AstraZeneca eplontersen ATTR-CM trial fails as stabilizers dominate background therapy

The CARDIO-TTRansform study enrolled patients with transthyretin cardiomyopathy and randomized them to eplontersen or placebo on top of standard care. Most participants entered already taking oral stabilizers, which prior NEJM data showed reduce mortality and hospitalizations. The silencer arm produced no incremental improvement on the primary composite endpoint of cardiovascular death or heart-failure events, collapsing the trial and prompting questions about whether injectable silencers add value once stabilizers are in use.

This outcome aligns with mechanistic differences: stabilizers prevent tetramer dissociation while silencers reduce hepatic transthyretin production. Real-world registries indicate stabilizer uptake reached 60-70% by 2025, creating a high bar for add-on agents. The design did not pre-specify a stabilizer-naïve subgroup large enough to test eplontersen monotherapy, limiting causal inference about silencer efficacy in untreated patients.

Analysts now project accelerated uptake of BridgeBio's acoramidis and Alnylam's vutrisiran only in stabilizer-intolerant cases. Regulators may require future ATTR-CM trials to stratify by background therapy or enrich for untreated cohorts. Ethical concerns arise over exposing participants to injectable agents when oral options already confer substantial benefit, underscoring the need for adaptive designs that reflect evolving standards of care.

Next steps include pooled analyses of silencer trials restricted to stabilizer-naïve patients and potential label revisions for existing ATTR therapies.