Novartis Miss in Myotonic Dystrophy Lands on Dyne Therapeutics, Which Built Its Accelerated-Approval Path on the Same Endpoint

by Carter Whitfield · September 8, 2026

Equities Reporter, The SmallCap Signal

Novartis said Tuesday that delpacibart etedesiran, known as del-desiran, did not meet the primary endpoint of its Phase III HARBOR study in myotonic dystrophy type 1, and the read-through travelled straight down the market-capitalization scale to a Boston-area developer that has staked its regulatory strategy on the identical measurement.

According to the Novartis media release, HARBOR was a global, randomized, double-blind, placebo-controlled trial of roughly 150 patients with DM1, dosed every eight weeks over 54 weeks. The primary endpoint was video hand opening time, or vHOT, a measure of how quickly the hand relaxes after squeezing. Novartis said del-desiran did not show a statistically significant improvement against placebo on that measure, though the company said evidence of clinical activity was observed in secondary endpoints and exploratory analyses. Novartis did not disclose numerical results for those secondary measures.

The company said safety findings in HARBOR were generally consistent with previously reported data, and that it is evaluating the full dataset and will engage with health authorities to determine the most appropriate development path for del-desiran. Shreeram Aradhye, the company's president of development and chief medical officer, said in the release that developing therapies for a disease as complex as DM1 remains challenging, that setbacks are part of scientific progress, and that the company remains committed to identifying the most appropriate development path.

That matters well beyond Basel. Del-desiran is one of three antibody oligonucleotide conjugate programs Novartis picked up in its acquisition of Avidity Biosciences, a $12 billion deal announced in October 2025 that formally closed in February 2026, according to BioSpace's Sept. 8 report on the trial update. For small- and mid-cap investors, the relevant question is narrower: what does a vHOT miss say about the next company to run the same test?

Dyne Therapeutics (Nasdaq: DYN) is the clearest answer. In a June 2025 release, Dyne said the FDA had granted Breakthrough Therapy Designation to DYNE-101 for DM1 and that, following a Type C meeting, the agency and the company agreed the next step toward accelerated approval was to submit a revised protocol for the registrational expansion cohort of the ACHIEVE trial with vHOT as the primary endpoint, serving as an intermediate clinical endpoint. The primary measure is change from baseline in middle-finger myotonia by vHOT at six months versus placebo.

Dyne's listed secondary endpoints in that cohort include a composite alternative splicing index known as CASI-22, quantitative muscle testing, the 10-meter walk/run test, a five-times sit-to-stand test, and the Myotonic Dystrophy Health Index patient-reported outcome, all at six months against placebo.

In other words, the endpoint that just failed to separate from placebo in a roughly 150-patient Novartis trial is the endpoint on which Dyne intends to build a U.S. accelerated-approval filing. That is not the same as saying Dyne's drug will fail — the two molecules are different, the dosing is different, and Novartis reported activity on secondary measures it has not quantified. But it does mean the regulatory instrument itself is now carrying a public failure, and that is a distinct risk from ordinary drug risk.

Dyne's timeline is close enough to make the question immediate. In its second-quarter results released July 29, the company said enrollment in the ACHIEVE registrational expansion cohort was completed in June 2026 with 71 participants, that topline data are expected in the first quarter of 2027, and that they are intended to support a potential accelerated-approval submission in the third quarter of 2027.

The same release put Dyne's cash, cash equivalents and marketable securities at $898.5 million as of June 30, 2026, with a runway guided into the second quarter of 2028. Dyne reported a second-quarter net loss of $178.6 million and research and development expense of $152.2 million. The company's other lead asset, DYNE-251 in Duchenne muscular dystrophy, has had its application accepted by the FDA with priority review and carries a PDUFA target action date of Jan. 21, 2027 — a nearer-term event that is unaffected by Tuesday's DM1 news.

Not every read is negative. BioSpace reported Tuesday that Jefferies analysts described Dyne as claiming frontrunner status in DM1 following the HARBOR result, citing what they characterized as stronger tissue penetration and better biodistribution for Dyne's candidate. The same report noted that while the del-desiran failure could carry negative read-through to the broader DM1 field, Dyne retains a path to succeed and potentially produce better data. Oppenheimer, per BioSpace, called the outcome a $12 billion disappointment for Novartis.

The tape did not wait for the nuance. Investrade's mid-morning market summary, timestamped 14:32:49 UTC on Sept. 8 — 10:32 a.m. ET, with the session still open — listed Dyne among the day's laggards at roughly 22 percent lower, alongside Sarepta Therapeutics down a similar amount, and Novartis itself down about 12 percent. Because those figures come from an intraday snapshot, they are levels during a live session, not closing prices, and they may look nothing like where the names finish.

Novartis had a compounding problem: BioSpace reported that Tuesday's DM1 miss followed the Friday failure of pelacarsen, an Lp(a)-lowering therapy that did not significantly reduce cardiovascular risk versus placebo in the Phase III Lp(a)HORIZON study, which is why the Swiss company's move was outsized relative to a single mid-stage-to-late-stage setback in a rare disease.

The narrower lesson for the small-cap side of the neuromuscular complex is about endpoint concentration. When an accelerated-approval pathway is built on a single functional measure that the FDA has accepted as an intermediate clinical endpoint, the first large public test of that measure becomes a shared event for everyone using it. Dyne's first-quarter 2027 readout now carries that weight in a way it did not on Friday.

Risk note: Dyne Therapeutics is a clinical-stage biotechnology company with no approved products and substantial operating losses. Outcomes of clinical trials and regulatory reviews are uncertain, and readouts of this kind can produce large moves in either direction. Nothing here is a recommendation to buy, sell or hold any security.