Development of potent and selective YAP-1 inhibitors towards cancer: Lead optimization and in vitro proof- of-concept studies
Introduction
YAP1 has been discovered as a potent oncogene that drives tumorigenesis and metastasis in various cancers. YAP1 is dispensable for the homeostasis of most adult tissues as evidenced by the relatively mild phenotypes of the YAP1 knockout mouse model suggesting that it could be a novel therapeutic target. It is observed to be regulated by proteasomal-mediated degradation which directed us to develop the compounds that promote YAP1 degradation. From high-throughput screening, we identified several compounds with a core structure that degrade YAP1 protein.
Methods
Structure Activity Relationship (SAR) studies, cell proliferation assay, western blot analysis, isothermal calorimetry (ITC), Surface Plasmon Resonance (SPR) assays, in vivo tumor models, qPCR.
Results
Structure Activity Relationship (SAR) studies followed by extensive validation identified a lead molecule, RL-77, which degrades YAP1 at nanomolar concentrations. RL-77 inhibited the proliferation of YAP1-dependent cell lines in vitro and reduced tumor growth in a xenotransplantation mouse model. Further, isothermal calorimetry (ITC) and Surface Plasmon Resonance (SPR) assays provided initial evidence of the binding of RL-77 to purified YAP1 protein. In silico modeling study supported RL-77 binding to YAP1. We synthesized PROTACs using RL-77 and identified two potent PROTACs, RLP-88 and RLP-89 that degrade YAP1 at low nanomolar concentration. We found that RL-77 has excellent stability in the plasma in vitro, however preliminary pharmacokinetic analysis suggested that RL-77 is rapidly cleared (T1/2 = 19 min) in mice. Considering this, we further synthesized small molecules and PROTACS around RL-77 and RLP-88 aiming to develop a lead molecules with improved potency, pharmacokinetic properties and selective YAP1 protein degradation activity.
Conclusion
Our aim is to develop novel small molecules that can be further developed into clinical compounds for the inhibition of YAP1 in cancers that depend on this potent oncogene and provide novel insights into mechanisms of YAP1 function in a variety of cancers. The lead optimization strategies, potency and selectivity (structure activity relationship, SAR), in vitro data of the novel compounds will be presented in the meeting.