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PubMed | The Institute for Molecular Medicine Finland, Wellspring Biosciences, Llc, Southern Research Institute, University of Alabama at Birmingham and ActivX Biosciences
Type: Journal Article | Journal: Journal of biomolecular screening | Year: 2016

During viral infection of human cells, host kinases mediate signaling activities that are used by all viruses for replication; therefore, targeting of host kinases is of broad therapeutic interest. Here, host kinases were globally screened during human influenza virus (H1N1) infection to determine the time-dependent effects of virus infection and replication on kinase function. Desthiobiotin-labeled analogs of adenosine triphosphate and adenosine diphosphate were used to probe and covalently label host kinases in infected cell lysates, and probe affinity was determined. Using infected human A549 cells, we screened for time-dependent signal changes and identified host kinases whose probe affinities differed significantly when compared to uninfected cells. Our screen identified 10 novel host kinases that have not been previously shown to be involved with influenza virus replication, and we validated the functional importance of these novel kinases during infection using targeted small interfering RNAs (siRNAs). The effects of kinase-targeted siRNA knockdowns on replicating virus levels were measured by quantitative reverse-transcription PCR and cytoprotection assays. We identified several novel host kinases that, when knocked down, enhanced or reduced the viral load in cell culture. This preliminary work represents the first screen of the changing host kinome in influenza virus-infected human cells.


PubMed | University of California at Irvine, University of Houston, Oncology Rinat Research & Development, Hoffmann-La Roche and 2 more.
Type: Journal Article | Journal: Oncotarget | Year: 2016

mTOR activation leads to enhanced survival signaling in acute myeloid leukemia (AML) cells. The active-site mTOR inhibitors (asTORi) represent a promising new approach to targeting mTOR in AKT/mTOR signaling. MLN0128 is an orally-administered, second-generation asTORi, currently in clinical development. We examined the anti-leukemic effects and the mechanisms of action of MLN0128 in AML cell lines and primary samples, with a particular focus on its effect in AML stem/progenitor cells. MLN0128 inhibited cell proliferation and induced apoptosis in AML by attenuating the activity of mTOR complex 1 and 2. Using time-of-flight mass cytometry, we demonstrated that MLN0128 selectively targeted and functionally inhibited AML stem/progenitor cells with high AKT/mTOR signaling activity. Using the reverse-phase protein array technique, we measured expression and phosphorylation changes in response to MLN0128 in 151 proteins from 24 primary AML samples and identified several pro-survival pathways that antagonize MLN0128-induced cellular stress. A combined blockade of AKT/mTOR signaling and these pro-survival pathways facilitated AML cell killing. Our findings provide a rationale for the clinical use of MLN0128 to target AML and AML stem/progenitor cells, and support the use of combinatorial multi-targeted approaches in AML therapy.


Zhao Z.,Chinese Academy of Sciences | Wu H.,Chinese Academy of Sciences | Wu H.,Anhui University of Science and Technology | Wang L.,Chinese Academy of Sciences | And 5 more authors.
ACS Chemical Biology | Year: 2014

The ATP site of kinases displays remarkable conformational flexibility when accommodating chemically diverse small molecule inhibitors. The so-called activation segment, whose conformation controls catalytic activity and access to the substrate binding pocket, can undergo a large conformational change with the active state assuming a 'DFG-in' and an inactive state assuming a 'DFG-out' conformation. Compounds that preferentially bind to the DFG-out conformation are typically called 'type II' inhibitors in contrast to 'type I' inhibitors that bind to the DFG-in conformation. This review surveys the large number of type II inhibitors that have been developed and provides an analysis of their crystallographically determined binding modes. Using a small library of type II inhibitors, we demonstrate that more than 200 kinases can be targeted, suggesting that type II inhibitors may not be intrinsically more selective than type I inhibitors. © 2014 American Chemical Society.


Li S.,University of California at San Diego | Li S.,Wellspring Biosciences, Llc | Ni A.,University of California at San Diego | Feng G.-S.,University of California at San Diego
Acta Pharmacologica Sinica | Year: 2015

Bile acids (BAs) are traditionally considered as "physiological detergents" for emulsifying hydrophobic lipids and vitamins due to their amphipathic nature. But accumulating clinical and experimental evidence shows an association between disrupted BA homeostasis and various liver disease conditions including hepatitis infection, diabetes and cancer. Consequently, BA homeostasis regulation has become a field of heavy interest and investigation. After identification of the Farnesoid X Receptor (FXR) as an endogenous receptor for BAs, several nuclear receptors (SHP, HNF4α, and LRH-1) were also found to be important in regulation of BA homeostasis. Some post-translational modifications of these nuclear receptors have been demonstrated, but their physiological significance is still elusive. Gut secrets FGF15/19 that can activate hepatic FGFR4 and its downstream signaling cascade, leading to repressed hepatic BA biosynthesis. However, the link between the activated kinases and these nuclear receptors is not fully elucidated. Here, we review the recent literature on signal crosstalk in BA homeostasis. © 2015 CPS and SIMM .


