BridgeBio's Attruby nears blockbuster status as ATTR market tilts toward stabilizers

BridgeBio Pharma (BBIO) is closing in on blockbuster territory with its transthyretin amyloidosis drug Attruby, after second-quarter US sales of $222mn beat Wall Street consensus by six per cent, prompting Jefferies analysts to forecast the drug could surpass $1bn in annual global sales this year.

The strong performance contrasts with a disappointing quarter for Alnylam Pharmaceuticals (ALNY), whose rival silencer drug Amvuttra generated $1.01bn in quarterly revenue — missing analyst projections by four per cent despite delivering 106 per cent year-over-year growth. Alnylam shares fell sharply on the miss.

The divergence comes as the two companies increasingly compete for the same pool of first-line ATTR-cardiomyopathy patients, with the broader debate over silencer versus stabilizer therapies tilting in BridgeBio's favor following the phase three failure of Wainua, a silencer drug developed by AstraZeneca (AZN) and Ionis Pharmaceuticals (IONS), in the CARDIO-TTRansform trial.

BridgeBio chief executive Neil Kumar said on the company's earnings call that the market was shaping up to be "a stabilizer-first market." He noted that the overall ATTR-cardiomyopathy market grew 19 per cent in the second quarter, which he described as substantially outstripping growth seen over the prior three quarters, with stabilizers dominating share among front-line patients.

Jefferies analysts, writing ahead of the earnings release, noted that in the CARDIO-TTRansform trial, 57 per cent of patients in each arm were already on a stabilizer at baseline, with a further 24 per cent initiating one during the trial. The analysts concluded that the failure suggests adding a silencer to a stabilizer regimen offers no meaningful incremental benefit.

BridgeBio had previously targeted 30 to 40 per cent of the overall ATTR-cardiomyopathy market — a goal it equates to more than $4bn in peak sales. The company said it would update that guidance after reviewing detailed CARDIO-TTRansform results, which are scheduled to be presented at the European Society of Cardiology Congress in Munich later this month. In Europe, Attruby is marketed as Beyonttra by Bayer, which has not broken out specific sales figures.