Design, Synthesis And Structure-activity Relationship Of Tetrapeptide Epoxyketone Proteasome Inhibitors

The ubiquitin-proteasome system(UPS)plays a central role in maintaining cellular homeostasis,such as cell-cycle regulation,activation of transcription factors,DNA repair,obsolete proteins and apoptosis induction.The derangements of UPS could cause a variety of diseases including malignancies,neurodegenerative diseases,systematic autoimmunity.The first generation proteasome inhibior bortezomib was approved by FDA in 2003 and was used for the treatment of relapsed and refractory multiple myeloma.But it showed serious side effects in clinical uses,especially in the peripheral nerve,which was due to the poor selectivities among ?5??2 and ?1 subunits.To overcome the side effects,the sencond generation proteasome inhibitor Carfilzomib was developed and approved by FDA in 2012 for the treatment of relapsed MM patients who have received at least two prior therapies including bortezomib.However,the poor water solubility and serious cardiovascular events limited its further development.Thus there is a great need to design and develop soluble tetrapeptidyl epoxyketone with fewer side effects to meet the clinical need.A series of novel tetrapeptidyl epoxyketone inhibitors of 20S proteasome were designed and synthesized.Compound 9,which exhibited better rat and mice liver microsomal stabilities for t2/1 is 5-fold as long as reference Carfilzomib.Whole blood and tissue proteasome inhibition for ?5 activity proved the efficacy of compound 9.Mechanism study in vitro proved compound 9 stopped cell cycle progression at the G2/M stage and showed distinct apoptosis promoting effect with time-dependent and dose-dependent relationship.Compound 9 also displayed strong in vivo anticancer efficacy in human PC-3,RPMI-8226 and ARH77 cell xenograft mouse models at different doses and exhibited lower binding affinity to hERG ion channel.