LB: Therapeutic targeting of DM1 disease mechanism using a quercetin–vorinostat combination

Topic:

Pre-Clinical Research

Poster Number: 472 LBT

Author(s):

SUBODH MISHRA, PhD, The RNA Institute, University at Albany, Albany, NY USA, John Andrew Berglund, PhD, The RNA Institute, University at Albany, NY, USA, John Cleary, PhD, The RNA Institute, University at Albany, NY, USA, Kaalak Ready, PhD, The RNA Institute, University at Albany, NY, USA, Masayuki Nakamori, MD, PhD, Department of Neurology and Clinical Neuroscience, Yamaguchi University Graduate School of Medicine

Background: Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic neuromuscular disorder caused by CTG repeat expansion in 3´UTR of DMPK gene. Transcription of the expanded allele produces toxic gain-of-function CUG repeat–expanded RNA that aberrantly sequesters MBNL proteins into nuclear ribonuclear foci, leading to widespread mis-splicing and downstream dysfunction. These pathogenic pathways are mechanistically interconnected, such that modulation of a single pathway is unlikely to achieve broad molecular correction. Therapeutic strategies that engage multiple pathogenic pathways represent a critical need for effective molecular correction in DM1.
Objective: We recently identified quercetin as a CTG repeat-selective small molecule that reduces toxic CUG RNA, rescues DM1 mis-splicing in patient-derived cells, and in its bioavailable form, EMIQ, improves toxic RNA burden, splicing defects, and myotonia in DM1 mice. To evaluate a focused combination strategy, here we paired quercetin with the HDAC inhibitor vorinostat and quantified effects on MBNL-dependent splicing correction, selective toxic RNA reduction, and tolerability relative to each molecule alone.
Results and conclusion: We tested the quercetin–vorinostat combination in a DM1 MYOD1-engineered myogenic line and in DM1 patient-derived myotubes (DM05) and assessed in vivo efficacy in DM1 HSALR mice. In the DM1 MYOD1-engineered myogenic line, the mis-splicing of MBNL1 exon 5 showed 56% rescue with vorinostat (5 µM) alone and 45% rescue with quercetin (32 µM) alone, whereas the combination treatment showed 101% mis-splicing rescue. A similar additive pattern was observed for MBNL2 exon 5 (quercetin: 33%; vorinostat: 66%; combination: 100%). Consistent with data from the first DM1 cell line, in DM05 patient-derived myotubes , MBNL1 exon 5 showed 47% rescue with vorinostat and 57% with quercetin, whereas the combination showed 102% rescue, with a similar pattern for MBNL2 exon 5 (quercetin: 50%; vorinostat: 56%; combination: 103%). In unaffected cells, combination treatment did not induce a statistically significant change in splicing, indicating disease selectivity. In DM1 HSALR mice, EMIQ and vorinostat combination treatment resulted in additive myotonia improvement relative to either single molecule treatment. These findings support the quercetin and vorinostat combination as a disease-selective therapeutic strategy.