A novel chemical tool for the rapid preparation of PROTAC conjugates by persons without extensive synthetic experience or special laboratory equipment.

The human aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is a pivotal regulator of human physiology and pathophysiology. Allosteric inhibition of AhR was previously thought to be untenable. Here, we identify carvones as noncompetitive, insurmountable antagonists of AhR and characterize the structural and functional consequences of their binding. Carvones do not displace radiolabeled ligands from binding to AhR but instead bind allosterically within the bHLH/PAS-A region of AhR. Carvones do not influence the translocation of ligand-activated AhR into the nucleus but inhibit the heterodimerization of AhR with its canonical partner ARNT and subsequent binding of AhR to the promoter of CYP1A1. As a proof of concept, we demonstrate physiologically relevant Ahr-antagonism by carvones in vivo in female mice. These substances establish the molecular basis for selective targeting of AhR regardless of the type of ligand(s) present and provide opportunities for the treatment of disease processes modified by AhR.

Oncogenic mutations in gene encoding FLT3 kinase are often detected in acute myeloid leukaemia (AML) patients, and several potent kinase inhibitors have been developed. However, the FLT3 inhibitor treatment often leads to the resistance development and subsequent relapse. Targeted degradation of oncogenic protein kinases has emerged as a feasible pharmacological strategy, providing more robust effect over traditional competitive inhibitors. Based on previously developed competitive inhibitor of FLT3 and CDK9, we have designed and prepared a novel pomalidomide-based PROTAC. A series of biochemical and cellular experiments showed selectivity towards FLT3-ITD bearing AML cells and confirmed proteasome-dependent mechanism of action. Dual FLT3-ITD and CDK9 protein degradation resulted in the block of FLT3-ITD downstream signalling pathways, apoptosis activation and cell cycle arrest of FLT3-ITD AML cells. Moreover, transcriptional repression caused by CDK9 degradation significantly reduced expression of crucial genes involved in AML pathogenesis. The obtained results indicate the beneficial impact of simultaneous FLT3-ITD/CDK9 degradation for AML therapy.