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With its recent data drop for an oligonucleotide candidate, Dyne Therapeutics signals it may become a frontrunner in this disease space alongside Avidity Biosciences, Lupin and AMO Pharma.
Last month, Dyne Therapeutics announced positive results in a Phase I/II trial of its candidate DYNE-101. The milestone places Dyne among the companies closest to developing a disease-modifying treatment for myotonic dystrophy type 1.
Myotonic dystrophy type 1
(DM1) is a form of muscular dystrophy caused by
DMPK
mutations on chromosome 19. It affects muscles and many organs across multiple systems that depend on muscular activity. Also known as Steinert disease, it is characterized by the inability to relax muscles at will.
DM1 affects 140,000 people in the United States alone, and although there are drugs that address its symptoms, there are no currently approved disease-modifying treatments for the condition. There are, however, more than
two dozen
investigational drugs in development for DM1.
Among the companies looking to fill the unmet need is Dyne, whose DYNE-101 is an antisense oligonucleotide fused with a fragment antibody that binds to the transferrin receptor 1 in muscles.
In the Phase I/II
ACHIEVE trial
, key findings included DMPK RNA level reductions, CASI-22 improvements, early and sustained improvement in myotonia as measured by grip myotonia assessment, and multiple other strength and timed assessments.
The trial utilized a multiple ascending dose cohort to identify 6.8 mg/kg every 8 weeks as the optimal dose for future studies.
Dyne stated in its press release that it plans to initiate a global registrational expansion cohort of the trial to potentially support a submission for FDA Accelerated Approval in the first half of 2026.
Meanwhile,
Avidity Biosciences
is developing AOC 1001, an antibody oligonucleotide conjugate that targets the
DMPK
gene to treat DM1. Also known as del-desiran, this investigational treatment is currently being studied in the
Phase III HARBOR
trial and Avidity has announced plans to submit marketing applications in 2026.
In March 2024, Avidity announced positive long-term del-desiran data from the
Phase II MARINA-OLE
trial showing reversal of disease progression in people living with DM1 across multiple endpoints compared to a matched natural history study population over one year. Those endpoints included grip myotonia assessment, muscle strength and activities of daily living.
According to Avidity, additional data from the ongoing
Phase I/II MARINA
trial for AOC 1001, in which patients were split into placebo-controlled single-dose and multiple ascending dose arms, will be released in the first quarter of this year.
While clinical-stage investigational oligonucleotide-based therapy candidates are catching up, repurposed drugs such as metformin, tideglusib and mexiletine are also undergoing Phase III trials to treat DM1.
Metformin
, a biguanide currently approved for type 2 diabetes mellitus, is currently slated for
Phase III
trials in DM1. In previous
Phase II
trials, metformin increased the 6-minute walking distance for DM1 patients versus placebo.
While it has positive benefits ranging from anticancer effects to cardiovascular protection to neuroprotection, metformin is also associated with adverse effects such as gastrointestinal discomfort and lactic acidosis in high doses.
Another approach is
AMO Pharma
’s tideglusib (also known as AMO-02), a glycogen synthase kinase 3 beta inhibitor currently in Phase III clinical trials.
Despite not reaching its primary endpoint in the
Phase II/III REACH-CDM
trial due to a strong placebo effect, tideglusib had achieved clinically and statistically significant benefits in various functional and objective assessments as of May 2024. As a result, after meeting with the FDA, AMO Pharma is forging ahead with a
Phase III
trial of tideglusib.
Elsewhere,
Lupin
is working on repurposing mexiletine, a class I antiarrhythmic drug that is currently in Phase III trials for DM1. In contrast to previous trials that used mexiletine capsules for immediate-release effects, Lupin intends to use mexiletine granules for prolonged-release oral suspension formulations for its Phase III
HERCULES
and
ATLAS
trials.
Like tideglusib, mexiletine reached Phase III despite less-than-stellar mid-stage results. In its case,
Phase II
trial data demonstrated no significant change in 6-minute walk distance at 6 months for patients on mexiletine capsules compared to placebo.
Also worthy of mention is ARTHex. While clinical data is scant for
the
company’s ATX-01, it was enrolling patients into its
Phase I/IIa ArthemiR
trial as of October 2024. The drug is based on microRNA technology.
As progress currently stands, antibody-oligonucleotide conjugates appear to be more effective at targeting the genetic source of DM1 and have a more convincing mechanism of action than small molecules and repurposed drugs.
However, even though genetic therapies are advancing quickly, the DM1 space is risky. Consider that Ionis Pharmaceuticals stopped working on its antisense compound
IONIS-DMPK-2.5Rx
in January 2017 after failing to achieve adequate concentration levels in muscles in Phase I/II trials.
If all goes well in the late-stage gene therapy space for DM1, expect new treatments to hit the market within the next three to four years at the earliest.