MyoKardia Doses First Patient in Danicamtiv Trial for Dilated Cardiomyopathy

MyoKardia announced the first patient has been dosed in the company’s Phase 2 clinical trial of danicamtiv (formerly MYK-491) in people with primary dilated cardiomyopathy (DCM) thought to be caused by genetic mutations of the sarcomere. Danicamtiv is MyoKardia’s most advanced clinical candidate being developed for the treatment of genetic dilated cardiomyopathy (DCM) and other targeted populations with conditions of reduced systolic function.

DCM is a disease of the myocardium characterized by left ventricular enlargement. The weakened and distended left ventricle lacks sufficient contractile force to adequately pump oxygenated blood out to meet the body’s needs. Danicamtiv binds directly to and activates myosin, the heart’s motor protein, to boost the power of each contraction without impacting the ability of the heart to relax and fill with oxygenated blood. In clinical studies, danicamtiv has been well tolerated and has been shown to activate myosin, resulting in enhanced left ventricular contractility, including meaningful improvements in stroke volume, and improved left atrial volume and function.

“Our precision medicine approach to drug discovery and development starts with matching the biology of disease with the mechanism of our molecule. This Phase 2 proof-of-concept trial of danicamtiv is based on our knowledge of the genetics underpinning reduced contractility among a targeted population of patients with dilated cardiomyopathies, as well as our understanding of danicamtiv’s ability to increase the force of contraction. We anticipate the study providing a robust efficacy signal and numerous new insights which will guide the design of our next set of clinical trials,” said Jay Edelberg, M.D., Ph.D., MyoKardia’s Chief Medical Officer. “With its distinct mechanism, danicamtiv has the potential to make a meaningful difference in the cardiac performance of DCM patients with sarcomeric genetic mutations, for whom treatment options today are non-specific and mostly palliative.”

MyoKardia’s Phase 2 study of danicamtiv will enroll patients with DCM with documented genetic variants of MYH7 or titin. Pathogenic variants in single genes encoding proteins of the sarcomere have been associated with the contractile dysfunction underlying approximately 20-30 percent of dilated cardiomyopathies. Patients with these genetic mutations may be particularly suited to treatment with danicamtiv since danicamtiv’s mechanism may correct the very defect that results in cardiac dysfunction. The MYH7 gene mutations are known to reduce the force-generating capacity of the heart by impairing the formation of myosin-actin cross-bridges responsible for cardiac muscle contraction. Biochemical assays using cardiac fibers with variants in MYH7 indicate danicamtiv can rescue the impaired force production that the mutation causes. Titin, an essential component of the sarcomere, provides structure, flexibility and stability as the muscle proteins contract and relax. In MyoKardia’s in vitro studies of engineered tissues with titin variant, contractility was augmented by 31 percent using a danicamtiv-like myosin activator.

The Phase 2 open-label trial will enroll up to twenty-four patients with primary MYH7 or titin DCM into two cohorts of twelve. Patients will receive danicamtiv in two sequential dose periods totaling 9-15 days of treatment. The primary endpoint is safety and tolerability, and secondary endpoints will assess the preliminary effect, compared with baseline, of treatment with danicamtiv on cardiac pharmacodynamic parameters as measured by echocardiography. Topline data are anticipated in the second half of 2021, assuming conditions related to the COVID-19 pandemic continue to allow for enrollment and study conduct in line with current expectations.

Dilated cardiomyopathy is a life-threatening, progressive disease with diverse causes. Genetic abnormalities contributing to DCM are estimated to be present in about 30-40% of DCM patients, corresponding to an estimated prevalence of 250,000 to 500,000 people in the U.S., with the majority of the mutations identified being associated with sarcomeric proteins. Such pathogenic variants of the sarcomere, including those associated with titin and MYH7, impair the ability of the heart muscle proteins to function effectively.

People with DCM may suffer from shortness of breath, debilitating fatigue, fainting and swelling of the extremities and irregular heart rhythms. As DCM progresses, the left ventricle of the heart becomes weaker, leading to systolic heart failure, or heart failure with reduced ejection fraction (HFrEF). Dilated cardiomyopathy, regardless of cause, is the most common diagnosis in patients requiring either mechanical circulatory support or a cardiac transplant.

There are currently no therapeutic options that target DCM’s biologic underpinnings to increase the force of contraction and improve cardiac function or slow disease progression. Pharmacologic therapies developed over the past 35 years have improved both the prognosis and quality of life of DCM patients, however 5-year mortality still approaches 50 percent in community-based studies.

Danicamtiv (formerly MYK-491) is an oral, small molecule, selective cardiac myosin activator. In the heart, myosin is the motor protein that binds to actin to generate the force and movement of contraction. In patients with dilated cardiomyopathy and systolic heart failure, the left ventricle of the heart is too distended and weak to adequately pump blood to meet the body’s needs. Danicamtiv has been shown to increase the probability for myosin-actin engagement while preserving the detachment of myosin from actin at the end of contraction, thereby improving cardiac contractility while preserving diastolic function and allowing for normal filling.

Emerging clinical and preclinical evidence show that danicamtiv also directly activates myosin to improve left atrial volume and function. Danicamtiv has been well tolerated in early clinical studies intended to assess safety and tolerability. MyoKardia intends to advance danicamtiv in further clinical studies to characterize clinical benefit, starting with a Phase 2 clinical trial in patients with genetic dilated cardiomyopathy. MyoKardia also plans to study danicamtiv in patients with systolic heart failure and paroxysmal or persistent atrial fibrillation.