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Alnylam’s stock soars by nearly 50 percent on trial results for heart drug

The Cambridge biotech says it will seek approval for the medicine’s use to treat people with an often fatal condition.

An Alnylam scientist at the company's Cambridge headquarters.Alnylam

Alnylam Pharmaceuticals’ share price surged by nearly 50 percent Wednesday after the Cambridge company said its approved drug for a rare nerve condition succeeded in a late-stage trial in patients with an increasingly common heart disorder.

The drug, called Onpattro, was approved in 2018 to treat peripheral nerve disease linked to transthyretin amyloidosis, an inherited disorder that causes misfolded protein to collect in various tissues. An estimated 20,000 to 30,000 people suffer from the condition worldwide, according to Yvonne Greenstreet, Alnylam’s chief executive.

Based on the results of the latest study, Alnylam plans to ask US regulators by the end of the year to approve Onpattro to treat transthyretin amyloid cardiomyopathy, in which the proteins accumulate in the heart. Once considered rare, the progressive disorder is now believed to afflict more than 250,000 people worldwide and often leads to heart failure and death, Greenstreet said.


The drug has a list price of about $450,000 a year and generated sales of $475 million worldwide last year. If the Food and Drug Administration approves Onpattro for the more common heart disease, Greenstreet said, she expected it would become a blockbuster, with billions of dollars in sales.

“We’re moving from rare to more common to very common diseases,” Greenstreet said of Alnylam drug developers in an interview.

Alnylam’s share price closed at $212.01 Wednesday on the Nasdaq, up 49 percent.

The study involved 360 patients who received injections every three weeks for a year. Those who got the drug performed significantly better than those who received a placebo in a test of how far they could walk in six minutes. The drug, also known as patisiran, met the secondary goal of improving scores on a patient questionnaire about quality of life.

Dr. John Berk, a pulmonologist at Boston Medical Center, tested Onpattro at his hospital and the Boston University School of Medicine. He said 30 percent of the patients in the drug and placebo arms were also taking Vyndamax, a Pfizer pill approved in 2019 that slows the progression of the heart disease but typically doesn’t stop it.


Regardless of whether they also took Vyndamax, patients who received the Alnylam drug maintained their walking ability better than those who got a placebo.

“Patisiran represents potentially a quantum leap forward,” Berk said.

Alnylam didn’t share details showing precisely how the drug performed, but it plans to do so at a scientific conference next month. Safety data was encouraging, the company said.

The results of Alnylam’s study had been eagerly anticipated in the biotech industry, in part because of the startling recent failure of Palo Alto, Calif.-based BridgeBio’s drug to treat the same condition. Analysts were shocked last December when patients who received BridgeBio’s drug performed worse in the six-minute walk test than those who received a placebo.

Founded in 2002, Alnylam develops drugs that rely on RNA interference, a Nobel Prize-winning scientific innovation that “silences” disease-causing genes. RNAi represents one of the most promising frontiers in drug development, and Alnylam has used it to win five drug approvals in four years.

The firm, which has a market value of about $25 billion, wants to harness RNAi to treat common diseases such as high blood pressure and gout with one or two injections a year.

“I don’t think the world yet appreciates how phenomenal this is going to be,” Greenstreet said in a Globe interview last November, shortly after she was named to succeed John Maraganore, who had run Alnylam since its founding. “It’s just mind-blowing.”


Jonathan Saltzman can be reached at