Pharma & R&D

Dyne, Sarepta Shares Tumble After Novartis Muscle-Disease Drug Trial Failure

By Intent.Health Team • September 08, 2026
dyne sarepta shares

What's Happening

Shares of Dyne Therapeutics and Sarepta Therapeutics fell sharply on September 8 after Novartis said an experimental treatment for a muscle-wasting disorder had failed to meet the main goal of a late-stage clinical trial.

The setback raised concerns among investors about whether similar approaches can succeed in treating myotonic dystrophy type 1 (DM1), a rare genetic disorder for which there are currently no approved treatments. Dyne's shares fell nearly 18%, while Sarepta's dropped more than 9% and PepGen's fell more than 5%. Novartis shares also fell 10.9% on the Swiss exchange. (Reuters)

The reaction was particularly strong for Dyne because its experimental drug, DYNE-101, is being tested using the same type of clinical endpoint that Novartis's drug failed to improve.

Novartis' Drug Failed Its Main Trial Goal

The treatment was being tested in myotonic dystrophy type 1

Novartis said its experimental drug, del-desiran, failed to show a statistically significant improvement over placebo on video hand opening time, the primary endpoint of its late-stage study. (Reuters)

Video hand opening time measures how quickly a person's hand relaxes after they squeeze it.

That measurement is particularly relevant in DM1 because the disease causes myotonia, in which muscles have difficulty relaxing after contraction.

The result means the trial did not demonstrate the required statistically significant improvement on one of its most important measures of treatment effectiveness.

Why the Failure Is So Important for the Muscle-Disease Field

DM1 is notoriously difficult to treat

Myotonic dystrophy type 1 is a genetic disorder that causes progressive muscle weakness and delayed muscle relaxation. (Reuters)

There are currently no approved treatments for the underlying disease.

Drug development has also been unusually difficult.

Several pharmaceutical companies have abandoned or shelved DM1 programs over the past decade, including Biogen, according to Reuters. (Reuters)

That history means each late-stage failure carries significance well beyond one individual company.

A successful drug could potentially establish an important new treatment category. A failure, by contrast, raises questions about whether particular biological approaches or clinical strategies can work at all.

Dyne Was Hit Particularly Hard

DYNE-101 uses the same key endpoint

The market reaction was strongest for Dyne because its candidate DYNE-101 is also being developed for DM1 and uses video hand opening time as a key trial goal. (Reuters)

Investors therefore immediately questioned whether the same endpoint could fail again in Dyne's study.

Cantor Fitzgerald analyst Eric Schmidt said Novartis' result makes Dyne's own trial "much more risky." (Reuters)

That does not mean DYNE-101 will necessarily fail.

Two drugs can target the same disease but differ in their molecular mechanisms, delivery methods, potency and clinical effects.

However, the Novartis outcome has clearly increased perceived risk around the entire development area.

Novartis' $12 Billion Acquisition Is Now Under Scrutiny

The drug came through the Avidity acquisition

Novartis acquired the drug through its $12 billion acquisition of Avidity Biosciences. (Reuters)

The failed trial therefore has implications for how investors view not only the drug but also the strategic value of that acquisition.

Oppenheimer analyst Kostas Biliouris described the setback as a "$12 billion disappointment," reflecting the size of the deal that brought the program into Novartis. (Reuters)

The failure does not necessarily mean Novartis has lost the full economic value of the acquisition. Avidity's broader platform and other programs remain relevant.

But the trial outcome reduces confidence in one of the assets that supported the acquisition rationale.

Novartis Has Not Abandoned the Drug Yet

The company is reviewing the full dataset

Novartis did not immediately disclose detailed numerical trial results.

Instead, the company said it is evaluating the full dataset and plans to engage with health authorities to determine the most appropriate next steps for del-desiran. (Reuters)

That leaves open several possibilities.

The company could determine that another aspect of the data supports continued development, potentially with a modified study design or a different regulatory strategy.

Or it could conclude that the current approach does not provide a viable path forward.

Until the full dataset is evaluated, the ultimate fate of del-desiran remains uncertain.

Researchers Are Asking Whether the Endpoint or the Drug Mechanism Failed

One failure can have multiple explanations

The biggest scientific question now is whether Novartis failed because of the specific clinical endpoint, or because the underlying biological mechanism does not work well enough.

H.C. Wainwright analyst Ananda Ghosh said the central question is whether the result represents an "endpoint miss" or a more fundamental failure of the drug's mechanism. (Reuters)

That distinction is crucial.

If the problem is mainly the endpoint, other DM1 therapies using different measurements could still succeed.

If the underlying biological approach itself is ineffective, developers using similar strategies could face much greater obstacles.

Sarepta Is Also Affected

Its program is at an earlier stage

Sarepta is developing SRP-1003, an experimental small interfering RNA therapy for type 1 myotonic dystrophy.

The program is currently in an early-stage clinical trial. (Reuters)

Because Sarepta's program is less advanced, its development path has more time to incorporate lessons from Novartis' result.

