Characterization of LY3023414, a Novel PI3K/mTOR Dual Inhibitor Eliciting Transient Target Modulation to Impede Tumor Growth.

The PI3K/AKT/mTOR pathway is among the most frequently altered pathways in cancer cell growth and survival. LY3023414 is a complex fused imidazoquinolinone with high solubility across a wide pH range designed to inhibit class I PI3K isoforms and mTOR kinase. Here, we describe the in vitro and in vivo activity of LY3023414. LY3023414 was highly soluble at pH 2-7. In biochemical testing against approximately 266 kinases, LY3023414 potently and selectively inhibited class I PI3K isoforms, mTORC1/2, and DNA-PK at low nanomolar concentrations. In vitro, inhibition of PI3K/AKT/mTOR signaling by LY3023414 caused G1 cell-cycle arrest and resulted in broad antiproliferative activity in cancer cell panel screens. In vivo, LY3023414 demonstrated high bioavailability and dose-dependent dephosphorylation of PI3K/AKT/mTOR pathway downstream substrates such as AKT, S6K, S6RP, and 4E-BP1 for 4 to 6 hours, reflecting the drug's half-life of 2 hours. Of note, equivalent total daily doses of LY3023414 given either once daily or twice daily inhibited tumor growth to similar extents in multiple xenograft models, indicating that intermittent target inhibition is sufficient for antitumor activity. In combination with standard-of-care drugs, LY3023414 demonstrated additive antitumor activity. The novel, orally bioavailable PI3K/mTOR inhibitor LY3023414 is highly soluble and exhibits potent in vivo efficacy via intermittent target inhibition. It is currently being evaluated in phase I and II trials for the treatment of human malignancies. Mol Cancer Ther; 15(10); 2344-56. ©2016 AACR.

A novel CDK9 inhibitor shows potent antitumor efficacy in preclinical hematologic tumor models.

DNA-dependent RNA polymerase II (RNAP II) largest subunit RPB1 C-terminal domain (CTD) kinases, including CDK9, are serine/threonine kinases known to regulate transcriptional initiation and elongation by phosphorylating Ser 2, 5, and 7 residues on CTD. Given the reported dysregulation of these kinases in some cancers, we asked whether inhibiting CDK9 may induce stress response and preferentially kill tumor cells. Herein, we describe a potent CDK9 inhibitor, LY2857785, that significantly reduces RNAP II CTD phosphorylation and dramatically decreases MCL1 protein levels to result in apoptosis in a variety of leukemia and solid tumor cell lines. This molecule inhibits the growth of a broad panel of cancer cell lines, and is particularly efficacious in leukemia cells, including orthotopic leukemia preclinical models as well as in ex vivo acute myeloid leukemia and chronic lymphocytic leukemia patient tumor samples. Thus, inhibition of CDK9 may represent an interesting approach as a cancer therapeutic target, especially in hematologic malignancies.

Methacholine-induced pulmonary gas trapping in a mouse model of allergic asthma: effect of inhaled budesonide and ciglitazone.

Previously, we found pulmonary gas trapping to be a rapid, simple and objective measure of methacholine-induced airway obstruction in naïve mice. In this study we extended that finding by using methacholine-induced pulmonary gas trapping to differentiate airway responses of ovalbumin-sensitized, ovalbumin-exposed (Positive Control) and ovalbumin-sensitized, sodium chloride-exposed (Negative Control) mice. Additionally, pulmonary gas trapping and enhanced pause were compared following methacholine exposure in sensitized and nonsensitized mice. Finally, we examined by nose-only inhalation the ability of the glucocorticosteroid budesonide and the peroxisome proliferator-activated receptor-gamma agonist ciglitazone to modify methacholine-induced airway responses in ovalbumin-sensitized mice. Positive Controls exhibited a 7.8-fold increase in sensitivity and a 2.4-fold enhancement in the maximal airway obstruction to methacholine versus Negative Controls. Following methacholine, individual Positive and Negative Control mouse enhanced pause values overlapped in 9 of 9 studies, whereas individual Positive and Negative Control mouse excised lung gas volume values overlapped in only 1 of 9 studies, and log[excised lung gas volume] correlated (P=0.023) with in vivo log[enhanced pause] in nonsensitized mice. Finally, budesonide (100.0 or 1000.0 microg/kg) reduced methacholine-mediated airway responses and eosinophils and neutrophils, whereas ciglitazone (1000.0 microg/kg) had no effect on methacholine-induced pulmonary gas trapping, but reduced eosinophils. In conclusion, pulmonary gas trapping is a more reproducible measure of methacholine-mediated airway responses in ovalbumin-sensitized mice than enhanced pause. Also, excised lung gas volume changes can be used to monitor drug interventions like budesonide. Finally, this study highlights the importance of running a positive comparator when examining novel treatments like ciglitazone.

A transforming mutation in the pleckstrin homology domain of AKT1 in cancer.

Although AKT1 (v-akt murine thymoma viral oncogene homologue 1) kinase is a central member of possibly the most frequently activated proliferation and survival pathway in cancer, mutation of AKT1 has not been widely reported. Here we report the identification of a somatic mutation in human breast, colorectal and ovarian cancers that results in a glutamic acid to lysine substitution at amino acid 17 (E17K) in the lipid-binding pocket of AKT1. Lys 17 alters the electrostatic interactions of the pocket and forms new hydrogen bonds with a phosphoinositide ligand. This mutation activates AKT1 by means of pathological localization to the plasma membrane, stimulates downstream signalling, transforms cells and induces leukaemia in mice. This mechanism indicates a direct role of AKT1 in human cancer, and adds to the known genetic alterations that promote oncogenesis through the phosphatidylinositol-3-OH kinase/AKT pathway. Furthermore, the E17K substitution decreases the sensitivity to an allosteric kinase inhibitor, so this mutation may have important clinical utility for AKT drug development.