Papers by Jonathan A Winger
Neuro-oncology, Nov 1, 2018
Cancer Research, Jul 1, 2017
Oxygen is one of the key modulators of tumor microenvironment whereby low oxygen or hypoxia is as... more Oxygen is one of the key modulators of tumor microenvironment whereby low oxygen or hypoxia is associated with resistance to chemo- and radio- therapies and poor patient outcomes. Hypoxia favors an immunosuppressive tumor microenvironment by promoting Treg recruitment and activation and suppressing T cell and NK cell proliferation and effector function and pro-inflammatory cytokine secretion. Therefore, reversing tumor hypoxia could create an immunopermissive microenvironment and improve the efficacy of several immunotherapies. Omniox has developed an oxygen carrier OMX that can specifically deliver oxygen to hypoxic tumor regions without affecting oxygenation of tissues within physiologic oxygen levels. Due to its biochemical features, OMX is well tolerated in small (rats and mice) and large (sheep and dogs) animals. Following intravenous administration, OMX extravasates through leaky tumor vasculature and accumulates within immunocompetent rodent orthotopic glioblastoma models as well as spontaneous canine brain tumors. Consequently, OMX decreases hypoxia levels in the tumor tissue measured directly using oxygen sensor probes and indirectly with exogenous hypoxia markers using ELISA, immunohistochemistry and flow cytometry methods. Here we evaluated OMX’ activity in reversing the immunosupressive tumor microenvironment using a combination of immunohistochemistry, flow cytometry and Luminex methods. Moreover, we investigated the efficacy of OMX in improving mouse survival and effectiveness of checkpoint inhibitors (CPI). Similar to previously published findings, we demonstrated that T lymphocytes are mostly excluded from hypoxic tumor areas in the GL261 model. A single OMX treatment in GL261 tumor-bearing mice reduces tumor hypoxia, enhances T cell localization in previously hypoxic tumor areas, and increases CD8 accumulation by ~4-fold. Specifically, OMX treatment increased the activated cytotoxic T lymphocytes (CTLs) fraction by ~2 fold and reduced the immunosuppressive Treg fraction by 2-fold, resulting in a 3-fold increase of Teff/Treg ratio, which indicates a switch from an immunosupressive to an immunopermissive microenvironment. When combined with CPI, OMX reverses the immunosuppressive tumor microenvironment by increasing CD8 T cell infiltration, proliferation and cytotoxic activity, and modulating IFNg and IFNg-inducible cytokines that may polarize T cells towards a Th1 phenotype. Furthermore, treatment of late-stage GL261 tumor-bearing mice with the combination of OMX-CPI increases mouse survival by 80%. By delivering oxygen specifically to the hypoxic tumor microenvironment, OMX may restore anti-cancer immune responses in glioblastoma patients and synergize with radiotherapy and immunotherapy to enhance tumor control and improve patient outcomes. Citation Format: Natacha Le Moan, Philberta Leung, Sarah Ng, Tina Davis, Carol Liang, Jonathan W. Winger, Stephen P. Cary, Nicolas Butowski, Ana Krtolica. Omx a hypoxia modulator reverses the immunosuppressive glioblastoma microenvironment by stimulating T cell infiltration and activation that results in increased number of long-term survivors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4686. doi:10.1158/1538-7445.AM2017-4686
Journal of Biological Chemistry, 2007
Springer series in translational stroke research, 2017
Of the ~795,000 strokes that occur each year in the USA, ~695,000 are ischemic strokes (IS) where... more Of the ~795,000 strokes that occur each year in the USA, ~695,000 are ischemic strokes (IS) where a clot occludes a major cerebral artery. About half of these IS patients present with so-called penumbra, defined as a hypoperfused tissue immediately surrounding the ischemic core that is severely deprived of oxygen and at risk for deterioration. Collateral vessels can provide sufficient oxygen and nutrients to temporarily maintain neuronal structure in the penumbra but not enough to support function. Thus, the at-risk tissue has the potential for functional recovery if blood flow is restored, but will irreversibly infarct if recanalization is not achieved, resulting in neurological deterioration. Additionally, though collateral circulation can transiently maintain penumbra viability, injury mechanisms such as excitotoxicity and ATP depletion will have already been initiated. Thus, it is imperative to administer therapies that can alleviate ischemia-induced cell death, restore energy metabolism, and halt pathogenic cascades as soon as possible after occlusion in order to protect the at-risk tissue until reperfusion therapies can be employed. Excitingly, the recent breakthroughs in acute IS reperfusion therapy have opened new opportunities for such adjunct neuroprotective treatments. This chapter provides a description of the penumbra tissue, followed by a brief overview of the emerging standard of care for acute IS based on the recent positive clinical trials using IV tPA and mechanical thrombectomy devices. We will then describe the promising use of adjunctive therapies to enhance the benefits of recanalization therapies. In particular, we will discuss the concept of oxygen therapy and oxygen carriers as a valid approach for “combination therapy” to protect the penumbra until reperfusion. Finally, we will discuss the future challenges of clinical trials in acute IS patients and highlight the need for new trial designs to test the potential benefit of combination therapies.
