Academic Appointments

Honors & Awards

  • Alavi-Mandell Award, Society of Nuclear Medicine and Molecular Imaging (2019)
  • Basic Science Teacher of the Year Award, Radiology, Stanford University (2019)
  • Exceptional Mentor Award, American Medical Women’s Association (2018)
  • SNMMI Journal of Nuclear Medicine Editor’s Choice - Best Article Award, Society of Nuclear Medicine and Molecular Imaging (2016)
  • Suffrage Science Award, Medical Research Council (2016)
  • Alavi-Mandell Award, Society of Nuclear Medicine and Molecular Imaging (2015)
  • First Prize Poster & Abstract Award, TSPO Symposium on Microglia Imaging & Biology - Manchester, UK, - (2014)
  • Poster Presentation Award, World Molecular Imaging Congress - Savannah, Georgia, - (2013)
  • Travel Fellowship, Alzheimer's Association International Conference - Boston, USA, - (2013)
  • Travel Award, World Molecular Imaging Congress - Kyoto, Japan, - (2010)
  • Travel Award, International Symposium on Radiopharmaceutical Sciences - Aachen, Germany, - (2007)
  • Best Oral Presentation Award, Royal Australian Chemistry Institute Drug Design Conference, - (2006)
  • Australian Postgraduate Award, - (2005-2008)
  • John A Lamberton Research Scholarship, - (2005-2008)
  • Travel Award, International Symposium on Radiopharmaceutical Sciences - Iowa, USA, - (2005)
  • First Class Honours in Pharmacology, - (2004)
  • University Medal, The University of Sydney (2004)
  • Dean’s Honour List, - (2003)
  • Roland H. Thorp Prize in Pharmacology, - (2003)

Professional Education

  • Ph.D., University of Sydney, Pharmacology (2008)
  • B.S., University of Sydney, Pharmacology/Medicinal Chemistry (2004)

Current Research and Scholarly Interests

The primary aim of my lab is to enable early detection and precision treatment of brain diseases by developing translational molecular imaging agents for visualizing neuroimmune interactions underlying conditions such as Alzheimer’s disease, multiple sclerosis, and stroke.

We are researching how the brain and its resident immune cells interact with the peripheral immune system at very early, through to late stages of disease. Our approach involves the discovery, characterization, and validation of clinically relevant immune cell biomarkers, followed by the design of novel positron emission tomography (PET) radiotracers specifically targeting these biomarkers. After preclinical validation, we translate promising imaging probes to the clinic for monitoring disease progression and response to immunomodulatory drugs.

Stanford Advisees

All Publications

  • TREM1 disrupts myeloid bioenergetics and cognitive function in aging and Alzheimer disease mouse models. Nature neuroscience Wilson, E. N., Wang, C., Swarovski, M. S., Zera, K. A., Ennerfelt, H. E., Wang, Q., Chaney, A., Gauba, E., Ramos Benitez, J. A., Le Guen, Y., Minhas, P. S., Panchal, M., Tan, Y. J., Blacher, E., A Iweka, C., Cropper, H., Jain, P., Liu, Q., Mehta, S. S., Zuckerman, A. J., Xin, M., Umans, J., Huang, J., Durairaj, A. S., Serrano, G. E., Beach, T. G., Greicius, M. D., James, M. L., Buckwalter, M. S., McReynolds, M. R., Rabinowitz, J. D., Andreasson, K. I. 2024


    Human genetics implicate defective myeloid responses in the development of late-onset Alzheimer disease. A decline in peripheral and brain myeloid metabolism, triggering maladaptive immune responses, is a feature of aging. The role of TREM1, a pro-inflammatory factor, in neurodegenerative diseases is unclear. Here we show that Trem1 deficiency prevents age-dependent changes in myeloid metabolism, inflammation and hippocampal memory function in mice. Trem1 deficiency rescues age-associated declines in ribose 5-phosphate. In vitro, Trem1-deficient microglia are resistant to amyloid-β42 oligomer-induced bioenergetic changes, suggesting that amyloid-β42 oligomer stimulation disrupts homeostatic microglial metabolism and immune function via TREM1. In the 5XFAD mouse model, Trem1 haploinsufficiency prevents spatial memory loss, preserves homeostatic microglial morphology, and reduces neuritic dystrophy and changes in the disease-associated microglial transcriptomic signature. In aging APPSwe mice, Trem1 deficiency prevents hippocampal memory decline while restoring synaptic mitochondrial function and cerebral glucose uptake. In postmortem Alzheimer disease brain, TREM1 colocalizes with Iba1+ cells around amyloid plaques and its expression is associated with Alzheimer disease clinical and neuropathological severity. Our results suggest that TREM1 promotes cognitive decline in aging and in the context of amyloid pathology.

    View details for DOI 10.1038/s41593-024-01610-w

    View details for PubMedID 38539014

    View details for PubMedCentralID 4369837

  • PET Imaging of Innate Immune Activation Using 11C Radiotracers Targeting GPR84. JACS Au Kalita, M., Park, J. H., Kuo, R. C., Hayee, S., Marsango, S., Straniero, V., Alam, I. S., Rivera-Rodriguez, A., Pandrala, M., Carlson, M. L., Reyes, S. T., Jackson, I. M., Suigo, L., Luo, A., Nagy, S. C., Valoti, E., Milligan, G., Habte, F., Shen, B., James, M. L. 2023; 3 (12): 3297-3310


    Chronic innate immune activation is a key hallmark of many neurological diseases and is known to result in the upregulation of GPR84 in myeloid cells (macrophages, microglia, and monocytes). As such, GPR84 can potentially serve as a sensor of proinflammatory innate immune responses. To assess the utility of GPR84 as an imaging biomarker, we synthesized 11C-MGX-10S and 11C-MGX-11Svia carbon-11 alkylation for use as positron emission tomography (PET) tracers targeting this receptor. In vitro experiments demonstrated significantly higher binding of both radiotracers to hGPR84-HEK293 cells than that of parental control HEK293 cells. Co-incubation with the GPR84 antagonist GLPG1205 reduced the binding of both radiotracers by >90%, demonstrating their high specificity for GPR84 in vitro. In vivo assessment of each radiotracer via PET imaging of healthy mice illustrated the superior brain uptake and pharmacokinetics of 11C-MGX-10S compared to 11C-MGX-11S. Subsequent use of 11C-MGX-10S to image a well-established mouse model of systemic and neuro-inflammation revealed a high PET signal in affected tissues, including the brain, liver, lung, and spleen. In vivo specificity of 11C-MGX-10S for GPR84 was confirmed by the administration of GLPG1205 followed by radiotracer injection. When compared with 11C-DPA-713-an existing radiotracer used to image innate immune activation in clinical research studies-11C-MGX-10S has multiple advantages, including its higher binding signal in inflamed tissues in the CNS and periphery and low background signal in healthy saline-treated subjects. The pronounced uptake of 11C-MGX-10S during inflammation, its high specificity for GPR84, and suitable pharmacokinetics strongly support further investigation of 11C-MGX-10S for imaging GPR84-positive myeloid cells associated with innate immune activation in animal models of inflammatory diseases and human neuropathology.

    View details for DOI 10.1021/jacsau.3c00435

    View details for PubMedID 38155640

    View details for PubMedCentralID PMC10751761

  • Application of Machine Learning Driven Computational Approaches for Novel CNS PET Tracer Development Jackson, I., Luo, A., Webb, E., Zhang, B., Guo, A., Nagy, S., Shao, X., Kuo, R., Carlson, M., Alam, I., Rodriguez, A., Winton, W., Stauff, J., Kalita, M., Scott, P., James, M. ELSEVIER SCIENCE INC. 2023: S40-S41
  • Development and Initial Assessment of [18F]OP-801: a Novel Hydroxyl Dendrimer PET Tracer for Preclinical Imaging of Innate Immune Activation in the Whole Body and Brain. Molecular imaging and biology Carlson, M. L., Jackson, I. M., Azevedo, E. C., Reyes, S. T., Alam, I. S., Kellow, R., Castillo, J. B., Nagy, S. C., Sharma, R., Brewer, M., Cleland, J., Shen, B., James, M. L. 2023


    PURPOSE: Innate immune activation plays a critical role in the onset and progression of many diseases. While positron emission tomography (PET) imaging provides a non-invasive means to visualize and quantify such immune responses, most available tracers are not specific for innate immune cells. To address this need, we developed [18F]OP-801 by radiolabeling a novel hydroxyl dendrimer that is selectively taken up by reactive macrophages/microglia and evaluated its ability to detect innate immune activation in mice following lipopolysaccharide (LPS) challenge.PROCEDURES: OP-801 was radiolabeled in two steps: [18F]fluorination of a tosyl precursor to yield [18F]3-fluoropropylazide, followed by a copper-catalyzed click reaction. After purification and stability testing, [18F]OP-801 (150-250 muCi) was intravenously injected into female C57BL/6 mice 24 h after intraperitoneal administration of LPS (10 mg/kg, n=14) or saline (n=6). Upon completing dynamic PET/CT imaging, mice were perfused, and radioactivity was measured in tissues of interest via gamma counting or autoradiography.RESULTS: [18F]OP-801 was produced with >95% radiochemical purity, 12-52 muCi/mug specific activity, and 4.3±1.5% decay-corrected yield. Ex vivo metabolite analysis of plasma samples (n=4) demonstrated high stability in mice (97±3% intact tracer >120 min post-injection). PET/CT images of mice following LPS challenge revealed higher signal in organs known to be inflamed in this context, including the liver, lung, and spleen. Gamma counting confirmed PET findings, showing significantly elevated signal in the same tissues compared to saline-injected mice: the liver (p=0.009), lung (p=0.030), and spleen (p=0.004). Brain PET/CT images (summed 50-60 min) revealed linearly increasing [18F]OP-801 uptake in the whole brain that significantly correlated with murine sepsis score (r=0.85, p<0.0001). Specifically, tracer uptake was significantly higher in the brain stem, cortex, olfactory bulb, white matter, and ventricles of LPS-treated mice compared to saline-treated mice (p<0.05).CONCLUSION: [18F]OP-801 is a promising new PET tracer for sensitive and specific detection of activated macrophages and microglia that warrants further investigation.

    View details for DOI 10.1007/s11307-023-01850-5

    View details for PubMedID 37735280

  • Development of [18F]DASA-10 for enhanced imaging of pyruvate kinase M2. Nuclear medicine and biology Kendirli, M. T., Malek, R., Silveira, M. B., Acosta, C., Zhang, S., Azevedo, C., Nagy, S. C., Habte, F., James, M. L., Recht, L. D., Beinat, C. 2023; 124-125: 108382


    The aim of this study was to develop a positron emission tomography (PET) radiotracer for measuring pyruvate kinase M2 (PKM2) with improved physicochemical and pharmacokinetic properties compared to [18F]DASA-23.First, we synthesized [18F]DASA-10 and tested its uptake and retention compared to [18F]DASA-23 in human and mouse glioma cell lines. We then confirmed the specificity of [18F]DASA-10 by transiently modulating the expression of PKM2 in DU145 and HeLa cells. Next, we determined [18F]DASA-10 pharmacokinetics in healthy nude mice using PET imaging and subsequently assessed the ability of [18F]DASA-10 versus [18F]DASA-23 to enable in vivo detection of intracranial gliomas in syngeneic C6 rat models of glioma.[18F]DASA-10 demonstrated excellent cellular uptake and retention with values significantly higher than [18F]DASA-23 in all cell lines and timepoints investigated. [18F]DASA-10 showed a 73 % and 65 % reduced uptake respectively in DU145 and HeLa cells treated with PKM2 siRNA as compared to control siRNA treated cells. [18F]DASA-10 showed favorable biodistribution and pharmacokinetic properties and a significantly improved tumor-to-brain ratio in rat C6 glioma models relative to [18F]DASA-23 (3.2 ± 0.8 versus 1.6 ± 0.3, p = 0.01).[18F]DASA-10 is a new PET radiotracer for molecular imaging of PKM2 with potential to overcome the prior limitations observed with [18F]DASA-23. [18F]DASA-10 shows promise for clinical translation to enable imaging of brain malignancies owing to its low background signal in the healthy brain.

    View details for DOI 10.1016/j.nucmedbio.2023.108382

    View details for PubMedID 37634399

  • PET imaging of TREM1 identifies CNS-infiltrating myeloid cells in a mouse model of multiple sclerosis. Science translational medicine Chaney, A. M., Cropper, H. C., Jain, P., Wilson, E., Simonetta, F., Johnson, E. M., Alam, I. S., Patterson, I. T., Swarovski, M., Stevens, M. Y., Wang, Q., Azevedo, C., Nagy, S. C., Ramos Benitez, J., Deal, E. M., Vogel, H., Andreasson, K. I., James, M. L. 2023; 15 (702): eabm6267


    Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS) that causes substantial morbidity and diminished quality of life. Evidence highlights the central role of myeloid lineage cells in the initiation and progression of MS. However, existing imaging strategies for detecting myeloid cells in the CNS cannot distinguish between beneficial and harmful immune responses. Thus, imaging strategies that specifically identify myeloid cells and their activation states are critical for MS disease staging and monitoring of therapeutic responses. We hypothesized that positron emission tomography (PET) imaging of triggering receptor expressed on myeloid cells 1 (TREM1) could be used to monitor deleterious innate immune responses and disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We first validated TREM1 as a specific marker of proinflammatory, CNS-infiltrating, peripheral myeloid cells in mice with EAE. We show that the 64Cu-radiolabeled TREM1 antibody-based PET tracer monitored active disease with 14- to 17-fold higher sensitivity than translocator protein 18 kDa (TSPO)-PET imaging, the established approach for detecting neuroinflammation in vivo. We illustrate the therapeutic potential of attenuating TREM1 signaling both genetically and pharmacologically in the EAE mice and show that TREM1-PET imaging detected responses to an FDA-approved MS therapy with siponimod (BAF312) in these animals. Last, we observed TREM1+ cells in clinical brain biopsy samples from two treatment-naïve patients with MS but not in healthy control brain tissue. Thus, TREM1-PET imaging has potential for aiding in the diagnosis of MS and monitoring of therapeutic responses to drug treatment.

