I read AstraZeneca’s July trial update twice because the numbers didn’t match the hype. Wainua, the antisense drug AstraZeneca and Ionis already sell for hereditary ATTR-PN, missed the primary endpoint in its Phase 3 CARDIO-TTRansform trial in patients with ATTR-CM.
That’s the same misfolded transthyretin protein, just parked in the heart instead of peripheral nerves. Old yardstick: silence the protein, wherever it clumps, and the clinical benefit follows. New yardstick, after this trial: mechanism doesn’t travel across organs the way sponsors assumed. Analysts don’t expect a CM filing now.
The failure doesn’t sit still. Alnylam’s nucresiran uses the same RNA-silencing approach and now carries an open question about whether suppressing transthyretin is enough without also targeting deposited amyloid. Intellia’s gene-editing candidate nex-z faces its own credibility gap: the FDA slapped a clinical hold on both Phase 3 MAGNITUDE trials in October 2025 after a Grade 4 liver enzyme spike led to a patient hospitalization. The hold has since lifted.
BridgeBio’s Attruby, a stabilizer rather than a silencer, is the clean winner here. Its ATTRibute-CM follow-on data showed a statistically significant 34% cut in cardiovascular hospitalizations versus Pfizer’s tafamidis, though it’s an indirect comparison, not a head-to-head trial.
AstraZeneca still has its own backup, the antibody depleter cliramitug, running Phase 3 through mid-2027. Worth tracking which mechanism the field bets on next.
— Rebecca Lauren