OPC-X screen: Discovery of small molecule inhibitors to overcome extrinsic inhibition of remyelination.

Project Summary/Abstract
Multiple Sclerosis (MS) is a chronic inflammatory, neurodegenerative disease involving the destruction of myelin
sheaths on neurons resulting in axonal damage leading to permanent functional deficits including paralysis and
loss of vision. In MS, the blood-brain barrier is disrupted allowing fibrinogen to enter the brain and fibrinogen is
a driver of neuropathology. It prevents remyelination and repair of damaged neurons by blocking multipotent
oligodendrocyte progenitor cells (OPCs) from differentiating into myelin producing oligodendrocytes (OL) and
directs OPC cell fate to astrocytes. The rationale for our IGNITE (PAR-21-124) grant is to develop a novel high
throughput OPC-X screen to identify compounds that in the presence of fibrinogen promote OPC differentiation
to mature OLs and decrease the OPC fate-switch to astrocytes to facilitate remyelination of neurons in MS to
slow disease progression. We have already developed a medium throughput OPC-X screen in a 96 well format.
We made the novel finding that fibrinogen prevents remyelination by activating bone morphogenetic protein
(BMP) receptors in OPCs and showed in the assay that small molecule BMP receptor inhibitors (DMH1 and
LDN-212854) increase OL production >80% in a dose-dependent manner and suppressed differentiation to
astrocytes. To validate the utility of the assay we showed that LDN-212854 was effective in vivo in two EAE
animal models of MS; it significantly improved clinical scores, reduced fibrinogen deposition, demyelination, and
myelin damage and increased OPC differentiation to OLs. Our in vitro screening assay is unique because while
some compounds have been identified that increase myelination in MS by stimulating differentiation of OPCs to
OL, they are not designed to overcome the inhibition of remyelination caused by extrinsic factors such as
fibrinogen, are ineffective in our assay and may not promote remyelination under conditions that might be most
relevant to the disease. This is important because therapies to overcome extrinsic inhibition of remyelination are
not widely available and may be critical in the ultimate success in developing more effective treatments of MS.
In the R61 component of the IGNITE grant we will optimize our OPC-X screen for compound screening. In the
R33 component, we will screen 28,690 compounds that increase OPC differentiation to OL in the presence of
fibrinogen. These compounds consist of bio-annotated compounds, comprising FDA approved drugs and
compounds selected on the basis of structural diversity, physicochemical properties consistent with brain
permeability and drug-like properties, including Lipinsky criteria. Effective “hits” will be further screened in
secondary assays we have developed; a safety assay to exclude potential adverse hemorrhagic effects and
assays to identify compounds that may regulate BMP receptor activation, cholesterol synthesis or have
additional anti-inflammatory effects by blocking fibrin-induced inflammation. These compounds will be further
developed in future studies by us to improve drug like properties, with a goal of transitioning to future clinical
development to treat MS patients.

Grant Number: 4R33NS133257-02
NIH Institute/Center: NIH
Principal Investigator: Katerina Akassoglou