Bruton's tyrosine kinase proteolysis-targeting chimeras (BTK-PROTACs) have emerged as a promising approach to address the limitations of BTK inhibitors. However, conducting the rational discovery of orally bioavailable BTK-PROTACs presents significant challenges. In this study, dimensionality reduction analysis and model molecule validation were utilized to identify some key structural features for improving the oral absorption of BTK-PROTACs. The results were applied to optimize the newly discovered BTK-PROTACs B1 and B2. Compound C13 was discovered with improved oral bioavailability, high BTK degradation activity, and selectivity. It exhibited inhibitory effects against different hematologic cancer cells and attenuated the BTK-related signaling pathway. The oral administration of C13 effectively reduced BTK protein levels and suppressed tumor growth. This study led to the discovery of a new orally bioavailable BTK-PROTAC for the treatment of lymphoma, and we hope that the strategy will find wide utility.
A series of 3,4-disubstituted piperidine derivatives were obtained based on a conformational restriction strategy and a lead compound, A12, that exhibited potent in vitro and in vivo antitumor efficacies; however, obvious safety issues limited its further development. Thus, systematic exploration of the structure−activity relationship of compound A12, involving the phenyl group, hinge-linkage, and piperidine moiety, led to the discovery of the superior 3,4,6-trisubstituted piperidine derivative E22. E22 showed increased potency in Akt1 and cancer cell inhibition, remarkably reduced human ether-a-go-go-related gene blockage, and significantly improved safety profiles. Compound E22 also exhibited good kinase selectivity, had a good pharmacokinetic profile, and displayed very potent in vivo antitumor efficacy, with over 90% tumor growth inhibition in the SKOV3 xenograft model. Further mechanistic studies were conducted to demonstrate that compound E22 could significantly inhibit the phosphorylation of proteins downstream of Akt kinase in cells and tumor tissue from the xenograft model.
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