Hypoxia is a hallmark of cancer and a driver of tumor progression and poor patient outcomes. By g... more Hypoxia is a hallmark of cancer and a driver of tumor progression and poor patient outcomes. By generating an immunosuppressive tumor microenvironment that limits cytotoxic T lymphocyte (CTL) infiltration and activation, hypoxia limits the effectiveness of cancer immunotherapy and thus promotes tumor cell evasion of the host immune response. Omniox has developed a first-in-class anti-cancer immunotherapeutic, OMX, specifically designed to reverse tumor hypoxia to enhance cancer immunotherapy efficacy. In preclinical models, we have demonstrated that OMX accumulates in rodent subcutaneous and orthotopic tumors, as well as spontaneous canine melanomas and brain tumors, resulting in significant tumor hypoxia reduction.Here, using multiple subcutaneous syngeneic mouse tumor models (MC38, CT26, 4T1), we assessed OMX effects on intratumoral CTLs and immunosuppressive regulatory T cells (Treg), as well as the anti-tumor potential of OMX as a single agent and in combination with established immunotherapies. Using quantitative immunohistochemistry, we confirmed reports that hypoxic tumor areas are devoid of CTLs. Accordingly, by flow cytometry we observed a negative correlation between tumor hypoxia and CTL infiltration. While OMX single agent treatment did not affect the overall CD45-positive leukocyte population, Treg cells were selectively depleted and the CTL:Treg ratio was substantially increased, suggesting that OMX induced a shift towards immunosensitization. Consistent with this finding, we observed OMX single agent anti-tumor efficacy in MC38 colon tumors. Impressively, anti-tumor effects of OMX single agent were equivalent to that of a single treatment of the checkpoint inhibitor anti-CTLA4. We next assessed whether OMX would enhance the efficacy of checkpoint inhibitors when used in combination. In CT26 colon tumors, OMX exhibited combination anti-tumor activity with anti-CTLA4, giving rise to faster cures and a greater number of complete and durable responders compared to anti-CTLA4 alone. Of note, this enhanced response was observed for both early-stage and late-stage CT26 tumors. In 4T1 breast tumors, known to be insensitive to checkpoint inhibitors, treatment of early-stage (~60mm3) tumors with combination OMX and anti-PD1 resulted in a 27% response rate, compared to a 0% response rate to anti-PD1 alone. Taken together, our data suggest that OMX, by delivering oxygen to hypoxic tumor areas, induces a microenvironmental change from an immunosuppressive to an immunopermissive state. Given that OMX is well-tolerated in both small and large animals, and that its mechanism of action is upstream of numerous major immunosuppressive pathways, OMX holds great clinical potential to synergize with multiple immunotherapeutic agents to enhance tumor control by restoring anti-cancer immune responses in cancer patients. Citation Format: Kevin G. Leong, Yuqiong Pan, Jonathan A. Winger, Stephen P. Cary, Natacha Le Moan, Ana Krtolica. Enhancement of anti-cancer immunity by OMX, a novel oxygen carrier immunotherapeutic that ameliorates the hypoxic tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1627. doi:10.1158/1538-7445.AM2017-1627
Hypoxia, or lack of oxygen, is a key modulator of the tumor microenvironment and is associated wi... more Hypoxia, or lack of oxygen, is a key modulator of the tumor microenvironment and is associated with immunosuppression, invasiveness, angiogenesis, radiotherapy resistance and poor patient outcomes. Methods to increase oxygen in the hypoxic tumor niche have failed due to the long distance oxygen must diffuse from dysfunctional vasculature to the hypoxic cells. To address this problem, we engineered OMX oxygen carriers that bind oxygen with high affinity and can specifically deliver oxygen to severely hypoxic tumor regions without afecting normoxic tissues. Here, we show that OMX extravasates through leaky tumor vasculature, penetrates into and delivers oxygen to hypoxic tumor tissue. This reduces hypoxia in the tumor microenvironment and sensitizes tumors to therapy. Specifically, OMX accumulation in tumors leads to an increase in tumor oxygenation in mouse human xenograft and immunocompetent rat orthotopic models, as assessed