BRISBANE - MyoKardia, Inc. (Nasdaq: MYOK) today announced results from the dose-ranging MAVERICK-HCM Phase 2 clinical trial of mavacamten for the treatment of non-obstructive hypertrophic cardiomyopathy (HCM).

Data were presented during a late-breaker session at the American College of Cardiology's 69th Annual Scientific Session together with the World Congress of Cardiology (ACC.20/WCC Virtual) In the MAVERICK-HCM study, mavacamten was generally well tolerated, and statistically significant improvements in key biomarkers of cardiac injury and wall stress were observed. Further, subgroup analyses of study participants with indicators of more advanced disease demonstrated clinical responses across multiple parameters among patients on active treatment versus placebo.

'Non-obstructive HCM is especially challenging to treat as there are no proven or approved pharmacological therapies. Thus, for patients who develop symptoms refractory to medications, cardiac transplantation may be the only option,' said Carolyn Ho, M.D., Medical Director of the Cardiovascular Genetics Center at Brigham and Women's Hospital and lead author on behalf of the MAVERICK-HCM study investigators. 'Although the primary objective of MAVERICK was to assess the safety and tolerability of mavacamten in non-obstructive HCM, in exploratory analyses we observed an encouraging result with reductions in serum levels of NT-proBNP, a biomarker of hemodynamic stress, and also cardiac troponin I, a biomarker of myocardial injury. We believe MAVERICK is the first study to show an improvement in important serum biomarkers in this patient population and suggests that there is potential physiological benefit from the drug. We were also intrigued by findings that patients with more severe disease expression, those with elevated serum troponin levels or evidence of diastolic dysfunction by echo, may have achieved functional benefit. These findings, combined with mavacamten's tolerability profile, are encouraging, and they provide direction for further evaluation of mavacamten for patients with non-obstructive HCM.'

'MAVERICK has succeeded in providing us with the important data we needed to proceed in our planned clinical trials in non-obstructive HCM, as well as a targeted subset of patients with heart failure with preserved ejection fraction, or HFpEF. We gained unique insights into dosing strategies using markers linked to clinical benefit, as well as how to identify patients who may be most likely to benefit from mavacamten,' said Jay Edelberg, M.D. Ph.D., MyoKardia's Senior Vice President of Development. 'The MAVERICK results also further our confidence in mavacamten's development in obstructive HCM, as we approach our Phase 3 EXPLORER-HCM readout, which is expected in the second quarter.'

About the Phase 2 MAVERICK-HCM Clinical Trial

The Phase 2 MAVERICK-HCM trial assessed the safety and tolerability of a range of exposures over 16 weeks of treatment in patients with symptomatic, non-obstructive HCM. All study participants were required to be diagnosed with non-obstructive HCM, with left ventricular wall thickness either 15mm or 13mm with a family history of HCM, New York Heart Association (NYHA) classifications of Class II or III, and NT-proBNP levels of greater than 300 pg/mL at rest. Baseline characteristics, such as age, weight, gender, pathogenic mutation status, background beta blocker use, NYHA classification and exercise capacity were evenly distributed between active and placebo arms.

A total of 59 participants were enrolled in the study and randomized into one of three groups to receive once-daily doses of mavacamten or placebo. The active mavacamten treatment arms were designed to assess a range of drug concentrations around target levels of 200 ng/mL and 500 ng/mL. All participants in the active treatment arms began the study receiving 5mg doses of mavacamten. At Week 4, pharmacokinetic (PK) assessments were conducted and doses were adjusted in a blinded fashion per the protocol based on the participant's assigned cohort. Following the 16-week treatment period, participants were monitored for an additional 8 weeks and became eligible to participate in MyoKardia's MAVA Long-Term Extension (LTE) study.

About Non-obstructive HCM and Heart Failure with preserved Ejection Fraction

Hypertrophic cardiomyopathy is the most common genetic form of heart disease, affecting an estimated one in every 500 people worldwide. There are two main forms of HCM, obstructive HCM and non-obstructive HCM, which often share the same underlying genetic defects in the sarcomere that result in hypercontractility. In non-obstructive HCM, the heart contracts excessively and the left ventricle becomes abnormally thick, restricting the ability of the heart to relax and fill or pump to meet the body's needs, but no physical obstruction is present in the outflow tract of the left ventricle. Non-obstructive HCM affects an estimated one-third of all HCM patients and presents unique treatment challenges. Patients may progress to a more advanced state of disease than those with obstructive disease before being diagnosed, and there are no approved pharmacological treatment options available. As non-obstructive HCM progresses, symptoms begin to resemble those of a congestive heart failure patient and heart transplantation may become the only viable treatment option.

Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous clinical syndrome, which in many patients is characterized by impairment of the left ventricle's ability to relax and fill during diastole, resulting in insufficient blood flow to meet the body's needs. HFpEF is estimated to affect approximately three million people in the U.S. and is associated with significant morbidity and mortality. There are currently no approved therapies for HFpEF.

About Mavacamten (MYK-461)

Mavacamten is a novel, oral, allosteric inhibitor of cardiac myosin being developed for the treatment of hypertrophic cardiomyopathy (HCM). Mavacamten is intended to reduce cardiac muscle contractility by inhibiting the excessive myosin-actin cross-bridge formation that underlies the excessive contractility, left ventricular hypertrophy and reduced compliance characteristic of HCM. MyoKardia is currently evaluating mavacamten in multiple clinical trials for the treatment of obstructive and non-obstructive HCM. The pivotal Phase 3 clinical trial, known as EXPLORER-HCM, is being conducted in patients with symptomatic, obstructive HCM and MyoKardia anticipates data from this program in the second quarter of 2020. Two long-term follow-up studies are also ongoing, the PIONEER open-label extension study of obstructive HCM patients from MyoKardia's Phase 2 PIONEER trial and the MAVA-LTE, an extension study for patients who have completed either EXPLORER-HCM or MAVERICK-HCM, the company's Phase 2 clinical trial of symptomatic non-obstructive HCM patients. In April 2016, the U.S. FDA granted Orphan Drug Designation for mavacamten for the treatment of symptomatic obstructive HCM.

About MyoKardia

MyoKardia is a clinical-stage biopharmaceutical company discovering and developing targeted therapies for the treatment of serious cardiovascular diseases. The company is pioneering a precision medicine approach to its discovery and development efforts by 1) understanding the biomechanical underpinnings of disease; 2) targeting the proteins that modulate a given condition; 3) identifying patient populations with shared disease characteristics and 4) applying learnings from research and clinical studies to inform and guide pipeline growth and product advancement. MyoKardia's initial focus is on small molecule therapeutics aimed at the proteins of the heart that modulate cardiac muscle contraction to address diseases driven by excessive contraction, impaired relaxation, or insufficient contraction. Among its discoveries are three clinical-stage therapeutics: mavacamten (formerly MYK-461); danicamtiv (formerly MYK-491) and MYK-224.

Forward-Looking Statements

Statements we make in this press release may include statements which are not historical facts and are considered forward-looking within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are usually identified by the use of words such as 'anticipates,' 'believes,' 'estimates,' 'expects,' 'intends,' 'may,' 'plans,' 'projects,' 'seeks,' 'should,' 'will,' and variations of such words or similar expressions. We intend these forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 27A of the Securities Act and Section 21E of the Securities Exchange Act and are making this statement for purposes of complying with those safe harbor provisions. These forward-looking statements, including statements regarding the clinical and therapeutic potential of mavacamten, our plans to advance the clinical development of mavacamten in non-obstructive HCM patients and a targeted population of HFpEF patients, the anticipated data readout from our Phase 3 EXPLORER trial of mavacamten, our plans to consult with the FDA on potential pathways to registration and to provide a regulatory update, the initiation, progress and availability of data from our ongoing and planned clinical trials, and the timing of these events, reflect our current views about our plans, intentions, expectations, strategies and prospects, which are based on the information currently available to us and on assumptions we have made. Although we believe that our plans, intentions, expectations, strategies and prospects as reflected in or suggested by those forward-looking statements are reasonable, we can give no assurance that the plans, intentions, expectations or strategies will be attained or achieved. Furthermore, actual results may differ materially from those described in the forward-looking statements and will be affected by a variety of risks and factors that are beyond our control including, without limitation, risks associated with the development and regulation of our product candidates, as well as those set forth in our Annual Report on Form 10-K for the year ended December 31, 2019, and our other filings with the SEC. Except as required by law, we assume no obligation to update publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

Contact:

Michelle Corral

Tel: 650-351-4690

Email: ir@myokardia.com

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