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C2 - Epigenetic Editing and RNA Editing

700: EPI-321: A Novel Epigenetic Gene Therapy for FSHD Targeting D4Z4 Epigenome

Type: Poster Session

Poster Board Number: 700
Presentation Details
Session Title: Wednesday Posters: Epigenetic Editing and RNA Editing

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common types of adult muscular dystrophies with an annual incidence rate of about 1 in 10,000, affecting approximately 1 million people globally. With no cure available, current therapeutic strategies only involve managing symptoms to improve overall quality of life. Misexpression of disease-causing protein, DUX4, in muscle leads to slow and progressive muscle degeneration through activation of apoptotic and other downstream pathways. DUX4 gene is encoded at the distal region 4q35 chromosome from D4Z4 macrosatellite array. In FSHD patients, the D4Z4 marosatellite array is hypomethylated, leading to stochastic and transient DUX4 expression, which makes the development of cure challenging. At Epic-Bio, we leverage our proprietary Gene Expression Modulation System (GEMS) platform to develop a treatment for FSHD that targets the D4Z4 epigenome and permanently suppress DUX4 expression. Our product, EPI-321 is a single vector AAV serotype rh74 encoding an ultracompact, catalytically inactive Cas protein (effector) fused to gene-suppressing modulators, under the expression of the muscle specific promoter, CK8e, and a guide RNA targeting D4Z4 locus. Our preclinical studies showed that EPI-321 administration leads to robust and dose-dependent suppression of DUX4 and DUX4-downstream gene expression in ten different FSHD patient-derived immortalized and primary myoblasts in vitro, irrespective of the number of D4Z4 repeats, and showed antiapoptotic activity as measured by Caspase 3/7 staining. Mechanistically, EPI-321 showed re-methylation of the D4Z4 target locus leading to suppression of DUX4 expression. Further, in vivo evaluation of EPI-321 in humanized FSHD mouse model showed a dose-dependent suppression of DUX4-pathway at the mRNA and protein level, and antiapoptotic activity in muscle tissues. Additionally, 3D engineered human muscle tissue (3D EMT) using FSHD patient-derived immortalized myoblasts transduced by EPI-321 resulted in efficient suppression of DUX4 and DUX4-pathway genes up to 46 days and demonstrated significant dose dependent improvement in muscle contractility, shown by increased twitch and tetanic force post-treatment. Taken together, our findings provide robust evidence for EPI-321 as a potential single-administration gene therapy for treating FSHD by permanently suppressing the pathogenic DUX4 gene through epigenetic silencing. We intend to submit an Investigational New Drug (IND) application this year and are looking forward to commencing first-in-human trials in 2024.

Plain Language Summary
Facioscapulohumeral muscular dystrophy (FSHD) is a progressive muscle degeneration disorder affecting about 1 million people globally, with no cure available. Epic Bio is developing EPI-321, a potential one-time treatment targeting the root cause of FSHD by addressing the DUX4 gene at the epigenetic level. Unlike other CRISPR-based therapies, EPI-321 doesn't alter the DNA sequence itself. EPI-321 permanently turns off DUX4 gene that is misregulated in FSHD causing it to be inappropriately expressed which leads to muscle degeneration over time. In our experiments at Epic Bio, EPI-321 showed promising results. In muscle cells derived from FSHD patients, it effectively reduced the activity of the harmful DUX4. In humanized mice with FSHD, EPI-321 treatment successfully reached their muscle tissue and also reduced the activity of the DUX4 gene. In addition to reducing the activity of the DUX4 gene, EPI-321 also showed the positive effect of improving muscle strength in our studies.

Alexandra Collin de L'Hortet, Abhinav Adhikari, Siddaraju Boregowda, Hao Zheng, Vishi Agarwal, Andrew Norton, Nalinda Wasala

Epic-Bio, South San Francisco, CA"

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