by direct oxygen measurement (oxygen probe), by18F-FMISO PET in vivo imaging and by IHC and ELISA assessment of hypoxia markers (pimonidazole, CAIX, CCI, HIF-1). Moreover, OMX-mediated tumor oxygenation increases efficacy of radiation therapy as demonstrated by ex-vivo clonogenic assay and tumor growth delay. Importantly, while radiation alone only moderately delays tumor growth, combination of OMX and radiation therapy leads to tumor eradication in >50% of tumors. In addition to the enhancement of radiation therapy with OMX, we are currently exploring the capacity of OMX to ameliorate immunosuppressive microenvironment caused by hypoxia. Results from a Phase 0 clinical trial in canine cancer patients indicate that OMX is well tolerated and safe to use in combination with standard of care radiation therapy even in aged and fragile canine patient populations. Similar to rodent tumor models, OMX penetrates the tumor tissue in spontaneous canine brain and melanoma tumors. Furthermore, OMX accumulation correlates with reduced hypoxia in the tumor microenvironment as assessed by multiple hypoxia markers using quantitative IHC and ELISA. Taken together, these preclinical safety and efficacy data in both rodents and canines strongly support our IND submission to initiate human clinical trials in newly diagnosed glioblastoma patients. Results from completed and ongoing studies support the potential of OMX as modulator of hypoxic tumor microenvironment that may significantly impact the effectiveness of radiotherapy, chemotherapy and immunotherapy in a variety of solid tumors where hypoxia is major contributor to therapeutic resistance. Citation Format: Ana Krtolica, Natacha Le Moan, Philberta Leung, Youngho Seo, Jonathan Winger, Henry Van Brocklin, Michael Kent, Stephen Cary. Sensitizing the hypoxic tumor microenvironment with OMX, a breakthrough oxygen delivery protein: From protein engineering to clinical trial. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2790.
The accepted model for activation and deactivation of the nitric oxide (NO) receptor soluble guan... more The accepted model for activation and deactivation of the nitric oxide (NO) receptor soluble guanylate cyclase (sGC) involves the formation and decay of a 5-coordinate ferrous-nitrosyl heme species. Using electronic absorption spectroscopy and kinetic analysis, the rate of dissociation of NO from the sGC heme and the rate of deactivation of NO-stimulated sGC were measured, and a discrepancy was found indicating that the 5-coordinate ferrous-nitrosyl species is not responsible for full activation of sGC. Therefore, the accepted model for activation and deactivation of sGC cannot be correct. It was shown that sGC could be isolated as a ferrous-nitrosyl complex with diminished activity relative to the fully stimulated enzyme, and that full activity could be recovered by addition of excess NO. This demonstrates that activation of the enzyme happens via the binding of NO to a non-heme site on the enzyme, indicating that the paradigm for activation and deactivation of sGC must be revised. Additionally, the catalytic domains of sGC were successfully expressed and purified for the first time. They are active as heterodimers, as is the full-length sGC, and are activated 300-fold by the presence of Mn2+ as compared to the physiological cofactor Mg2+. This degree of activation is reminiscent of activation of the full-length enzyme by NO, suggesting mechanistic similarities. The catalytic domains are inhibited by interaction with the N-terminal regulatory domain of sGC in trans , suggesting a domain-scale mechanism of activation by NO in which NO binding causes relief of an autoinhibitory interaction between the regulatory domain and the catalytic domain.Ph.D.BiochemistryBiological SciencesMolecular biologyPharmacy sciencesPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124593/2/3150119.pd
Stroke, Apr 1, 2022
