Synthesis and Profiling of a Novel Potent Selective Inhibitor of CHK1 Kinase Possessing Unusual N-trifluoromethylpyrazole Pharmacophore Resistant to Metabolic N-dealkylation

Abstract

Checkpoint-mediated dependency of tumor cells can be deployed to selectively kill them without substantial toxicity to normal cells. Specifically, loss of CHK1, a serine threonine kinase involved in the surveillance of the G-M checkpoint in the presence of replication stress inflicted by DNA-damaging drugs, has been reported to dramatically influence the viability of tumor cells. CHK1's pivotal role in maintaining genomic stability offers attractive opportunity for increasing the selectivity, effectivity, and reduced toxicity of chemotherapy. Some recently identified CHK1 inhibitors entered clinical trials in combination with DNA antimetabolites. Herein, we report synthesis and profiling of MU380, a nontrivial analogue of clinically profiled compound SCH900776 possessing the highly unusual N-trifluoromethylpyrazole motif, which was envisioned not to undergo metabolic oxidative dealkylation and thereby provide greater robustness to the compound. MU380 is a selective and potent inhibitor of CHK1 which sensitizes a variety of tumor cell lines to hydroxyurea or gemcitabine up to 10 times. MU380 shows extended inhibitory effects in cells, and unlike SCH900776, does not undergo N-dealkylation to the significantly less selective metabolite. Compared with SCH900776, MU380 in combination with GEM causes higher accumulation of DNA damage in tumor cells and subsequent enhanced cell death, and is more efficacious in the A2780 xenograft mouse model. Overall, MU380 represents a novel state-of-the-art CHK1 inhibitor with high potency, selectivity, and improved metabolic robustness to oxidative N-dealkylation..

Novel CHK1 inhibitor MU380 exhibits significant single-agent activity in TP53-mutated chronic lymphocytic leukemia cells

“…Specifically, SCH900776 contains the N-methylpyrazole motif, which undergoes oxidative demethylation resulting in the formation of significantly less selective metabolite and a rapid decrease of active concentration in plasma. 26 In contrast, MU380 contains highly unusual N-trifluoromethylpyrazole pharmacophore, which provides substantially better metabolic robustness and pharmacokinetic profile. 26 The newly developed enantioselective synthesis of MU380 described here provides access to gram quantities of enantiomerically pure substance, which enables thorough in vivo testing of the compound.…”

“…Subsequently, we developed compound MU380, a non-trivial analog of SCH900776 which contains unusual N-trifluoromethylpyrazole moiety protecting the molecule from oxidative dealkylation and thus improving its metabolic stability. 26 With our current study, we present a robust enantioselective synthesis of MU380, and demonstrate its single-agent efficacy in lymphoid cancer cells. Significantly, to the best of our knowledge, we have for the first time demonstrated the potential for CHK1 inhibition to affect high-risk CLL cells with TP53 defects.…”

“…Finally, we found neat acetic acid to be the optimal solvent: cyclization was rapid and provided the desired pyrazolo[1,5-a]pyrimidine intermediate 4 in high yield (95%) and optical purity (96% ee). Using part of the sequence we had previously reported, 26 compound 4 was converted into advanced intermediate 11, utilizing the in-house prepared boronate 9. Optical purity of 11 (96% ee) was again determined by HPLC on chiral stationary phase, confirming that no loss of stereochemical integrity was associated with the post-cyclization steps of the sequence.…”

“…Our novel inhibitor showed satisfactory target-specific effects in a pilot study using cell lines established from solid tumors. 26 Herein, we first explored whether MU380 also efficiently inhibits CHK1 in lymphoid tumor cells. We treated NALM-6 and MEC-1 cell lines with gemcitabine, a potent inductor of RS, and analyzed impact of Single-agent CHK1 inhibition in CLL haematologica | 2019; 104 (12) the inhibitor on CHK1 protein.…”

The CHK1 inhibitor MU380 significantly increases the sensitivity of human docetaxel‐resistant prostate cancer cells to gemcitabine through the induction of mitotic catastrophe

“…Interestingly, androgen receptor (AR) signaling has been reported to specifically regulate DDR genes and its activity strongly correlates with the enhanced activation of ATR-CHK1 axis, castration resistance, metastasis, and decreased survival of PCa patients [17,18]. Given the high-rate mutation events in DDR in mCRPC, CHK1 remains an essential molecule for controlling DDR and cell cycle and its targeting represents a particularly intriguing strategy for anticancer therapy [19,20].…”