DYNE-101 achieves durable knockdown of toxic human nuclear DMPK RNA and correction of splicing in the hTfR1/DMSXL mouse model of DM1


Pre-Clinical Research

Poster Number: 144


Stefano Zanotti, Dyne Therapeutics, Tyler Picariello, Dyne Therapeutics, Nelson Hsia, Dyne Therapeutics, Timothy Weeden, Dyne Therapeutics, Ryan Russo, Dyne Therapeutics, Lydia Schlaefke, Dyne Therapeutics, Monica Yao, Dyne Therapeutics, Aiyun Wen, Dyne Therapeutics, Scott Hildebrand, Dyne Therapeutics, John Najim, Dyne Therapeutics, Qifeng Qiu, Dyne Therapeutics, Brendan Quinn, Dyne Therapeutics, John Davis, Dyne Therapeutics, Oxana Beskrovnaya, Dyne Therapeutics

Introduction: Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease caused by the expansion of CUG repeats in the 3’-untranslated region of the dystrophia myotonica protein kinase (DMPK) RNA. The expanded CUG repeats form hairpin-loop structures that sequester splicing regulators into toxic nuclear foci, leading to a spliceopathy that drives DM1 clinical manifestations. Naked antisense oligonucleotides (ASO) designed to knockdown (KD) DMPK have shown promise in preclinical models; however, clinical application has failed because of insufficient delivery to muscle upon systemic administration. The FORCETM platform, consisting of an antigen-binding fragment (Fab) that specifically binds transferrin receptor 1 (TfR1), conjugated to a therapeutic oligonucleotide payload, was designed to overcome these limitations.

Methods: DYNE-101, is a Fab-conjugated gapmer ASO that targets human DMPK. hTfR1/DMSXL mice, a novel model expressing human TfR1 and a human DMPK with >1,000 CUG repeats, received 10 mg/kg ASO equivalent of DYNE-101 or vehicle on days 0 and 7. On day 28, DMPK RNA levels and splicing were assessed in the heart and skeletal muscles, while DMPK foci were assessed in the heart. Non-GLP dose-range finding toxicology studies were conducted in non-human primates (NHPs).

Results: hTfR1/DMSXL mice administered with DYNE-101 exhibited a durable 40 to 49% KD of toxic human DMPK RNA, leading to spicing correction in the heart and skeletal muscle. These effects were accompanied by a 49% DMPK foci reduction in the heart. Analysis of gene expression in nuclear and cytoplasmic fractions provided direct evidence that DYNE-101 reduced accumulation of toxic human DMPK RNA trapped in cell nucleus. DYNE-101 was well tolerated in NHPs after repeat dosing.

Conclusion: These data demonstrate that DYNE-101 targets toxic DMPK in the nucleus, thereby driving splicing correction in cardiac and skeletal muscle with a long-lasting effect. DYNE-101 is well-tolerated in NHP, supporting advancement into the clinic.