– First cross-sectional, retrospective study to describe selective elevation of fast but not slow skeletal muscle fiber injury biomarkers in BMD and DMD patient samples, published in Muscle & Nerve –

– Data supports Edgewise strategy to advance EDG-5506, a small molecule drug candidate designed to protect injury-susceptible fast skeletal muscle fibers, in clinical development for BMD and DMD –

BOULDER, Colo.--(BUSINESS WIRE)-- Edgewise Therapeutics, Inc., (NASDAQ: EWTX), a clinical-stage biopharmaceutical company focused on developing orally bioavailable, small molecule therapies for rare muscle disorders, today announced the publication of the first cross-sectional, retrospective study to describe selective elevation of fast but not slow skeletal muscle fiber injury biomarkers in the blood of patients with Becker and Duchenne muscular dystrophy (BMD, DMD) in the journal, Muscle & Nerve.

Human skeletal muscle is composed of fast and slow fibers in roughly equal proportion. Previous studies have demonstrated that DMD patient muscle is more prone to fast fiber injury compared to slow fiber injury. This study extends these findings to examine fiber-type specific biomarkers of muscle injury in patient blood. The results build on previous reports and suggest that slow skeletal muscle fibers do not appear to leak muscle proteins associated with muscle injury and damage in BMD and DMD. Furthermore, the study demonstrated that fast skeletal troponin I (TNNI2) may represent a more sensitive biomarker of muscle injury than creatine kinase (CK), particularly in the setting of BMD or older DMD patients where plasma CK is commonly lower than in young DMD patients. These data further support EDG-5506’s unique mechanism of action aimed at protecting injury-susceptible fast skeletal muscle fibers in BMD and DMD.

“We are pleased to share our findings that elevation of fast skeletal muscle fiber injury biomarkers may be more informative, compared to slow skeletal muscle injury biomarkers, of muscle injury in patients with BMD and DMD,” said Alan Russell, Ph.D., Chief Scientific Officer of Edgewise and senior author of the study. “These data guided the design of our lead clinical candidate, EDG-5506, which selectively protects injury-susceptible fast skeletal muscle fibers for BMD and DMD. Indeed, EDG-5506, in preclinical models, acts as a muscle stabilizer by protecting muscle through limiting excessive contraction. This protection reduces injury and the leak of muscle proteins that in the long term protects against fibrosis and functional declines associated with prolonged inflammation and degradation of the muscle.”

Kevin Koch, Ph.D., President and Chief Executive Officer added, “These data are invaluable as we continue to advance EDG-5506 in clinical development. We are excited about the potential of EDG-5506 for patients affected by BMD and DMD, who are currently underserved with limited treatment options.”

About the Skeletal Muscle Study

One of the hallmarks of injured skeletal muscle is the appearance of elevated skeletal muscle proteins in circulation. Human skeletal muscle generally consists of a mosaic of slow (type I) and fast (type IIa, IIx/d) fibers, defined by their myosin isoform expression. Recently, measurement of circulating fiber‐type specific isoforms of troponin I has been used as a biomarker to suggest that muscle injury in healthy volunteers results in the appearance of muscle proteins from fast but not slow fibers. Data from this study demonstrates that this is also the case in severe myopathy patients with Becker and Duchenne muscular dystrophy (BMD, DMD).

An ELISA test that selectively measures fast and slow skeletal troponin I (TNNI2 and TNNI1) was used to measure a cross‐section of patient plasma samples from healthy volunteers (N=50), BMD (N=49) and DMD (N=132) patients. CK activity, which is a type of protein found in skeletal and heart muscles, was also measured from the same samples for comparison.

The fast skeletal troponin, TNNI2, was elevated in BMD and DMD and correlated with the injury biomarker, CK. In contrast, the slow skeletal troponin, TNNI1, levels were indistinguishable from levels in healthy volunteers. There was an inverse relationship between CK and TNNI2 levels and age but no relationship for TNNI1. Of note, a surprising discrepancy between TNNI1 and TNNI2 in patient plasma may have implications for the interpretation of elevated muscle protein levels in BMD, DMD and other dystrophinopathies.

This is the first cross-sectional, retrospective study to describe differences between fast and slow skeletal muscle fiber biomarkers in BMD and DMD patient plasma. Findings of differential troponin levels is consistent with previous studies of muscle injury after eccentric exercise in healthy volunteers. This appears to be distinct from muscle injury via sepsis or trauma where both fast and slow TNNI are elevated. Previous studies have demonstrated preferential fast fiber injury in DMD patients. Our data extend these findings to suggest that slow fibers do no not appear to leak muscle proteins in the context of BMD/DMD. The majority of healthy volunteers (83%) had TNNI2 levels below the lower level of detection of the ELISA (