BridgeBio Pharma has published results from the Phase III ATTRibute-CM trial evaluating acoramidis in patients with transthyretin amyloid cardiomyopathy (ATTR-CM).
The trial results were published, which were published in the New England Journal of Medicine, show a better hierarchal outcome in the acoramidis treatment arm compared to the placebo.
The hierarchical outcome was measured using the Finkelstein and Schoenfeld (FS) test, which measures composite endpoints including mortality, morbidity, and function in the order of clinical importance, and was reported as a win ratio.
The composite endpoints order of priority as part of the primary hierarchal outcome was all-cause mortality (ACM), frequency of cardiovascular-related hospitalization (CVH), change from baseline in N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and change from baseline in 6-minute walk distance (6MWD).
The analysis favoured the treatment arm with a win ratio of 1.8, with 63.7% pairwise comparisons favouring acoramidis and 35.9% favouring placebo. The ACM and CHV outcomes also contributed to the win ratio in favour of acoramidis, with 58% of all pairwise comparisons favouring the treatment.
The overall incidence of adverse events was 98.1% and 97.6% in the treatment and placebo groups, respectively. The incidence of serious adverse events in the treatment and placebo groups was 54.6% and 64.9%, respectively.
A genetic mutation of the gene for transthyretin (TTR) protein causes ATTR, which leads to the production of an abnormal form of the protein causing protein build-up in the organs. ATTR-CM is caused by TTR protein build-up in the heart muscle causing thickening and stiffening of the muscle. This impairs the heart’s ability to function properly and can lead to stroke or death.
Acoramidis is a TTR stabiliser and works by mimicking disease protective action of the TTR-stabilising mutation T119M. The randomised, double-blind placebo-controlled Phase III ATTRibute-CM trial (NCT03860935) evaluated acoramidis in 632 patients with ATTR-CM.
The US-based company had previously reported that patients in the acoramidis treatment arm demonstrated an 81% absolute survival rate and a 0.29 observed mean annual CVH frequency.
BridgeBio submitted the new drug application (NDA) with the US Food and Drug Administration (FDA) on 5 December 2023. The agency has a 60-day filing review period to determine whether the NDA is complete and accepted for review.
The company plans to file additional marketing authorisation applications to global health authorities this year.
ATTR-CM treatment landscape
Multiple companies are developing therapies for ATTR-CM. One of the more clinically advanced therapy programmes includes Alnylam Pharmaceuticals’s Onpattro (patisiran).
The Phase III trial (NCT03997383) for the RNA interference (RNAi) therapy met its primary endpoint but the FDA refused to approve the therapy despite positive results. In October 2023, the agency issued a complete response letter (CRL) stating that the drug “could not be approved in its present form”. Following the CRL, Alnylam stated that it would no longer seek US approval for the therapy in ATTR-CM indication.
Gene therapies are also being developed to treat ATTR-CM. Intellia Therapeutics and Regeneron Pharmaceuticals’ CRISPR/Cas9 genome editing therapy NTLA-2001 is currently in Phase I trial (NCT04601051).
Neurimmune’s monoclonal antibody therapy NI006 demonstrated a positive safety profile in the Phase I trial. NI006 is being developed in partnership with AstraZeneca.
