Researchers say the drug tafamidis has shown in clinical trials that it can lessen the effects of a heart condition known as ATTR-CM.

There’s a form of heart failure that may be more common than thought. And there’s no treatment for it.

But an existing drug just passed a critical step and may soon be approved to treat this overlooked condition.

On average, people live three to five years after getting a diagnosis of transthyretin amyloid cardiomyopathy, or ATTR-CM.

It’s a rare disease in which certain proteins gradually build up in the tissues of the heart, eventually making it more difficult for the heart to pump blood to the rest of the body.

It can eventually lead to heart failure.

However, in a clinical trial whose results were published last week, a drug called tafamidis lessened some of the worst effects of ATTR-CM.

Researchers reported that the chance of death was reduced by 30 percent, heart-related hospitalizations were reduced by 32 percent, and declines in quality of life were slowed for people who received the drug versus those who received a placebo.

“This is a fascinating set of discoveries, really is breakthrough science,” Dr. Clyde Yancy, chief of cardiology at Northwestern University’s Feinberg School of Medicine in Chicago, told Healthline. “The impact on patients is uncertain because this isn’t a terribly common condition, but it is a condition of great consequences.”

The most important thing, Yancy says, is that it’s a step forward toward treating a condition that had been considered untreatable.

“Even though the scope is a small number of patients at present, it could reach a large number of patients down the road,” he said.

A 2017 estimate put the percentage of people in the United States who have ATTR-CM at 0.001 percent. The percentage is slightly higher among men over age 60.

With this disease, a protein called transthyretin unravels, travels to the heart, and clumps together there in deposits.

That unraveling and accumulation can be hereditary or caused by aging.

Those amyloid deposits grow and eventually interfere with heart function.

But tafamidis was found to prevent those proteins from coming apart and accumulating in the heart.

It’s administered orally, Dr. Mathew Maurer, a Columbia University cardiologist who worked on the clinical trials, told Healthline. He says he doesn’t know what the drug might cost.

Maurer did think new technologies will be able to catch ATTR-CM earlier, which might reveal that the condition may not be quite as rare as it’s currently thought to be.

That 2017 estimate, for instance, found evidence that the frequency of the condition is underestimated and, in part due to aging populations, is likely rising.

Maurer also thinks the disease is underdiagnosed. That’s likely, at least in part, because diagnosis had previously required a biopsy. Now, the disease can be detected with noninvasive imaging, he says.

That rise in frequency has given new urgency to find drugs — and a bigger market for drug manufacturers to try to break into.

In addition to tafamidis, other new drugs are focused on limiting the body’s production of the protein in the first place.

Yancy points to patisiran and inotersen as two drugs under testing that work this way.

“The new drugs that are being developed either prevent the protein from being permanently affixed to the heart or cause them to elude it,” he said. This approach is “not just a breakthrough for amyloid cardiomyopathy — it’s a brand-new way of treating diseases.”

Amyloid deposits like those that build up in the heart under ATTR-CM accumulate in the brain in Alzheimer’s and multiple sclerosis.

Drugs like these might one day be able to treat those conditions.

“This really does reflect a new horizon, some might even say a new frontier,” Yancy said. “This science is now sufficiently robust that it can be used for other diseases where proteins accumulate.”