints that were discussed and presented during the BSCB-Biochemical Society 2024 Cell Migration meeting in Birmingham, UK in April 2024. Kindly put together by Sara Morais da Silva, Reviews Editor at Journal of Cell Science.
List by | Reinier Prosee |
‘In preprints’ from Development 2022-2023
A list of the preprints featured in Development's 'In preprints' articles between 2022-2023
List by | Alex Eve, Katherine Brown |
preLights peer support – preprints of interest
This is a preprint repository to organise the preprints and preLights covered through the 'preLights peer support' initiative.
List by | preLights peer support |
The Society for Developmental Biology 82nd Annual Meeting
This preList is made up of the preprints discussed during the Society for Developmental Biology 82nd Annual Meeting that took place in Chicago in July 2023.
List by | Joyce Yu, Katherine Brown |
CSHL 87th Symposium: Stem Cells
Preprints mentioned by speakers at the #CSHLsymp23
List by | Alex Eve |
Journal of Cell Science meeting ‘Imaging Cell Dynamics’
This preList highlights the preprints discussed at the JCS meeting 'Imaging Cell Dynamics'. The meeting was held from 14 - 17 May 2023 in Lisbon, Portugal and was organised by Erika Holzbaur, Jennifer Lippincott-Schwartz, Rob Parton and Michael Way.
List by | Helen Zenner |
9th International Symposium on the Biology of Vertebrate Sex Determination
This preList contains preprints discussed during the 9th International Symposium on the Biology of Vertebrate Sex Determination. This conference was held in Kona, Hawaii from April 17th to 21st 2023.
List by | Martin Estermann |
Alumni picks – preLights 5th Birthday
This preList contains preprints that were picked and highlighted by preLights Alumni - an initiative that was set up to mark preLights 5th birthday. More entries will follow throughout February and March 2023.
List by | Sergio Menchero et al. |
CellBio 2022 – An ASCB/EMBO Meeting
This preLists features preprints that were discussed and presented during the CellBio 2022 meeting in Washington, DC in December 2022.
List by | Nadja Hümpfer et al. |
Fibroblasts
The advances in fibroblast biology preList explores the recent discoveries and preprints of the fibroblast world. Get ready to immerse yourself with this list created for fibroblasts aficionados and lovers, and beyond. Here, my goal is to include preprints of fibroblast biology, heterogeneity, fate, extracellular matrix, behavior, topography, single-cell atlases, spatial transcriptomics, and their matrix!
List by | Osvaldo Contreras |
EMBL Synthetic Morphogenesis: From Gene Circuits to Tissue Architecture (2021)
A list of preprints mentioned at the #EESmorphoG virtual meeting in 2021.
List by | Alex Eve |
FENS 2020
A collection of preprints presented during the virtual meeting of the Federation of European Neuroscience Societies (FENS) in 2020
List by | Ana Dorrego-Rivas |
Planar Cell Polarity – PCP
This preList contains preprints about the latest findings on Planar Cell Polarity (PCP) in various model organisms at the molecular, cellular and tissue levels.
List by | Ana Dorrego-Rivas |
BioMalPar XVI: Biology and Pathology of the Malaria Parasite
[under construction] Preprints presented at the (fully virtual) EMBL BioMalPar XVI, 17-18 May 2020 #emblmalaria
List by | Dey Lab, Samantha Seah |
1
Cell Polarity
Recent research from the field of cell polarity is summarized in this list of preprints. It comprises of studies focusing on various forms of cell polarity ranging from epithelial polarity, planar cell polarity to front-to-rear polarity.
List by | Yamini Ravichandran |
TAGC 2020
Preprints recently presented at the virtual Allied Genetics Conference, April 22-26, 2020. #TAGC20
List by | Maiko Kitaoka et al. |
3D Gastruloids
A curated list of preprints related to Gastruloids (in vitro models of early development obtained by 3D aggregation of embryonic cells). Updated until July 2021.
List by | Paul Gerald L. Sanchez and Stefano Vianello |
ECFG15 – Fungal biology
Preprints presented at 15th European Conference on Fungal Genetics 17-20 February 2020 Rome
List by | Hiral Shah |
ASCB EMBO Annual Meeting 2019
A collection of preprints presented at the 2019 ASCB EMBO Meeting in Washington, DC (December 7-11)
List by | Madhuja Samaddar et al. |
EMBL Seeing is Believing – Imaging the Molecular Processes of Life
Preprints discussed at the 2019 edition of Seeing is Believing, at EMBL Heidelberg from the 9th-12th October 2019
List by | Dey Lab |
Autophagy
Preprints on autophagy and lysosomal degradation and its role in neurodegeneration and disease. Includes molecular mechanisms, upstream signalling and regulation as well as studies on pharmaceutical interventions to upregulate the process.