Patricelli M.P.,Wellspring Biosciences, Llc | Janes M.R.,Wellspring Biosciences, Llc | Li L.-S.,Wellspring Biosciences, Llc | Hansen R.,Wellspring Biosciences, Llc | And 13 more authors.
Cancer Discovery | Year: 2016

KRAS gain-of-function mutations occur in approximately 30% of all human cancers. Despite more than 30 years of KRAS-focused research and development efforts, no targeted therapy has been discovered for cancers with KRAS mutations. Here, we describe ARS-853, a selective, covalent inhibitor of KRASG12C that inhibits mutant KRAS–driven signaling by binding to the GDP-bound oncoprotein and preventing activation. Based on the rates of engagement and inhibition observed for ARS-853, along with a mutant-specific mass spectrometry–based assay for assessing KRAS activation status, we show that the nucleotide state of KRASG12C is in a state of dynamic flux that can be modulated by upstream signaling factors. These studies provide convincing evidence that the KRASG12C mutation generates a “hyperexcitable” rather than a “statically active” state and that targeting the inactive, GDP-bound form is a promising approach for generating novel anti-RAS therapeutics. © 2016 American Association for Cancer Research.


Pemovska T.,University of Helsinki | Johnson E.,Pfizer | Kontro M.,University of Helsinki | Repasky G.A.,University of Helsinki | And 9 more authors.
Nature | Year: 2015

The BCR-ABL1 fusion gene is a driver oncogene in chronic myeloid leukaemia and 30-50% of cases of adult acute lymphoblastic leukaemia. Introduction of ABL1 kinase inhibitors (for example, imatinib) has markedly improved patient survival, but acquired drug resistance remains a challenge. Point mutations in the ABL1 kinase domain weaken inhibitor binding and represent the most common clinical resistance mechanism. The BCR-ABL1 kinase domain gatekeeper mutation Thr315Ile (T315I) confers resistance to all approved ABL1 inhibitors except ponatinib, which has toxicity limitations. Here we combine comprehensive drug sensitivity and resistance profiling of patient cells ex vivo with structural analysis to establish the VEGFR tyrosine kinase inhibitor axitinib as a selective and effective inhibitor for T315I-mutant BCR-ABL1-driven leukaemia. Axitinib potently inhibited BCR-ABL1(T315I), at both biochemical and cellular levels, by binding to the active form of ABL1(T315I) in a mutation-selective binding mode. These findings suggest that the T315I mutation shifts the conformational equilibrium of the kinase in favour of an active (DFG-in) A-loop conformation, which has more optimal binding interactions with axitinib. Treatment of a T315I chronic myeloid leukaemia patient with axitinib resulted in a rapid reduction of T315I-positive cells from bone marrow. Taken together, our findings demonstrate an unexpected opportunity to repurpose axitinib, an anti-angiogenic drug approved for renal cancer, as an inhibitor for ABL1 gatekeeper mutant drug-resistant leukaemia patients. This study shows that wild-type proteins do not always sample the conformations available to disease-relevant mutant proteins and that comprehensive drug testing of patient-derived cells can identify unpredictable, clinically significant drug-repositioning opportunities. © 2015 Macmillan Publishers Limited.


Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 225.02K | Year: 2013

DESCRIPTION (provided by applicant): The development of drugs that inhibit the K-Ras oncogene represents one of the greatest unmet needs in the treatment of human cancer. The Ras gene is the most frequently mutated oncogene in cancer, with a greater than 30% cumulative mutation frequency across all cancer types. Cancers with Ras mutations are aggressive and respond poorly to standard therapies. Previous attempts to target K-Ras have failed due to the difficulty of competing with the picomolar nucleotide affinity for the active sit and due to the high similarity of most GTPases. Our scientific co-founder, Professor Kevan Shokat, has discovered a novel, small molecule approach to target the most chemically tractable K-Ras mutant that contains a glycine-12 to cysteine mutation. The G12C mutation is the most common K-Ras mutation in lung cancer. Indeed, 43% of all lung cancers with K-Ras mutations contain the G12C mutation. This mutation positions a chemically reactive sulfhydryl group on the surface of K-Ras. Wehave carried out a preliminary 500 compound library screen based on mass spectrometry for molecules which bind covalently to K-rasG12C, H-rasG12C and counterscreened against WT K-Ras. 17 hits were identified from the screening library, and the first roundoptimization of the initial hits led to the discovery of a potent inhibitor JO-01-18. We have now solved the crystal structure of JO-01-148 bound to K-Ras G12C and identified a previously undescribed allosteric pocket on the surface of the protein adjacent to the cysteine moiety. This pocket makes it possible to identify irreversible inhibitors that bind in the pocket and selectively target the cysteine at position 12. Importantly, these small molecules inhibit only mutant K-Ras and not the normal protein. We have now solved more than 10 X-ray crystal structures of irreversible inhibitors bound to this allosteric pocket and synthesized more than 120 compounds. A clear SAR has been established. We are now proposing to further validate our lead G12C compounds in biochemical and cellular assays. The Phase I specific aims are: (1) Develop assays to evaluate K-Ras effector binding; (2) Demonstrate that the G12C irreversible binders can disrupt K-Ras effector binding; and (3) Demonstrate that the G12C irreversible binders can differentially affect tumor cells with G12C mutation compared to cells with wild type K-Ras and other K-Ras mutations. The Phase I milestone is the identification of K-ras G12C inhibitors that suppress proliferation of tumor cells with G12C K-ras mutation five-fold more potently (as measured by IC50 values) relative to tumor cells with other K-Ras mutations or wild type Ras. Collectively, we expect the Phase I results to demonstrate that we can generate a small molecule inhibitor that will specifically inhibit the growth of tumor cells wih K-Ras G12C mutation. If our approach is successful, our Phase II studies will more fully examine the safety, efficacy, and PK/biodistribution of a lead formulation for advancement to an IND application.PUBLIC HEALTH RELEVANCE PUBLIC HEALTH RELEVANCE: The K-Ras oncogene is present in gt80% of pancreatic tumors, gt40% of colon tumors and gt20% of lung tumors. Cancers with K-Ras mutations are aggressive and respond poorly to standard therapies. Thus,a drug that directly targets mutant K-Ras is highly desired to address this unmet medical need. The success of the proposed project would represent a significant advance for patients whose tumors harbor K-Ras mutations and have limited therapeutic options.


PubMed | Wellspring Biosciences, Llc
Type: Journal Article | Journal: Cancer discovery | Year: 2016

KRAS gain-of-function mutations occur in approximately 30% of all human cancers. Despite more than 30 years of KRAS-focused research and development efforts, no targeted therapy has been discovered for cancers with KRAS mutations. Here, we describe ARS-853, a selective, covalent inhibitor of KRAS(G12C) that inhibits mutant KRAS-driven signaling by binding to the GDP-bound oncoprotein and preventing activation. Based on the rates of engagement and inhibition observed for ARS-853, along with a mutant-specific mass spectrometry-based assay for assessing KRAS activation status, we show that the nucleotide state of KRAS(G12C) is in a state of dynamic flux that can be modulated by upstream signaling factors. These studies provide convincing evidence that the KRAS(G12C) mutation generates a hyperexcitable rather than a statically active state and that targeting the inactive, GDP-bound form is a promising approach for generating novel anti-RAS therapeutics.A cell-active, mutant-specific, covalent inhibitor of KRAS(G12C) is described that targets the GDP-bound, inactive state and prevents subsequent activation. Using this novel compound, we demonstrate that KRAS(G12C) oncoprotein rapidly cycles bound nucleotide and responds to upstream signaling inputs to maintain a highly active state.


Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 215.38K | Year: 2014

DESCRIPTION (provided by applicant): The lack of effective treatments for mutant RAS driven cancers remains a critical unmet need in modern cancer therapy. Several lines of recent evidence suggest that Kinase Suppressor of RAS (KSR) is a viable target forsmall molecule therapeutics. It has been established that KSR binds constitutively to MEK and transiently to RAF and Erk during active RAS signaling, and these binding events are all mediated at least in part through KSR's protein kinase domain. Recent structural studies by Wellspring's scientific co-founder, Kevan Shokat suggest that KSR's kinase domain functions as a bifunctional dynamic scaffold, bringing together key proteins for RAS signaling (MEK and RAF) and allosterically modulating RAF mediated MEKphosphorylation. A generic kinase inhibitor with the ability to modulate the allosteric switch in KSR was recently reported by Shokat and coworkers, suggesting a possible starting point to develop novel drugs that function as chemical suppressors of


PubMed | Sloan Kettering Cancer Center and Wellspring Biosciences, Llc
Type: Journal Article | Journal: Science (New York, N.Y.) | Year: 2016

It is thought that KRAS oncoproteins are constitutively active because their guanosine triphosphatase (GTPase) activity is disabled. Consequently, drugs targeting the inactive or guanosine 5-diphosphate-bound conformation are not expected to be effective. We describe a mechanism that enables such drugs to inhibit KRAS(G12C) signaling and cancer cell growth. Inhibition requires intact GTPase activity and occurs because drug-bound KRAS(G12C) is insusceptible to nucleotide exchange factors and thus trapped in its inactive state. Indeed, mutants completely lacking GTPase activity and those promoting exchange reduced the potency of the drug. Suppressing nucleotide exchange activity downstream of various tyrosine kinases enhanced KRAS(G12C) inhibition, whereas its potentiation had the opposite effect. These findings reveal that KRAS(G12C) undergoes nucleotide cycling in cancer cells and provide a basis for developing effective therapies to treat KRAS(G12C)-driven cancers.

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