    View details for DOI 10.1126/scitranslmed.abm6267

    View details for PubMedID 37379371

  • Clinical Radiosynthesis and Translation of [18F]OP-801: A Novel Radiotracer for Imaging Reactive Microglia and Macrophages. ACS chemical neuroscience Jackson, I. M., Carlson, M. L., Beinat, C., Malik, N., Kalita, M., Reyes, S., Azevedo, E. C., Nagy, S. C., Alam, I. S., Sharma, R., La Rosa, S. A., Moradi, F., Cleland, J., Shen, B., James, M. L. 2023


    Positron emission tomography (PET) is a powerful tool for studying neuroinflammatory diseases; however, current PET biomarkers of neuroinflammation possess significant limitations. We recently reported a promising dendrimer PET tracer ([18F]OP-801), which is selectively taken up by reactive microglia and macrophages. Here, we describe further important characterization of [18F]OP-801 in addition to optimization and validation of a two-step clinical radiosynthesis. [18F]OP-801 was found to be stable in human plasma for 90 min post incubation, and human dose estimates were calculated for 24 organs of interest; kidneys and urinary bladder wall without bladder voiding were identified as receiving the highest absorbed dose. Following optimization detailed herein, automated radiosynthesis and quality control (QC) analyses of [18F]OP-801 were performed in triplicate in suitable radiochemical yield (6.89 ± 2.23% decay corrected), specific activity (37.49 ± 15.49 GBq/mg), and radiochemical purity for clinical imaging. Importantly, imaging mice with tracer (prepared using optimized methods) 24 h following the intraperitoneal injection of liposaccharide resulted in the robust brain PET signal. Cumulatively, these data enable clinical translation of [18F]OP-801 for imaging reactive microglia and macrophages in humans. Data from three validation runs of the clinical manufacturing and QC were submitted to the Food and Drug Administration (FDA) as part of a Drug Master File (DMF). Subsequent FDA approval to proceed was obtained, and a phase 1/2 clinical trial (NCT05395624) for first-in-human imaging in healthy controls and patients with amyotrophic lateral sclerosis is underway.

    View details for DOI 10.1021/acschemneuro.3c00028

    View details for PubMedID 37310119

  • Development and initial evaluation of a novel 11C-labeled PET tracer to image GPR84 expressing-myeloid cells during neuroinflammation Kalita, M., Park, J., Hayee, S., Marsango, S., Carlson, M., Reyes, S., Nagy, S., Straniero, V., Pandrala, M., Jackson, I., Alam, I., Valoti, E., Milligan, G., Shen, B., James, M. SOC NUCLEAR MEDICINE INC. 2023
  • Is There a Role of Artificial Intelligence in Preclinical Imaging? Seminars in nuclear medicine Kuper, A., Blanc-Durand, P., Gafita, A., Kersting, D., Fendler, W. P., Seibold, C., Moraitis, A., Luckerath, K., James, M. L., Seifert, R. 2023


    This review provides an overview of the current opportunities for integrating artificial intelligence methods into the field of preclinical imaging research in nuclear medicine. The growing demand for imaging agents and therapeutics that are adapted to specific tumor phenotypes can be excellently served by the evolving multiple capabilities of molecular imaging and theranostics. However, the increasing demand for rapid development of novel, specific radioligands with minimal side effects that excel in diagnostic imaging and achieve significant therapeutic effects requires a challenging preclinical pipeline: from target identification through chemical, physical, and biological development to the conduct of clinical trials, coupled with dosimetry and various pre, interim, and post-treatment staging images to create a translational feedback loop for evaluating the efficacy of diagnostic or therapeutic ligands. In virtually all areas of this pipeline, the use of artificial intelligence and in particular deep-learning systems such as neural networks could not only address the above-mentioned challenges, but also provide insights that would not have been possible without their use. In the future, we expect that not only the clinical aspects of nuclear medicine will be supported by artificial intelligence, but that there will also be a general shift toward artificial intelligence-assisted in silico research that will address the increasingly complex nature of identifying targets for cancer patients and developing radioligands.

    View details for DOI 10.1053/j.semnuclmed.2023.03.003

    View details for PubMedID 37037684

  • Imaging CD19+ B Cells in an Experimental Autoimmune Encephalomyelitis Mouse Model using Positron Emission Tomography. Journal of visualized experiments : JoVE Reyes, S. T., Azevedo, E. C., Cropper, H. C., Nagy, S., Deal, E. M., Chaney, A. M., James, M. L. 2023


    Multiple sclerosis (MS) is the most common demyelinating central nervous system (CNS) disease affecting young adults, often resulting in neurological deficits and disability as the disease progresses. B lymphocytes play a complex and critical role in MS pathology and are the target of several therapeutics in clinical trials. Currently, there is no way to accurately select patients for specific anti-B cell therapies or to non-invasively quantify the effects of these treatments on B cell load in the CNS and peripheral organs. Positron emission tomography (PET) imaging has enormous potential to provide highly specific, quantitative information regarding the in vivo spatiotemporal distribution and burden of B cells in living subjects. This paper reports methods to synthesize and employ a PET tracer specific for human CD19+ B cells in a well-established B cell-driven mouse model of MS, experimental autoimmune encephalomyelitis (EAE), which is induced with human recombinant myelin oligodendrocyte glycoprotein 1-125. Described here are optimized techniques to detect and quantify CD19+ B cells in the brain and spinal cord using in vivo PET imaging. Additionally, this paper reports streamlined methods for ex vivo gamma counting of disease-relevant organs, including bone marrow, spinal cord, and spleen, together with high-resolution autoradiography of CD19 tracer binding in CNS tissues.

    View details for DOI 10.3791/64133

    View details for PubMedID 36744792

  • Multimodal imaging of capsid and cargo reveals differential brain targeting and liver detargeting of systemically-administered AAVs. Biomaterials Seo, J. W., Ajenjo, J., Wu, B., Robinson, E., Raie, M. N., Wang, J., Tumbale, S. K., Buccino, P., Anders, D. A., Shen, B., Habte, F. G., Beinat, C., James, M. L., Reyes, S. T., Ravindra Kumar, S., Miles, T. F., Lee, J. T., Gradinaru, V., Ferrara, K. W. 2022: 121701


    The development of gene delivery vehicles with high organ specificity when administered systemically is a critical goal for gene therapy. We combine optical and positron emission tomography (PET) imaging of 1) reporter genes and 2) capsid tags to assess the temporal and spatial distribution and transduction of adeno-associated viruses (AAVs). AAV9 and two engineered AAV vectors (PHP.eB and CAP-B10) that are noteworthy for maximizing blood-brain barrier transport were compared. CAP-B10 shares a modification in the 588 loop with PHP.eB, but also has a modification in the 455 loop, added with the goal of reducing off-target transduction. PET and optical imaging revealed that the additional modifications retained brain receptor affinity. In the liver, the accumulation of AAV9 and the engineered AAV capsids was similar (15% of the injected dose per cc and not significantly different between capsids at 21h). However, the engineered capsids were primarily internalized by Kupffer cells rather than hepatocytes, and liver transduction was greatly reduced. PET reporter gene imaging after engineered AAV systemic injection provided a non-invasive method to monitor AAV-mediated protein expression over time. Through comparison with capsid tagging, differences between brain localization and transduction were revealed. In summary, AAV capsids bearing imaging tags and reporter gene payloads create a unique and powerful platform to assay the pharmacokinetics, cellular specificity and protein expression kinetics of AAV vectors in vivo, a key enabler for the field of gene therapy.

    View details for DOI 10.1016/j.biomaterials.2022.121701

    View details for PubMedID 35985893

  • ICOS ImmunoPET Enables Visualization of Activated T Cells and Early Diagnosis of Murine Acute Gastrointestinal GvHD. Blood advances Xiao, Z., Alam, I. S., Simonetta, F., Chen, W., Scheller, L., Murty, S., Lohmeyer, J. K., Lopes Ramos, T. L., James, M. L., Negrin, R. S., Gambhir, S. S. 2022


    Allogeneic hematopoietic cell transplantation (HCT) is a well-established and potentially curative treatment for a broad range of hematological diseases, bone marrow failure states and genetic disorders. Acute graft-versus-host-disease (GvHD), mediated by donor T cells attacking host tissue, still represents a major cause of morbidity and mortality following allogeneic HCT. Current approaches to diagnosis of gastrointestinal acute GvHD rely on clinical and pathological criteria that manifest at late stages of disease. New strategies allowing for GvHD prediction and diagnosis, prior to symptom onset, are urgently needed. Noninvasive antibody-based PET (immunoPET) imaging of T cell activation post allogeneic HCT is a promising strategy towards this goal. In this work, we identified Inducible T-cell COStimulator (ICOS) as a potential immunoPET target for imaging activated T cells during GvHD. We demonstrate that the use of the 89Zr-DFO-ICOS monoclonal antibody (mAb) PET tracer, allows in vivo visualization of donor T cell activation in target tissues, namely the intestinal tract, in a murine model of acute GvHD. Importantly, we demonstrate that the 89Zr-DFO-ICOS mAb PET tracer does not affect GvHD pathogenesis or the graft-versus-tumor (GvT) effect of the transplant procedure. Our data identify ICOS immunoPET as a promising strategy for early GvHD diagnosis prior to the appearance of clinical symptoms.

    View details for DOI 10.1182/bloodadvances.2022007403

    View details for PubMedID 35790103

  • Engineering genetically-encoded synthetic biomarkers for breath-based cancer detection Vermesh, O., D'Souza, A., Alam, I., Wardak, M., McLaughlin, T., El Rami, F., Sathirachinda, A., Bell, J., Pitteri, S., James, M., Hori, S., Gross, E., Gambhir, S. AMER ASSOC CANCER RESEARCH. 2022
  • In Silico Approaches for Addressing Challenges in CNS Radiopharmaceutical Design. ACS chemical neuroscience Jackson, I. M., Webb, E. W., Scott, P. J., James, M. L. 2022


    Positron emission tomography (PET) is a highly sensitive and versatile molecular imaging modality that leverages radiolabeled molecules, known as radiotracers, to interrogate biochemical processes such as metabolism, enzymatic activity, and receptor expression. The ability to probe specific molecular and cellular events longitudinally in a noninvasive manner makes PET imaging a particularly powerful technique for studying the central nervous system (CNS) in both health and disease. Unfortunately, developing and translating a single CNS PET tracer for clinical use is typically an extremely resource-intensive endeavor, often requiring synthesis and evaluation of numerous candidate molecules. While existing in vitro methods are beginning to address the challenge of derisking molecules prior to costly in vivo PET studies, most require a significant investment of resources and possess substantial limitations. In the context of CNS drug development, significant time and resources have been invested into the development and optimization of computational methods, particularly involving machine learning, to streamline the design of better CNS therapeutics. However, analogous efforts developed and validated for CNS radiotracer design are conspicuously limited. In this Perspective, we overview the requirements and challenges of CNS PET tracer design, survey the most promising computational methods for in silico CNS drug design, and bridge these two areas by discussing the potential applications and impact of computational design tools in CNS radiotracer design.

    View details for DOI 10.1021/acschemneuro.2c00269

    View details for PubMedID 35606334

  • Radiosynthesis and initial preclinical evaluation of [11C]AZD1283 as a potential P2Y12R PET radiotracer. Nuclear medicine and biology Jackson, I. M., Buccino, P. J., Azevedo, E. C., Carlson, M. L., Luo, A. S., Deal, E. M., Kalita, M., Reyes, S. T., Shao, X., Beinat, C., Nagy, S. C., Chaney, A. M., Anders, D. A., Scott, P. J., Smith, M., Shen, B., James, M. L. 2022


    INTRO: Chronic neuroinflammation and microglial dysfunction are key features of many neurological diseases, including Alzheimer's Disease and multiple sclerosis. While there is unfortunately a dearth of highly selective molecular imaging biomarkers/probes for studying microglia in vivo, P2Y12R has emerged as an attractive candidate PET biomarker being explored for this purpose. Importantly, P2Y12R is selectively expressed on microglia in the CNS and undergoes dynamic changes in expression according to inflammatory context (e.g., toxic versus beneficial/healing states), thus having the potential to reveal functional information about microglia in living subjects. Herein, we identified a high affinity, small molecule P2Y12R antagonist (AZD1283) to radiolabel and assess as a candidate radiotracer through in vitro assays and in vivo positron emission tomography (PET) imaging of both wild-type and total knockout mice and a non-human primate.METHODS: First, we evaluated the metabolic stability and passive permeability of non-radioactive AZD1283 in vitro. Next, we radiolabeled [11C]AZD1283 with radioactive precursor [11C]NH4CN and determined stability in formulation and human plasma. Finally, we investigated the in vivo stability and kinetics of [11C]AZD1283 via dynamic PET imaging of naive wild-type mice, P2Y12R knockout mouse, and a rhesus macaque.RESULTS: We determined the half-life of AZD1283 in mouse and human liver microsomes to be 37 and>160min, respectively, and predicted passive CNS uptake with a small amount of active efflux, using a Caco-2 assay. Our radiolabeling efforts afforded [11C]AZD1283 in an activity of 12.69±10.64mCi with high chemical and radiochemical purity (>99%) and molar activity of 1142.84±504.73mCi/mumol (average of n=3). Of note, we found [11C]AZD1283 to be highly stable in vitro, with >99% intact tracer present after 90min of incubation in formulation and 60min of incubation in human serum. PET imaging revealed negligible brain signal in healthy wild-type mice (n=3) and a P2Y12 knockout mouse (0.55±0.37%ID/g at 5min post injection). Strikingly, high signal was detected in the liver of all mice within the first 20min of administration (peak uptake=58.28±18.75%ID/g at 5min post injection) and persisted for the remaining duration of the scan. Ex vivo gamma counting of mouse tissues at 60min post-injection mirrored in vivo data with a mean %ID/g of 0.9%±0.40, 0.02%±0.01, and 106±29.70% in the blood, brain, and liver, respectively (n=4). High performance liquid chromatography (HPLC) analysis of murine blood and liver metabolite samples revealed a single radioactive peak (relative area under peak: 100%), representing intact tracer. Finally, PET imaging of a rhesus macaque also revealed negligible CNS uptake/binding in monkey brain (peak uptake=0.37 Standard Uptake Values (SUV)).CONCLUSION: Despite our initial encouraging liver microsome and Caco-2 monolayer data, in addition to the observed high stability of [11C]AZD1283 in formulation and human serum, in vivo brain uptake was negligible and rapid accumulation was observed in the liver of both naive wildtype and P2Y12R knockout mice. Liver signal appeared to be independent of both metabolism and P2Y12R expression due to the confirmation of intact tracer in this tissue for both wildtype and P2Y12R knockout mice. In Rhesus Macaque, negligible uptake of [11C]AZD1283 brain indicates a lack of potential for translation or its further investigation in vivo. P2Y12R is an extremely promising potential PET biomarker, and the data presented here suggests encouraging metabolic stability for this scaffold; however, the mechanism of liver uptake in mice should be elucidated prior to further analogue development.

