Disease Modifying Therapies – Mechanism of Action Poster Presentation

P0376 - RAM-589.555 favors neuroprotective/anti-inflammatory profile of CNS-resident glial cells in acute relapse EAE affected mice (ID 1276)

Speakers
  • R. Zilkha-Falb
Authors
  • T. Rachutin-Zalogin
  • L. Kleaver
  • M. Gurevich
  • A. Achiron
Presentation Number
P0376
Presentation Topic
Disease Modifying Therapies – Mechanism of Action

Abstract

Background

Targeting RNA Polymerase-1 (POL1) machinery is a new strategy for suppression of multiple sclerosis (MS) relapse activity. Oral administration of POL1 inhibitor RAM-589.555, which is characterized by high permeability and bioavailability in naïve mice, ameliorates proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) by suppressing activated autoreactive lymphocytes.

Objectives

To assess the accessibility of RAM-589.555 to the central nervous system (CNS) of EAE-mice and further investigate its immunomodulatory effects on CNS-resident astro- and micro-glial cells in-vitro and in-vivo.

Methods

Effects of RAM-589.555 on activated microglia and astrocyte viability, proliferation, and secretion of neurotrophic factors were assessed in-vitro. The pharmacokinetic of RAM-589.555 was evaluated in the blood and central nervous system (CNS) of EAE affected mice. High-dimensional single-cell mass cytometry was applied to characterize the effect of RAM-589.555 on EAE-affected mice’s CNS-resident micro- and astro-glial cells and CNS-infiltrating immune cells, which were obtained seven days after RAM-589.555 administration at EAE onset. Simultaneously, the expression level of pre-rRNA, the POL1 end product, was assessed in blood cells, microglia, and astrocytes to monitor RAM-589.555 effects.

Results

RAM-589.555 demonstrated blood and CNS permeability in EAE mice. In-vitro, incubation with 400 nM of RAM-589.555 significantly reduced viability and proliferation of lipopolysaccharide (LPS)-activated microglia by 70% and 45% (p<0.05), respectively, while tumor necrosis factor a (TNFα)-activated astrocytes were not affected. The secretion of neurotrophic factors was preserved. Furthermore, seven days after administration of RAM-589.555 at EAE onset, the level of pre-rRNA transcript in peripheral blood mononuclear cells (PBMC) was decreased by 38.6% (p=0.02), while levels of pre-rRNA transcript in microglia and astrocytes remained unchanged. The high-dimensional single-cell mass cytometry analysis showed decreased percentages of CNS-resident microglia and astrocytes, diminished proinflammatory cytokines (IL-1β, IL-6, IL-12, IL-17, TNFα and IFNγ) and an increase of their anti-inflammatory cytokines (IL-4, IL-10 and TGFβ) in RAM-589.555-treated compared to vehicle-treated mice (p<0.05).

Conclusions

These data correlate RAM-589.555-induced clinical amelioration and its CNS permeability to decreased CNS-inflammation, and decreased micro- and astro-gliosis, while restoring micro- and astro-glial anti-inflammatory and neuroprotective capacity.

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