posted on 2024-03-07, 15:40authored byScott E. Collibee, Antonio Romero, Alexander R. Muci, Darren T. Hwee, Chihyuan Chuang, James J. Hartman, Alykhan S. Motani, Luke Ashcraft, Andre DeRosier, Mark Grillo, Qing Lu, Fady I. Malik, Bradley P. Morgan
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.