    View details for DOI 10.1016/j.nucmedbio.2022.05.001

    View details for PubMedID 35680502

  • TRACKING INNATE IMMUNE ACTIVATION IN A MOUSE MODEL OF PARKINSON'S DISEASE USING TREM1 AND TSPO PET TRACERS. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Lucot, K. L., Stevens, M. Y., Bonham, T. A., Azevedo, E. C., Chaney, A. M., Webber, E. D., Jain, P., Klockow, J. L., Jackson, I. M., Carlson, M. L., Graves, E. E., Montine, T. J., James, M. L. 2022


    Parkinson's disease (PD) is associated with aberrant innate immune responses, including microglial activation and infiltration of peripheral myeloid cells into the central nervous system (CNS). Methods to investigate innate immune activation in PD are limited and have not yet elucidated key interactions between neuroinflammation and peripheral inflammation. Translocator protein 18 kDa (TSPO)-positron emission tomography (PET) is a widely evaluated imaging approach for studying activated microglia and peripheral myeloid lineage cells in vivo, however it is yet to be fully explored in PD. Herein we investigate the utility of TSPO-PET, in addition to PET imaging of triggering receptor expressed on myeloid cells 1 (TREM1) - a novel biomarker of proinflammatory myeloid cells - for detecting innate immune responses in the 6-hydroxydopamine (6-OHDA) mouse model of dopaminergic neuron degeneration. Methods: C57/BL6J and TREM1-knockout mice were stereotaxically injected with 6-OHDA in the left striatum; control mice were saline-injected. At day 7 or 14 post-surgery, mice were administered 18F-GE-180, 64Cu-TREM1-mAb or 64Cu-Isotype control-mAb and imaged by PET/CT. Ex vivo autoradiography (ARG) was performed to obtain high resolution images of tracer binding within the brain. Immunohistochemistry was conducted to verify myeloid cell activation and dopaminergic cell death and quantitative PCR and flow cytometry were completed to assess levels of target in the brain. Results: PET/CT images of both tracers showed elevated signal within the striatum of 6-OHDA-injected mice compared to those injected with saline. ARG afforded higher resolution brain images and revealed significant TSPO and TREM1 tracer binding within the ipsilateral striatum of 6-OHDA- compared to saline-injected mice at both 7- and 14-days post-toxin. Interestingly, 18F-GE-180 enabled detection of inflammation in the brain and peripheral tissues (blood and spleen) of 6-OHDA mice, whereas 64Cu-TREM1-mAb appeared to be more sensitive and specific for detecting neuroinflammation, in particular infiltrating myeloid cells, in these mice, as demonstrated by flow cytometry findings and higher tracer binding signal-to-background ratios in brain. Conclusion: TSPO- and TREM1-PET tracers are promising tools for investigating different cell types involved in innate immune activation in the context of dopaminergic neurodegeneration, thus warranting further investigation in other PD rodent models and human postmortem tissue to assess their clinical potential.

    View details for DOI 10.2967/jnumed.121.263039

    View details for PubMedID 35177426

  • Whole-body PET imaging of T cell response to Glioblastoma. Clinical cancer research : an official journal of the American Association for Cancer Research Nobashi, T. W., Mayer, A. T., Xiao, Z., Chan, C. T., Chaney, A. M., James, M. L., Gambhir, S. S. 2021


    PURPOSE: Immunotherapy is a promising approach for many oncological malignancies, including glioblastoma, however, there are currently no available tools or biomarkers to accurately assess whole-body immune responses in glioblastoma patients treated with immunotherapy. Here, the utility of OX40, a co-stimulatory molecule mainly expressed on activated effector T cells known to play an important role in eliminating cancer cells, was evaluated as a positron emission tomography (PET) imaging biomarker to quantify and track response to immunotherapy.EXPERIMENTAL DESIGN: A subcutaneous vaccination approach of CpG oligodeoxynucleotide, OX40 mAb, and tumor lysate at a remote site in a murine orthotopic glioma model was developed to induce activation of T cells distantly while monitoring their distribution in stimulated lymphoid organs with respect to observed therapeutic effects. To detect OX40-positive T cells we utilized our in-house developed 89Zr-DFO-OX40 mAb and in vivo PET/CT imaging.RESULTS: ImmunoPET with 89Zr-DFO-OX40 mAb revealed strong OX40-positive responses with high specificity, not only in the nearest lymph node from vaccinated area (mean, 20.8%ID/cc) but also in the spleen (16.7%ID/cc) and the tumor draining lymph node (11.4%ID/cc). When the tumor was small (< 106 p/sec/cm2/sr in bioluminescence imaging), a high number of responders and % shrinkage in tumor signal was indicated after only a single cycle of vaccination.CONCLUSIONS: The results highlight the promise of clinically translating cancer vaccination as a potential glioma therapy, as well as the benefits of monitoring efficacy of these treatments using immunoPET imaging of T cell activation.

    View details for DOI 10.1158/1078-0432.CCR-21-1412

    View details for PubMedID 34548318

  • A Clinical PET Imaging Tracer ([18F]DASA-23) to Monitor Pyruvate Kinase M2 Induced Glycolytic Reprogramming in Glioblastoma. Clinical cancer research : an official journal of the American Association for Cancer Research Beinat, C., Patel, C. B., Haywood, T., Murty, S., Naya, L., Castillo, J. B., Reyes, S. T., Phillips, M., Buccino, P., Shen, B., Park, J. H., Koran, M. E., Alam, I. S., James, M. L., Holley, D., Halbert, K., Gandhi, H., He, J. Q., Granucci, M., Johnson, E., Liu, D. D., Uchida, N., Sinha, R., Chu, P., Born, D. E., Warnock, G. I., Weissman, I., Hayden Gephart, M., Khalighi, M. M., Massoud, T. F., Iagaru, A., Davidzon, G., Thomas, R., Nagpal, S., Recht, L. D., Gambhir, S. S. 2021


    PURPOSE: Pyruvate kinase M2 (PKM2) catalyzes the final step in glycolysis, a key process of cancer metabolism. PKM2 is preferentially expressed by glioblastoma (GBM) cells with minimal expression in healthy brain. We describe the development, validation, and translation of a novel positron emission tomography (PET) tracer to study PKM2 in GBM. We evaluated 1-((2-fluoro-6-[18F]fluorophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine ([18F]DASA-23) in cell culture, mouse models of GBM, healthy human volunteers, and GBM patients.EXPERIMENTAL DESIGN: [18F]DASA-23 was synthesized with a molar activity of 100.47 {plus minus} 29.58 GBq/mol and radiochemical purity >95%. We performed initial testing of [18F]DASA-23 in GBM cell culture and human GBM xenografts implanted orthotopically into mice. Next we produced [18F]DASA-23 under FDA oversight, and evaluated it in healthy volunteers, and a pilot cohort of glioma patients.RESULTS: In mouse imaging studies, [18F]DASA-23 clearly delineated the U87 GBM from surrounding healthy brain tissue and had a tumor-to-brain ratio (TBR) of 3.6 {plus minus} 0.5. In human volunteers, [18F]DASA-23 crossed the intact blood-brain barrier and was rapidly cleared. In GBM patients, [18F]DASA-23 successfully outlined tumors visible on contrast-enhanced magnetic resonance imaging (MRI). The uptake of [18F]DASA-23 was markedly elevated in GBMs compared to normal brain, and it identified a metabolic non-responder within 1-week of treatment initiation.CONCLUSIONS: We developed and translated [18F]DASA-23 as a new tracer that demonstrated the visualization of aberrantly expressed PKM2 for the first time in human subjects. These results warrant further clinical evaluation of [18F]DASA-23 to assess its utility for imaging therapy-induced normalization of aberrant cancer metabolism.

    View details for DOI 10.1158/1078-0432.CCR-21-0544

    View details for PubMedID 34475101

  • A new in silico approach to revolutionize CNS PET tracer design and enhance translational success Jackson, I., Luo, A., Webb, E., Stevens, M., Scott, P., James, M. ELSEVIER SCIENCE INC. 2021: S24-S25
  • Sanjiv Sam Gambhir (1962-2020). Nature biomedical engineering Wu, A. M., James, M. L., Kodukulla, M. I. 2021

    View details for DOI 10.1038/s41551-020-00668-8

    View details for PubMedID 33420477

  • Hippocampal subfield imaging and fractional anisotropy show parallel changes in Alzheimer's disease tau progression using simultaneous tau-PET/MRI at 3T. Alzheimer's & dementia (Amsterdam, Netherlands) Carlson, M. L., Toueg, T. N., Khalighi, M. M., Castillo, J., Shen, B., Azevedo, E. C., DiGiacomo, P., Mouchawar, N., Chau, G., Zaharchuk, G., James, M. L., Mormino, E. C., Zeineh, M. M. 2021; 13 (1): e12218


    Introduction: Alzheimer's disease (AD) is the most common form of dementia, characterized primarily by abnormal aggregation of two proteins, tau and amyloid beta. We assessed tau pathology and white matter connectivity changes in subfields of the hippocampus simultaneously in vivo in AD.Methods: Twenty-four subjects were scanned using simultaneous time-of-flight 18F-PI-2620 tau positron emission tomography/3-Tesla magnetic resonance imaging and automated segmentation.Results: We observed extensive tau elevation in the entorhinal/perirhinal regions, intermediate tau elevation in cornu ammonis 1/subiculum, and an absence of tau elevation in the dentate gyrus, relative to controls. Diffusion tensor imaging showed parahippocampal gyral fractional anisotropy was lower in AD and mild cognitive impairment compared to controls and strongly correlated with early tau accumulation in the entorhinal and perirhinal cortices.Discussion: This study demonstrates the potential for quantifiable patterns of 18F-PI2620 binding in hippocampus subfields, accompanied by diffusion and volume metrics, to be valuable markers of AD.

    View details for DOI 10.1002/dad2.12218

    View details for PubMedID 34337132

  • Simultaneous FDG-PET/MRI detects hippocampal subfield metabolic differences in AD/MCI. Scientific reports Carlson, M. L., DiGiacomo, P. S., Fan, A. P., Goubran, M., Khalighi, M. M., Chao, S. Z., Vasanawala, M., Wintermark, M., Mormino, E., Zaharchuk, G., James, M. L., Zeineh, M. M. 2020; 10 (1): 12064


    The medial temporal lobe is one of the most well-studied brain regions affected by Alzheimer's disease (AD). Although the spread of neurofibrillary pathology in the hippocampus throughout the progression of AD has been thoroughly characterized and staged using histology and other imaging techniques, it has not been precisely quantified in vivo at the subfield level using simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI). Here, we investigate alterations in metabolism and volume using [18F]fluoro-deoxyglucose (FDG) and simultaneous time-of-flight (TOF) PET/MRI with hippocampal subfield analysis of AD, mild cognitive impairment (MCI), and healthy subjects. We found significant structural and metabolic changes within the hippocampus that can be sensitively assessed at the subfield level in a small cohort. While no significant differences were found between groups for whole hippocampal SUVr values (p=0.166), we found a clear delineation in SUVr between groups in the dentate gyrus (p=0.009). Subfield analysis may be more sensitive for detecting pathological changes using PET-MRI in AD compared to global hippocampal assessment.

    View details for DOI 10.1038/s41598-020-69065-0

    View details for PubMedID 32694602

  • Neuroinflammation PET imaging: Current opinion and future directions. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Jain, P., Chaney, A., Carlson, M. L., Jackson, I. M., Rao, A., James, M. L. 2020


    Neuroinflammation is a pathological hallmark of numerous neurologic diseases. Positron emission tomography (PET) imaging enables a non-invasive means to investigate, quantify, and track the spatiotemporal dynamics of various immune cells in living subjects. Translocator protein 18 kDa (TSPO)-PET is a technique for detecting glial activation that has yielded valuable clinical data linking neuroinflammation to cognitive decline in neurodegenerative diseases and has also been used preliminarily as a therapy monitoring tool. However, considerable limitations of TSPO-PET have prompted identification of other more cell-specific and functionally relevant biomarkers. This review analyzes the clinical potential of available and emerging PET biomarkers of innate and adaptive immune responses, with mention of exciting future directions for the field.

    View details for DOI 10.2967/jnumed.119.229443

    View details for PubMedID 32620705

  • Physiological blood-brain transport is impaired with age by a shift in transcytosis. Nature Yang, A. C., Stevens, M. Y., Chen, M. B., Lee, D. P., Stahli, D., Gate, D., Contrepois, K., Chen, W., Iram, T., Zhang, L., Vest, R. T., Chaney, A., Lehallier, B., Olsson, N., du Bois, H., Hsieh, R., Cropper, H. C., Berdnik, D., Li, L., Wang, E. Y., Traber, G. M., Bertozzi, C. R., Luo, J., Snyder, M. P., Elias, J. E., Quake, S. R., James, M. L., Wyss-Coray, T. 2020


    The vascular interfaceof the brain, known as the blood-brain barrier (BBB), is understood to maintain brain function in part via its low transcellular permeability1-3. Yet, recent studies have demonstrated that brain ageing is sensitive to circulatory proteins4,5. Thus, it is unclear whether permeability to individually injected exogenous tracers-as isstandard in BBB studies-fully represents blood-to-brain transport. Here we label hundreds of proteins constituting the mouse blood plasma proteome, and upon their systemic administration, study the BBB with its physiological ligand. We find that plasma proteins readily permeate the healthy brain parenchyma, with transport maintained by BBB-specific transcriptional programmes. Unlike IgG antibody, plasma protein uptake diminishes in the aged brain, driven by an age-related shift in transport from ligand-specific receptor-mediated to non-specific caveolar transcytosis. This age-related shift occurs alongside a specific loss of pericyte coverage. Pharmacological inhibition of the age-upregulated phosphatase ALPL, a predicted negative regulator of transport, enhances brain uptake of therapeutically relevant transferrin, transferrin receptor antibody and plasma. These findings reveal the extent of physiological protein transcytosis to the healthy brain, a mechanism of widespread BBB dysfunction with age and a strategy for enhanced drug delivery.

