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Analyses of compounds in clinical development have shown that ligand efficient-molecules with privileged physical properties and low dose are less likely to fail in the various stages of clinical testing, have fewer postapproval withdrawals, and are less likely to receive black box safety warnings. However, detailed side-by-side examination of molecular interactions and properties within single drug classes are lacking. As a class, VEGF receptor tyrosine kinase inhibitors (VEGFR TKIs) have changed the landscape of how cancer is treated, particularly in clear cell renal cell carcinoma, which is molecularly linked to the VEGF signaling axis. Despite the clear role of the molecular target, member molecules of this validated drug class exhibit distinct clinical efficacy and safety profiles in comparable renal cell carcinoma clinical studies. The first head-to-head randomized phase III comparative study between active VEGFR TKIs has confirmed significant differences in clinical performance ) Lancet 378:193-1939. To elucidate how fundamental drug potency-efficiency is achieved and impacts differentiation within the VEGFR TKI class, we determined potencies, time dependence, selectivities, and X-ray structures of the drug-kinase complexes using a VEGFR2 TK construct inclusive of the important juxtamembrane domain. Collectively, the studies elucidate unique drug-kinase interactions that are dependent on distinct juxtamembrane domain conformations, resulting in significant potency and ligand efficiency differences. The identified structural trends are consistent with in vitro measurements, which translate well to clinical performance, underscoring a principle that may be broadly applicable to prospective drug design for optimal in vivo performance.T he VEGF receptor (VEGFR) tyrosine kinases (TKs) are the clinically validated drug target of four structurally diverse TK inhibitors (TKIs) that have been approved in the renal cell carcinoma (RCC) setting (1, 2). The clear cell histology subtype of RCC is molecularly linked to the VEGF signaling axis by virtue of the ∼90% incidence of Von Hippel-Lindau (VHL) dysregulation. With VHL inactivation, hypoxia-inducible factor-α accumulates, leading to overproduction of the angiogenic factor VEGF among others. It is, therefore, generally accepted that on-target VEGFR TK inhibition accounts for the RCC efficacy seen within this class of TKIs. In addition to efficacy in RCC, VEGF signaling inhibition has been linked to side effects, with the most prominent being hypertension, which is consistently seen within the TKI class and the related monoclonal antibody to VEGF, bevacizumab (3).Despite the clear role of VEGF signaling on both hypertension and efficacy in RCC, these on-target pharmacologic effects differ in frequency and degree between approved VEGFR TKI drugs, indicating that the extent of VEGF signal blockade may not be equivalent. Recent reports have analyzed similar RCC clinical studies across leading VEGFR TKIs for comparison purposes (1, 2). Clear distinction in both efficacy...

Summary Crizotinib, an inhibitor of anaplastic lymphoma kinase (ALK), has also recently shown efficacy in the treatment of lung cancers with ROS1 translocations. Resistance to crizotinib developed in a patient with metastatic lung adenocarcinoma harboring a CD74–ROS1 rearrangement who had initially shown a dramatic response to treatment. We performed a biopsy of a resistant tumor and identified an acquired mutation leading to a glycine-to-arginine substitution at codon 2032 in the ROS1 kinase domain. Although this mutation does not lie at the gatekeeper residue, it confers resistance to ROS1 kinase inhibition through steric interference with drug binding. The same resistance mutation was observed at all the meta-static sites that were examined at autopsy, suggesting that this mutation was an early event in the clonal evolution of resistance. (Funded by Pfizer and others; ClinicalTrials.gov number, NCT00585195.)

Oncogenic c-ros oncogene1 (ROS1) fusion kinases have been identified in a variety of human cancers and are attractive targets for cancer therapy. The MET/ALK/ROS1 inhibitor crizotinib (Xalkori, PF-02341066) has demonstrated promising clinical activity in ROS1 fusion-positive non-small cell lung cancer. However, emerging clinical evidence has shown that patients can develop resistance by acquiring secondary point mutations in ROS1 kinase. In this study we characterized the ROS1 activity of PF-06463922, a novel, orally available, CNS-penetrant, ATP-competitive small-molecule inhibitor of ALK/ROS1. In vitro, PF-06463922 exhibited subnanomolar cellular potency against oncogenic ROS1 fusions and inhibited the crizotinib-refractory ROS1 G2032R mutation and the ROS1 G2026M gatekeeper mutation. Compared with crizotinib and the second-generation ALK/ROS1 inhibitors ceritinib and alectinib, PF-06463922 showed significantly improved inhibitory activity against ROS1 kinase. A crystal structure of the PF-06463922-ROS1 kinase complex revealed favorable interactions contributing to the high-affinity binding. Taken together, our results indicate that PF-06463922 has potential for treating ROS1 fusion-positive cancers, including those requiring agents with CNS-penetrating properties, as well as for overcoming crizotinib resistance driven by ROS1 mutation.PF-06463922 | ROS1 | kinase inhibitor R eceptor tyrosine kinases (RTKs) are vital conduits of extracellular signals that direct cell growth and survival pathways. Unregulated RTK activation through chromosomal rearrangements, point mutations, and gene amplification has been shown to be responsible for the initiation and progression of many cancers. The orphan RTK c-ros oncogene1 (ROS1) normally is expressed transiently in various tissues during development with little to no expression in adult tissues (1). Elevated full-length c-ROS1 expression levels have been observed in 20-30% of patients with nonsmall cell lung cancer (NSCLC) by gene expression profiling (2-4) and in 13% of patients with lung adenocarcinoma using immunohistochemistry (IHC) (5). However, its function, both in normal physiology and disease, remains poorly defined mainly because of its still unidentified ligand. Chromosomal rearrangements resulting in oncogenic activation of ROS1 have been observed in a subset of patients with glioblastoma (6-9), NSCLC (10-14), cholangiocarcinoma (15), ovarian cancer (16), angiosarcoma (17), inflammatory myofibroblastic tumors (18), and Spitzoid melanoma (19). To date, interchromosomal translocations or intrachromosomal deletions have resulted in the production of 20 different N-terminal ROS1 fusion genes in a variety of cancers (Table S1).ROS1 is a distinct receptor with a kinase domain that is phylogenetically related to the anaplastic lymphoma kinase/lymphocyte-specific protein tyrosine kinase (ALK/LTK) and insulin receptor (INSR) RTK families (20), suggesting that tyrosine kinase inhibitors for these receptors could have cross-activity against ROS1. A recent phase I/II cl...

