A series of novel anaplastic lymphoma kinase (ALK) degraders were designed and synthesized based on proteolysis-targeting chimera (PROTAC) technology by linking two alectinib analogs (36 and 37) with pomalidomide through linkers of different lengths and types. The most promising degrader 17 possessed a high ALK-binding affinity and potent antiproliferative activity in the ALK-dependent cell lines and did not exhibit obvious cytotoxicity in ALK fusion-negative cells. More importantly, the efficacy of compound 17 in a Karpas 299 xenograft mouse model was further evaluated based on its ALK-sustained degradation ability in vivo. The reduction in tumor weight in the compound 17-treated group (10 mg/kg/day, I.V.) reached 75.82%, while alectinib reduced tumor weight by 63.82% at a dose of 20 mg/kg/day (P.O.). Taken together, our findings suggest that alectinib-based PROTACs associated with the degradation of ALK may have promising beneficial effects for treating ALK-driven malignancies.

Hydrophobic tagging (HyT) is a potential therapeutic strategy for targeted protein degradation (TPD). Norbornene was discovered as an unprecedented hydrophobic tag in this study and was used to degrade the anaplastic lymphoma kinase (ALK) fusion protein by linking it to ALK inhibitors. The most promising degrader, Hyt-9, potently reduced ALK levels through Hsp70 and the ubiquitinÀ proteasome system (UPS) in vitro without compensatory upregulation of ALK. Furthermore, Hyt-9 exhibited a significant tumorinhibiting effect in vivo with moderate oral bioavailability. More importantly, norbornene can also be used to degrade the intractable enhancer of zeste homolog 2 (EZH2) when tagged with the EZH2 inhibitor tazemetostat. Thus, the discovery of novel hydrophobic norbornene tags shows promise for the future development of TPD technology.

BiographiesShaowen Xie received his B.S. degree in pharmacy from China Pharmaceutical University in 2017. Currently, he is a doctoral candidate in the field of medicinal chemistry at China Pharmaceutical University. His research primarily focuses on the development and mechanism investigation of small molecule degraders targeting specific proteins.

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Hydrophobic tagging (HyT) is a potential therapeutic strategy for targeted protein degradation (TPD). Norbornene was discovered as an unprecedented hydrophobic tag in this study and was used to degrade the anaplastic lymphoma kinase (ALK) fusion protein by linking it to ALK inhibitors. The most promising degrader, Hyt‐9, potently reduced ALK levels through Hsp70 and the ubiquitin−proteasome system (UPS) in vitro without compensatory upregulation of ALK. Furthermore, Hyt‐9 exhibited a significant tumor‐inhibiting effect in vivo with moderate oral bioavailability. More importantly, norbornene can also be used to degrade the intractable enhancer of zeste homolog 2 (EZH2) when tagged with the EZH2 inhibitor tazemetostat. Thus, the discovery of novel hydrophobic norbornene tags shows promise for the future development of TPD technology.