But the stock-market reaction shows that investors already see a greater risk around the broader DM1 treatment space.

PepGen Shares Also Fell

PepGen is another company developing a treatment for myotonic dystrophy, and its shares fell more than 5% following the Novartis announcement. (Reuters)

The decline shows that investors interpreted the trial failure as a sector-level signal, not simply an isolated problem with Novartis' particular drug.

For small biotechnology companies, these sector-wide shifts can matter significantly because their valuations often depend heavily on expectations surrounding one or two clinical programs.

Biogen's Earlier Exit Shows How Difficult the Disease Is

The DM1 field has already seen companies step away after struggling to produce viable treatments.

Reuters noted that Biogen was among companies that abandoned or shelved programs for the disorder over the last decade. (Reuters)

That history increases the significance of Novartis' result.

When a disease already has a record of clinical-development failures, a late-stage miss can make investors question whether the remaining programs face the same fundamental challenges.

Dyne Plans to Release More Data

One-year results are coming this month

Despite the market reaction, Dyne has not suggested that Novartis' failure means DYNE-101 will not work.

The company plans to present additional one-year data at medical conferences later in September. (Reuters)

Those results could become important because they may provide more information about whether DYNE-101 produces a clinically meaningful effect and whether the treatment's impact differs from what was seen with del-desiran.

Investors will likely scrutinize the data particularly closely because of the overlap in trial endpoints.

The Problem Is Bigger Than One Drug

There are very few treatment options

DM1 affects multiple aspects of muscle function and can progressively worsen over time.

The absence of an approved treatment for the underlying disorder means patients and clinicians have limited disease-specific options.

That creates substantial unmet medical need, but it also makes the drug-development challenge more difficult.

Companies are trying to demonstrate meaningful benefits in a rare, progressive disease where clinical outcomes can be complicated and where relatively small patient populations limit the amount of data that can be collected.

Why Rare-Disease Clinical Trials Can Be Difficult

Patient populations are small

Rare diseases often involve relatively small patient populations.

That can make recruitment harder and can limit the statistical power available to detect treatment differences.

When a trial uses a sensitive but relatively narrow endpoint, a drug can potentially show biological activity without reaching statistical significance on the designated primary measure.

That does not guarantee that the treatment works, but it underscores why trial design is particularly important in rare-disease development.

Investor Reactions Are Reflecting More Than the Trial Result

The sharp share-price movements show how heavily biotechnology valuations depend on clinical milestones.

For Dyne, a nearly 18% decline in one day represents a significant repricing based largely on concerns about another company's trial. (Reuters)

That illustrates the interconnected nature of rare-disease biotech investing.

Companies working in the same therapeutic area often have similar scientific assumptions, patient populations and clinical endpoints. As a result, one company's failure can immediately affect the perceived probability of success for its competitors.

The Setback Could Change Development Strategies

The industry may now reassess how DM1 trials are designed.

Companies could examine whether different endpoints, longer follow-up periods or alternative measures of patient function provide better evidence of benefit.

Regulators may also receive questions about how best to evaluate therapies in a disease where measurable functional improvements can be difficult to capture.

The ultimate impact will depend on what additional information comes from Novartis and from other programs.

Why This Matters

The Novartis failure is important because DM1 has no approved disease-modifying treatment and several companies are trying to solve the same difficult problem. (Reuters)

The immediate financial impact is visible in the share-price declines at Dyne, Sarepta and PepGen.

But the larger significance is scientific.

Developers now need to determine whether Novartis' result represents a problem with one particular drug, one particular endpoint or a broader weakness in the therapeutic strategy being pursued across the field.

That distinction could determine whether the next generation of DM1 medicines moves forward confidently or faces a much more cautious development environment.

Looking Ahead

The next important event will be Dyne's presentation of additional one-year DYNE-101 data later this month. (Reuters)

Those results could either reassure investors that Dyne's program is meaningfully different or reinforce concerns raised by the Novartis failure.

For Novartis, the next step is a deeper review of the del-desiran dataset and discussions with health regulators about the drug's future development.

For Sarepta and PepGen, the setback provides an opportunity to reassess their own clinical strategies before reaching later stages of development.

The field now has a critical question to answer: was Novartis' failure a failure of one drug, or a warning for the broader approach to treating myotonic dystrophy type 1?

Key Takeaways

What This Means for Healthcare Marketers

This story is a strong example of how one clinical event can immediately change the market intelligence around an entire therapeutic category.

For companies operating in rare disease, the most important signals are not limited to their own clinical programs. A competitor's trial result can change physician expectations, investor confidence, partnership interest and the perceived attractiveness of an entire disease area.

For healthcare marketers and commercial teams, this means tracking competitor trials, clinical endpoints, regulatory decisions and investor reactions alongside direct demand signals.

In rare disease especially, a single late-stage result can rapidly reshape the competitive landscape before any product reaches the market.