Structural and Thermodynamic Model for the Activation of Cardiac Troponin

Cardiac Troponin Activator Increases Cardiac Contractility in Rats

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.

The role of NMR in advancing small molecule drug discovery

Navigating the ever-evolving landscape of nuclear magnetic resonance (NMR) poses challenges for the industry. This work explores promising approaches that illuminate protein-ligand interactions in the context of structural dynamics, facilitating targeted drug discovery. I acknowledge existing limitations and highlight future opportunities, which may pave the way for broader NMR integration and faster therapeutic development.

Discovery of novel cardiac troponin activators using fluorescence polarization-based high throughput screening assays

The large unmet demand for new heart failure therapeutics is widely acknowledged. Over the last decades the contractile myofilaments themselves have emerged as an attractive target for the development of new therapeutics for both systolic and diastolic heart failure. However, the clinical use of myofilament-directed drugs has been limited, and further progress has been hampered by incomplete understanding of myofilament function on the molecular level and screening technologies for small molecules that accurately reproduce this function in vitro. In this study we have designed, validated and characterized new high throughput screening platforms for small molecule effectors targeting the interactions between the troponin C and troponin I subunits of the cardiac troponin complex. Fluorescence polarization-based assays were used to screen commercially available compound libraries, and hits were validated using secondary screens and orthogonal assays. Hit compound-troponin interactions were characterized using isothermal titration calorimetry and NMR spectroscopy. We identified NS5806 as novel calcium sensitizer that stabilizes active troponin. In good agreement, NS5806 greatly increased the calcium sensitivity and maximal isometric force of demembranated human donor myocardium. Our results suggest that sarcomeric protein-directed screening platforms are suitable for the development of compounds that modulate cardiac myofilament function.