Novel Pyrazolo [1,5-a]-1,3,5-Triazine Derivatives as CDK7 Inhibitors: Synthesis and Biological Insights in Pancreatic Ductal Adenocarcinoma Models.

Pancreatic ductal adenocarcinoma (PDAC), the most prevalent form of pancreatic tumor, is one of the most aggressive and lethal tumor types. Cyclin-dependent kinase 7 (CDK7) has been recently identified as a promising target in multiple human and mouse PDAC preclinical tumor models, due to significant downregulation of gene transcription and preferential inhibition of the mitotic cell cycle. With the aim of finding new CDK7 inhibitors, new indolyl and 7-aza-indolyl pyrazolo [1,5-a]-1,3,5-triazine derivatives are efficiently synthesized and screened for antiproliferative activity against three immortalized cell lines (SUIT 2.28, PATU-T, PANC-1) of PDAC. 8 out of 33 derivatives show remarkable cytotoxicity with IC50 values ranging from 0.19 to 1.58 µM and remarkable inhibition of cell migration from the earliest time point of 4 h, persisting until 24 h. The two most active compounds are further evaluated in clinically relevant models,including gemcitabine-resistant and primary cells (PATU-T GR, PDAC3), confirming their potent activity. They induce apoptosis, upregulate apoptotic gene expression, and disrupt the cell cycle, significantly reducing the viability of spheroidal PATU-T cultures. Additionally, both compounds effectively inhibit CDK7, as demonstrated by an enzyme-linked immunosorbent assay in cell extracts and by a specific enzymatic activity assay.