    View details for DOI 10.1038/s41586-020-2453-z

    View details for PubMedID 32612231

  • PET/MR imaging of sigma-1 receptor pinpoints previously undetectable abnormalities in chronic pelvic pain Yoon, D., Fast, A., Shen, B., James, M. L., Lum, D., Biswal, S. SOC NUCLEAR MEDICINE INC. 2020
  • Visualizing innate immune activation in a mouse model of Parkinson's disease using a highly specific TREM1-PET tracer. Lucot, K., Stevens, M., Jain, P., Bonham, T., Webber, E., Klockow, J., Azevedo, E., Chaney, A., Graves, E., Montine, T., James, M. SOC NUCLEAR MEDICINE INC. 2020
  • TREM1-PET imaging of pro-inflammatory myeloid cells distinguishes active disease from remission in Multiple Sclerosis Chaney, A., Wilson, E., Jain, P., Cropper, H., Swarovski, M., Lucot, K., Vogel, H., Andreasson, K., James, M. L. SOC NUCLEAR MEDICINE INC. 2020
  • Demarcation of Sepsis-Induced Peripheral and Central Acidosis with pH-Low Insertion Cyclic (pHLIC) Peptide. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Henry, K. E., Chaney, A. M., Nagle, V. L., Cropper, H. C., Mozaffari, S., Slaybaugh, G., Parang, K., Andreev, O., Reshetnyak, Y. K., James, M. L., Lewis, J. S. 2020


    Acidosis is a key driver for many diseases, including cancer, sepsis, and stroke. The spatiotemporal dynamics of dysregulated pH across disease remains elusive and current diagnostic strategies do not provide localization of pH alterations. We sought to explore if PET imaging using hydrophobic cyclic peptides that partition into the cellular membrane at low extracellular pH (denoted as "pHLIC") can permit accurate in vivo visualization of acidosis. Methods: Acid-sensitive cyclic peptide c[E4W5C] pHLIC was conjugated to bifunctional maleimide-NO2A and radiolabeled with copper-64 (t = 12.7 h). C57BL/6J mice were administered LPS (15 mg/kg) or saline (vehicle) and serially imaged with [64Cu]Cu-c[E4W5C] over 24 h. Ex vivo autoradiography was performed on resected brain slices and subsequently stained with cresyl violet to enable high-resolution spatial analysis of tracer accumulation. A non- pH-sensitive cell-penetrating control peptide (c[R4W5C]) was used to confirm specificity of [64Cu]Cu-c[E4W5C]. CD11b (macrophage/microglia) and TMEM119 (microglia) immunostaining was performed to correlate extent of neuroinflammation with [64Cu]Cu-c[E4W5C] PET signal. Results: [64Cu]Cu-c[E4W5C] radiochemical yield and purity was >95% and >99% respectively, with molar activity >0.925 MBq/nmol. Significantly increased [64Cu]Cu-c[E4W5C] uptake was observed in LPS-treated mice (vs. vehicle) within peripheral tissues including blood, lungs, liver, and small intestines (P < 0.001-0.05). Additionally, there was significantly increased [64Cu]Cu-c[E4W5C] uptake in the brains of LPS-treated animals. Autoradiography confirmed increased uptake in the cerebellum, cortex, hippocampus, striatum, and hypothalamus of LPS-treated mice (vs. vehicle). Immunohistochemical (IHC) analysis revealed microglial/macrophage infiltrate, suggesting activation in brain regions containing increased tracer uptake. [64Cu]Cu-c[R4W5C] demonstrated significantly reduced uptake in the brain and periphery of LPS mice compared to the acid-mediated [64Cu]Cu-c[E4W5C] tracer. Conclusion: Here, we demonstrate that a pH-sensitive PET tracer specifically detects acidosis in regions associated with sepsis-driven pro-inflammatory responses. This study suggests that [64Cu]Cu-pHLIC is a valuable tool to noninvasively assess acidosis associated with both central and peripheral innate immune activation.

    View details for DOI 10.2967/jnumed.119.233072

    View details for PubMedID 32005774

  • Training the next generation of radiopharmaceutical scientists. Nuclear medicine and biology Gee, A. D., Andersson, J. n., Bhalla, R. n., Choe, Y. S., Dick, D. W., Herth, M. M., Hostetler, E. D., Jáuregui-Haza, U. J., Huang, Y. Y., James, M. L., Jeong, J. M., Korde, A. n., Kuge, Y. n., Kung, H. F., Lapi, S. E., Osso, J. A., Parent, E. n., Patt, M. n., Pricile, E. F., Riss, P. J., Santos-Oliveira, R. n., Taylor, S. n., Vasdev, N. n., Vercouillie, J. n., Wadsak, W. n., Yang, Z. n., Zhu, H. n., Scott, P. J. 2020; 88-89: 10–13

    View details for DOI 10.1016/j.nucmedbio.2020.06.004

    View details for PubMedID 32650289

  • Histologic evaluation of activation of acute inflammatory response in a mouse model following ultrasound-mediated blood-brain barrier using different acoustic pressures and microbubble doses. Nanotheranostics Pascal, A. n., Li, N. n., Lechtenberg, K. J., Rosenberg, J. n., Airan, R. D., James, M. L., Bouley, D. M., Pauly, K. B. 2020; 4 (4): 210–23


    Rationale: Localized blood-brain barrier (BBB) opening can be achieved with minimal to no tissue damage by applying pulsed focused ultrasound alongside a low microbubble (MB) dose. However, relatively little is known regarding how varying treatment parameters affect the degree of neuroinflammation following BBB opening. The goal of this study was to evaluate the activation of an inflammatory response following BBB opening as a function of applied acoustic pressure using two different microbubble doses. Methods: Mice were treated with 650 kHz ultrasound using varying acoustic peak negative pressures (PNPs) using two different MB doses, and activation of an inflammatory response, in terms of microglial and astrocyte activation, was assessed one hour following BBB opening using immunohistochemical staining. Harmonic and subharmonic acoustic emissions (AEs) were monitored for all treatments with a passive cavitation detector, and contrast-enhanced magnetic resonance imaging (CE-MRI) was performed following BBB opening to quantify the degree of opening. Hematoxylin and eosin-stained slides were assessed for the presence of microhemorrhage and edema. Results: For each MB dose, BBB opening was achieved with minimal activation of microglia and astrocytes using a PNP of 0.15 MPa. Higher PNPs were associated with increased activation, with greater increases associated with the use of the higher MB dose. Additionally, glial activation was still observed in the absence of histopathological findings. We found that CE-MRI was most strongly correlated with the degree of activation. While acoustic emissions were not predictive of microglial or astrocyte activation, subharmonic AEs were strongly associated with marked and severe histopathological findings. Conclusions: Our study demonstrated that there were mild histologic changes and activation of the acute inflammatory response using PNPs ranging from 0.15 MPa to 0.20 MPa, independent of MB dose. However, when higher PNPs of 0.25 MPa or above were applied, the same applied PNP resulted in more severe and widespread histological findings and activation of the acute inflammatory response when using the higher MB dose. The potential activation of the inflammatory response following ultrasound-mediated BBB opening should be considered when treating patients to maximize therapeutic benefit.

    View details for DOI 10.7150/ntno.49898

    View details for PubMedID 32802731

    View details for PubMedCentralID PMC7425053

  • Radionuclide Imaging for Neuroscience: Current Opinion and Future Directions. Molecular imaging Gee, A. D., Herth, M. M., James, M. L., Korde, A., Scott, P. J., Vasdev, N. 2020; 19: 1536012120936397


    This meeting report summarizes a Consultants Meeting that was held at International Atomic Energy Agency headquarters in Vienna to provide an update on radionuclide imaging for neuroscience applications.

    View details for DOI 10.1177/1536012120936397

    View details for PubMedID 32907484

  • On the consensus nomenclature rules for radiopharmaceutical chemistry - Reconsideration of radiochemical conversion. Nuclear medicine and biology Herth, M. M., Ametamey, S. n., Antuganov, D. n., Bauman, A. n., Berndt, M. n., Brooks, A. F., Bormans, G. n., Choe, Y. S., Gillings, N. n., Häfeli, U. O., James, M. L., Kopka, K. n., Kramer, V. n., Krasikova, R. n., Madsen, J. n., Mu, L. n., Neumaier, B. n., Piel, M. n., Rösch, F. n., Ross, T. n., Schibli, R. n., Scott, P. J., Shalgunov, V. n., Vasdev, N. n., Wadsak, W. n., Zeglis, B. M. 2020; 93: 19–21


    Radiochemical conversion is an important term to be included in the "Consensus nomenclature rules for radiopharmaceutical chemistry". Radiochemical conversion should be used to define reaction efficiency by measuring the transformation of components in a crude reaction mixture at a given time, whereas radiochemical yield is better suited to define the efficiency of an entire reaction process including, for example, separation, isolation, filtration, and formulation.

    View details for DOI 10.1016/j.nucmedbio.2020.11.003

    View details for PubMedID 33232876

  • Quantitative PET in the 2020s: A Roadmap. Physics in medicine and biology Meikle, S. R., Sossi, V. n., Roncali, E. n., Cherry, S. R., Banati, R. n., Mankoff, D. A., Jones, T. n., James, M. L., Sutcliffe, J. n., Ouyang, J. n., Petibon, Y. n., Ma, C. n., El Fakhri, G. n., Surti, S. n., Karp, J. S., Badawi, R. D., Yamaya, T. n., Akamatsu, G. n., Schramm, G. n., Rezaei, A. n., Nuyts, J. n., Fulton, R. R., Kyme, A. Z., Lois, C. n., Sari, H. n., Price, J. n., Boellaard, R. n., Jeraj, R. n., Bailey, D. L., Eslick, E. M., Willowson, K. P., Dutta, J. n. 2020


    Positron emission tomography (PET) plays an increasingly important role in research and clinical applications, catalysed by remarkable technical advances and a growing appreciation of the need for reliable, sensitive biomarkers of human function in health and disease. Over the last 30 years a large amount of the physics and engineering effort in PET has been motivated by the dominant clinical application during that period, oncology. This has led to important developments such as PET/CT, whole-body PET, 3D PET, accelerated statistical image reconstruction, and time-of-flight PET. Despite impressive improvements in image quality as a result of these advances, the emphasis on static, semi-quantitative "hot spot" imaging for oncologic applications has meant that the capability of PET for quantifying biologically relevant parameters based on tracer kinetics has not been fully exploited. More recent advances, such as PET/MR and total body PET, have opened up the ability to address a vast range of new research questions from which a future expansion of applications and radiotracers appears highly likely. Many of these new applications and tracers will, at least initially, require quantitative analyses that more fully exploit the exquisite sensitivity of PET and the tracer principle on which it is based. It is also expected that they will require more sophisticated quantitative analysis methods than those that are currently available. At the same time, artificial intelligence is revolutionizing data analysis and impacting the relationship between the statistical quality of the acquired data and the information we can extract from the data. In this roadmap, leaders of the key sub-disciplines of the field identify the challenges and opportunities to be addressed over the next 10 years that will enable PET to realise its full quantitative potential, initially in research laboratories and, ultimately, in clinical practice.

    View details for DOI 10.1088/1361-6560/abd4f7

    View details for PubMedID 33339012

  • Positron emission tomography imaging of novel AAV capsids maps rapid brain accumulation. Nature communications Seo, J. W., Ingham, E. S., Mahakian, L. n., Tumbale, S. n., Wu, B. n., Aghevlian, S. n., Shams, S. n., Baikoghli, M. n., Jain, P. n., Ding, X. n., Goeden, N. n., Dobreva, T. n., Flytzanis, N. C., Chavez, M. n., Singhal, K. n., Leib, R. n., James, M. L., Segal, D. J., Cheng, R. H., Silva, E. A., Gradinaru, V. n., Ferrara, K. W. 2020; 11 (1): 2102


    Adeno-associated viruses (AAVs) are typically single-stranded deoxyribonucleic acid (ssDNA) encapsulated within 25-nm protein capsids. Recently, tissue-specific AAV capsids (e.g. PHP.eB) have been shown to enhance brain delivery in rodents via the LY6A receptor on brain endothelial cells. Here, we create a non-invasive positron emission tomography (PET) methodology to track viruses. To provide the sensitivity required to track AAVs injected at picomolar levels, a unique multichelator construct labeled with a positron emitter (Cu-64, t1/2 = 12.7 h) is coupled to the viral capsid. We find that brain accumulation of the PHP.eB capsid 1) exceeds that reported in any previous PET study of brain uptake of targeted therapies and 2) is correlated with optical reporter gene transduction of the brain. The PHP.eB capsid brain endothelial receptor affinity is nearly 20-fold greater than that of AAV9. The results suggest that novel PET imaging techniques can be applied to inform and optimize capsid design.

    View details for DOI 10.1038/s41467-020-15818-4

    View details for PubMedID 32355221

  • Sanjiv Sam Gambhir (November 23, 1962-July 18, 2020). Molecular imaging and biology James, M. n., Iagaru, A. n. 2020

    View details for DOI 10.1007/s11307-020-01528-2

    View details for PubMedID 32797347

  • Development of a CD19 PET tracer for detecting B cells in a mouse model of multiple sclerosis. Journal of neuroinflammation Stevens, M. Y., Cropper, H. C., Lucot, K. L., Chaney, A. M., Lechtenberg, K. J., Jackson, I. M., Buckwalter, M. S., James, M. L. 2020; 17 (1): 275


    B cells play a central role in multiple sclerosis (MS) through production of injurious antibodies, secretion of pro-inflammatory cytokines, and antigen presentation. The therapeutic success of monoclonal antibodies (mAbs) targeting B cells in some but not all individuals suffering from MS highlights the need for a method to stratify patients and monitor response to treatments in real-time. Herein, we describe the development of the first CD19 positron emission tomography (PET) tracer, and its evaluation in a rodent model of MS, experimental autoimmune encephalomyelitis (EAE).Female C57BL/6 J mice were induced with EAE through immunization with myelin oligodendrocyte glycoprotein (MOG1-125). PET imaging of naïve and EAE mice was performed 19 h after administration of [64Cu]CD19-mAb. Thereafter, radioactivity in organs of interest was determined by gamma counting, followed by ex vivo autoradiography of central nervous system (CNS) tissues. Anti-CD45R (B220) immunostaining of brain tissue from EAE and naïve mice was also conducted.Radiolabelling of DOTA-conjugated CD19-mAb with 64Cu was achieved with a radiochemical purity of 99% and molar activity of 2 GBq/μmol. Quantitation of CD19 PET images revealed significantly higher tracer binding in whole brain of EAE compared to naïve mice (2.02 ± 0.092 vs. 1.68 ± 0.06 percentage of injected dose per gram, % ID/g, p = 0.0173). PET findings were confirmed by ex vivo gamma counting of perfused brain tissue (0.22 ± 0.020 vs. 0.12 ± 0.003 % ID/g, p = 0.0010). Moreover, ex vivo autoradiography of brain sections corresponded with PET imaging results and the spatial distribution of B cells observed in B220 immunohistochemistry-providing further evidence that [64Cu]CD19-mAb enables visualization of B cell infiltration into the CNS of EAE mice.CD19-PET imaging can be used to detect elevated levels of B cells in the CNS of EAE mice, and has the potential to impact the way we study, monitor, and treat clinical MS.

