Fragment Optimization of Reversible Binding to the Switch II Pocket on KRAS Leads to a Potent, In Vivo Active KRAS Inhibitor.

Activating mutations in KRAS are the most frequent oncogenic alterations in cancer. The oncogenic hotspot position 12, located at the lip of the switch II pocket, offers a covalent attachment point for KRAS inhibitors. To date, KRAS inhibitors have been discovered by first covalently binding to the cysteine at position 12 and then optimizing pocket binding.

BI-3406, a Potent and Selective SOS1-KRAS Interaction Inhibitor, Is Effective in KRAS-Driven Cancers through Combined MEK Inhibition.

is the most frequently mutated driver of pancreatic, colorectal, and non-small cell lung cancers. Direct KRAS blockade has proved challenging, and inhibition of a key downstream effector pathway, the RAF-MEK-ERK cascade, has shown limited success because of activation of feedback networks that keep the pathway in check. We hypothesized that inhibiting SOS1, a KRAS activator and important feedback node, represents an effective approach to treat KRAS-driven cancers.

Intracellular Trapping of the Selective Phosphoglycerate Dehydrogenase (PHGDH) Inhibitor Disrupts Serine Biosynthesis.

Phosphoglycerate dehydrogenase (PHGDH) is known to be the rate-limiting enzyme in the serine synthesis pathway in humans. It converts glycolysis-derived 3-phosphoglycerate to 3-phosphopyruvate in a co-factor-dependent oxidation reaction. Herein, we report the discovery of , a prodrug of the co-factor nicotinamide adenine dinucleotide (NADH/NAD)-competitive PHGDH inhibitor , which has shown high selectivity against the majority of other dehydrogenase targets.

The novel BET bromodomain inhibitor BI 894999 represses super-enhancer-associated transcription and synergizes with CDK9 inhibition in AML.

Bromodomain and extra-terminal (BET) protein inhibitors have been reported as treatment options for acute myeloid leukemia (AML) in preclinical models and are currently being evaluated in clinical trials. This work presents a novel potent and selective BET inhibitor (BI 894999), which has recently entered clinical trials (NCT02516553). In preclinical studies, this compound is highly active in AML cell lines, primary patient samples, and xenografts.

Synergistic activity of BET inhibitor BI 894999 with PLK inhibitor volasertib in AML in vitro and in vivo.

Interactions between a new potent Bromodomain and extraterminal domain (BET) inhibitor BI 894999 and the polo-like kinase (PLK) inhibitor volasertib were studied in acute myeloid leukemia cell lines in vitro and in vivo. We provide data for the distinct mechanisms of action of these two compounds with a potential utility in AML based on gene expression, cell cycle profile and modulation of PD biomarkers such as MYC and HEXIM1. In contrast to BI 894999, volasertib treatment neither affects MYC nor HEXIM1 expression, but augments and prolongs the decrease of MYC expression caused by BI 894999 treatment.

Efficacy and mechanism of action of volasertib, a potent and selective inhibitor of Polo-like kinases, in preclinical models of acute myeloid leukemia.

Polo-like kinase 1 (Plk1), a member of the Polo-like kinase family of serine/threonine kinases, is a key regulator of multiple steps in mitosis. Here we report on the pharmacological profile of volasertib, a potent and selective Plk inhibitor, in multiple preclinical models of acute myeloid leukemia (AML) including established cell lines, bone marrow samples from AML patients in short-term culture, and subcutaneous as well as disseminated in vivo models in immune-deficient mice. Our results indicate that volasertib is highly efficacious as a single agent and in combination with established and emerging AML drugs, including the antimetabolite cytarabine, hypomethylating agents (decitabine, azacitidine), and quizartinib, a signal transduction inhibitor targeting FLT3.

Satb1 and Satb2 are dispensable for X chromosome inactivation in mice.

Satb1 and Satb2 have been recently described as regulators of embryonic stem (ES) cell pluripotency and as silencing factors in X chromosome inactivation. The influence of the pluripotency machinery on X chromosome inactivation and the lack of an X chromosome inactivation defect in Satb1(-/-) and Satb2(-/-) mice raise the question of whether or not Satb proteins are directly and/or redundantly involved in this process. Here, we analyzed X chromosome inactivation in fibroblastic cells that were derived from female Satb1(-/-)Satb2(-/-) embryos.

Satb1 and Satb2 regulate embryonic stem cell differentiation and Nanog expression.

Satb1 and the closely related Satb2 proteins regulate gene expression and higher-order chromatin structure of multigene clusters in vivo. In examining the role of Satb proteins in murine embryonic stem (ES) cells, we find that Satb1(-/-) cells display an impaired differentiation potential and augmented expression of the pluripotency determinants Nanog, Klf4, and Tbx3. Metastable states of self-renewal and differentiation competence have been attributed to heterogeneity of ES cells in the expression of Nanog.

Hematopoietic precursor cells transiently reestablish permissiveness for X inactivation.

Xist is the trigger for X inactivation in female mammals. The long noncoding Xist RNA localizes along one of the two female X chromosomes and initiates chromosome-wide silencing in the early embryo. In differentiated cells, Xist becomes dispensable for the maintenance of the inactive X, and its function for initiation of silencing is lost.

Blurring cis and trans in gene regulation.

In this issue of Cell, Axel and colleagues (Lomvardas et al., 2006) report that a single enhancer of an odorant receptor (OR) gene cluster interacts with multiple OR gene promoters on different chromosomes. This study suggests a mechanism that allows olfactory sensory neurons to choose randomly and express only one out of more than 1000 OR genes.

A chromosomal memory triggered by Xist regulates histone methylation in X inactivation.

We have elucidated the kinetics of histone methylation during X inactivation using an inducible Xist expression system in mouse embryonic stem (ES) cells. Previous reports showed that the ability of Xist to trigger silencing is restricted to an early window in ES cell differentiation. Here we show that this window is also important for establishing methylation patterns on the potential inactive X chromosome.

Initial evaluation of a new optic laryngoscope blade.

We report on a new optic laryngoscope blade that provides two views of the larynx during tracheal intubation. The availability of an alternative direct view of the larynx may improve the ability of anesthesia providers to observe the tracheal tube passing through the vocal cords when using a Macintosh laryngoscope blade. The optic port improved visualization of passage of the endotracheal tube in obese patients.