CRBN ligand expansion for Hematopoietic Prostaglandin D2 Synthase (H-PGDS) targeting PROTAC design and their in vitro ADME profiles

An increasing number of research reports are describing modifications of the E3 ligand, in particular, cereblon (CRBN) ligands, to improve the chemical and metabolic stabilities as well as the physical properties of PROTACs. In this study, phenyl-glutarimide (PG) and 6-fluoropomalidomide (6-F-POM), recently used as CRBN ligands for PROTAC design, were applied to hematopoietic prostaglandin D2 synthase (H-PGDS)-targeted PROTACs. Both PROTAC-5 containing PG and PROTAC-6 containing 6-F-POM were found to have potent activities to induce H-PGDS degradation. Furthermore, we obtained in vitro ADME data on the newly designed PROTACS as well as our previously reported PROTACs(H-PGDS) series. Although all PROTACs(H-PGDS) are relatively stable toward metabolism, they had poor PAMPA values. Nevertheless, PROTAC-5 showed Papp values similar to TAS-205, which is in Phase 3 clinical trials, and is expected to be the key to improving the pharmacokinetics of PROTACs.