    View details for DOI 10.1186/s12974-020-01880-8

    View details for PubMedID 32948198

  • Tau PET imaging with 18F-PI-2620 in aging and neurodegenerative diseases. European journal of nuclear medicine and molecular imaging Mormino, E. C., Toueg, T. N., Azevedo, C. n., Castillo, J. B., Guo, W. n., Nadiadwala, A. n., Corso, N. K., Hall, J. N., Fan, A. n., Trelle, A. N., Harrison, M. B., Hunt, M. P., Sha, S. J., Deutsch, G. n., James, M. n., Fredericks, C. A., Koran, M. E., Zeineh, M. n., Poston, K. n., Greicius, M. D., Khalighi, M. n., Davidzon, G. A., Shen, B. n., Zaharchuk, G. n., Wagner, A. D., Chin, F. T. 2020


    In vivo measurement of the spatial distribution of neurofibrillary tangle pathology is critical for early diagnosis and disease monitoring of Alzheimer's disease (AD).Forty-nine participants were scanned with 18F-PI-2620 PET to examine the distribution of this novel PET ligand throughout the course of AD: 36 older healthy controls (HC) (age range 61 to 86), 11 beta-amyloid+ (Aβ+) participants with cognitive impairment (CI; clinical diagnosis of either mild cognitive impairment or AD dementia, age range 57 to 86), and 2 participants with semantic variant primary progressive aphasia (svPPA, age 66 and 78). Group differences in brain regions relevant in AD (medial temporal lobe, posterior cingulate cortex, and lateral parietal cortex) were examined using standardized uptake value ratios (SUVRs) normalized to the inferior gray matter of the cerebellum.SUVRs in target regions were relatively stable 60 to 90 min post-injection, with the exception of very high binders who continued to show increases over time. Robust elevations in 18F-PI-2620 were observed between HC and Aβ+ CI across all AD regions. Within the HC group, older age was associated with subtle elevations in target regions. Mildly elevated focal uptake was observed in the anterior temporal pole in one svPPA patient.Preliminary results suggest strong differences in the medial temporal lobe and cortical regions known to be impacted in AD using 18F-PI-2620 in patients along the AD trajectory. This work confirms that 18F-PI-2620 holds promise as a tool to visualize tau aggregations in AD.

    View details for DOI 10.1007/s00259-020-04923-7

    View details for PubMedID 32572562

  • Longitudinal translocator protein-18 kDa-positron emission tomography imaging of peripheral and central myeloid cells in a mouse model of complex regional pain syndrome PAIN Cropper, H. C., Johnson, E. M., Haight, E. S., Cordonnier, S. A., Chaney, A. M., Forman, T. E., Biswal, A., Stevens, M. Y., James, M. L., Tawfik, V. L. 2019; 160 (9): 2136–48
  • Imaging the invaders: TREM1 as a novel PET imaging biomarker of peripheral infiltrating myeloid cells and potential therapeutic target in multiple sclerosis. Chaney, A., Cropper, H., Johnson, E., Stevens, M., James, M. SOC NUCLEAR MEDICINE INC. 2019
  • [F-18]-SuPAR: A Radiofluorinated Probe for Noninvasive Imaging of DNA Damage-Dependent Poly(ADP-ribose) Polymerase Activity BIOCONJUGATE CHEMISTRY Shuhendler, A. J., Cui, L., Chen, Z., Shen, B., Chen, M., James, M. L., Witney, T. H., Bazalova-Carter, M., Gambhir, S. S., Chin, F. T., Graves, E. E., Rao, J. 2019; 30 (5): 1331–42


    Poly(ADP ribose) polymerase (PARP) enzymes generate poly(ADP ribose) post-translational modifications on target proteins for an array of functions centering on DNA and cell stress. PARP isoforms 1 and 2 are critically charged with the surveillance of DNA integrity and are the first line guardians of the genome against DNA breaks. Here we present a novel probe ([18F]-SuPAR) for noninvasive imaging of PARP-1/2 activity using positron emission tomography (PET). [18F]-SuPAR is a radiofluorinated nicotinamide adenine dinucleotide (NAD) analog that can be recognized by PARP-1/2 and incorporated into the long branched polymers of poly(ADP ribose) (PAR). The measurement of PARP-1/2 activity was supported by a reduction of radiotracer uptake in vivo following PARP-1/2 inhibition with talazoparib treatment, a potent PARP inhibitor recently approved by FDA for treatment of breast cancer, as well as ex vivo colocalization of radiotracer analog and poly(ADP ribose). With [18F]-SuPAR, we were able to map the dose- and time-dependent activation of PARP-1/2 following radiation therapy in breast and cervical cancer xenograft mouse models. Tumor response to therapy was determined by [18F]-SuPAR PET within 8 h of administration of a single dose of radiation equivalent to one round of stereotactic ablative radiotherapy.

    View details for DOI 10.1021/acs.bioconjchem.9b00089

    View details for Web of Science ID 000468368300008

    View details for PubMedID 30973715

  • Radiolabeling and pre-clinical evaluation of a first-in-class CD19 PET Tracer for imaging B cells in multiple sclerosis Stevens, M., Cropper, H., Jackson, I., Chaney, A., Lechtenberg, K., Buckwalter, M., James, M. L. SOC NUCLEAR MEDICINE INC. 2019
  • Microglial Modulation as a Target for Chronic Pain: From the Bench to the Bedside and Back. Anesthesia and analgesia Haight, E. S., Forman, T. E., Cordonnier, S. A., James, M. L., Tawfik, V. L. 2019; 128 (4): 737–46


    With a widespread opioid epidemic and profound biopsychosocial implications, chronic pain is a multifaceted public health issue requiring urgent attention. The treatment of chronic pain is particularly important to anesthesiologists given our unique role as perioperative physicians and pain medicine specialists. The present review details the recent shift from a neuronal theory of chronic pain to one that includes complex neuron-glia interactions. In particular, we highlight microglia, the myeloid-lineage cells of the central nervous system, as initiators of a postinjury neuroimmune response that contributes to the acute to chronic pain transition. We discuss ever-advancing preclinical studies, wherein significant success has been made through pharmacologic and genetic modulation of microglia, and we emphasize where these approaches have made the transition to the clinical realm. Furthermore, we highlight the most current, novel efforts to visualize glial activation in vivo using positron emission tomography and improve the diagnosis of chronic pain through radiotracer binding of specific targets, like the 18 kDa translocator protein in microglia and myeloid-lineage cells. Our rapidly advancing knowledge about microglia and their involvement in pain suggests that the era of glial-targeted therapeutics is just beginning so long as we refocus our attention on optimizing preclinical studies using a clinically informed approach, before translation.

    View details for PubMedID 30883419

  • Microglial Modulation as a Target for Chronic Pain: From the Bench to the Bedside and Back ANESTHESIA AND ANALGESIA Haight, E. S., Forman, T. E., Cordonnier, S. A., James, M. L., Tawfik, V. L. 2019; 128 (4): 737–46
  • Peripheral TREM1 responses to brain and intestinal immunogens amplify stroke severity Nature Immunology Liu, Q., Johnson, E., et al 2019
  • Longitudinal TSPO-PET imaging of peripheral and central myeloid cells in a mouse model of complex regional pain syndrome. Pain Cropper, H. C., Johnson, E. M., Haight, E. n., Cordonnier, S. A., Chaney, A. M., Forman, T. E., Biswal, A. n., Stevens, M. Y., James, M. L., Tawfik, V. L. 2019


    Complex regional pain syndrome (CRPS) is a severely disabling disease characterized by pain, temperature changes, motor dysfunction and edema that most often occurs as an atypical response to a minor surgery or fracture. Inflammation involving activation and recruitment of innate immune cells, including both peripheral and central myeloid cells (i.e. macrophages and microglia, respectively), is a key feature of CRPS. However, the exact role and time-course of these cellular processes relative to the known acute and chronic phases of the disease are not fully understood. Positron emission tomography (PET) of translocator protein-18kDa (TSPO) is a method for non-invasively tracking these activated innate immune cells. Here, we reveal the temporal dynamics of peripheral and central inflammatory responses over 20 weeks in a tibial fracture/casting mouse model of CRPS through longitudinal TSPO-PET using [F]GE-180. PET tracer uptake quantification in the tibia revealed increased peripheral inflammation as early as 2 days post-fracture and lasting 7 weeks. Centralized inflammation was detected in the spinal cord and brain of fractured mice at 7 and 21 days post-injury. Spinal cord tissue immunofluorescent staining revealed TSPO expression in microglia (CD11b+) at 7 days, but was restricted mainly to endothelial cells (PECAM1+) at baseline and 7 weeks. Our data suggest early and persistent peripheral myeloid cell activation, and transient central microglial activation are limited to the acute phase of CRPS. Moreover, we show that TSPO-PET can be used to noninvasively monitor the spatiotemporal dynamics of myeloid cell activation in CRPS progression with potential to inform disease phase-specific therapeutics.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

    View details for PubMedID 31095093

  • Positron emission tomography imaging of activated T cells by targeting OX40 reveals spatiotemporal immune dynamics and predicts response to in situ tumor vaccination Mayer, A. T., Alam, I. S., Sagiv-Barfi, I., Wang, K., Vermesh, O., Czerwinski, D. K., Johnson, E. M., James, M. L., Levy, R., Gambhir, S. S. AMER ASSOC CANCER RESEARCH. 2018
  • PET Imaging of Neuroinflammation Using [11C]DPA-713 in a Mouse Model of Ischemic Stroke. Journal of visualized experiments : JoVE Chaney, A. M., Johnson, E. M., Cropper, H. C., James, M. L. 2018


    Neuroinflammation is central to the pathological cascade following ischemic stroke. Non-invasive molecular imaging methods have the potential to provide critical insights into the temporal dynamics and role of certain neuroimmune interactions in stroke. Specifically, Positron Emission Tomography (PET) imaging of translocator protein 18 kDa (TSPO), a marker of activated microglia and peripheral myeloid-lineage cells, provides a means to detect and track neuroinflammation in vivo. Here, we present a method to accurately quantify neuroinflammation using [11C]N,N-Diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl]acetamide ([11C]DPA-713), a promising second generation TSPO-PET radiotracer, in distal middle cerebral artery occlusion (dMCAO) compared to sham-operated mice. MRI was performed 2 days post-dMCAO surgery to confirm stroke and define the infarct location and volume. PET/Computed Tomography (CT) imaging was carried out 6 days post-dMCAO to capture the peak increase in TSPO levels following stroke. Quantitation of PET images was conducted to assess the uptake of [11C]DPA-713 in the brain and spleen of dMCAO and sham mice to assess central and peripheral levels of inflammation. In vivo [11C]DPA-713 brain uptake was confirmed using ex vivo autoradiography.

    View details for DOI 10.3791/57243

    View details for PubMedID 29985311

  • TSPO-PET Imaging Using [18F]PBR06 is a Potential Translatable Biomarker for Treatment Response in Huntington's Disease: Preclinical Evidence with the p75NTR Ligand LM11A-31. Human molecular genetics Simmons, D. A., James, M. L., Belichenko, N. P., Semaan, S., Condon, C., Kuan, J., Shuhendler, A. J., Miao, Z., Chin, F. T., Longo, F. M. 2018


    Huntington's Disease (HD) is an inherited neurodegenerative disorder that has no cure. HD therapeutic development would benefit from a non-invasive translatable biomarker to track disease progression and treatment response. A potential biomarker is using positron emission tomography (PET) imaging with a translocator protein 18kDa (TSPO) radiotracer to detect microglial activation, a key contributor to HD pathogenesis. The ability of TSPO-PET to identify microglial activation in HD mouse models, essential for a translatable biomarker, or therapeutic efficacy in HD patients or mice is unknown. Thus, this study assessed the feasibility of utilizing PET imaging with the TSPO tracer, [18F]PBR06, to detect activated microglia in multiple HD mouse models and to monitor response to treatment with LM11A-31, a p75NTR ligand known to reduce neuroinflammation in HD mice. [18F]PBR06-PET detected microglial activation in striatum, cortex and hippocampus of vehicle-treated R6/2 mice at a late disease stage and, notably, also in early and mid-stage symptomatic BACHD mice. After oral administration of LM11A-31 to R6/2 and BACHD mice, [18F]PBR06-PET discerned the reductive effects of LM11A-31 on neuroinflammation in both HD mouse models. [18F]PBR06-PET signal had a spatial distribution similar to ex vivo brain autoradiography and correlated with microglial activation markers: increased IBA-1 and TSPO immunostaining/blotting and striatal levels of cytokines IL-6 and TNFalpha. These results suggest [18F]PBR06-PET as a surrogate marker of therapeutic efficacy in HD mice with high potential as a translatable biomarker for preclinical and clinical HD trials.

    View details for PubMedID 29860333

  • [18F]FSPG-PET reveals increased cystine/glutamate antiporter (xc-) activity in a mouse model of multiple sclerosis. Journal of neuroinflammation Hoehne, A., James, M. L., Alam, I. S., Ronald, J. A., Schneider, B., D'Souza, A., Witney, T. H., Andrews, L. E., Cropper, H. C., Behera, D., Gowrishankar, G., Ding, Z., Wyss-Coray, T., Chin, F. T., Biswal, S., Gambhir, S. S. 2018; 15 (1): 55


    The cystine/glutamate antiporter (xc-) has been implicated in several neurological disorders and, specifically, in multiple sclerosis (MS) as a mediator of glutamate excitotoxicity and proinflammatory immune responses. We aimed to evaluate an xc-specific positron emission tomography (PET) radiotracer, (4S)-4-(3-[18F]fluoropropyl)-L-glutamate ([18F]FSPG), for its ability to allow non-invasive monitoring of xc- activity in a mouse model of MS.Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by subcutaneous injection of myelin oligodendrocyte glycoprotein (MOG35-55) peptide in complete Freund's adjuvant (CFA) followed by pertussis toxin. Control mice received CFA emulsion and pertussis toxin without MOG peptide, while a separate cohort of naïve mice received no treatment. PET studies were performed to investigate the kinetics and distribution of [18F]FSPG in naïve, control, pre-symptomatic, and symptomatic EAE mice, compared to 18F-fluorodeoxyglucose ([18F]FDG). After final PET scans, each mouse was perfused and radioactivity in dissected tissues was measured using a gamma counter. Central nervous system (CNS) tissues were further analyzed using ex vivo autoradiography or western blot. [18F]FSPG uptake in human monocytes, and T cells pre- and post-activation was investigated in vitro.[18F]FSPG was found to be more sensitive than [18F]FDG at detecting pathological changes in the spinal cord and brain of EAE mice. Even before clinical signs of disease, a small but significant increase in [18F]FSPG signal was observed in the spinal cord of EAE mice compared to controls. This increase in PET signal became more pronounced in symptomatic EAE mice and was confirmed by ex vivo biodistribution and autoradiography. Likewise, in the brain of symptomatic EAE mice, [18F]FSPG uptake was significantly higher than controls, with the largest changes observed in the cerebellum. Western blot analyses of CNS tissues revealed a significant correlation between light chain of xc- (xCT) protein levels, the subunit of xc- credited with its transporter activity, and [18F]FSPG-PET signal. In vitro [18F]FSPG uptake studies suggest that both activated monocytes and T cells contribute to the observed in vivo PET signal.These data highlight the promise of [18F]FSPG-PET as a technique to provide insights into neuroimmune interactions in MS and the in vivo role of xc- in the development and progression of this disease, thus warranting further investigation.

