Development of the First Covalent Monopolar Spindle Kinase 1 (MPS1/TTK) Inhibitor

Abstract

Monopolar spindle kinase 1 (MPS1/TTK) is a key element of the mitotic checkpoint and clinically evaluated as a target in the treatment of aggressive tumors such as triple-negative breast cancer. While long drug−target residence times have been suggested to be beneficial in the context of therapeutic MPS1 inhibition, no irreversible inhibitors have been reported. Here we present the design and characterization of the first irreversible covalent MPS1 inhibitor, RMS-07, targeting a poorly conserved cysteine in the kinase's hinge region. RMS-07 shows potent MPS1 inhibitory activity and selectivity against all protein kinases with an equivalent cysteine but also in a broader kinase panel. We demonstrate potent cellular target engagement and pronounced activity against various cancer cell lines. The covalent binding mode was validated by mass spectrometry and an X-ray crystal structure. This proof of MPS1 covalent ligandability may open new avenues for the design of MPS1-specific chemical probes or drugs.

Design, Synthesis, and Antitumor Activity of Potent and Selective EGFR L858R/T790M Inhibitors and Identification of a Combination Therapy to Overcome Acquired Resistance in Models of Non-small-cell Lung Cancer

“…The performed GSH stability assay for compound 28f and osimertinib was based on a similar assay described elsewhere . A total of 5 μL of a 10 mM compound 28f stock solution in DMSO was added to 5 μL of a 4 mM indoprofen solution in PBS as an internal standard.…”

“…The performed GSH stability assay for compound 28f and osimertinib was based on a similar assay described elsewhere. 54 A total of 5 μL of a 10 mM compound 28f stock solution in DMSO was added to 5 μL of a 4 mM indoprofen solution in PBS as an internal standard. The mixture was diluted with PBS buffer to a total volume of 1 mL of component A. Additionally, a freshly prepared solution of 10 mM GSH in PBS buffer was used as component B.…”

Technologies for Direct Detection of Covalent Protein–Drug Adducts

“…High-resolution structures of covalent adducts are available for various clinically approved TCIs including BTK inhibitors ibrutinib (PCI-32765, PDB: 5P9J) [108] and zanubrutinib (BGB-3111, PDB: 6J6M) [12], EGFR inhibitor afatinib (BIBW 2992, PDB: 4G5J) [14], and proteasome inhibitor bortezomib (PS-341, PDB: 2F16) [51]. The structural binding information can be used to gain insight into ligand binding driving target selectivity and/or reactivity [109][110][111][112] and can be combined with (covalent) docking studies [44,[113][114][115] to aid the structure-based design of covalent ligands with improved potency and/or selectivity [22,45,[116][117][118][119]. Structure-guided drug design approaches are employed to optimize the proximity of the electrophilic warhead to the nucleophilic amino acid [22].…”

30th Annual GP2A Medicinal Chemistry Conference

“…Notably, several reversible MPS1 inhibitors have entered clinical trials. Following a structure-based design approach, we were able to address a poorly conserved cysteine in the so-called hinge-region of the kinase to generate the first covalent MPS1 inhibitor, RMS07 [ 10 ]. BMX is a non-receptor tyrosine kinase belonging to the TEC-family and a close relative to Bruton’s tyrosine kinase, which is the target of FDA-approved drugs such as Ibrutinib and Acalabrutinib.…”