Novel small molecule mitochondriotropics reverse skeletal muscle pathology and improve resilience in the D2.mdx model of Duchenne muscular dystrophy

Topic:

Translational Research

Poster Number: O25

Author(s):

matt whiteman, MD PhD, University of Exeter Medical School / CSO MitoRx Therapeutics, Oxford, UK, Dean Campelj, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Ashleigh Philp, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Elinor Hortle, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Christina Nalkurthi, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Vamshikrishn Malyla, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Eve Borbilas, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Shatarupa Das, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Roberta Torregrossa, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Beatriz Martinez-Burgo, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Monika Sledziowska, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Nicole Hansbro, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Tom Schirris, PhD, QTM BioSciences B.V., Oss, The Netherlands, Norman Law, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Jonathan Rees, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Timothy Etheridge, PhD, Sports & Health Science, University of Exeter, UK., Matthew Whiteman, PhD, MitoRx Therapeutics, Harwell, Oxford, UK, Philip Hansbro, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia, Andrew Philp, PhD, University of Technology Sydney & Centenary Institute, Sydney, Australia

Clinical trials evaluating gene therapy and nucleic acid-based ASO approaches for DMD such as phase 3 CIFFREO (fordadistrogene movaparvovec ‘mini-dystrophin’) and DEMAND III (drisapersen, exon 51 skipping) have failed to achieve myoprotective efficacy despite partial skeletal muscle (SkM) dystrophin restoration. These clinical failures highlight the need for alternative therapeutic strategies to fill the huge urgent and unmet clinical need. To address this shortfall, we have developed novel small molecule first-in-class SkM-penetrating mitochondriotropics. Building on a foundation of extensive in vitro and in vivo investigations (SkM myotubes, C. elegans, rats etc), we identified and successfully “drugged” a novel defect (mitochondrial trans-sulfuration; TSF) which manifests in DMD patients and across experimental DMD models, and results in substantial SkM bioenergetic deficit. We therefore designed mitochondriotropic agents to overcome these specific skeleto-metabolic defects. We first optimised structural and physicochemical characteristics (including metabolic stability and profiling in vivo) and showed standard toxicological assessments were negative. From this work, we identified Myo2/4 as “leads”, exhibiting EC50 of < 100nM across screening and mechanistic assays, and using super-resolution microscopy with LC-MS/MS demonstrated rapid (i.e. < 60 min) mitochondrial accumulation. In vivo ADME/PK studies (0.1-5 mg/kg, i.p., qd) further showed dose-dependent SkM accumulation (e.g. gastrocnemius) within 1h of administration with concomitant formation of key metabolites confirming mitochondrial utilisation. In the D2.mdx mouse model, Myo2/4 (1-5 mg/kg i.p., q.d. or vehicle; n= ≥7) for 8 weeks from 5 weeks old, dose-dependently reversed SkM TSF deficiency and several hallmarks of DMD SkM pathology. Notably, ~75% reduction in fibrosis, abrogation of fibre enlargement, and significant dose-dependent improvements in SkM strength (p<0.05; mixed analysis, unpaired t-test) and fatigue recovery (Force [mN]) in SkM fibre bundles (p<0.05; ANOVA, post-hoc Bonferroni c.f. vehicle). Our studies clearly show successful functional (SkM) and target (mitochondria) engagement with SkM-penetrating mitochondriotropics which significantly reverse SkM pathology and restore SkM resilience in vivo. Our small SkM-protective molecules offer an entirely novel approach for the treatment of musculoskeletal conditions. Their unique MoA and our development for DMD will be discussed.