AstraZeneca’s (NYSE:AZN) rare disease division, Alexion, announced that its experimental treatment anselamimab did not achieve the primary objective in a significant late-stage study targeting patients with a severe and rare cardiac condition, causing the company’s stock to decline on Wednesday.
The Phase III CARES trial revealed that anselamimab failed to demonstrate a statistically significant advantage over placebo in lowering mortality and hospital admissions related to heart complications in patients suffering from advanced light chain (AL) amyloidosis.
The trial’s primary endpoint combined the duration until death from any cause and the frequency of hospitalizations for cardiovascular events.
This study enrolled 406 newly diagnosed individuals from 19 countries, with 281 classified as stage IIIa and 125 as stage IIIb according to the European adaptation of the Mayo 2004 staging criteria.
Participants were randomized in a 2:1 ratio to receive either anselamimab or placebo, alongside standard therapies for the disease. These therapies included cyclophosphamide, bortezomib, dexamethasone, and, in roughly 80% of patients, daratumumab.
Although the primary goal was not met, Alexion highlighted that anselamimab showed a “highly clinically meaningful improvement” in survival rates and cardiovascular-related hospitalizations within a predefined patient subgroup. The company, however, did not disclose detailed subgroup results.
Ashutosh Wechalekar, the trial’s lead investigator and a professor at University College London, stated that the subgroup findings indicate the drug might help by removing damaging protein deposits from organs.
“While the study did not meet the primary endpoint in the overall patient population, results from a pre-defined subgroup suggest that anselamimab… may address a leading cause of organ damage and functional impairment in these patients,” he said in a statement.
Anselamimab targets and clears amyloid fibrils—abnormal protein aggregates that accumulate in organs.
In AL amyloidosis, these misfolded light chain proteins are generated by defective plasma cells in the bone marrow.
If left untreated, they can lead to progressive organ failure, particularly affecting the heart and kidneys, with most patients succumbing to heart-related complications.
Alexion reported that anselamimab was well tolerated, with side effects evenly distributed between the treatment and placebo groups.
All participants were eligible to enter an open-label extension phase, receiving anselamimab alongside standard care for up to 24 months.
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