Dyne Therapeutics Presents New Preclinical Data from its Myotonic Dystrophy Type 1 Program During American Society of Gene & Cell Therapy Annual Meeting Demonstrating Sustained Knockdown of Toxic Human Nuclear DMPK RNA

- Robust Reduction in DMPK RNA in Multiple Muscles at Four Weeks in Novel In Vivo Model Developed by Dyne; Additional In Vitro Data Support Advancement of Lead DM1 Candidate -

- DM1 Program One of Three IND Submissions Planned Between Q4 2021 and Q4 2022 -

- Company to host webcast today at 4:00 p.m. ET -

WALTHAM, Mass., May 14, 2021 (GLOBE NEWSWIRE) -- Dyne Therapeutics, Inc. (Nasdaq: DYN), a muscle disease company focused on advancing innovative life-transforming therapeutics for people living with genetically driven diseases, is presenting new preclinical data from its myotonic dystrophy type 1 (DM1) program during the American Society of Gene & Cell Therapy (ASGCT) 24^th Annual Meeting today, including results demonstrating sustained knockdown of toxic human nuclear DMPK RNA, the genetic basis of the disease.

“We are excited to present these data at ASGCT, which continue to validate our FORCE platform and our approach to developing a potential therapy for people living with DM1. In particular, we are seeing impressive reductions in toxic human nuclear DMPK RNA with twice the duration and at half the dose compared to the data we reported in January of this year in the same model,” said Romesh Subramanian, Ph.D., chief scientific officer of Dyne. “This reinforces the advantage of the FORCE platform and its potential to enable targeted delivery of therapeutic oligonucleotides to muscle and supports our goal of offering monthly or less frequent dosing. We believe the preclinical hTfR1/DMSXL model that we developed establishes a new standard to evaluate pharmacodynamics in DM1 and has the potential for translation to human disease.”

Dyne’s lead DM1 candidate consists of an antigen-binding fragment antibody (Fab) conjugated to an antisense oligonucleotide (ASO) to enable targeted muscle tissue delivery to reduce accumulation of toxic DMPK RNA in the nucleus, release splicing proteins, allow normal mRNA processing and translation of normal proteins, and potentially stop or reverse the disease. To assess the ability of its lead DM1 candidate to reduce toxic human nuclear DMPK RNA, Dyne developed an innovative hTfR1/DMSXL mouse model that expresses the human TfR1 and carries a human DMPK gene that represents a severe DM1 phenotype with more than 1,000 CTG repeats. In January 2021, Dyne reported data showing that two doses (2 x 10 mg/kg) of its lead DM1 candidate resulted in significant toxic human nuclear DMPK knockdown at 14 days. New data being presented at ASGCT are consistent with these findings, with the candidate demonstrating an approximately 40 percent reduction in DMPK heart foci at 14 days.