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The primary objective is to assess the long-term safety and tolerability of mavacamten in participants with hypertrophic cardiomyopathy (HCM) previously enrolled in 1 of 2 placebo-controlled trials: MAVERICK-HCM (MYK-461-006) for non-obstructive HCM (nHCM) and EXPLORER-HCM (MYK-461-005) for obstructive HCM (oHCM). All participants will receive active study drug (mavacamten) once daily (QD) for a duration of up to 2 years (104 weeks) but their status (active or placebo) in the Parent Study will remain blinded as the studies will be enrolling in parallel. All participants will undergo the same assessments and visit schedule (per cohort) to preserve the blind of study drug assignment in the Parent Study, however assessments may vary based on the cohort.

Participant Eligibility

Participants must have completed dosing through to the Parent Study EOT Visit and the 8-week post-treatment period in the respective parent studies to be considered eligible. If the participant completed the Parent Study EOS assessments within 28 days of Screening into the MAVA-LTE study, the assessments from the Parent Study EOS Visit may be used as the screening assessments.

Inclusion Criteria:
1. Has completed the Parent Study through to the EOS Visit within 90 days of signing consent
2. Is able to understand and comply with the study procedures
3. Body weight is greater than 45kg at the Screening Visit or Day 1
4. Has adequate acoustic windows to enable accurate TTEs
5. Has documented LVEF > 50% by echocardiography core lab read of screening TTE at rest
6. Has safety laboratory parameters within normal limits; however, a participant with safety laboratory parameters outside normal limits may be included if they meet all of the following criteria:
-The safety laboratory parameter outside normal limits is considered by the Investigator to be clinically unimportant
– If there is an alanine aminotransferase or aspartate aminotransferase result, the value must be <3x the ULN
– The body size-adjusted eGFR is >30mL/min/1.73m2
7. Female participants must not be pregnant or lactating and, if sexually active, must use one of the following highly effective birth control methods from the Screening Visit through 90 days after the last dose of investigational medicinal product (IMP)

Exclusion Criteria:
1. Has persistent or permanent atrial fibrillation not on anticoagulation for at least 4 weeks prior and/or is not adequately rate-controlled
2. Is currently taking, or has taken within 14 days of screening, a prohibited medication such as a cytochrome P450 (CYP) 2C19 inhibitor, a strong CYP 3A4 inhibitor, or St. John's Wort
3. Has QTcF >500 ms at Screening or any other ECG abnormality considered by the Investigator to pose a risk to participant safety
4. Has documented obstructive coronary artery disease (>70% stenosis in one or more epicardial coronary arteries) or history of MI
5. Has known moderate or severe (based on Investigator's judgement) aortic valve stenosis at Screening Visit
6. Has hypersensitivity to any of the components of the mavacamten formulation
7. Has participated in a clinical trial in which the participant received any investigational drug (or is currently using an investigational device) within 30 days prior to screening, or at least 5 times the respective elimination half-life (whichever is longer), except for participation in MAVERICK-HCM or EXPLORER-HCM
8. Has a history of syncope or a history of sustained ventricular tachyarrhythmia with exercise between Parent Study EOS Visit and Screening Visit
9. Has a history of resuscitated sudden cardiac arrest or known history of appropriate implantable cardioverter-defibrillator (ICD) discharge for life-threatening ventricular arrhythmia between Parent Study EOS Visit and Screening Visit
10. Currently treated with disopyramide or ranolazine (within 14 days prior to screening visit) or treatment with dispyramide or ranolazine is planned during the study
11. currently treated or planned treatment during the study with a combination of beta blocker and verapamil or a combination of beta blocker and diltiazem
12. Has any acute or serious comorbid condition (eg, major infection or hematologic, renal, metabolic, gastrointestinal, or endocrine dysfunction) that, in the judgement of the Investigator, could lead to premature termination of study participation or interfere with the measurement or interpretation of the efficacy and safety assessments in the study
13. History of clinically significant malignant disease that developed since enrollment in the Parent Study
-Participants who have been successfully treated for non-metastatic cutaneous squamous cell or basal cell carcinoma or have been adequately treated for cervical carcinoma in situ or breast ductal carcinoma in situ (DCIS) can be included in the study
14. Is unable to comply with the study requirements, including the number of required visit to the clinical site
15. Is employed by or is a relative of someone employed by MyoKardia, the Investigator, or his/her staff or family


Carly Ohmart
(206) 685-4346

Additional Study Details

Full Study Title
A Long-term Safety Extension Study of Mavacamten (MYK-461) in Adults with Hypertrophic Cardiomyopahty Who Have Completed the MAVERICK-HCM (MYK-461-006) or EXPLORER-HCM (MYK-461-005) Trials

Study ID: 20191607
Start Date: 07/19/2019
End Date: 07/19/2020

Principal Investigator: David Owens, MD
Sub-Investigator: Kelley Branch, MD

Accepts Healthy Volunteers?

Study Site(s)

University of Washington Medical Center

1959 NE Pacific St.
Seattle, Washington 98195


Use the link below to send a message to the study coordinator, or call the number above to speak directly with a study representative.

I am interested in this research study.