People living with mixed-phenotype transthyretin amyloid cardiomyopathy (ATTR-CM) who were treated with tafamidis lived longer, had fewer heart-related hospital stays and fewer deaths compared to those who didn’t take the medication, according to a recent study published in the journal Cardiology and Therapy.
ATTR amyloidosis happens when a protein called transthyretin (TTR) doesn’t fold the way it should and forms sticky clumps (called amyloid fibrils) that build up in the heart, nerves and other organs. Some people mainly have heart issues, some have nerve problems, and others have a mix of both — these mixed cases are called “mixed-phenotype ATTR-CM.”
Tafamidis helps by keeping the TTR protein stable and slowing down these harmful amyloid buildups. It’s already approved for treating solely heart-related ATTR-CM, but there haven’t been many real-world studies showing how well tafamidis works for people with mixed-phenotype ATTR-CM.
A global patient registry called the Transthyretin Amyloidosis Outcomes Survey (THAOS), which wrapped up in 2023, followed over 6,700 people with ATTR amyloidosis across 33 countries. In a new analysis of the registry data, researchers focused on patients with mixed-phenotype ATTR-CM and compared outcomes between the 116 patients who were on tafamidis and the 223 patients who were not.
After about 2.5 years, people with mixed-phenotype ATTR-CM on tafamidis were more likely to still be alive — about 82% were still living, versus 75% of those not taking it. For those with wild-type ATTR-CM (the form of the disease caused by aging), tafamidis made an even bigger difference: about 84% were alive compared to 49% without it. Patients taking tafamidis also spent less time in the hospital for heart-related issues, with fewer visits and shorter stays. They did have slightly more hospital visits overall, but tafamidis users had fewer deaths (11% vs 18%).
There weren’t any new safety concerns with tafamidis, and very few people — less than 5% — stopped taking it because of side effects.
Read more about treatment and care for ATTR-CM
“These data parallel recent results for patients with predominantly cardiac ATTR-CM” and “are consistent with long-term safety and effectiveness of tafamidis in real-world patients with mixed-phenotype ATTR-CM,” the researchers said.
However, there are limits to what this study can show: it wasn’t a controlled trial (i.e. the researchers didn’t compare to a group of patients taking a placebo), follow-up time was relatively short (approximately 1 year) and there were differences between the groups that could affect the results. The smaller numbers in some subgroups also make it hard to draw firm conclusions.
Even so, the findings provide evidence that tafamidis offers real benefits for people dealing with mixed-phenotype ATTR-CM, while highlighting the need for further research.
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