Chinese local officials frequently employ relational repression to demobilize protesters.When popular action occurs, they investigate activists' social ties, locate individuals who might be willing to help stop the protest, assemble a work team, and dispatch it to conduct thought work. Work team members are then expected to use their personal influence to persuade relatives, friends and fellow townspeople to stand down. Those who fail are subject to punishment, including suspension of salary, removal from office, and prosecution. Relational repression sometimes works. When local authorities have considerable say over work team members and bonds with protesters are strong, relational repression can help demobilize protesters and halt popular action. Even if relational repression does not end a protest entirely, it can limit its length and scope by reducing tension at times of high strain and providing a channel for negotiation. Often, however, as in a 2005 environmental protest in Zhejiang, insufficiently tight ties and limited concern about consequences creates a commitment deficit, partly because thought workers recognize their ineffectiveness with many protesters and partly because they anticipate little or no punishment for failing to demobilize anyone other than a close relative.The practice and effectiveness of relational, "soft" repression in China casts light on how social ties can demobilize as well as mobilize contention and ways in which state and social power can be combined to serve state ends.Keywords: protest control; soft repression; policing; work teams; thought work; social networks Relational Repression in China: Using Social Ties to Demobilize Protesters For some years now, students of contentious politics have been calling for a broader understanding of protest control. 1 They argue that existing scholarship has been overly focused on state-based and "hard" forms of repression at the expense of less heavy-handed ways to suppress popular action. In order to redress this imbalance, a number of studies have explored how surveillance, Relational repression is a control technique that uses social ties to demobilize protesters. In China, it amounts to relying on relatives, friends, and native-place connections to defuse popular  For helpful comments, we would like to thank Loren Brandt, Lei Guang, Rongbin Han, William Hurst, Andrew Kipnis, Richard Madsen, Barry Naughton, Jean Oi, Eva Pils, Scott Rozelle, Rachel Stern, Nicolai Volland, Xueguang Zhou, the journal's two anonymous referees, and especially Lianjiang Li. Generous financial support was provided by the China Fieldwork Fund and a Residential Research Fellowship from the Institute of East Asian Studies, UC-Berkeley. 1For typologies of protest control, see Jennifer Earl, "Tanks, tear gas, and taxes: toward a theory of movement repression, " Sociological Theory, Vol. 21, No. 1 (2003) Studies, Vol. 10, No. 1 (2011), pp. 21-37. 3 Myra Marx Ferree, "Soft repression: ridicule, stigma, and silencing in gender-based movements," Re...

The checkpoint kinase Chk1 is an important mediator of cell cycle arrest following DNA damage. The 1.7 A resolution crystal structures of the human Chk1 kinase domain and its binary complex with an ATP analog has revealed an identical open kinase conformation. The secondary structure and side chain interactions stabilize the activation loop of Chk1 and enable kinase activity without phosphorylation of the catalytic domain. Molecular modeling of the interaction of a Cdc25C peptide with Chk1 has uncovered several conserved residues that are important for substrate selectivity. In addition, we found that the less conserved C-terminal region negatively impacts Chk1 kinase activity.

Cell death plays an important role in host-pathogen interactions. Crystal proteins (toxins) are essential components of Bacillus thuringiensis (Bt) biological pesticides because of their specific toxicity against insects and nematodes. However, the mode of action by which crystal toxins to induce cell death is not completely understood. Here we show that crystal toxin triggers cell death by necrosis signaling pathway using crystal toxin Cry6Aa-Caenorhabditis elegans toxin-host interaction system, which involves an increase in concentrations of cytoplasmic calcium, lysosomal lyses, uptake of propidium iodide, and burst of death fluorescence. We find that a deficiency in the necrosis pathway confers tolerance to Cry6Aa toxin. Intriguingly, the necrosis pathway is specifically triggered by Cry6Aa, not by Cry5Ba, whose amino acid sequence is different from that of Cry6Aa. Furthermore, Cry6Aa-induced necrosis pathway requires aspartic protease (ASP-1). In addition, ASP-1 protects Cry6Aa from over-degradation in C. elegans. This is the first demonstration that deficiency in necrosis pathway confers tolerance to Bt crystal protein, and that Cry6A triggers necrosis represents a newly added necrosis paradigm in the C. elegans. Understanding this model could lead to new strategies for nematode control.

We report a facile synthesis of bifunctional Fe3O4-Ag(125)I heterodimers for use as dual-modality imaging agents in magnetic resonance (MR) and single-photon emission computed tomography (SPECT). We introduced (125)I, which is a clinically used radioisotope, as a SPECT reporter, into Fe3O4-Ag heterodimer nanoparticles to provide a new type of bifunctional contrast agent for MRI and SPECT imaging.