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MyoKardia pops as heart drug passes most important test

Shares of MyoKardia, a California-based drug developer, rose by as much as 70% Monday morning on news that the company’s most advanced drug succeeded in a large clinical trial and is now moving forward to an approval review.The late-stage trial enrolled a patients with a condition similar to heart failure. The study found that, when evaluating several measures of cardiovascular health, the patients given MyoKardia’s drug improved significantly more than those given placebo. MyoKardia said patients who took its drug also showed “meaningful improvements” in quality of life.The company plans to submit its drug, known as mavacamten, for approval in this patient group sometime in the first quarter next year. More detailed results from the trial will be presented at an upcoming cardiovascular medical meeting, according to MyoKardia.

Arguably, MyoKardia’s future depended on the outcome of the Phase 3 EXPLORER trial. Positive results would not only validate the mavacamten program, but also other experimental drugs in the company’s pipeline that work in a similar way.

MyoKardia has been trying to show that these drugs can regulate a protein involved with muscle contraction and, in turn, improve heart health. In the case of mavacamten, the company has been testing it in patients with hypertrophic cardiomyopathy, or HCM, a typically inherited condition where the heart muscle gets thicker over time, making it harder to pump blood. Some estimates hold that HCM affects roughly one in 500 people, which would equate to around 700,000 to 725,000 patients in the U.S.

MyoKardia puts the figure around 630,000, with the majority of patients undiagnosed. Of the 100,000 or so who are diagnosed, two-thirds have a form of HCM classified as obstructive, meaning the blood flow from the heart’s left ventricle to the aorta is blocked or reduced. It was these patients who researchers enrolled in the EXPLORER trial.

The results unveiled Monday show 37% of patients on mavacamten hit the trial’s main goal, compared to 17% of patients in the placebo arm. To hit the goal, patients had to either improve on a heart failure scale and modestly increase the maximum amount of oxygen they can use while exercising, or they had to have a more robust increase in oxygen uptake without their scale score worsening.

MyoKardia said patients tolerated its drug comparatively well. Between 8% and 9% of patients in both the mavacamten and placebo groups experienced serious adverse events. Overall, 2% of participants dropped out before the trial completed, though the company said none were due to reduced ejection fraction or heart failure symptoms.

In a note to clients, Cantor Fitzgerald analyst Alethia Young called the results a “home run” and said they could support a price tag of $75,000 should the drug gain approval. Young models $2 billion in peak mavacamten sales for the obstructive HCM treatment market and around $600 million in peak sales for the non-obstructive market.

MyoKardia’s share price opened at almost $102 on Monday, up from $61 at Friday’s market close.