ABSTRACT
Demyelinating diseases, including multiple sclerosis, are characterized by loss of myelin-producing
oligodendrocytes in the central nervous system and cause severe disability for millions of patients.
Existing therapies for MS exclusively modulate the immune system to prevent additional myelin loss;
no regenerative therapies are available that replenish lost oligodendrocytes and repair lost myelin.
Multiple researchers have used high-throughput screening of small-molecule libraries to identify drugs
that increase the formation of oligodendrocytes from oligodendrocyte progenitor cells (OPCs) in vitro
and enhance functional remyelination in vivo. One such molecule, the FDA-approved antihistamine
clemastine, was recently shown to enhance optic nerve conduction velocity in MS patients with optic
neuritis, providing the first clinical evidence that small molecule treatments can enhance remyelination
in the human CNS.
While this trial provides proof-of-concept for future remyelinating therapeutics, greater clarity around
the optimal pathways and targets controlling oligodendrocyte formation is critical to the success of
future translational efforts. Our multi-disciplinary team has leveraged synergistic expertise in glial
biology, chemical biology, and organic synthesis to provide compelling preliminary evidence, now
published in Nature and Cell Chemical Biology, that almost all promyelinating small molecules identified
by HTS enhance oligodendrocyte formation by inhibiting a small number of adjacent enzymes within
cholesterol biosynthesis. Inhibition of these enzymes causes accumulation of specific, structurally-
related cholesterol precursors (8,9-unsaturated sterols) which are sufficient to enhance the formation
of oligodendrocytes from OPCs. Mass spectrometry-based sterol profiling has demonstrated more
than three dozen promyelinating small molecules function by this mechanism, including clemastine.
This application advances two parallel goals. First, we seek to understand how 8,9-unsaturated sterol
accumulation drives oligodendrocyte formation, including defining the optimal sterols and elucidating
their cellular target (Aims 1 and 2). Additionally, we aim to optimize the first selective and brain-
penetrant EBP inhibitor and to validate that this molecule promotes remyelination in vivo and human
myelin formation in vitro (Aim 3). Organic synthesis is a key technique throughout the application,
enabling the synthesis of novel 8,9-unsaturated sterols (Aim 1), photoaffinity pulldown reagents (Aim
2), and novel derivatives of our recently-published EBP-inhibiting lead molecules CW9009 and
CW9956. Together these studies will accelerate the emerging field of remyelinating therapeutics by
developing optimized small molecules for further drug development and identifying novel drug targets
that underlie the oligodendrocyte-enhancing effects of 8,9-unsaturated sterols.