    View details for DOI 10.1186/s12974-018-1080-1

    View details for PubMedID 29471880

    View details for PubMedCentralID PMC5822551

  • Imaging activated T cells predicts response to cancer vaccines. The Journal of clinical investigation Alam, I. S., Mayer, A. T., Sagiv-Barfi, I. n., Wang, K. n., Vermesh, O. n., Czerwinski, D. K., Johnson, E. M., James, M. L., Levy, R. n., Gambhir, S. S. 2018


    In situ cancer vaccines are under active clinical investigation, given their reported ability to eradicate both local and disseminated malignancies. Intratumoral vaccine administration is thought to activate a T cell-mediated immune response, which begins in the treated tumor and cascades systemically. In this study, we describe a PET tracer (64Cu-DOTA-AbOX40) that enabled noninvasive and longitudinal imaging of OX40, a cell-surface marker of T cell activation. We report the spatiotemporal dynamics of T cell activation following in situ vaccination with CpG oligodeoxynucleotide in a dual tumor-bearing mouse model. We demonstrate that OX40 imaging was able to predict tumor responses on day 9 after treatment on the basis of tumor tracer uptake on day 2, with greater accuracy than both anatomical and blood-based measurements. These studies provide key insights into global T cell activation following local CpG treatment and indicate that 64Cu-DOTA-AbOX40 is a promising candidate for monitoring clinical cancer immunotherapy strategies.

    View details for PubMedID 29596062

  • Successful treatment of chronic knee pain following localization by a sigma-1 receptor radioligand and PET/MRI: a case report JOURNAL OF PAIN RESEARCH Cipriano, P., Lee, S., Yoon, D., Shen, B., Tawfik, V., Curtin, C., Dragoo, J. L., James, M., Mccurdy, C., Chin, F., Biswal, S. 2018; 11: 2353–56


    The ability to accurately diagnose and objectively localize pain generators in chronic pain sufferers remains a major clinical challenge since assessment relies on subjective patient complaints and relatively non-specific diagnostic tools. Developments in clinical molecular imaging, including advances in imaging technology and radiotracer design, have afforded the opportunity to identify tissues involved in pain generation based on their pro-nociceptive condition. The sigma-1 receptor (S1R) is a pro-nociceptive receptor upregulated in painful, inflamed tissues, and it can be imaged using the highly specific radioligand 18F-FTC-146 with PET.A 50-year-old woman with a 7-year history of refractory, left-knee pain of unknown origin was referred to our pain management team. Over the past several years, she had undergone multiple treatments, including a lateral retinacular release, radiofrequency ablation of a peripheral nerve, and physical therapy. While certain treatments provided partial relief, her pain would inevitably return to its original state. Using simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) with the novel radiotracer 18F-FTC-146, imaging showed increased focal uptake of 18F-FTC-146 in the intercondylar notch, corresponding to an irregular but equivocal lesion identified in the simultaneously acquired MRI. These imaging results prompted surgical removal of the lesion, which upon resection was identified as an inflamed, intraarticular synovial lipoma. Removal of the lesion relieved the patient's pain, and to date the pain has not recurred.We present a case of chronic, debilitating knee pain that resolved with surgery following identification of the pathology with a novel clinical molecular imaging approach that detects chronic pain generators at the molecular and cellular level. This approach has the potential to identify and localize pain-associated pathology in a variety of chronic pain syndromes.

    View details for PubMedID 30349360

  • [18F]FSPG-PET reveals increased cystine/glutamate antiporter (xc-) activity in a mouse model of multiple sclerosis Journal of Neuroinflammation Hoehne, A., James, M. L., Alam, I. S., Ronald, J., Schneider, B., D'Souza, A., Witney, T. H., Andrews, L., Cropper, H., Behera, D., Gowrishankar, G., Ding, Z., Wyss-Coray, T., Chin, F., Biswal, S., Gambhir, S. S. 2018; 15 (1)
  • PET Imaging of Neuroinflammation Using [11C]DPA-713 in a Mouse Model of Ischemic Stroke JoVE Chaney, A., Johnson, E. M., Cropper, H. C., James, M. L. 2018

    View details for DOI 10.3791/57243

  • 11C-DPA-713 versus 18F-GE-180: A preclinical comparison of TSPO-PET tracers to visualize acute and chronic neuroinflammation in a mouse model of ischemic stroke. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Chaney, A. n., Cropper, H. C., Johnson, E. M., Lechtenberg, K. J., Peterson, T. C., Stevens, M. Y., Buckwalter, M. S., James, M. L. 2018


    Neuroinflammation plays a key role in neuronal injury following ischemic stroke. Positron emission tomography (PET) imaging of translocator protein 18 kDa (TSPO) permits longitudinal, non-invasive visualization of neuroinflammation in both pre-clinical and clinical settings. Many TSPO tracers have been developed, however it is unclear which tracer is the most sensitive and accurate for monitoring the in vivo spatiotemporal dynamics of neuroinflammation across applications. Hence, there is a need for head-to-head comparisons of promising TSPO-PET tracers across different disease states. Accordingly, the aim of this study was to directly compare two promising second-generation TSPO tracers; 11C-DPA-713 and 18F-GE-180, for the first time at acute and chronic time-points following ischemic stroke. Methods: Following distal middle cerebral artery occlusion (dMCAO) or sham surgery, mice underwent consecutive PET/CT imaging with 11C-DPA-713 and 18F-GE-180 at 2, 6, and 28 days after stroke. T2-weighted magnetic resonance (MR) images were acquired to enable delineation of ipsilateral (infarct) and contralateral brain regions of interest (ROIs). PET images were analyzed by calculating % injected dose per gram (%ID/g) in MR-guided ROIs. Standardized uptake value ratios were determined using the contralateral thalamus as a pseudo-reference region (SUVTh). Ex vivo autoradiography and immunohistochemistry were performed to verify in vivo findings. Results: Significantly increased tracer uptake was observed in the ipsilateral compared to contralateral ROI (SUVTh, 50-60 min summed data) at acute and chronic time-points using 11C-DPA-713 and 18F-GE-180. Ex vivo autoradiography confirmed in vivo findings demonstrating increased TSPO-tracer uptake in infarcted versus contralateral brain tissue. Importantly, a significant correlation was identified between microglial/macrophage activation (CD68 immunostaining) and 11C-DPA-713-PET signal, that was not evident with 18F-GE-180. No significant correlations were observed between TSPO-PET and activated astrocytes (GFAP immunostaining). Conclusion: Both 11C-DPA-713 and 18F-GE-180-PET enable detection of neuroinflammation at early and chronic time-points following cerebral ischemia in mice. 11C-DPA-713-PET reflects the extent of microglial activation in infarcted dMCAO mouse brain tissue more accurately compared to 18F-GE-180, and appears to be slightly more sensitive. These results highlight the potential of 11C-DPA-713 for tracking microglial activation in vivo after stroke, and warrants further investigation in both pre-clinical and clinical settings.

    View details for PubMedID 29976695

  • Multimodal assessment of SERS nanoparticle biodistribution post ingestion reveals new potential for clinical translation of Raman imaging BIOMATERIALS Campbell, J. L., SoRelle, E. D., Ilovich, O., Liba, O., James, M. L., Qiu, Z., Perez, V., Chan, C. T., de la Zerda, A., Zavaleta, C. 2017; 135: 42-52


    Despite extensive research and development, new nano-based diagnostic contrast agents have faced major barriers in gaining regulatory approval due to their potential systemic toxicity and prolonged retention in vital organs. Here we use five independent biodistribution techniques to demonstrate that oral ingestion of one such agent, gold-silica Raman nanoparticles, results in complete clearance with no systemic toxicity in living mice. The oral delivery mimics topical administration to the oral cavity and gastrointestinal (GI) tract as an alternative to intravenous injection. Biodistribution and clearance profiles of orally (OR) vs. intravenously (IV) administered Raman nanoparticles were assayed over the course of 48 h. Mice given either an IV or oral dose of Raman nanoparticles radiolabeled with approximately 100 μCi (3.7MBq) of (64)Cu were imaged with dynamic microPET immediately post nanoparticle administration. Static microPET images were also acquired at 2 h, 5 h, 24 h and 48 h. Mice were sacrificed post imaging and various analyses were performed on the excised organs to determine nanoparticle localization. The results from microPET imaging, gamma counting, Raman imaging, ICP-MS, and hyperspectral imaging of tissue sections all correlated to reveal no evidence of systemic distribution of Raman nanoparticles after oral administration and complete clearance from the GI tract within 24 h. Paired with the unique signals and multiplexing potential of Raman nanoparticles, this approach holds great promise for realizing targeted imaging of tumors and dysplastic tissues within the oral cavity and GI-tract. Moreover, these results suggest a viable path for the first translation of high-sensitivity Raman contrast imaging into clinical practice.

    View details for DOI 10.1016/j.biomaterials.2017.04.045

    View details for PubMedID 28486147

  • Human umbilical cord plasma proteins revitalize hippocampal function in aged mice NATURE Castellano, J. M., Mosher, K. I., Abbey, R. J., McBride, A. A., James, M. L., Berdnik, D., Shen, J. C., Zou, B., Xie, X. S., Tingle, M., Hinkson, I. V., Angst, M. S., Wyss-Coray, T. 2017; 544 (7651): 488-?


    Ageing drives changes in neuronal and cognitive function, the decline of which is a major feature of many neurological disorders. The hippocampus, a brain region subserving roles of spatial and episodic memory and learning, is sensitive to the detrimental effects of ageing at morphological and molecular levels. With advancing age, synapses in various hippocampal subfields exhibit impaired long-term potentiation, an electrophysiological correlate of learning and memory. At the molecular level, immediate early genes are among the synaptic plasticity genes that are both induced by long-term potentiation and downregulated in the aged brain. In addition to revitalizing other aged tissues, exposure to factors in young blood counteracts age-related changes in these central nervous system parameters, although the identities of specific cognition-promoting factors or whether such activity exists in human plasma remains unknown. We hypothesized that plasma of an early developmental stage, namely umbilical cord plasma, provides a reservoir of such plasticity-promoting proteins. Here we show that human cord plasma treatment revitalizes the hippocampus and improves cognitive function in aged mice. Tissue inhibitor of metalloproteinases 2 (TIMP2), a blood-borne factor enriched in human cord plasma, young mouse plasma, and young mouse hippocampi, appears in the brain after systemic administration and increases synaptic plasticity and hippocampal-dependent cognition in aged mice. Depletion experiments in aged mice revealed TIMP2 to be necessary for the cognitive benefits conferred by cord plasma. We find that systemic pools of TIMP2 are necessary for spatial memory in young mice, while treatment of brain slices with TIMP2 antibody prevents long-term potentiation, arguing for previously unknown roles for TIMP2 in normal hippocampal function. Our findings reveal that human cord plasma contains plasticity-enhancing proteins of high translational value for targeting ageing- or disease-associated hippocampal dysfunction.

    View details for DOI 10.1038/nature22067

    View details for PubMedID 28424512

  • F]DASA-23 for Imaging Tumor Glycolysis Through Noninvasive Measurement of Pyruvate Kinase M2. Molecular imaging and biology Beinat, C., Alam, I. S., James, M. L., Srinivasan, A., Gambhir, S. S. 2017


    A hallmark of cancer is metabolic reprogramming, which is exploited by cancer cells to ensure rapid growth and survival. Pyruvate kinase M2 (PKM2) catalyzes the final step in glycolysis, a key step in tumor metabolism and growth. Recently, we reported the radiosynthesis of the first positron emission tomography tracer for visualizing PKM2 in vivo-i.e., [(11)C]DASA-23. Due to the highly promising imaging results obtained with [(11)C]DASA-23 in rodent model glioblastoma, we set out to generate an F-18-labeled version of this tracer, with the end goal of clinical translation in mind. Herein, we report the radiosynthesis of 1-((2-fluoro-6-[(18)F]fluorophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine ([(18)F]DASA-23) and our initial investigation of its binding properties in cancer cells.We synthesized [(18)F]DASA-23 via fluorination of 1-((2-fluoro-6-nitrophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine (10) with K[(18)F]F/K2.2.2 in N,N-dimethylformamide at 110 °C for 20 min. Subsequently, we evaluated uptake of [(18)F]DASA-23 in HeLa cervical adenocarcinoma cells and in vitro stability in human and mouse serum.We successfully prepared [(18)F]DASA-23 in 2.61 ± 1.54 % radiochemical yield (n = 10, non-decay corrected at end of synthesis) with a specific activity of 2.59 ± 0.44 Ci/μmol. Preliminary cell uptake experiments revealed high uptake in HeLa cells, which was effectively blocked by pretreating cells with the structurally distinct PKM2 activator, TEPP-46. [(18)F]DASA-23 remained intact in human and mouse serum up to 120 min.Herein, we have identified a F-18-labeled PKM2 specific radiotracer which shows potential for in vivo imaging. The promising cell uptake results reported herein warrant the further evaluation of [(18)F]DASA-23 for its ability to detect and monitor cancer noninvasively.

