BridgeBio's Attruby Shows Potential to Reverse Cardiac Damage in ATTR-CM at ESC Congress

BridgeBio Pharma (BBIO) presented long-term data at the ESC Congress 2026 showing its drug Attruby (acoramidis) is the first therapy to demonstrate potential reversal of cardiac structural disease in transthyretin amyloid cardiomyopathy (ATTR-CM), a progressive and fatal heart condition. The findings were simultaneously published in the European Journal of Heart Failure, and BridgeBio announced the data in an August 30 press release. BridgeBio shares closed at $76.59.

The 42-month cardiac magnetic resonance imaging (CMR) data from the Phase 3 ATTRibute-CM open-label extension showed that 54% of acoramidis-treated patients had clinically meaningful improvement in left ventricular systolic function at Month 30 versus 20% on placebo. At Month 42, 53% of patients receiving continuous acoramidis maintained that improvement, and 46% showed improvement in left ventricular mass index, indicating favorable structural remodeling of the heart. Both metrics were more than double the proportion observed in a natural history cohort.

This matters because the current standard of care, Pfizer’s tafamidis (Vyndamax), is positioned as slowing or stabilizing ATTR-CM. A credible reversal signal, where the heart actually gets better rather than just not getting worse, would reframe the treatment goal and give Attruby a genuine differentiation lever in a market projected to exceed $10 billion. Acoramidis is a near-complete transthyretin stabilizer, binding to at least 90% of TTR protein to prevent the amyloid fibril formation that damages heart tissue.

The signal comes with an important caveat: it is drawn from a completer analysis of patients who survived and stayed in the trial for 42 months. That introduces survivor bias. The open-label extension has no placebo control at that time point, and all-cause mortality in the continuous-acoramidis arm was approximately 30%. Those are not unusual numbers for ATTR-CM, but they temper the “reversal” framing. The most rigorously controlled signal in the dataset is the 65 additional days alive and out of hospital by Month 36 versus placebo, a finding that came from the randomized, placebo-controlled portion of the trial.

BridgeBio is not waiting for confirmation. It dosed the first patient in ASCEND-ATTR, a Phase 3b/4 study designed to determine whether long-term acoramidis treatment produces sustained improvement in cardiac structure, function, and amyloid burden. That trial will provide the randomized evidence the completer analysis cannot. Additional data is expected at the Heart Failure Society of America meeting in October.

What to watch next: the ASCEND-ATTR readout and whether the reversal narrative shifts prescribing behavior away from tafamidis in the near term. Attruby generated $222.4 million in US revenue in Q2 2026. For more on BridgeBio’s commercial trajectory, see our Attruby post-approval launch analysis.

What It Means for the Trade

The reversal claim is the most commercially potent sentence in the ATTR-CM market, and it is worth separating what the data supports from what the launch team will say. Pfizer positions tafamidis as stabilization — slow the decline, don’t expect improvement. If acoramidis can credibly claim that a majority of treated patients improve on cardiac function and structure — 54% improving LV systolic function at Month 30 versus 20% on placebo, with 46% showing LV mass index improvement at Month 42 — the treatment goal in this disease changes from “manage decline” to “expect recovery.” That is a label-adjacent narrative that moves prescribing decisions, because cardiologists who believed the best available therapy merely slowed the clock have a reason to reassess every diagnosed patient. At $222.4 million in Q2 U.S. revenue, Attruby is still early in its launch curve, and a reversal narrative is exactly the kind of message that accelerates it.

The disciplined read of the data itself: this is a completer analysis from an open-label extension, which is the weakest vantage point a company can publish from, and BridgeBio’s own framing is honest about it. The patients measured at 42 months are the ones who survived and stayed on drug — approximately 30% all-cause mortality in the continuous-acoramidis arm means the analysis population is selected for tolerance and resilience. The 20% placebo-arm improvers complicate the story too: some LV recovery happens in this disease regardless of therapy, which is why the natural-history cohort comparison matters but cannot substitute for randomized evidence. The number to anchor on is the randomized portion’s finding: 65 additional days alive and out of hospital at Month 36 versus placebo. That result carries the statistical weight; the CMR data is the narrative built on top of it.

Mechanism and Market Context

The mechanistic case for why near-complete TTR stabilization could plausibly reverse cardiac structure is real. Amyloid infiltration is a deposition disease: if you stop new fibril formation almost entirely — acoramidis binds at least 90% of circulating TTR — the heart’s own clearance mechanisms get a chance to work against a static deposit rather than a growing one, and myocardial function can improve as amyloid burden eases. CMR is the right instrument to see this, and the LV mass index improvement at Month 42 is the structural version of the story. Tafamidis, the incumbent, is a somewhat less complete stabilizer, which is the mechanistic basis for the differentiation claim — a difference that shows up in TTR stabilization rates and now, if ASCEND-ATTR confirms it, in structural outcomes.

The market math explains why the market cap cares. ATTR-CM is projected to exceed $10 billion, the diagnosis rate is climbing as cardiologists learn to distinguish it from hypertrophic cardiomyopathy, and the first credible “reversal” claim in a two-horse market tends to concentrate share in a way that safety-or-convenience differentiators cannot. Acoramidis’s near-complete stabilization is a mechanistic argument tafamidis cannot copy — Pfizer’s molecule is what it is.

Risks and What Could Go Wrong

1. ASCEND-ATTR, the Phase 3b/4 designed to test sustained structural improvement with randomized evidence, reads out ambiguous — the reversal narrative deflates and the launch message reverts to “at least as good as tafamidis.”
2. Pfizer counters with its own long-term extension imaging data before BridgeBio’s confirmatory trial reads out, muddying the differentiation window.
3. The completer-analysis caveat gets adopted by payers: coverage policy is written on randomized data, and the reversal framing could trigger stricter prior authorization if it outpaces the evidence.
4. Survival remains the unanswered question — stabilization-class drugs ultimately compete on mortality data, and each incremental readout either strengthens or weakens the case.

Position read: BBIO at $76.59 is carrying a real launch, a hot narrative, and a confirmatory trial that will grade it. The trade is to respect the gap between randomized evidence (strong) and extension narrative (promising) — the October HFSA data and ASCEND-ATTR are the checkpoints where the reversal story either hardens into a franchise or stays a conference talking point.