Background: Tissue hypoxia plays a critical role in the events leading to cell death in ischemic ... more Background: Tissue hypoxia plays a critical role in the events leading to cell death in ischemic stroke. Despite promising results in preclinical and small clinical pilot studies, inhaled oxygen supplementation has not translated to improved outcomes in large clinical trials. Moreover, clinical observations suggest that indiscriminate oxygen supplementation can adversely affect outcome, highlighting the need to develop novel approaches to selectively deliver oxygen to affected regions. This study tested the hypothesis that intravenous delivery of a novel oxygen carrier (Omniox-Ischemic Stroke [OMX-IS]), which selectively releases oxygen into severely ischemic tissue, could delay infarct progression in an established canine thromboembolic large vessel occlusion stroke model that replicates key dynamics of human infarct evolution. Methods: After endovascular placement of an autologous clot into the middle cerebral artery, animals received OMX-IS treatment or placebo 45 to 60 minutes after stroke onset. Perfusion-weighted magnetic resonance imaging was performed to define infarct progression dynamics to stratify animals into fast versus slow stroke evolvers. Serial diffusion-weighted magnetic resonance imaging was performed for up to 5 hours to quantify infarct evolution. Histology was performed postmortem to confirm final infarct size. Results: In fast evolvers, OMX-IS therapy substantially slowed infarct progression (by ≈1 hour, P <0.0001) and reduced the final normalized infarct volume as compared to controls (0.99 versus 0.88, control versus OMX-IS drug, P <0.0001). Among slow evolvers, OMX-IS treatment delayed infarct progression by approximately 45 minutes; however, this did not reach statistical significance ( P =0.09). The final normalized infarct volume also did not show a significant difference (0.93 versus 0.95, OMX-IS drug versus control, P =0.34). Postmortem histologically determined infarct volumes showed excellent concordance with the magnetic resonance imaging defined ischemic lesion volume (bias: 1.33% [95% CI, −15% to 18%). Conclusions: Intravenous delivery of a novel oxygen carrier is a promising approach to delay infarct progression after ischemic stroke, especially in treating patients with large vessel occlusion stroke who cannot undergo definitive reperfusion therapy within a timely fashion.
Stroke, Feb 1, 2016
Introduction: After vascular occlusion, there are two major zones of injury: the infarct core tha... more Introduction: After vascular occlusion, there are two major zones of injury: the infarct core that rapidly dies, and the surrounding penumbra, which is hypoxic and at risk for infarction. Restoring blood flow by vascular recanalization (ie. endovascular +/- IV tPA) to prevent the penumbra from infarcting has become the new standard of care for acute ischemic stroke patients presenting with salvageable tissue. However, not all patients benefit from recanalization. Regardless of successful or partial reperfusion, secondary hypoxic events within the rescued penumbra can cause selective neuronal loss (SNL) that may account for suboptimal clinical recovery. OMX is a breakthrough oxygen delivery protein tuned to release oxygen specifically in hypoxic tissue and reduce hypoxia to prevent SNL within the reperfused penumbra. Methods: To mimic the clinical situation whereby occlusion is followed by gradual reperfusion after spontaneous or therapeutic thrombolysis, we used the endothelin-1 induced middle cerebral artery occlusion (MCAO) model. OMX was administered intravenously up to 2h post-MCAO. Short and long-term histological and behavioral outcomes were used to assess hypoxia, apoptosis, gliosis, SNL, infarct volume and sensorimotor functions. Results: Despite reperfusion, hypoxic tissue persists and progressively infarcts in vehicle-treated rats. However, OMX-treated rats showed no infarct expansion over 7d, indicating that OMX prevents infarction of the majority of hypoxic tissue. OMX reduces hypoxia and caspase 3/9 activity in a dose-dependent manner and significantly prevents SNL and gliosis. When administered post-MCAO, OMX significantly improves both sensory and motor functions (∼30-80% improvement, * p <0.05) in aged rats up to 28d post-MCAO. Moreover, extensive toxicology studies demonstrate that OMX is well tolerated in multiple species and can be used safely in combination with tPA. Conclusions: OMX is a promising therapeutic candidate that can be administered in combination with reperfusion therapies to stabilize the at-risk hypoxic tissue and ameliorate long-term clinical outcomes in stroke patients.