    View details for DOI 10.1007/s11307-017-1068-8

    View details for PubMedID 28236227

  • Imaging B cells in a mouse model of multiple sclerosis using (64)Cu-Rituximab-PET. Journal of nuclear medicine : official publication, Society of Nuclear Medicine James, M. L., Hoehne, A. n., Mayer, A. T., Lechtenberg, K. n., Moreno, M. n., Gowrishankar, G. n., Ilovich, O. n., Natarajan, A. n., Johnson, E. M., Nguyen, J. n., Quach, L. n., Han, M. n., Buckwalter, M. n., Chandra, S. n., Gambhir, S. S. 2017


    B lymphocytes are a key pathological feature of multiple sclerosis (MS), and are becoming an important therapeutic target for this condition. Currently, there is no approved technique to non-invasively visualize B cells in the central nervous system (CNS) to monitor MS disease progression and response to therapies. Here we evaluated (64)Cu-Rituximab, a radiolabeled antibody specifically targeting the human B cell marker CD20, for its ability to image B cells in a mouse model of MS using positron emission tomography (PET). Methods: To model CNS infiltration by B cells, experimental autoimmune encephalomyelitis (EAE) was induced in transgenic mice that express human CD20 on B cells. EAE mice were given subcutaneous injections of Myelin Oligodendrocyte Glycoprotein fragment1-125 (MOG1-125) emulsified in complete Freund's adjuvant. Control mice received complete Freund's adjuvant alone. PET imaging of EAE and control mice was performed 1, 4, and 19h following (64)Cu-Rituximab administration. Mice were perfused and sacrificed after final PET scan, and radioactivity in dissected tissues was measured with a gamma-counter. CNS tissues from these mice were immunostained to quantify B cells or further analyzed via digital autoradiography. Results: Lumbar spinal cord PET signal was significantly higher in EAE mice compared to controls at all evaluated time points (e.g., 1h post-injection: 5.44 ± 0.37 vs. 3.33 ± 0.20 %ID/g, p<0.05). (64)Cu-Rituximab-PET signal in brain regions ranged between 1.74 ± 0.11 and 2.93 ± 0.15 %ID/g for EAE mice compared to 1.25±0.08 and 2.24±0.11%ID/g for controls, p<0.05 for all regions except striatum and thalamus at 1h post-injection. Similarly, ex vivo biodistribution results revealed notably higher (64)Cu-Rituximab uptake in brain and spinal cord of huCD20tg EAE, and B220 immunostaining verified that increased (64)Cu-Rituximab uptake in CNS tissues corresponded with elevated B cells. Conclusion: B cells can be detected in the CNS of EAE mice using (64)Cu-Rituximab-PET. Results from these studies warrant further investigation of (64)Cu-Rituximab in EAE models and consideration of use in MS patients to evaluate its potential for detecting and monitoring B cells in the progression and treatment of this disease. These results represent an initial step toward generating a platform to evaluate B cell-targeted therapeutics en route to the clinic.

    View details for PubMedID 28687602

  • Visualizing Nerve Injury in a Neuropathic Pain Model with [(18)F]FTC-146 PET/MRI. Theranostics Shen, B. n., Behera, D. n., James, M. L., Reyes, S. T., Andrews, L. n., Cipriano, P. W., Klukinov, M. n., Lutz, A. B., Mavlyutov, T. n., Rosenberg, J. n., Ruoho, A. E., McCurdy, C. R., Gambhir, S. S., Yeomans, D. C., Biswal, S. n., Chin, F. T. 2017; 7 (11): 2794–2805


    The ability to locate nerve injury and ensuing neuroinflammation would have tremendous clinical value for improving both the diagnosis and subsequent management of patients suffering from pain, weakness, and other neurologic phenomena associated with peripheral nerve injury. Although several non-invasive techniques exist for assessing the clinical manifestations and morphological aspects of nerve injury, they often fail to provide accurate diagnoses due to limited specificity and/or sensitivity. Herein, we describe a new imaging strategy for visualizing a molecular biomarker of nerve injury/neuroinflammation, i.e., the sigma-1 receptor (S1R), in a rat model of nerve injury and neuropathic pain. The two-fold higher increase of S1Rs was shown in the injured compared to the uninjured nerve by Western blotting analyses. With our novel S1R-selective radioligand, [(18)F]FTC-146 (6-(3-[(18)F]fluoropropyl)-3-(2-(azepan-1-yl)ethyl)benzo[d]thiazol-2(3H)-one), and positron emission tomography-magnetic resonance imaging (PET/MRI), we could accurately locate the site of nerve injury created in the rat model. We verified the accuracy of this technique by ex vivo autoradiography and immunostaining, which demonstrated a strong correlation between accumulation of [(18)F]FTC-146 and S1R staining. Finally, pain relief could also be achieved by blocking S1Rs in the neuroma with local administration of non-radioactive [(19)F]FTC-146. In summary, [(18)F]FTC-146 S1R PET/MR imaging has the potential to impact how we diagnose, manage and treat patients with nerve injury, and thus warrants further investigation.

    View details for PubMedID 28824716

  • [F-18]GE-180 PET Detects Reduced Microglia Activation After LM11A-31 Therapy in a Mouse Model of Alzheimer's Disease THERANOSTICS James, M. L., Belichenko, N. P., Shuhendler, A. J., Hoehne, A., Andrews, L. E., Condon, C., Nguyen, T. V., Reiser, V., Jones, P., Trigg, W., Rao, J., Gambhir, S. S., Longo, F. M. 2017; 7 (6): 1422-1436


    Microglial activation is a key pathological feature of Alzheimer's disease (AD). PET imaging of translocator protein 18 kDa (TSPO) is a strategy to detect microglial activation in vivo. Here we assessed flutriciclamide ([(18)F]GE-180), a new second-generation TSPO-PET radiotracer, for its ability to monitor response to LM11A-31, a novel AD therapeutic in clinical trials. AD mice displaying pathology were treated orally with LM11A-31 for 3 months. Subsequent [(18)F]GE-180-PET imaging revealed significantly lower signal in cortex and hippocampus of LM11A-31-treated AD mice compared to those treated with vehicle, corresponding with decreased levels of TSPO immunostaining and microglial Iba1 immunostaining. In addition to detecting decreased microglial activation following LM11A-31 treatment, [(18)F]GE-180 identified activated microglia in AD mice with greater sensitivity than another second-generation TSPO radiotracer, [(18)F]PBR06. Together, these data demonstrate the promise of [(18)F]GE-180 as a potentially sensitive tool for tracking neuroinflammation in AD mice and for monitoring therapeutic modulation of microglial activation.

    View details for DOI 10.7150/thno.17666

    View details for PubMedID 28529627

  • Further validation to support clinical translation of [(18)F]FTC-146 for imaging sigma-1 receptors. EJNMMI research Shen, B., James, M. L., Andrews, L., Lau, C., Chen, S., Palner, M., Miao, Z., Arksey, N. C., Shuhendler, A. J., Scatliffe, S., Kaneshige, K., Parsons, S. M., McCurdy, C. R., Salehi, A., Gambhir, S. S., Chin, F. T. 2015; 5 (1): 49-?


    This study aims to further evaluate the specificity and selectivity of [(18)F]FTC-146 and obtain additional data to support its clinical translation.The binding of [(19)F]FTC-146 to vesicular acetylcholine transporter (VAChT) was evaluated using [(3)H]vesamicol and PC12(A123.7) cells in an in vitro binding assay. The uptake and kinetics of [(18)F]FTC-146 in S1R-knockout mice (S1R-KO) compared to wild-type (WT) littermates was assessed using dynamic positron emission tomography (PET) imaging. Ex vivo autoradiography and histology were conducted using a separate cohort of S1R-KO/WT mice, and radiation dosimetry was calculated from WT mouse data (extrapolated for human dosing). Toxicity studies in Sprague-Dawley rats were performed with a dose equivalent to 250× the anticipated clinical dose of [(19)F]FTC-146 mass.VAChT binding assay results verified that [(19)F]FTC-146 displays negligible affinity for VAChT (K i = 450 ± 80 nM) compared to S1R. PET images demonstrated significantly higher tracer uptake in WT vs. S1R-KO brain (4.57 ± 1.07 vs. 1.34 ± 0.4 %ID/g at 20-25 min, n = 4, p < 0.05). In S1R-KO mice, it was shown that rapid brain uptake and clearance 10 min post-injection, which are consistent with previous S1R-blocking studies in mice. Three- to fourfold higher tracer uptake was observed in WT relative to S1R-KO mouse brains by ex vivo autoradiography. S1R staining coincided well with the autoradiographic data in all examined brain regions (r (2) = 0.85-0.95). Biodistribution results further demonstrated high [(18)F]FTC-146 accumulation in WT relative to KO mouse brain and provided quantitative information concerning tracer uptake in S1R-rich organs (e.g., heart, lung, pancreas) for WT mice vs. age-matched S1R-KO mice. The maximum allowed dose per scan in humans as extrapolated from mouse dosimetry was 33.19 mCi (1228.03 MBq). No significant toxicity was observed even at a 250X dose of the maximum carrier mass [(19)F]FTC-146 expected to be injected for human studies.Together, these data indicate that [(18)F]FTC-146 binds specifically to S1Rs and is a highly promising radiotracer ready for clinical translation to investigate S1R-related diseases.

    View details for DOI 10.1186/s13550-015-0122-2

    View details for PubMedID 26384292

  • PET imaging of tumor glycolysis downstream of hexokinase through noninvasive measurement of pyruvate kinase M2. Science translational medicine Witney, T. H., James, M. L., Shen, B., Chang, E., Pohling, C., Arksey, N., Hoehne, A., Shuhendler, A., Park, J., Bodapati, D., Weber, J., Gowrishankar, G., Rao, J., Chin, F. T., Gambhir, S. S. 2015; 7 (310): 310ra169-?


    Cancer cells reprogram their metabolism to meet increased biosynthetic demands, commensurate with elevated rates of replication. Pyruvate kinase M2 (PKM2) catalyzes the final and rate-limiting step in tumor glycolysis, controlling the balance between energy production and the synthesis of metabolic precursors. We report here the synthesis and evaluation of a positron emission tomography (PET) radiotracer, [(11)C]DASA-23, that provides a direct noninvasive measure of PKM2 expression in preclinical models of glioblastoma multiforme (GBM). In vivo, orthotopic U87 and GBM39 patient-derived tumors were clearly delineated from the surrounding normal brain tissue by PET imaging, corresponding to exclusive tumor-associated PKM2 expression. In addition, systemic treatment of mice with the PKM2 activator TEPP-46 resulted in complete abrogation of the PET signal in intracranial GBM39 tumors. Together, these data provide the basis for the clinical evaluation of imaging agents that target this important gatekeeper of tumor glycolysis.

    View details for DOI 10.1126/scitranslmed.aac6117

    View details for PubMedID 26491079

  • Microglial Malfunction: The Third Rail in the Development of Alzheimer's Disease. Trends in neurosciences Mhatre, S. D., Tsai, C. A., Rubin, A. J., James, M. L., Andreasson, K. I. 2015; 38 (10): 621-636


    Studies of Alzheimer's disease (AD) have predominantly focused on two major pathologies: amyloid-β (Aβ) and hyperphosphorylated tau. These misfolded proteins can accumulate asymptomatically in distinct regions over decades. However, significant Aβ accumulation can be seen in individuals who do not develop dementia, and tau pathology limited to the transentorhinal cortex, which can appear early in adulthood, is usually clinically silent. Thus, an interaction between these pathologies appears to be necessary to initiate and propel disease forward to widespread circuits. Recent multidisciplinary findings strongly suggest that the third factor required for disease progression is an aberrant microglial immune response. This response may initially be beneficial; however, a maladaptive microglial response eventually develops, fueling a feed-forward spread of tau and Aβ pathology.

    View details for DOI 10.1016/j.tins.2015.08.006

    View details for PubMedID 26442696

    View details for PubMedCentralID PMC4670239

  • PET Imaging of Translocator Protein (18 kDa) in a Mouse Model of Alzheimer's Disease Using N-(2,5-Dimethoxybenzyl)-2-18F-Fluoro-N-(2-Phenoxyphenyl)Acetamide. Journal of nuclear medicine : official publication, Society of Nuclear Medicine James, M. L., Belichenko, N. P., Nguyen, T. V., Andrews, L. E., Ding, Z., Liu, H., Bodapati, D., Arksey, N., Shen, B., Cheng, Z., Wyss-Coray, T., Gambhir, S. S., Longo, F. M., Chin, F. T. 2015; 56 (2): 311-316


    Herein we aimed to evaluate the utility of N-(2,5-dimethoxybenzyl)-2-(18)F-fluoro-N-(2-phenoxyphenyl)acetamide ((18)F-PBR06) for detecting alterations in translocator protein (TSPO) (18 kDa), a biomarker of microglial activation, in a mouse model of Alzheimer's disease (AD).Wild-type (wt) and AD mice (i.e., APP(L/S)) underwent (18)F-PBR06 PET imaging at predetermined time points between the ages of 5-6 and 15-16 mo. MR images were fused with PET/CT data to quantify (18)F-PBR06 uptake in the hippocampus and cortex. Ex vivo autoradiography and TSPO/CD68 immunostaining were also performed using brain tissue from these mice.PET images showed significantly higher accumulation of (18)F-PBR06 in the cortex and hippocampus of 15- to 16-mo-old APP(L/S) mice than age-matched wts (cortex/muscle: 2.43 ± 0.19 vs. 1.55 ± 0.15, P < 0.005; hippocampus/muscle: 2.41 ± 0.13 vs. 1.55 ± 0.12, P < 0.005). And although no significant difference was found between wt and APP(L/S) mice aged 9-10 mo or less using PET (P = 0.64), we were able to visualize and quantify a significant difference in (18)F-PBR06 uptake in these mice using autoradiography (cortex/striatum: 1.13 ± 0.04 vs. 0.96 ± 0.01, P < 0.05; hippocampus/striatum: 1.266 ± 0.003 vs. 1.096 ± 0.017, P < 0.001). PET results for 15- to 16-mo-old mice correlated well with autoradiography and immunostaining (i.e., increased (18)F-PBR06 uptake in brain regions containing elevated CD68 and TSPO staining in APP(L/S) mice, compared with wts).(18)F-PBR06 shows great potential as a tool for visualizing TSPO/microglia in the progression and treatment of AD.

    View details for DOI 10.2967/jnumed.114.141648

    View details for PubMedID 25613536

  • Antiviral drug ganciclovir is a potent inhibitor of microglial proliferation and neuroinflammation. journal of experimental medicine Ding, Z., Mathur, V., Ho, P. P., James, M. L., Lucin, K. M., Hoehne, A., Alabsi, H., Gambhir, S. S., Steinman, L., Luo, J., Wyss-Coray, T. 2014; 211 (2): 189-198


    Aberrant microglial responses contribute to neuroinflammation in many neurodegenerative diseases, but no current therapies target pathogenic microglia. We discovered unexpectedly that the antiviral drug ganciclovir (GCV) inhibits the proliferation of microglia in experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis (MS), as well as in kainic acid-induced excitotoxicity. In EAE, GCV largely prevented infiltration of T lymphocytes into the central nervous system (CNS) and drastically reduced disease incidence and severity when delivered before the onset of disease. In contrast, GCV treatment had minimal effects on peripheral leukocyte distribution in EAE and did not inhibit generation of antibodies after immunization with ovalbumin. Additionally, a radiolabeled analogue of penciclovir, [(18)F]FHBG, which is similar in structure to GCV, was retained in areas of CNS inflammation in EAE, but not in naive control mice, consistent with the observed therapeutic effects. Our experiments suggest GCV may have beneficial effects in the CNS beyond its antiviral properties.

