Cardiac Troponin Activator CK-963 Increases Cardiac Contractility in Rats

Abstract

Novel cardiac troponin activators were identified using a high throughput cardiac myofibril ATPase assay and confirmed using a series of biochemical and biophysical assays. HTS hit 2 increased rat cardiomyocyte fractional shortening without increasing intracellular calcium concentrations, and the biological target of 1 and 2 was determined to be the cardiac thin filament. Subsequent optimization to increase solubility and remove PDE-3 inhibition led to the discovery of CK-963 and enabled pharmacological evaluation of cardiac troponin activation without the competing effects of PDE-3 inhibition. Rat echocardiography studies using CK-963 demonstrated concentration-dependent increases in cardiac fractional shortening up to 95%. Isothermal calorimetry studies confirmed a direct interaction between CK-963 and a cardiac troponin chimera with a dissociation constant of 11.5 ± 3.2 μM. These results provide evidence that direct activation of cardiac troponin without the confounding effects of PDE-3 inhibition may provide benefit for patients with cardiovascular conditions where contractility is reduced.

Emerging Concepts of Mechanisms Controlling Cardiac Tension: Focus on Familial Dilated Cardiomyopathy (DCM) and Sarcomere-Directed Therapies

“…Promising troponin-activating compounds have been developed by investigators at Cytokinetics using a high-throughput assay employing ATPase activity of cardiac myofibrils [102]. These investigators have reported detailed findings in the development of CK-963 and discuss in their recent paper next steps in future clinicals trial with follow-up compounds [102]. Studies reported by He et al [79] provide an example of advances in development of small molecules acting as thin filament activators without PDE III inhibition.…”

Discovery of Nelutroctiv (CK-136), a Selective Cardiac Troponin Activator for the Treatment of Cardiovascular Diseases Associated with Reduced Cardiac Contractility

“…A myotrope that targeted cardiac troponin, a mechanism distinct from cardiac myosin activators, was envisioned. Cardiac troponin activators have been previously reported, and levosimendan was studied clinically; however, the potent phosphodiesterase-3 (PDE-3) inhibitory activity of levosimendan makes it difficult to assess the pharmacological effect of any potential cardiac troponin activity of this compound. − A previous communication outlined a path to find potent, selective cardiac troponin activators devoid of PDE-3 inhibitory activity that show significant increases in cardiac contractility with a shallow pharmacokinetic/pharmacodynamic (PK/PD) profile. This research documents the discovery of the novel, selective cardiac troponin activator, nelutroctiv, devoid of PDE-3 inhibition, with wide a pharmacodynamic window, clear PK/PD relationship, and a preclinical PK profile supporting advancement into clinical development…”

“…Cardiac sarcomere activators continue to be explored as potential new treatments in heart failure with reduced ejection fraction (HFrEF). , An area of continued unmet medical need for heart failure patients is in conditions where the contractility of the right ventricle is reduced. For example, congenital heart disease (CHD) is characterized by a range of cardiac birth defects that affect the normal function of the heart .…”