Discovery and characterization of novel potent BCR-ABL degraders by conjugating allosteric inhibitor.

The oncogenic fusion protein BCR-ABL is the driving force of leukemogenesis in chronic myeloid leukemia (CML). Despite the great advance in CML treatment through the application of tyrosine kinase inhibitors (TKIs) against BCR-ABL, disease recurrence after TKI discontinuation and clinical resistance mainly due to BCR-ABL mutations continue to be an issue. Herein we report our efforts to synthesize a novel series of CRBN-recruiting proteolysis-targeting chimeras (PROTACs) targeting BCR-ABL based on the allosteric inhibitor asciminib. Our efforts have led to the discovery of compound 30 (SIAIS100) through extensive SAR studies by the optimization of linker parameters as well as linker attachment points of both target-binding warhead and CRBN ligands, which exhibited the most potent degradative activity with a DC50 value of 2.7 nM and Dmax of 91.2% against BCR-ABL and has an IC50 value of 12 nM in BCR-ABL + K562 cells. The binding model and the stability evaluation of 30-induced ternary complex formation were also elucidated through computational simulations. Furthermore, 30 induced sustained and robust BCR-ABL degradation and maintained the efficacy for 96 h post-washout. Moreover, the proteomics analysis showed that 30 degraded BCR-ABL and three CRBN's neo-substrates, including IKZF1, IKZF3, and ZFP91. Additionally, 30 also exerted degradative activity against a panel of clinically relevant resistance-conferring mutations of BCR-ABL, including gatekeeper mutation T315I, several single mutations associated with TKI resistance, and certain highly resistant compound mutations. Our study provided a deeper understanding of the development of PROTACs targeting BCR-ABL and novel potential therapeutic agents for CML treatment.

A functional SNP rs895819 on pre-miR-27a is associated with bipolar disorder by targeting NCAM1.

The aberrant expression or genomic mutations of microRNA are associated with several human diseases. This study analyzes the relationship between genetic variations of miRNA and schizophrenia or bipolar disorder. We performed case-control studies for ten SNPs in a total sample of 1584 subjects. All these ten SNPs were on or near mature microRNAs. We identified the association between bipolar disorder and the T/C polymorphism at rs895819. To illustrate the function of miR-27a, we constructed several miR-27a knockout (KO) cell lines, determined candidates of miR-27a, and then verified NCAM1 as a target gene of miR-27a. Further studies revealed that the T/C polymorphism on miR-27a led to the differential expression of mature and precursor miR-27a without affecting the expression of primary miR-27a. Furthermore, the C mutation on pre-miR-27a suppresses cell migration and dopamine expression levels. Our study highlights the importance of miR-27a and its polymorphism at rs895819 in bipolar disorder.

Discovery of novel BCR-ABL PROTACs based on the cereblon E3 ligase design, synthesis, and biological evaluation.

Protein degradation is a promising strategy for drug development. Proteolysis-targeting chimeras (PROTACs) hijacking the E3 ligase cereblon (CRBN) exhibit enormous potential and universal degradation performance due to the small molecular weight of CRBN ligands. In this study, the CRBN-recruiting PROTACs were explored on the degradation of oncogenic fusion protein BCR-ABL, which drives the pathogenesis of chronic myeloid leukemia (CML). A series of novel PROTACs were synthesized by conjugating BCR-ABL inhibitor dasatinib to the CRBN ligand including pomalidomide and lenalidomide, and the extensive structure-activity relationship (SAR) studies were performed focusing on optimization of linker parameters. Therein, we uncovered that pomalidomide-based degrader 17 (SIAIS056), possessing sulfur-substituted carbon chain linker, exhibits the most potent degradative activity in vitro and favorable pharmacokinetics in vivo. Besides, degrader 17 also degrades a variety of clinically relevant resistance-conferring mutations of BCR-ABL. Furthermore, degrader 17 induces significant tumor regression against K562 xenograft tumors. Our study indicates that 17 as an efficacious BCR-ABL degrader warrants intensive investigation for the future treatment of BCR-ABL+ leukemia.