BMC Structural Biology, Oct 7, 2008
Biochemistry, Feb 17, 2005
The catalytic domains (alpha(cat) and beta(cat)) of alpha1beta1 soluble guanylate cyclase (sGC) w... more The catalytic domains (alpha(cat) and beta(cat)) of alpha1beta1 soluble guanylate cyclase (sGC) were expressed in Escherichia coli and purified to homogeneity. alpha(cat), beta(cat), and the alpha(cat)beta(cat) heterodimeric complex were characterized by analytical gel filtration and circular dichroism spectroscopy, and activity was assessed in the absence and presence of two different N-terminal regulatory heme-binding domain constructs. Alpha(cat) and beta(cat) were inactive separately, but together the domains exhibited guanylate cyclase activity. Analysis by gel filtration chromatography demonstrated that each of the approximately 25-kDa domains form homodimers. Heterodimers were formed when alpha(cat) and beta(cat) were combined. Results from circular dichroism spectroscopy indicated that no major structural changes occur upon heterodimer formation. Like the full-length enzyme, the alpha(cat)beta(cat) complex was more active in the presence of Mn(2+) as compared to the physiological cofactor Mg(2+), although the magnitude of the difference was much larger for the catalytic domains than for the full-length enzyme. The K(M) for Mn(2+)-GTP was measured to be 85 +/- 18 microM, and in the presence of Mn(2+)-GTP, the K(D) for the alpha(cat)beta(cat) complex was 450 +/- 70 nM. The N-terminal heme-bound regulatory domain of the beta1 subunit of sGC inhibited the activity of the alpha(cat)beta(cat) complex in trans, suggesting a domain-scale mechanism of regulation by NO. A model in which binding of NO to sGC causes relief of an autoinhibitory interaction between the regulatory heme-binding domain and the catalytic domains of sGC is proposed.
Cancer Research, Jul 1, 2018
Background: Hypoxia, a common feature in solid tumors such as glioblastoma (GB), is associated wi... more Background: Hypoxia, a common feature in solid tumors such as glioblastoma (GB), is associated with resistance to chemo- and radio-therapies and poor patient outcomes. In addition, hypoxia promotes the immune escape of tumors. Therefore, reversing tumor hypoxia to create an immunopermissive microenvironment can improve antitumor response, and combined with immunotherapy approaches such as checkpoint inhibitors (CPI), may increase therapeutic efficacy. OMX is an oxygen carrier well tolerated in small (rats and mice) and large (sheep and dogs) animals. Following intravenous administration, OMX extravasates through leaky tumor vasculature and efficiently accumulates in orthotopic rodent GB and spontaneous canine brain tumors. Consequently, OMX significantly reduces hypoxia and improves the efficacy of radiotherapy and CPI. Methods: We used in vivo bioluminescence imaging of tumor, immunohistochemistry, flow cytometry, and cytokine multiplex assays to evaluate OMX's ability to immunosensitize the GL261 brain tumor microenvironment and promote tumor cures. Results: A single dose of OMX in brain tumor-bearing mice reduces tumor hypoxia, enhances the recruitment and infiltration of tumor-specific CX3CR1+ CD8 T cells into the tumor (using the EphA2 as a GL261-specific tumor antigen), decreases Tregs and increases activation and proliferation of cytotoxic T lymphocytes (CTLs). Specifically, OMX increases the Teff/Treg ratio by ~3-fold, indicating a switch from an immunosuppressive to an immunopermissive microenvironment. Similarly, when combined with anti-PD-1, OMX decreases Tregs, increases CTL infiltration, proliferation and cytotoxic activity, and modulates IFNg and IFNg-inducible cytokines that polarize T cells towards a Th1 phenotype. Treatment with OMX alone resulted in a 55% tumor cure rate, comparable to anti-PD-1 treatment. Furthermore, in late-stage tumor-bearing mice, we observed a 40% tumor cure rate for the combination of OMX with anti-PD-1, while anti-PD-1 alone resulted only in 5% tumor cures. In symptomatic mice with very high tumor burden, in which the combination of anti-PD-1 with anti-CTLA4 does not provide tumor cures, the addition of OMX resulted in a 20% tumor cure rate. Following rechallenge with GL261 tumor cells injected on the other side of the brain, all mice treated with OMX alone or in combination with CPI survived, indicating the presence of long-term immunologic memory against glioma cells. The survival benefit observed with OMX could be predicted with an identified circulating chemokine biomarker signature (post-hoc test). Conclusion: By delivering oxygen specifically to the hypoxic tumor microenvironment, OMX may restore anticancer immune responses in GB patients and synergize with radiotherapy and immunotherapy to enhance tumor control and improve patient outcomes. Citation Format: Natacha Le Moan, Philberta Leung, Sarah Ng, Tina Davis, Carol Liang, Jonathan Winger, Stephen P. Cary, Nicholas Butowski, Ana Krtolica. The oxygen carrier omx restores antitumor immunity and cures tumors as a single agent or in combination with checkpoint inhibitors in an intracranial glioblastoma mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4726A.