List by | Sandra Malmgren Hill |
Lung Disease and Regeneration
This preprint list compiles highlights from the field of lung biology.
List by | Rob Hynds |
Cellular metabolism
A curated list of preprints related to cellular metabolism at Biorxiv by Pablo Ranea Robles from the Prelights community. Special interest on lipid metabolism, peroxisomes and mitochondria.
List by | Pablo Ranea Robles |
BSCB/BSDB Annual Meeting 2019
Preprints presented at the BSCB/BSDB Annual Meeting 2019
List by | Dey Lab |
MitoList
This list of preprints is focused on work expanding our knowledge on mitochondria in any organism, tissue or cell type, from the normal biology to the pathology.
List by | Sandra Franco Iborra |
Biophysical Society Annual Meeting 2019
Few of the preprints that were discussed in the recent BPS annual meeting at Baltimore, USA
List by | Joseph Jose Thottacherry |
ASCB/EMBO Annual Meeting 2018
This list relates to preprints that were discussed at the recent ASCB conference.
List by | Dey Lab, Amanda Haage |
Also in the immunology category:
Journal of Cell Science meeting ‘Imaging Cell Dynamics’
This preList highlights the preprints discussed at the JCS meeting 'Imaging Cell Dynamics'. The meeting was held from 14 - 17 May 2023 in Lisbon, Portugal and was organised by Erika Holzbaur, Jennifer Lippincott-Schwartz, Rob Parton and Michael Way.
List by | Helen Zenner |
Fibroblasts
The advances in fibroblast biology preList explores the recent discoveries and preprints of the fibroblast world. Get ready to immerse yourself with this list created for fibroblasts aficionados and lovers, and beyond. Here, my goal is to include preprints of fibroblast biology, heterogeneity, fate, extracellular matrix, behavior, topography, single-cell atlases, spatial transcriptomics, and their matrix!
List by | Osvaldo Contreras |
Single Cell Biology 2020
A list of preprints mentioned at the Wellcome Genome Campus Single Cell Biology 2020 meeting.
List by | Alex Eve |
Autophagy
Preprints on autophagy and lysosomal degradation and its role in neurodegeneration and disease. Includes molecular mechanisms, upstream signalling and regulation as well as studies on pharmaceutical interventions to upregulate the process.
List by | Sandra Malmgren Hill |
Antimicrobials: Discovery, clinical use, and development of resistance
Preprints that describe the discovery of new antimicrobials and any improvements made regarding their clinical use. Includes preprints that detail the factors affecting antimicrobial selection and the development of antimicrobial resistance.
List by | Zhang-He Goh |
Zebrafish immunology
A compilation of cutting-edge research that uses the zebrafish as a model system to elucidate novel immunological mechanisms in health and disease.
List by | Shikha Nayar |
Also in the pharmacology and toxicology category:
FENS 2020
A collection of preprints presented during the virtual meeting of the Federation of European Neuroscience Societies (FENS) in 2020
List by | Ana Dorrego-Rivas |
COVID-19 / SARS-CoV-2 preprints
List of important preprints dealing with the ongoing coronavirus outbreak. See http://covidpreprints.com for additional resources and timeline, and https://connect.biorxiv.org/relate/content/181 for full list of bioRxiv and medRxiv preprints on this topic
List by | Dey Lab, Zhang-He Goh |
1
Drug use in special populations
Any drugs that are being used in special populations: Patients with liver and kidney failure, in paediatrics, in geriatrics, and in pregnant or lactating patients. Includes the discovery of factors that could potentially affect drug use in these special populations.
List by | Zhang-He Goh |
Toxicology of toxicants, existing therapeutics, and investigational drugs
Preprints that describe the toxicology of environmental pollutants and existing and upcoming drugs. Includes both toxicokinetics and toxicodynamics, as well as technological improvements that will help in the characterisation of this field.
List by | Zhang-He Goh |
Antimicrobials: Discovery, clinical use, and development of resistance
Preprints that describe the discovery of new antimicrobials and any improvements made regarding their clinical use. Includes preprints that detail the factors affecting antimicrobial selection and the development of antimicrobial resistance.
List by | Zhang-He Goh |
Anticancer agents: Discovery and clinical use
Preprints that describe the discovery of anticancer agents and their clinical use. Includes both small molecules and macromolecules like biologics.
List by | Zhang-He Goh |
Advances in Drug Delivery
Advances in formulation technology or targeted delivery methods that describe or develop the distribution of small molecules or large macromolecules to specific parts of the body.
List by | Zhang-He Goh |