Image
A partnership between the Institut des Neurosciences de la Timone and targeting vector specialist Vect-Horus
A key to addressing molecules through our defense barriers
The genesis of the collaboration
The
story begins with the historic interactions between Frédéric Chavane of INT (Neopto team) and Michel Khrestchatisky, Director of the Institut de NeuroPhysiopathologie (INP) and co-founder of Vect-Horus, a Marseille-based biotech company associated with the INP as part of a public-private partnership and the creation of a Laboratoire Commun de Recherche (LabCom). Vect-Horus designs and develops vectors that facilitate the targeted delivery of molecules to the brain. The idea of this biotech is to use receptors present in the vascular system of the central nervous system, known as the blood-brain barrier (BBB), to enable the distribution of biomolecules in the brain. This barrier, whose function is to protect the brain, is highly selective, allowing only the nutrients required by the brain to pass through, by mobilizing transporters and receptors. The BBB is impermeable to the passage of most therapeutic agents developed by the pharmaceutical industry, and poses real problems for the development of new brain drugs. The company's strategy is therefore to develop ligands that target BBB receptors, and to conjugate them with therapeutic agents or imaging molecules in order to "lure" the BBB and enable the distribution of these agents in the brain.
Vect-Horus
wanted to visualize and quantify the passage of its vectors across the BBB with high spatial resolution. To meet this objective, INT provided Vect-Horus with its expertise and technological tools in wide-field optical imaging and biphotonic imaging. Sébastien Roux, a former INT researcher now working for Vect-Horus, was chosen to spearhead the partnership. A first collaboration contract started on this basis in 2015.
Over time, Vect-Horus has developed a new area of interest. This involves the scientific and clinical expertise of INT's NeOpTo team in ophthalmology, particularly concerning the blood-retinal barrier, which is not exactly identical to the BBB, and the interest in delivering drugs to the retina.
Did you say vectors?
Vectors are basically "Trojan horses" that bind to receptors and transporters on the surface of cerebral capillary endothelial cells, transporting therapeutic agents conjugated to these vectors through the vessels, by a mechanism known as transcytosis. Two types of vector have been developed by Vect-Horus:
- Peptide vectors: natural, linear peptides have very low proteolytic resistance (degradation).
- To overcome this limitation, Vect-Horus has developed expertise in peptide optimization, using various techniques such as cyclization and the introduction of non-natural amino acids, to produce stable peptide variants that are directed against the lipid receptor (LDLR).
- Single-domain antibodies (VHH): These small proteins represent the smallest functional antibody fragments allowing binding to an antigen. Using molecular biology approaches, these VHH vectors are optimized and diversified to generate variants that will bind to different receptors, notably the Transferrin receptor.
A dynamic visualization study
Vect-Horus
manufactures and selects vectors, then tests them in-house on in vitro and in vivo models to assess their efficacy. In vivo, different approaches can be used to validate vectors. For example, it is possible to conjugate the vector to a hypothermic molecule which, on its own, is unable to cross the blood-brain barrier. However, this molecule only lowers the body temperature of mice when it passes into the brain. The conjugate is therefore administered to mice whose body temperature is measured. If hypothermia is observed, this means that the hypothermia molecule has been transported to the brain by the vector. Other approaches are also used, such as conjugating the vector to an oligonucleotide that can modulate gene expression in the brain.
The limitation of these techniques, however, is that they do not allow easy study of the dynamics of the vector's cerebral distribution in vivo. This is where the added value of our collaboration with INT lies. The idea is to directly visualize the passage dynamics using photonic imaging techniques mastered at INT (notably on the InPhIm platform piloted by Ivo Vanzetta and Alberto Lombardini), by coupling the vector to a fluorophore that allows us to visually follow its passage (or not) from the blood compartment of the capillaries to the brain or retinal parenchyma. For the latter application, a specific model has been developed to resolve certain in vivo constraints and ensure good imaging quality.
These studies enable Vect-Horus to validate the efficacy of its vectors, which will then be evaluated on other models for therapeutic approaches, either with agents supplied by industrial partners, or developed by Vect-Horus or INP, enabling proof of concept to be provided. The pathologies targeted are mainly neuro-oncological or central neurodegenerative diseases (Alzheimer's, Parkinson's, AMD, etc.), or peripheral organ pathologies (tumors, myopathies). In this context, vectors can be refined to be specific to target organs other than the brain.
Promising results open up new prospects
In the end, a good correlation was found between INT imaging results and those obtained with other modalities at Vect-Horus, particularly for the brain. The more complex ophthalmology section requires further development. In addition, this collaboration has enabled us to provide proof-of-concept for the technology, and to document it with imaging data that will be very useful for discussions with industrial partners.
In terms of future developments, the two partners are considering renewing the collaboration contract, which could be extended to the study of other pathologies or imaging modalities in which INT has expertise.