Novartis' Avidity-Acquired DM1 Drug Del-Desiran Fails Phase 3 HARBOR Trial
- Del-desiran (delpacibart etedesiran), the antibody-oligonucleotide conjugate (AOC) Novartis picked up through its roughly $12B acquisition of Avidity Biosciences, failed to separate from placebo on the primary endpoint of the Phase 3 HARBOR trial.
- The 159-patient trial tested del-desiran against placebo in adults with myotonic dystrophy type 1 (DM1), a progressive muscle-wasting disease with no approved treatments.
- The primary endpoint, change in video hand opening time (vHOT) over 54 weeks, did not show a statistically significant improvement over placebo.
- Novartis said secondary and exploratory endpoints showed some evidence of clinical activity, and the company is reviewing the full dataset and plans to engage regulators on a path forward.
- Endpoints News framed the miss as Novartis' second major late-stage trial disappointment within days (following a setback for its Lp(a) drug pelacarsen), reporting that Novartis shares sank roughly 10% on the news.
The AOC platform itself isn't dead — secondary and exploratory signals suggest the biology worked, just not enough on this endpoint — but a primary miss on the lead asset from a $12B acquisition is about the worst possible first data readout for validating a new modality. Novartis bought Avidity for the platform, not just del-desiran, so the real question is whether this de-risks or re-risks the rest of the inherited AOC pipeline (cardiac, muscular dystrophy programs). Pair it with pelacarsen's stumble the same week and this reads less like bad luck than a pattern: aggressive, high-multiple platform bets hitting rocky Phase 3 data almost immediately. That's a harder story to sell investors than either miss alone, and it may cool appetite for the next big platform acquisition — Novartis' or anyone else's.
Updated: Novartis sinks after second disastrous trial failure, this time of Avidity-acquired drug ↗