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Investigating Mechanisms and Models Predictive of Accessibility of Therapeutics (IM2PACT) Into The Brain

Periodic Reporting for period 1 - IM2PACT (Investigating Mechanisms and Models Predictive of Accessibility of Therapeutics (IM2PACT) Into The Brain)

Reporting period: 2019-01-01 to 2019-12-31

The complex interplay between neurons and microvessels responsible for the coupling of brain activity and blood supply to the brain requires an integrated, functional unit, termed the ‘neurovascular unit’ (NVU). The composition of the NVU varies with vessel size, but typically includes capillary endothelial cells, neurons, astrocytes, pericytes and extracellular matrix components. In addition to ensuring neurovascular coupling, the NVU provides the first line of defence against the detrimental effects of potentially neurotoxic molecules and cells in the systemic circulation. The barrier between blood and nervous tissues is evident at multiple interfaces; the best described being the cerebrovascular blood-brain barrier (BBB). The barrier arises from the specialized capillary endothelial cells of the NVU, which differ from peripheral endothelial cells in that they are not fenestrated, they have minimal pinocytotic activity, very low rates of transcytosis, express drug efflux transporters and are coupled by tight junctions (TJ). The properties of the endothelium therefore also represent the primary barrier for the transport of drugs across the BBB, and is crucial in maintaining the homeostasis of the brain’s microenvironment. The other cells of the NVU may help maintain the barrier properties of endothelial cells and may also directly be involved in the barrier.
Most molecules and especially biologics do not cross the BBB and this is therefore a critical factor limiting the future application of neurotherapeutics. However, the need to develop CNS-active agents for neurological disorders including dementia or multiple sclerosis is greater than ever. This will require a more comprehensive understanding of BBB transport mechanisms and targets that could facilitate brain delivery. Recently, new opportunities for brain specific delivery of biologics have arisen. Challenging Receptor Mediated Transcytosis (RMT) and Carrier Mediated Transcytosis (CMT) with specific antibodies and peptides along with several drug delivery systems (including liposomes, nanoparticles, exosomes) or viral delivery agents have shown to deliver biopharmaceuticals into the CNS. Due to the lack of understanding of fundamental biological processes enabling the translocation of macromolecules or viruses through the BBB, the breakthrough of clinically relevant brain delivery approaches is still waiting to arise.
The overall goal of the IM2PACT consortium is to address critical gaps in the field by comprehensively investigating the molecular and cellular properties of the BBB in human patient material, cutting-edge human in vitro models and in vivo preclinical models in order to understand BBB transport mechanisms and identify new BBB targets for brain delivery in health and disease. IM2PACT will robustly validate the models by establishing the ability of these models to truly predict in vivo CNS exposures of therapeutics, through an EU network of BBB translational scientists. The synergistic expertise of the partners in cellular and molecular biology, neuroscience, pharmacology, virology, drug delivery and bioinformatics along with the chemical/analytical resources, powerful biologics production facilities and direct link to the clinic brought by the EFPIA partners will enable rapid identification of new target mechanisms for brain delivery of therapeutics to treat neurodegenerative diseases and potentially wider applications in other CNS disorders.
In this first year of IM2PACT, the project coordination team has established an effective project management strategy and successfully addressed the challenges of initiating a large complex programme of work. The coordination team through regular meetings every two weeks have enabled timely progression of the consortium to achieve the critical deliverables and milestones of the first year. Any critical issues are identified rapidly and discussions with relevant stakeholders are held to develop solutions and implement them effectively. The main results achieved so far have included:

1. In workpackage (WP) 1, the investigation of existing molecular datasets to identify new candidate blood-brain-barrier (BBB) transport mechanisms. This revealed 5 potential candidates which are presently under investigation to prioritise deeper investigation.

2. In WP1, two key protocols for isolation of BBB endothelial cells have now been established:
(i) The first is a micro-vessel enrichment protocol, validated across multiple labs that has allowed the first single cell RNA sequencing experiment to be performed, which in turn has allowed the identification of 3 novel BBB transport candidates.
(ii) The second is a laser capture micro dissection protocol to allow rapid retrieval of brain capillary endothelial cells for either RNA-sequencing or proteomics.

3. In WP1, the phenotyping of preclinical models of diabetes has now been completed and single cell RNA sequencing to assess the effects of metabolic dysfunction on brain endothelial cells will be commenced.

4. In WP2, three independent labs have completed evaluation of available BBB differentiation protocols. Whilst there is still further development required to produce true endothelial cells, the cellular model produced is reproducible and exhibits strong barrier properties as well as expressing key BBB transport proteins

The other WPs have made a strong start to their programme of research and will be in a strong position to deliver important outputs over the next year.
IM2PACT has already moved research ahead of the state of the art through identification of new BBB transporter candidates. Once these candidates are prioritised, further work will commence to experimentally validate their potential for improving therapeutic access into the brain. Over the next year, IM2PACT will generate a large body of de novo molecular data on the BBB that will add a significant body of knowledge to the field. We therefore expect to rapidly utilise this data to develop cellular and preclinical models for the duration of the IM2PACT project. In addition, IM2PACT researchers will continue to investigate better stem cell models of the BBB and several novel strategies are under investigation. We expect these will mark a watershed in the field in finally achieving a genuine brain capillary endothelial cell phenotype that will be highly valued by researchers in the BBB field. The potential impact on society of IM2PACT research is very significant as getting therapeutic into the brain remains a major challenge for drug development.