High-Throughput Cardiac Hypertrophy Phenotyping Supports Lead Optimization of GRK5 Inhibitors

Cardiac hypertrophy poses a clinical challenge in heart failure progression with limited therapeutic options to reverse the process of pathological remodeling. We present a high-throughput phenotypic screening assay designed to support lead optimization from novel approaches. A mixed cell culture from neonatal rat hearts was established, allowing simultaneous assessment of cardiomyocytes and noncardiomyocytes within a shared physiologically relevant microenvironment. Customized CellProfiler-based image analysis extracted multiparametric morphological data that was merged in a "Hypertrophy Score" metric for quantitative analyses. The assay was applied to investigate G protein-coupled receptor kinase 5 (GRK5) as a promising target in cardiac hypertrophy. Structure-activity and -property relationships from a focused GRK5 inhibitor collection revealed a negative influence on cellular efficacy by lipophilic and covalently reactive compounds. Correlating biochemical with cellular data eliminated GRK6 as a common off-target concern and underlined the value of potent GRK5 versus GRK2 inhibition. Diastereomers 4a/b were identified as valuable chemical probes.