The original goals of the proposal were to apply medicinal chemistry to generate more potent and drug-like analogs of small molecules that stimulate differentiation of cardiomyocytes from embryonic stem cells (ESCs) and potentially other progenitor cell types found in adult human heart. During the grant period, we over-achieved each Aim and provided large numbers of drug-like small molecules for cardiomyocyte differentiation studies. In addition, other related information was gained that has considerably expanded our understanding related to developing regenerative medicines.

1. Synthetic Chemistry: From an initial screen of thousands of compounds, six ‘hits’ were identified. Almost 1400 compounds were synthesized as analogs of these “hits” with the goal of generating more effective novel compounds as possible therapeutics for heart disease.

2. Assay development and screening: Novel synthetic chemical analogs were studied in cell-based assays to evaluate potency of stimulating cardiac cell development relative to the starting ‘hit’ compounds. The biological data contributed to structure activity relationship (SAR) studies, and provided valuable information about parts of the molecules important for cardiomyocyte stem cell differentiation and for other important pharmaceutical properties. The iterative feedback from the biological testing helped to guide the next generation design of new and ever more effective compounds.

3. Chemical optimization. Focused structure activity relationship (SAR) studies for 4 chemical series from the ESC cardiogenesis differentiation screen were done. SAR for 2 additional chemical classes was done but those agents proved less potent. In addition to SAR, considerable information was obtained leading to improved solubility and membrane permeability of compounds in development, which became a focus of the chemical optimizations. The most potent compounds increased stem cell differentiation to cardiomyocytes 5-10 fold. The compounds were non-toxic, reasonably tractable to make, stable and were water-soluble and hence relatively easy to handle.

4. A number of biological signaling pathways were identified as affiliated with cardiomyocyte differentiation. One such pathway also is involved in anti-cancer activities. Thus, our efforts in identifying cardiomyocyte differentiation agents led us to study novel biology associated with cancer. One “hit” of this signaling pathway was chosen to do synthetic chemistry and “hit” to lead refinement. Approximately 100 compounds were synthesized and tested for inhibition of this signaling pathway.

In summary, the work has already led to a number of promising drug-like compounds ready for efficacy testing in animal models and thus, efforts have greatly accelerated the timeline of getting compounds to human patients. A total of 1500 compounds were synthesized to optimize the potency and properties of cardiomyocyte differentiation agents. The most potent stimulated production of human cardiomyocytes 5-10-fold compared to vehicle-stimulated cells.