The accepted model for activation and deactivation of the nitric oxide (NO) receptor soluble guan... more The accepted model for activation and deactivation of the nitric oxide (NO) receptor soluble guanylate cyclase (sGC) involves the formation and decay of a 5-coordinate ferrous-nitrosyl heme species. Using electronic absorption spectroscopy and kinetic analysis, the rate of dissociation of NO from the sGC heme and the rate of deactivation of NO-stimulated sGC were measured, and a discrepancy was found indicating that the 5-coordinate ferrous-nitrosyl species is not responsible for full activation of sGC. Therefore, the accepted model for activation and deactivation of sGC cannot be correct. It was shown that sGC could be isolated as a ferrous-nitrosyl complex with diminished activity relative to the fully stimulated enzyme, and that full activity could be recovered by addition of excess NO. This demonstrates that activation of the enzyme happens via the binding of NO to a non-heme site on the enzyme, indicating that the paradigm for activation and deactivation of sGC must be revised. Additionally, the catalytic domains of sGC were successfully expressed and purified for the first time. They are active as heterodimers, as is the full-length sGC, and are activated 300-fold by the presence of Mn2+ as compared to the physiological cofactor Mg2+. This degree of activation is reminiscent of activation of the full-length enzyme by NO, suggesting mechanistic similarities. The catalytic domains are inhibited by interaction with the N-terminal regulatory domain of sGC in trans , suggesting a domain-scale mechanism of activation by NO in which NO binding causes relief of an autoinhibitory interaction between the regulatory domain and the catalytic domain.Ph.D.BiochemistryBiological SciencesMolecular biologyPharmacy sciencesPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124593/2/3150119.pd
Electronic Poster Abstracts, 2020
Stroke, 2022
Background: Tissue hypoxia plays a critical role in the events leading to cell death in ischemic ... more Background: Tissue hypoxia plays a critical role in the events leading to cell death in ischemic stroke. Despite promising results in preclinical and small clinical pilot studies, inhaled oxygen supplementation has not translated to improved outcomes in large clinical trials. Moreover, clinical observations suggest that indiscriminate oxygen supplementation can adversely affect outcome, highlighting the need to develop novel approaches to selectively deliver oxygen to affected regions. This study tested the hypothesis that intravenous delivery of a novel oxygen carrier (Omniox-Ischemic Stroke [OMX-IS]), which selectively releases oxygen into severely ischemic tissue, could delay infarct progression in an established canine thromboembolic large vessel occlusion stroke model that replicates key dynamics of human infarct evolution. Methods: After endovascular placement of an autologous clot into the middle cerebral artery, animals received OMX-IS treatment or placebo 45 to 60 minutes a...
BMC Structural Biology, 2009
Background Imatinib represents the first in a class of drugs targeted against chronic myelogenous... more Background Imatinib represents the first in a class of drugs targeted against chronic myelogenous leukemia to enter the clinic, showing excellent efficacy and specificity for Abl, Kit, and PDGFR kinases. Recent screens carried out to find off-target proteins that bind to imatinib identified the oxidoreductase NQO2, a flavoprotein that is phosphorylated in a chronic myelogenous leukemia cell line. Results We examined the inhibition of NQO2 activity by the Abl kinase inhibitors imatinib, nilotinib, and dasatinib, and obtained IC50 values of 80 nM, 380 nM, and >100 μM, respectively. Using electronic absorption spectroscopy, we show that imatinib binding results in a perturbation of the protein environment around the flavin prosthetic group in NQO2. We have determined the crystal structure of the complex of imatinib with human NQO2 at 1.75 Å resolution, which reveals that imatinib binds in the enzyme active site, adjacent to the flavin isoalloxazine ring. We find that phosphorylation...
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Papers by Jonathan A Winger