MyoKardia Presents Mavacamten Clinical and Non-Clinical Data at the American Heart Association’s Scientific Sessions 2020

ECHO Data from EXPLORER-HCM Show Mavacamten Treatment Improved Cardiac Structure and Mitral Valve Function in Obstructive Hypertrophic Cardiomyopathy Patients

Markers of Physical Activity from MAVERICK-HCM Accelerometry Data Correlated with Markers of HCM Severity in Non-Obstructive HCM

Non-Clinical Data Show Mavacamten Surrogate Preserved Cardiac Function in Disease Model, Slowing Progression

BRISBANE, Calif., Nov. 13, 2020 (GLOBE NEWSWIRE) — MyoKardia, Inc. (Nasdaq: MYOK) today presented clinical and non-clinical data related to mavacamten, MyoKardia’s investigative therapeutic in late-stage development for the potential treatment of hypertrophic cardiomyopathy (HCM), at the American Heart Association’s Scientific Sessions 2020. Three poster presentations were made available detailing exploratory analyses from Myokardia’s Phase 3 EXPLORER-HCM study of mavacamten for the treatment of obstructive HCM and from the Phase 2 MAVERICK-HCM study of mavacamten in patients with non-obstructive HCM, as well as non-clinical results of a mavacamten surrogate compound in a large animal model.

“These data add detail to the emerging picture of mavacamten’s beneficial impact on the HCM heart, including improvements in cardiac pathophysiology, diastolic function and biomarkers of disease progression,” said Jay Edelberg, M.D., Ph.D., MyoKardia’s Chief Medical Officer. “HCM is characterized by the thickening of the heart muscle and constraints on diastolic filling. Having repeatedly demonstrated that mavacamten can have a profound effect on reducing the obstruction of the left ventricular outflow tract in HCM, echocardiography data from our EXPLORER-HCM trial show that in just 30 weeks of treatment, mavacamten is gradually bringing measures of cardiac structure closer to a normal state, improving parameters of diastolic function and reducing biomarkers of disease. We are optimistic that these changes may ultimately point to the benefits of mavacamten treatment in the progression of HCM.”

Mavacamten Favorably Impacts Key Pathophysiologic Processes in Obstructive Hypertrophic Cardiomyopathy: Results From the EXPLORER-HCM Study

An exploratory analysis from the Phase 3 EXPLORER-HCM clinical trial of mavacamten for the potential treatment of symptomatic, obstructive HCM investigated the changes from baseline to Week 30 on specific measures of the heart’s structure and function using serial echocardiograms (ultrasounds of the heart).

• Treatment with mavacamten led to statistically significant reductions in left ventricular mass (LVMI), indicating that mavacamten is having an effect on cardiac structure. LVMI has been shown to be a predictor of HCM-related mortality.
• Mavacamten treatment improved left ventricular relaxation (which in turn led to improved cardiac filling pressures). Statistically significant improvements (p<0.0001 for difference from placebo) were achieved across diverse echocardiographic measurements of diastolic function (LA volume index, lateral e’, lateral E/e’, septal e’, and septal E/e’).
• Significantly more mavacamten-treated patients achieved resolution of mitral valve systolic anterior motion (SAM) compared to placebo (80.9% vs. 34.0%; p<0.0001), and 9% achieved resolution of mitral regurgitation (MR) in the mavacamten group vs. none in placebo (p=0.0006). SAM and MR may cause or contribute to obstruction of the left ventricular outflow tract and are known to impact cardiac performance and increase risk of serious cardiovascular complications, such as arrhythmias.
• Mavacamten treatment resulted in significant reductions in cardiac biomarkers of myocardial wall stress and injury compared to placebo. Specifically, there was an 80% greater reduction in NT-proBNP and a 41% greater reduction in cardiac troponin in the mavacamten treatment group vs. placebo.
• Patients with the highest degree of obstruction at baseline achieved greater improvements in echocardiographic parameters and biomarker reductions.

Accelerometer-measured Activity in Non-obstructive Hypertrophic Cardiomyopathy: Patient-generated Activity Measures Correlate With, and are Convolutional Neural Network Predictors of, Clinical Parameters in the MAVERICK-HCM Study

MyoKardia’s Phase 2 MAVERICK-HCM study of mavacamten was the first study to examine quantitative levels of activity in a non-obstructive HCM patient population. As part of the MAVERICK-HCM study, patients were asked to wear ActiGraph GT9X Link wrist-worn monitors for up to 14 days between screening and day 1 and between weeks 12 and 16 to record daily activity. A multitask convolutional neural network (CNN) trained on raw accelerometry, was also used to jointly predict clinical markers of HCM severity.

Markers of physical activity drawn from accelerometry, including average daily accelerometer units (ADAUs) and step count, were associated with standard clinical markers of HCM severity. Out the 59 patients enrolled in MAVERICK-HCM, 50 patients wore the accelerometer for ≥1 compliant day. Patients in MAVERICK-HCM averaged 3,000 steps per day. Results from the accelerometry exploratory analyses showed that higher physical activity correlated with key clinical markers of HCM, including exercise capacity as measured by peak VO2, changes in NT-proBNP levels, and improvements in patient reported outcomes using the Kansas City Cardiomyopathy Questionnaire (KCCQ), indicating that accelerometry measures may be a useful indicator of drug activity. CNN predictions of clinical measures from activity data found strong correlations for pVO₂, NT-proBNP, KCCQ score, and E over e prime. These findings indicate that deep learning models can be constructed to predict markers of HCM severity from patients’ raw accelerometry data.

Chronic Treatment With A Mavacamten-like Myosin-modulator (MYK-581) Prevents Left-atrial Remodeling, Decreases Cardiac Troponin Leakage, And Blunts Mortality In A Mini-pig Model Of Inherited Hypertrophic Cardiomyopathy

Results from an in vivo study in a genetic mini-pig model of HCM showed that chronic administration of a mavacamten-like myosin-modulator blunted chronic cardiac troponin-T leakage and decreased mortality, both characteristic of HCM progression in this non-obstructive model. In addition, chronic treatment also reduced left-ventricular and prevented left-atrial remodeling, preserving normal left-atrial size as well as atrial myofibrillar structure and function. Taken together, these non-clinical observations provide additional evidence of mavacamten’s activity beyond the reduction of LVOT obstruction and support the emerging clinical evidence of mavacamten’s beneficial effects on overall cardiac structure in the HCM heart.

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.

MyoKardia’s mission is to change the world for people with serious cardiovascular disease through bold and innovative science.

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 benefit and future potential of mavacamten, the ability of our long-term studies to provide further evidence of mavacamten’s potential to alter the course of disease by gradually brining measures of cardiac structure to a normal state, usefulness of raw accelerometry data to predict markers of HCM severity in patients, and the ability of non-clinical observations to provide additional evidence of mavacamten’s activity beyond the reduction of LVOT obstruction, 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 and any ongoing effects of the COVID-19 pandemic, as well as those set forth in our Quarterly Report on Form 10-Q for the quarter ended September 30, 2020, 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.

Contacts
Michelle Corral
Executive Director, Corporate Communications and Investor Relations
MyoKardia, Inc.
650-351-4690
ir@myokardia.com

Hannah Deresiewicz (investors)
Stern Investor Relations, Inc.
212-362-1200
hannah.deresiewicz@sternir.com

Julie Normant (media)
W2O
628-213-3754
jnormart@w2ogroup.com