Novartis del-desiran Trial Failure Sends Stocks Lower
Novartis del-desiran trial failure undercuts the $12 billion Avidity deal rationale and pressures Amgen and healthcare stocks, raising R&D and M&A doubts.
KEY TAKEAWAYS
- The Phase III HARBOR study of del-desiran failed to meet the primary vHOT endpoint.
- The miss undercuts $12 billion Avidity rationale and prompted up to $3-$3.6 billion peak sales cuts.
- Investors reassessed cardiovascular RNA programs, pressuring Amgen's olpasiran outlook.
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Novartis AG’s delpacibart etedesiran (del-desiran) trial failure on Sept. 8, 2026, after the Phase III HARBOR study missed its primary video hand opening time (vHOT) endpoint, prompted a reassessment of the company’s $12 billion Avidity Biosciences acquisition. The setback also pressured peers including Amgen, weighing on healthcare stocks while AI-linked shares held up.
HARBOR Trial Misses Primary Endpoint
Novartis said in a Sept. 8 media release that the global Phase III HARBOR (NCT06411288) study of del-desiran for myotonic dystrophy type 1 (DM1) did not show a statistically significant improvement versus placebo on the primary endpoint of vHOT, a measure of hand myotonia (delayed muscle relaxation). The randomized, double-blind, placebo-controlled trial enrolled about 150 patients, lasted 54 weeks with dosing every eight weeks, and included secondary endpoints such as hand grip strength, quantitative muscle testing total score, the DM1-Activ activities-of-daily-living scale, and the 10-meter walk/run test.
The company reported qualitative evidence of clinical activity on secondary and exploratory analyses and said safety findings were generally consistent with prior data. Novartis added, "Novartis is evaluating the full HARBOR dataset and will engage with health authorities to determine the most appropriate development path for del-desiran."
Setbacks Pressure Peers and Strategy
Earlier, on Sept. 4, Novartis announced topline results from the Lp(a) HORIZON Phase III study of pelacarsen, which failed to meet its primary composite cardiovascular endpoint despite lowering lipoprotein(a) levels. This outcome, combined with a pause of rap-cel autoimmune trials after three patient deaths, makes the del-desiran miss the third major clinical setback for Novartis within about a week.
These setbacks intensified scrutiny of Novartis’ R&D and M&A strategy. The company acquired Avidity Biosciences for $12 billion, with del-desiran as the lead asset. Analysts subsequently cut up to $3–$3.6 billion from peak-sales estimates in some models. One sell-side firm had said del-desiran’s success was necessary to justify the acquisition price.
The weak read-through also pressured peers developing RNA cardiovascular therapies. Investors reassessed Amgen’s olpasiran outlook after the pelacarsen failure, despite a previously cited greater than 65% probability of Phase III success for olpasiran. Broader healthcare and biotech stocks declined while AI-linked shares remained resilient.
"Novartis is evaluating the full HARBOR dataset and will engage with health authorities to determine the most appropriate development path for del-desiran," the company said.
