MyoKardia’s Heart Drug Shines in Phase 3, FDA Filing Planned for 2021

Xconomy San Francisco — 

An experimental MyoKardia drug developed to treat an inherited cardiovascular condition that restricts blood flow is showing it can improve on the symptoms of this condition as well as the heart’s ability to function.

MyoKardia (NASDAQ: MYOK) is testing its drug, mavacamten, in patients who have obstructive hypertrophic cardiomyopathy (HCM), a hardening and thickening of the heart muscle that makes it harder for the left ventricle to pump blood to the body, causing patients to experience dizziness, fatigue, and shortness of breath. In some cases, the condition can lead to heart failure or sudden cardiac death.

According to preliminary Phase 3 results announced Monday, patients treated with the drug showed improvement in their HCM symptoms. Furthermore, those who received the drug were able to return to their daily lives sooner compared to those given a placebo, and the drug reduced a key measure used to assess whether surgery is needed. The drug hit those benchmarks while showing safety comparable to a placebo, early data show. Based on these results, MyoKardia CEO Tassos Gianakakos said the Brisbane, CA-based company plans to submit the drug for FDA review early next year.

“This data, given how robust and broad based the responses are, could really benefit the vast majority of obstructed HCM patients,” Gianakakos said on a conference call Monday.

MyoKardia’s stock price jumped following the the news, finishing the trading day at $96.90, up more than 58.6 percent from last Friday’s closing price.

HCM is caused by mutations in genes that make a protein used by heart muscle tissue. These mutated proteins cause excessive contractions that lead to the characteristic thickening of the heart muscle. The heart must work harder to pump but the thickening of the muscle’s walls can reduce or block the flow of blood to the body. Mavacamten is a small molecule designed to reduce the excessive heart muscle contractions that lead to HCM.

MyoKardia tested its drug in a Phase 3 study that enrolled 251 HCM patients from 13 countries. Patients were randomly assigned to receive a once-daily dose of mavacamten or a placebo. The main goal of the study was to show improvement in symptoms according to a scale used to assess heart failure severity, along with measuring the improvement in oxygen consumption during exercise—a composite endpoint that was developed with input from the FDA to assess the drug’s effect on both HCM symptoms and cardiac function, Jay Edelberg, the company’s senior vice president of clinical development said.

Patients in the 30-week study were permitted to continue taking medications that they were previously prescribed for HCM. The company reported that 37 percent of patients treated with mavacamten achieved the study’s primary goal compared to 17 percent of those given a placebo. The results also showed a reduction or elimination of the ventricular obstruction in a majority of patients. A “complete response”—heart failure severity reduced to the lowest classification and blood flow obstruction falling below the diagnostic threshold—was observed in 27 percent of patients in the treatment group compared to 1 percent in the placebo group. The data released Monday build on positive Phase 2 results MyoKardia reported in 2017.

Gianakakos said that full data from the Phase 3 study will be presented at a scientific meeting later this year. The company plans to submit an application for FDA review in the first quarter of 2021. MyoKardia is also eying the European market. Gianakakos said the company plans to speak with European regulators in the second half of this year, and potentially submit an application seeking approval in Europe by the end of next year.

Here’s more on the origins of MyoKardia, which was spun out of venture capital firm Third Rock Ventures in 2012.

Image: iStock/Rasi Bhadramani