Shares of Novartis (NVS) fell sharply on Tuesday after the company announced that its most advanced drug candidate from the $12 billion Avidity acquisition failed to meet the primary goal in a late-stage clinical trial. The stock dropped as much as 9.3% in Zurich trading, wiping out roughly CHF22 billion in market capitalization, as investors reassessed the pharmaceutical giant's growth prospects.
The disappointing result came from the Phase III HARBOR study, which tested delpacibart etedesiran (del-desiran) in patients with myotonic dystrophy type 1 (DM1). The drug did not show a statistically significant improvement over placebo on the primary endpoint of video hand opening time, a measure of how quickly patients can release a clenched fist. While Novartis reported "evidence of clinical activity" in secondary endpoints and exploratory analyses, the company did not disclose specific effect sizes, confidence intervals, or p-values, leaving investors with limited clarity.
Market Reaction and Valuation Impact
The market's response was swift and severe. By midday in Zurich, Novartis shares were trading at CHF113.84, down 9.3% from Monday's close of CHF125.46. The stock was also down 13.3% from Friday's close of CHF131.32, reflecting two consecutive pipeline setbacks. In New York, the ADR indicated a 12.1% decline to $140.68 in premarket trading, though such prices can be volatile.
The magnitude of the selloff—equivalent to roughly CHF22.1 billion in lost market value based on the company's 1.901 billion shares outstanding—exceeds the $12 billion purchase price of Avidity, suggesting investors are pricing in a broader loss of confidence in Novartis's pipeline. The failure of del-desiran, which had peak sales forecasts as high as $6 billion, comes just one day after the Phase III Lp(a)HORIZON study of pelacarsen also missed its primary endpoint.
What Went Wrong and What's Next
HARBOR was a 159-patient, 54-week pivotal trial with a one-to-one randomization, testing seven doses of del-desiran against placebo. The primary endpoint was video hand opening time, with key secondary measures including hand grip strength, quantitative muscle testing, and the DM1-Activ daily-living scale. The company had previously targeted a global filing in 2027, but that timeline is now uncertain.
Despite the miss, the scientific rationale behind del-desiran remains intact. The drug uses a muscle-targeting antibody to deliver small interfering RNA that aims to reduce toxic DMPK messenger RNA, the underlying genetic cause of DM1. However, investors had bought into a late-stage asset, not just a mechanism, and without a viable regulatory path, the drug's value in base-case valuations has been significantly reduced.
Avidity's Remaining Portfolio
Novartis still holds other assets from the Avidity deal. Del-zota, for Duchenne muscular dystrophy amenable to exon 44 skipping, has received FDA priority review and could launch in the first half of 2027 if approved. Del-brax, for facioscapulohumeral muscular dystrophy, showed positive Phase I/II biomarker results, with a Phase III readout expected in 2028. The antibody-oligonucleotide conjugate platform also offers potential for future muscle-targeted RNA drugs.
However, these programs are less advanced and harder to value than a fully enrolled Phase III asset. Novartis maintained its 5%–6% sales CAGR outlook for 2025–2030, but this guidance is company-wide and does not clarify how much revenue from del-desiran had been embedded in the original Avidity return assumptions.
Investor Watchpoints
Investors will be watching several key indicators in the coming weeks: the actual treatment effect on video hand opening time, performance on secondary endpoints with multiplicity rules, discussions with health authorities regarding a potential filing path, and any accounting impairments or changes in R&D spending around the acquired program.
The selloff reflects a sharp reduction in del-desiran's probability of success and a wider loss of confidence in Novartis's post-2030 growth bridge. The stock could recover if del-zota wins approval, del-brax moves faster through regulatory channels, and the core portfolio continues to perform. For now, the market is taking a cautious view, and the burden is on Novartis to demonstrate that its pipeline can deliver beyond the patent cliff.
