LY3009120 is a pan-RAF and RAF dimer inhibitor that inhibits all RAF isoforms and occupies both protomers in RAF dimers. Biochemical and cellular analyses revealed that LY3009120 inhibits ARAF, BRAF, and CRAF isoforms with similar affinity, while vemurafenib or dabrafenib have little or modest CRAF activity compared to their BRAF activities. LY3009120 induces BRAF-CRAF dimerization but inhibits the phosphorylation of downstream MEK and ERK, suggesting that it effectively inhibits the kinase activity of BRAF-CRAF heterodimers. Further analyses demonstrated that LY3009120 also inhibits various forms of RAF dimers including BRAF or CRAF homodimers. Due to these unique properties, LY3009120 demonstrates minimal paradoxical activation, inhibits MEK1/2 phosphorylation, and exhibits anti-tumor activities across multiple models carrying KRAS, NRAS, or BRAF mutation.

Ripretinib (DCC-2618) was designed to inhibit the full spectrum of mutant KIT and PDGFRA kinases found in cancers and myeloproliferative neoplasms, particularly in gastrointestinal stromal tumors (GISTs), in which the heterogeneity of drug-resistant KIT mutations is a major challenge. Ripretinib is a ''switch-control'' kinase inhibitor that forces the activation loop (or activation ''switch'') into an inactive conformation. Ripretinib inhibits all tested KIT and PDGFRA mutants, and notably is a type II kinase inhibitor demonstrated to broadly inhibit activation loop mutations in KIT and PDGFRA, previously thought only achievable with type I inhibitors. Ripretinib shows efficacy in preclinical cancer models, and preliminary clinical data provide proof-of-concept that ripretinib inhibits a wide range of KIT mutants in patients with drug-resistant GISTs.

We have previously demonstrated decreased Jun/AP-1 activity in the breast cancer cell line MCF-7 when compared to normal or immortalized mammary epithelial cells. In this paper, we overexpress Jun in MCF-7 cells (MCF7Jun) and demonstrate that it results in diverse biologic and biochemical changes, which mimic those seen clinically in breast cancer. Overexpression of Jun causes signi®cant alterations in the composition of AP-1, decreased junB and increased fra-1 expression and results in an increased biologic aggressiveness. MCF7Jun cells exhibit increased cellular motility, increased expression of a matrix degrading enzyme MMP-9, increased in vitro chemoinvasion and tumor formation in nude mice in the absence of exogenous estrogens. Furthermore, MCF7Jun cells are unresponsive to the growth stimulating e ects of estrogen and growth inhibitory e ects of tamoxifen. Analysis of the estrogen receptor (ER) expression and activity showed that the MCF7Jun cells have no detectable ER. MCF-7 cells overexpressing mutant forms of cJun were responsive to the growth stimulatory e ects of estrogen indicating that full-length cJun is required to acquire the estrogenindependent phenotype in breast cancer cells.

Summary Acquired resistance to ABL1 tyrosine kinase inhibitors (TKIs) through ABL1 kinase domain mutations, particularly the gatekeeper mutant T315I, is a significant problem for chronic myeloid leukemia (CML) patients. Using structure-based drug design, we developed compounds that bind to residues (Arg386/Glu282) ABL1 uses to switch between inactive and active conformations. The lead “switch-control” inhibitor, DCC-2036, potently inhibits both unphosphorylated and phosphorylated ABL1 by inducing a type II inactive conformation, and retains efficacy against the majority of clinically relevant CML resistance mutants, including T315I. DCC-2036 inhibits BCR-ABL1T315I-expressing cell lines, prolongs survival in mouse models of T315I-mutant CML and B-lymphoblastic leukemia, and inhibits primary patient leukemia cells expressing T315I in vitro and in vivo, supporting its clinical development in TKI-resistant Ph+ leukemia.

The antidiabetic thiazolidinediones, which include troglitazone and rosiglitazone, are ligands for the nuclear receptor peroxisome proliferator-a c t i v a t e d receptor (PPA R )-and exert their antihyperglycemic e ffects by regulation of PPA R--responsive genes. We report here that PPA R-activation by troglitazone depends on the experimental setting. Troglitazone acts as a partial agonist for PPA R-in transfected muscle (C2C12) and kidney (HEK 293T) cells, producing a submaximal transcriptional response (1.8-to 2.5-fold activation) compared with rosiglitazone (7.4-to 13-fold activation). Additionally, troglitazone antagonizes rosiglitazone-stimulated PPA R-transcriptional activity. Limited protease digestion of PPA R-suggests conformational differences in the receptor bound to troglitazone versus rosiglitazone. Consistent with this fin d i n g , an in vitro coactivator association assay demonstrated that troglitazone-bound PPA R-recruited the transcriptional coactivators p300 and steroid receptor coactivator 1 less efficiently than rosiglitazone-bound receptor. In contrast to these observations, troglitazone behaves as a full agonist of PPA R-in 3T3L1 adipocytes. Tw odimensional protein gel electrophoresis demonstrated that troglitazone and rosiglitazone regulated distinct but overlapping sets of genes in several cell types. Thus, troglitazone may behave as a partial agonist under certain physiological circumstances and as a full agonist in others. These differences could be caused by variations in the amount of specific cofactors, differences in PPA R response elements, or the presence of different isoforms of PPA R-. D i a b e t e s 4 9 :5 3 9-547, 2000 T ype 2 diabetes is characterized by decreased insulin sensitivity of peripheral tissues. Glucose homeostasis is maintained under these circumstances by increased insulin secretion from pancreatic -cells. In some cases, the -cell is unable to maintain increased output. The antidiabetic thiazolidinediones (TZDs), such as troglitazone, improve peripheral insulin sensitivity, leading to reduced blood glucose and insulin levels and the preservation of pancreatic function (1-4). Improvement of insulin sensitivity by TZDs is most likely due to the activation of the peroxisome proliferator-activated receptor (PPA R )-(5). The TZDs are high-affinity ligands for PPA R-in vitro, and the rank order of receptor affinity correlates with their in vivo hypoglycemic activity (6), with one reported exception (7). Although many of the molecular details are not clearly understood, a model has emerged in which activated PPA R-m o dulates the transcriptional activity of a set of genes encoding proteins that are important in glucose and lipid metabolism. H o w e v e r, the identity of these genes and the precise pathways leading to the normalization of insulin sensitivity remain largely unknown.R e c e n t l y, the X-ray crystal structure of the ligand-binding domain of PPA R-has been elucidated (3,8), revealing that ligand binding causes a conformational change within P PA R-such...