Three pipeline failures in one week. That is what Novartis handed its shareholders by Tuesday morning, and the market’s response was unambiguous. Shares tumbled about 10% in Zurich after Novartis said del-desiran missed its primary endpoint in the Phase III HARBOR study, wiping out roughly 24 billion Swiss francs in market value by the afternoon. The proximate cause was del-desiran. The deeper question is one portfolio managers have been reluctant to answer plainly: when Novartis paid $12 billion for Avidity Biosciences, was it buying three drugs, or a delivery platform? Tuesday’s result forces a reckoning either way.
What Happened
The global Phase III HARBOR study, which enrolled about 159 patients with myotonic dystrophy type 1 and ran for 54 weeks, came up short of statistical significance on its primary endpoint: video hand opening time. Despite the miss, Novartis said it saw “evidence of clinical activity” in secondary and exploratory outcomes, but it did not release numerical details alongside the topline update. That caveat is becoming a familiar consolation prize in late-stage pharma failures, and investors have learned to discount it accordingly.
The mechanism had generated real optimism: Phase I/II MARINA results published in the New England Journal of Medicine in February 2026 showed a reduction in DMPK mRNA and improvements across multiple functional measures. The gap between Phase II signals and Phase III confirmation is not new in drug development. But the gap here is particularly costly given what Novartis paid to close it.
Platform Bet or Single-Drug Gamble?
This is the debate that matters. Del-desiran was not just another program in the deal: it was the most advanced asset. Novartis bought Avidity not only for three late-stage programs in rare muscle diseases, but for its antibody-oligonucleotide conjugate platform. The bull case for the acquisition always rested on that platform logic: even if one drug stumbled, the AOC delivery technology would prove its worth across the other two programs and justify the price.
That argument is now under real stress. Reuters reported that Barclays had estimated peak annual sales of $3.1 billion for del-desiran and assigned it a 60% probability of success following positive Phase II data. Vontobel removed roughly $3 billion of risk-adjusted peak sales from its model for del-desiran and cut its Novartis price target to CHF 125. It did not deliver.
That creates a compounding problem: a deal meant to reduce acquisition dependency may instead accelerate it.
The Collateral Damage
The selloff was not contained to Novartis. Sarepta Therapeutics slid 7.6% in pre-open trading after the neuromuscular failure rattled investor confidence across the entire therapeutic class. The failure was particularly pointed for Sarepta because its SRP-1003 is also an siRNA targeting DMPK RNA in DM1, though using a different delivery mechanism than del-desiran. Dyne Therapeutics, with a similar DM1 focus, dropped even harder.
The del-desiran result comes just days after Novartis said pelacarsen failed to reduce the risk of cardiovascular events in a late-stage trial, and after the company temporarily paused screening, randomization and dosing in eight studies of its experimental CAR-T therapy rap-cel following three patient deaths. The one bright spot: Novartis reported positive Phase III topline results for remibrutinib in relapsing multiple sclerosis and said it plans to seek regulatory approval globally.
What Investors Are Missing
The market is pricing del-desiran as a binary failure and moving on. The more consequential question is whether the vHOT endpoint itself was flawed. If variability in the hand myotonia measure is what tripped up the study rather than a fundamental failure of the AOC biology, the platform could still retain value. In that scenario, del-zota in Duchenne muscular dystrophy with exon 44 mutations is the next real referendum on the delivery system, with a BLA filed to the FDA seeking accelerated approval.
Stocks to Watch
Novartis (NVS): Investors had been counting on del-desiran, pelacarsen, and remibrutinib to drive growth as Novartis faces patent expiries early in the next decade. Two of the three have now failed. Remibrutinib carries the near-term growth story almost alone.
Sarepta Therapeutics (SRPT): Marked down by association, not by its own data. The selloff reflects class risk, not a Sarepta-specific failure. That distinction matters for investors willing to hold through noise.
Ionis Pharmaceuticals (IONS): Ionis stock also fell following the Novartis week of failures, as the company has a long-running partnership with Novartis tied to pelacarsen. Its own pipeline is independent, but the sentiment overhang is real.
Roche: Competes in neuromuscular disease and stands to benefit if investor appetite for the class recovers around programs with cleaner endpoint designs. Worth watching as a counterweight to the AOC platform questions now circulating.
