Structure-Based Design of Orally Bioavailable 1H-Pyrrolo[3,2-c]pyridine Inhibitors of Mitotic Kinase Monopolar Spindle 1 (MPS1)

Abstract

The protein kinase MPS1 is a crucial component of the spindle assembly checkpoint signal and is aberrantly overexpressed in many human cancers. MPS1 is one of the top 25 genes overexpressed in tumors with chromosomal instability and aneuploidy. PTEN-deficient breast tumor cells are particularly dependent upon MPS1 for their survival, making it a target of significant interest in oncology. We report the discovery and optimization of potent and selective MPS1 inhibitors based on the 1H-pyrrolo[3,2-c]pyridine scaffold, guided by structure-based design and cellular characterization of MPS1 inhibition, leading to 65 (CCT251455). This potent and selective chemical tool stabilizes an inactive conformation of MPS1 with the activation loop ordered in a manner incompatible with ATP and substrate-peptide binding; it displays a favorable oral pharmacokinetic profile, shows dose-dependent inhibition of MPS1 in an HCT116 human tumor xenograft model, and is an attractive tool compound to elucidate further the therapeutic potential of MPS1 inhibition.

Understanding inhibitor resistance in Mps1 kinase through novel biophysical assays and structures

“…These assays are highly specific for Mps1, but hard to quantify. Another more recently demonstrated way of measuring Mps1 kinase activity is a mobility shift assay described by Naud et al [5]: phosphorylated and non-phosphorylated peptides are separated by electrophoresis based on their charges [14]. This mobility shift assay has been compared with a radiometric assay and found to be more robust [21].…”

“…Due to its importance for the viability of tumor cells, Mps1 kinase has become a potential target for cancer treatment [2]. Over the past years, several dozens of small compounds have been developed to inhibit the Mps1 kinase activity [2][3][4][5][6][7]. Recently, NMS-P715 has been described to suppress the growth of medulloblastoma cells, a common malignant brain tumor in children [8].…”

LEADOPT: An automatic tool for structure-based lead optimization, and its application in structural optimizations of VEGFR2 and SYK inhibitors

“…Naud et al recently identified a series of 1H-Pyrrolo[3,2-c]pyridine derivatives as inhibitors of MPS1 through structure-based drug design, and obtained a crystal structure of MPS1with one inhibitor (T2), N-(3,4-dimethoxyphenyl)-2-(1H-pyrazol-4-yl)-1H-pyrrolo[3,2-c] pyridin-6-amine (PDB code: 4C4E) [36]. Here the 1H-pyrrolo[3,2-c]pyridin-6-amine moiety of T2 was defined as the core scaffold (Table 4).…”

Predicting drug resistance before it occurs

“…An overlay of the structure of Mps1 in complex with NMS-P715 bound, 12 with Mps1 bound to ATP 30 and a recent structure in which the K553/E571 catalytic pair has a more catalytically competent conformation, 39 shows structural variability particularly in the area around Y568, neighboring the mutated I598. As Mps1 inhibitors exert (part of) their effect through interfering with the K553/E571 catalytic pair, 30 it is not unlikely that the I598F mutation may limit Y568 flexibility, Figure 4.…”

“…12 NMS-P715 is shown in yellow, the wild-type residues in grey, and mutated residues in coral. 12 (grey), with the crystal structures of an ATP bound 30 (green) and a pyrrolopyridine inhibitor 39 (blue). Only one main chain is shown for clarity.…”