Identification of the Clinical Development Candidate MRTX849, a Covalent KRASG12C Inhibitor for the Treatment of Cancer.

Capping off an era marred by drug development failures and punctuated by waning interest and presumed intractability toward direct targeting of KRAS, new technologies and strategies are aiding in the target's resurgence. As previously reported, the tetrahydropyridopyrimidines were identified as irreversible covalent inhibitors of KRASG12C that bind in the switch-II pocket of KRAS and make a covalent bond to cysteine 12. Using structure-based drug design in conjunction with a focused in vitro absorption, distribution, metabolism and excretion screening approach, analogues were synthesized to increase the potency and reduce metabolic liabilities of this series. The discovery of the clinical development candidate MRTX849 as a potent, selective covalent inhibitor of KRASG12C is described.

Discovery and preclinical development of AR453588 as an anti-diabetic glucokinase activator.

Glucose flux through glucokinase (GK) controls insulin release from the pancreas in response to high levels of glucose. Flux through GK is also responsible for reducing hepatic glucose output. Since many individuals with type 2 diabetes appear to have an inadequacy or defect in one or both of these processes, identifying compounds that can activate GK could provide a therapeutic benefit. Herein we report the further structure activity studies of a novel series of glucokinase activators (GKA). These studies led to the identification of pyridine 72 as a potent GKA that lowered post-prandial glucose in normal C57BL/6J mice, and after 14d dosing in ob/ob mice.

A Next-Generation TRK Kinase Inhibitor Overcomes Acquired Resistance to Prior TRK Kinase Inhibition in Patients with TRK Fusion-Positive Solid Tumors.

Larotrectinib, a selective TRK tyrosine kinase inhibitor (TKI), has demonstrated histology-agnostic efficacy in patients with TRK fusion-positive cancers. Although responses to TRK inhibition can be dramatic and durable, duration of response may eventually be limited by acquired resistance. LOXO-195 is a selective TRK TKI designed to overcome acquired resistance mediated by recurrent kinase domain (solvent front and xDFG) mutations identified in multiple patients who have developed resistance to TRK TKIs. Activity against these acquired mutations was confirmed in enzyme and cell-based assays and in vivo tumor models. As clinical proof of concept, the first 2 patients with TRK fusion-positive cancers who developed acquired resistance mutations on larotrectinib were treated with LOXO-195 on a first-in-human basis, utilizing rapid dose titration guided by pharmacokinetic assessments. This approach led to rapid tumor responses and extended the overall duration of disease control achieved with TRK inhibition in both patients.Significance: LOXO-195 abrogated resistance in TRK fusion-positive cancers that acquired kinase domain mutations, a shared liability with all existing TRK TKIs. This establishes a role for sequential treatment by demonstrating continued TRK dependence and validates a paradigm for the accelerated development of next-generation inhibitors against validated oncogenic targets. Cancer Discov; 7(9); 963-72. ©2017 AACR.See related commentary by Parikh and Corcoran, p. 934This article is highlighted in the In This Issue feature, p. 920.

Chk1 inhibition and Wee1 inhibition combine synergistically to impede cellular proliferation.

Inhibition of the checkpoint kinase Chk1, both as a monotherapy and in combination with DNA damaging cytotoxics, is a promising therapeutic approach for the treatment of a wide array of human cancers. However, much remains to be elucidated in regard to the patient populations that will respond best to a Chk1 inhibitor and the optimal therapeutics to combine with a Chk1 inhibitor. In an effort to discover sensitizing mutations and novel combination strategies for Chk1 inhibition, an siRNA screen was performed in combination with the selective Chk1 inhibitor AR458323. This screen employed a custom made library of siRNAs targeting 195 genes, most of which are involved in cell-cycle control or DNA damage repair. One of the most prominent and consistent hits across runs of the screen performed in three different cancer cell lines was Wee1 kinase. MK-1775 is a small molecule inhibitor of Wee1 that is currently in early stage clinical trials. In confirmation of the results obtained from the siRNA screen, AR458323 and MK-1775 synergistically inhibited proliferation in multiple cancer cell types. This antiproliferative effect correlated with a synergistic induction of apoptosis. In cellular mechanistic studies, the combination of the two molecules resulted in dramatic decreases in inhibitory phosphorylation of cyclin-dependent kinases, an increase in DNA damage, alterations in cell-cycle profile, and collapse of DNA synthesis. In conclusion, the clinical combination of a Chk1 inhibitor and a Wee1 inhibitor holds promise as an effective treatment strategy for cancer.

Single-agent inhibition of Chk1 is antiproliferative in human cancer cell lines in vitro and inhibits tumor xenograft growth in vivo.

Chk1 is a serine/threonine kinase that plays several important roles in the cellular response to genotoxic stress. Since many current standard-of-care therapies for human cancer directly damage DNA or inhibit DNA synthesis, there is interest in using small molecule inhibitors of Chk1 to potentiate their clinical activity. Additionally, Chk1 is known to be critically involved in cell cycle progression of unperturbed cells. Therefore, it is plausible that treatment with a Chkl inhibitor alone could also be an efficacious cancer therapy. Here we report that Chk1-A, a potent and highly selective small molecule inhibitor of Chk1, is antiproliferative as a single agent in a variety of human cancer cell lines in vitro. The inhibition of proliferation is associated with collapse of DNA replication and apoptosis. Rapid decreases in inhibitory phosphorylation of CDKs and a concomitant increase in CDK kinase activity and chromatin loading of Cdc45 suggest that the antiproliferative and proapoptotic activity of Chk1-A is at least in part due to deregulation of DNA synthesis. We extend these in vitro studies by demonstrating that Chk1-A inhibits the growth of tumor xenografts in vivo in a treatment regimen that is well tolerated. Together, these results suggest that single-agent inhibition of Chk1 may be an effective treatment strategy for selected human malignancies.

Identification, characterization, and crystal structure of Bacillus subtilis nicotinic acid mononucleotide adenylyltransferase.

The nadD gene, encoding the enzyme nicotinic acid mononucleotide (NaMN) adenylyltransferase (AT), is essential for the synthesis of NAD and subsequent viability of the cell. The nadD gene in Bacillus subtilis (yqeJ) was identified by sequence homology with other bacterial nadD genes and by biochemical characterization of the gene product. NaMN AT catalyzes the reversible adenylation of both NaMN and the nicotinamide mononucleotide (NMN) but shows specificity for the nicotinate. In contrast to other known NMN ATs, biophysical characterizations reveal it to be a dimer. The NaMN AT crystal structure was determined for both the apo enzyme and product-bound form, to 2.1 and 3.2 A, respectively. The structures reveal a "functional" dimer conserved in both crystal forms and a monomer fold common to members of the nucleotidyl-transferase alpha/beta phosphodiesterase superfamily. A structural comparison with family members suggests a new conserved motif (SXXXX(R/K)) at the N terminus of an alpha-helix, which is not part of the shared fold. Interactions of the nicotinic acid with backbone atoms indicate the structural basis for specificity.