    View details for DOI 10.1084/jem.20120696

    View details for PubMedID 24493798

    View details for PubMedCentralID PMC3920559

  • PET Imaging of Stroke-Induced Neuroinflammation in Mice Using [F-18]PBR06 MOLECULAR IMAGING AND BIOLOGY Lartey, F. M., Ahn, G., Shen, B., Cord, K., Smith, T., Chua, J. Y., Rosenblum, S., Liu, H., James, M. L., Chernikova, S., Lee, S. W., Pisani, L. J., Tirouvanziam, R., Chen, J. W., Palmer, T. D., Chin, F. T., Guzman, R., Graves, E. E., Loo, B. W. 2014; 16 (1): 109-117


    The purpose of this study is to evaluate the 18 kDa translocator protein (TSPO) radioligand [(18)F]N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ([(18)F]PBR06) as a positron emission tomography (PET) imaging biomarker of stroke-induced neuroinflammation in a rodent model.Stroke was induced by transient middle cerebral artery occlusion in Balb/c mice. Dynamic PET/CT imaging with displacement and preblocking using PK111195 was performed 3 days later. PET data were correlated with immunohistochemistry (IHC) for the activated microglial markers TSPO and CD68 and with autoradiography.[(18)F]PBR06 accumulation peaked within the first 5 min postinjection, then decreased gradually, remaining significantly higher in infarct compared to noninfarct regions. Displacement or preblocking with PK11195 eliminated the difference in [(18)F]PBR06 uptake between infarct and noninfarct regions. Autoradiography and IHC correlated well spatially with uptake on PET.[(18)F]PBR06 PET specifically images TSPO in microglial neuroinflammation in a mouse model of stroke and shows promise for imaging and monitoring microglial activation/neuroinflammation in other disease models.

    View details for DOI 10.1007/s11307-013-0664-5

    View details for PubMedID 23836504

  • Evaluation of s-1 receptor radioligand 18F-FTC-146 in rats and squirrel monkeys using PET. Journal of nuclear medicine : official publication, Society of Nuclear Medicine James, M. L., Shen, B., Nielsen, C. H., Behera, D., Buckmaster, C. L., Mesangeau, C., Zavaleta, C., Vuppala, P. K., Jamalapuram, S., Avery, B. A., Lyons, D. M., McCurdy, C. R., Biswal, S., Gambhir, S. S., Chin, F. T. 2014; 55 (1): 147-153


    The noninvasive imaging of σ-1 receptors (S1Rs) could provide insight into their role in different diseases and lead to novel diagnostic/treatment strategies. The main objective of this study was to assess the S1R radiotracer (18)F-FTC-146 in rats. Preliminary squirrel monkey imaging and human serum/liver microsome studies were performed to gain information about the potential of (18)F-FTC-146 for eventual clinical translation.The distribution and stability of (18)F-FTC-146 in rats were assessed via PET/CT, autoradiography, γ counting, and high-performance liquid chromatography (HPLC). Preliminary PET/MRI of squirrel monkey brain was conducted along with HPLC assessment of (18)F-FTC-146 stability in monkey plasma and human serum.Biodistribution studies showed that (18)F-FTC-146 accumulated in S1R-rich rat organs, including the lungs, pancreas, spleen, and brain. Pretreatment with known S1R compounds, haloperidol, or BD1047, before radioligand administration, significantly attenuated (18)F-FTC-146 accumulation in all rat brain regions by approximately 85% (P < 0.001), suggesting radiotracer specificity for S1Rs. Similarly, PET/CT and autoradiography results demonstrated accumulation of (18)F-FTC-146 in rat brain regions known to contain S1Rs and that this uptake could be blocked by BD1047 pretreatment. Ex vivo analysis of (18)F-FTC-146 in the brain showed that only intact radiotracer was present at 15, 30, and 60 min, whereas rapid metabolism of residual (18)F-FTC-146 was observed in rat plasma. Preliminary monkey PET/MRI studies demonstrated specific accumulation of (18)F-FTC-146 in the brain (mainly in cortical structures, cerebellum, and vermis) that could be attenuated by pretreatment with haloperidol. HPLC of monkey plasma suggested radioligand metabolism, whereas (18)F-FTC-146 appeared to be stable in human serum. Finally, liver microsome studies revealed that (18)F-FTC-146 has a longer half-life in human microsomes, compared with rodents.Together, these results indicate that (18)F-FTC-146 is a promising tool for visualizing S1Rs in preclinical studies and that it has potential for mapping these sites in the human brain.

    View details for DOI 10.2967/jnumed.113.120261

    View details for PubMedID 24337599

  • A F-18-Labeled Saxitoxin Derivative for in Vivo PET-MR Imaging of Voltage-Gated Sodium Channel Expression Following Nerve Injury JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Hoehne, A., Behera, D., Parsons, W. H., James, M. L., Shen, B., Borgohain, P., Bodapati, D., Prabhakar, A., Gambhir, S. S., Yeomans, D. C., Biswal, S., Chin, F. T., Du Bois, J. 2013; 135 (48): 18012-18015


    Both chronic and neuropathic pain conditions are associated with increased expression of certain voltage-gated sodium ion channel (NaV) isoforms in peripheral sensory neurons. A method for noninvasive imaging of these channels could represent a powerful tool for investigating aberrant expression of NaV and its role in pain pathogenesis. Herein, we describe the synthesis and evaluation of a positron emission tomography (PET) radiotracer targeting NaVs, the design of which is based on the potent, NaV-selective inhibitor saxitoxin. Both autoradiography analysis of sciatic nerves excised from injured rats as well as whole animal PET-MR imaging demonstrate that a systemically administered [(18)F]-labeled saxitoxin derivative concentrates at the site of nerve injury, consistent with upregulated sodium channel expression following axotomy. This type of PET agent has potential use for serial monitoring of channel expression levels at injured nerves throughout wound healing and/or following drug treatment. Such information may be correlated with pain behavioral analyses to help shed light on the complex molecular processes that underlie pain sensation.

    View details for DOI 10.1021/ja408300e

    View details for Web of Science ID 000328100000002

    View details for PubMedID 24261833

  • A (18)F-Labeled Saxitoxin Derivative for in Vivo PET-MR Imaging of Voltage-Gated Sodium Channel Expression Following Nerve Injury. Journal of the American Chemical Society Hoehne, A., Behera, D., Parsons, W. H., James, M. L., Shen, B., Borgohain, P., Bodapati, D., Prabhakar, A., Gambhir, S. S., Yeomans, D. C., Biswal, S., Chin, F. T., Bois, J. D. 2013; 135 (48): 18012-18015


    Both chronic and neuropathic pain conditions are associated with increased expression of certain voltage-gated sodium ion channel (NaV) isoforms in peripheral sensory neurons. A method for noninvasive imaging of these channels could represent a powerful tool for investigating aberrant expression of NaV and its role in pain pathogenesis. Herein, we describe the synthesis and evaluation of a positron emission tomography (PET) radiotracer targeting NaVs, the design of which is based on the potent, NaV-selective inhibitor saxitoxin. Both autoradiography analysis of sciatic nerves excised from injured rats as well as whole animal PET-MR imaging demonstrate that a systemically administered [(18)F]-labeled saxitoxin derivative concentrates at the site of nerve injury, consistent with upregulated sodium channel expression following axotomy. This type of PET agent has potential use for serial monitoring of channel expression levels at injured nerves throughout wound healing and/or following drug treatment. Such information may be correlated with pain behavioral analyses to help shed light on the complex molecular processes that underlie pain sensation.

    View details for DOI 10.1021/ja408300e

    View details for PubMedID 24261833

  • Colony-stimulating factor 1 receptor (CSF1R) signaling in injured neurons facilitates protection and survival JOURNAL OF EXPERIMENTAL MEDICINE Luo, J., Elwood, F., Britschgi, M., Villeda, S., Zhang, H., Ding, Z., Zhu, L., Alabsi, H., Getachew, R., Narasimhan, R., Wabl, R., Fainberg, N., James, M. L., Wong, G., Relton, J., Gambhir, S. S., Pollard, J. W., Wyss-Coray, T. 2013; 210 (1): 157-172


    Colony-stimulating factor 1 (CSF1) and interleukin-34 (IL-34) are functional ligands of the CSF1 receptor (CSF1R) and thus are key regulators of the monocyte/macrophage lineage. We discovered that systemic administration of human recombinant CSF1 ameliorates memory deficits in a transgenic mouse model of Alzheimer's disease. CSF1 and IL-34 strongly reduced excitotoxin-induced neuronal cell loss and gliosis in wild-type mice when administered systemically before or up to 6 h after injury. These effects were accompanied by maintenance of cAMP responsive element-binding protein (CREB) signaling in neurons rather than in microglia. Using lineage-tracing experiments, we discovered that a small number of neurons in the hippocampus and cortex express CSF1R under physiological conditions and that kainic acid-induced excitotoxic injury results in a profound increase in neuronal receptor expression. Selective deletion of CSF1R in forebrain neurons in mice exacerbated excitotoxin-induced death and neurodegeneration. We conclude that CSF1 and IL-34 provide powerful neuroprotective and survival signals in brain injury and neurodegeneration involving CSF1R expression on neurons.

    View details for DOI 10.1084/jem.20120412

    View details for Web of Science ID 000313560900014

    View details for PubMedID 23296467

    View details for PubMedCentralID PMC3549715

  • Integrin-Targeted Molecular Imaging of Experimental Abdominal Aortic Aneurysms by 18F-labeled Arg-Gly-Asp Positron-Emission Tomography CIRCULATION: CARDIOVASCULAR IMAGING Kitagawa, T., Kosuge, H., Chang, E., James, M. L., Yamamoto, T., Shen, B., Chin, F. T., Gambhir, S. S., Dalman, R. L., McConnell, M. V. 2013; 1 (6): 950-956
  • New Positron Emission Tomography (PET) Radioligand for Imaging sigma-1 Receptors in Living Subjects JOURNAL OF MEDICINAL CHEMISTRY James, M. L., Shen, B., Zavaleta, C. L., Nielsen, C. H., Mesangeau, C., Vuppala, P. K., Chan, C., Avery, B. A., Fishback, J. A., Matsumoto, R. R., Gambhir, S. S., McCurdy, C. R., Chin, F. T. 2012; 55 (19): 8272-8282


    σ-1 receptor (S1R) radioligands have the potential to detect and monitor various neurological diseases. Herein we report the synthesis, radiofluorination, and evaluation of a new S1R ligand 6-(3-fluoropropyl)-3-(2-(azepan-1-yl)ethyl)benzo[d]thiazol-2(3H)-one ([(18)F]FTC-146, [(18)F]13). [(18)F]13 was synthesized by nucleophilic fluorination, affording a product with >99% radiochemical purity (RCP) and specific activity (SA) of 2.6 ± 1.2 Ci/μmol (n = 13) at end of synthesis (EOS). Positron emission tomography (PET) and ex vivo autoradiography studies of [(18)F]13 in mice showed high uptake of the radioligand in S1R rich regions of the brain. Pretreatment with 1 mg/kg haloperidol (2), nonradioactive 13, or BD1047 (18) reduced the binding of [(18)F]13 in the brain at 60 min by 80%, 82%, and 81%, respectively, suggesting that [(18)F]13 accumulation in mouse brain represents specific binding to S1Rs. These results indicate that [(18)F]13 is a promising candidate radiotracer for further evaluation as a tool for studying S1Rs in living subjects.

    View details for DOI 10.1021/jm300371c

    View details for Web of Science ID 000309643500008

    View details for PubMedID 22853801



    Molecular imaging is revolutionizing the way we study the inner workings of the human body, diagnose diseases, approach drug design, and assess therapies. The field as a whole is making possible the visualization of complex biochemical processes involved in normal physiology and disease states, in real time, in living cells, tissues, and intact subjects. In this review, we focus specifically on molecular imaging of intact living subjects. We provide a basic primer for those who are new to molecular imaging, and a resource for those involved in the field. We begin by describing classical molecular imaging techniques together with their key strengths and limitations, after which we introduce some of the latest emerging imaging modalities. We provide an overview of the main classes of molecular imaging agents (i.e., small molecules, peptides, aptamers, engineered proteins, and nanoparticles) and cite examples of how molecular imaging is being applied in oncology, neuroscience, cardiology, gene therapy, cell tracking, and theranostics (therapy combined with diagnostics). A step-by-step guide to answering biological and/or clinical questions using the tools of molecular imaging is also provided. We conclude by discussing the grand challenges of the field, its future directions, and enormous potential for further impacting how we approach research and medicine.

    View details for DOI 10.1152/physrev.00049.2010

    View details for Web of Science ID 000306562500009

    View details for PubMedID 22535898

  • Preclinical Evaluation of Raman Nanoparticle Biodistribution for their Potential Use in Clinical Endoscopy Imaging SMALL Zavaleta, C. L., Hartman, K. B., Miao, Z., James, M. L., Kempen, P., Thakor, A. S., Nielsen, C. H., Sinclair, R., Cheng, Z., Gambhir, S. S. 2011; 7 (15): 2232-2240


    Raman imaging offers unsurpassed sensitivity and multiplexing capabilities. However, its limited depth of light penetration makes direct clinical translation challenging. Therefore, a more suitable way to harness its attributes in a clinical setting would be to couple Raman spectroscopy with endoscopy. The use of an accessory Raman endoscope in conjunction with topically administered tumor-targeting Raman nanoparticles during a routine colonoscopy could offer a new way to sensitively detect dysplastic lesions while circumventing Raman's limited depth of penetration and avoiding systemic toxicity. In this study, the natural biodistribution of gold surface-enhanced Raman scattering (SERS) nanoparticles is evaluated by radiolabeling them with (64) Cu and imaging their localization over time using micropositron emission tomography (PET). Mice are injected either intravenously (IV) or intrarectally (IR) with approximately 100 microcuries (μCi) (3.7 megabecquerel (MBq)) of (64) Cu-SERS nanoparticles and imaged with microPET at various time points post injection. Quantitative biodistribution data are obtained as % injected dose per gram (%ID g(-1)) from each organ, and the results correlate well with the corresponding microPET images, revealing that IV-injected mice have significantly higher uptake (p < 0.05) in the liver (5 h = 8.96% ID g(-1); 24 h = 8.27% ID g(-1)) than IR-injected mice (5 h = 0.09% ID g(-1); 24 h = 0.08% ID g(-1)). IR-injected mice show localized uptake in the large intestine (5 h = 10.37% ID g(-1); 24 h = 0.42% ID g(-1)) with minimal uptake in other organs. Raman imaging of excised tissues correlate well with biodistribution data. These results suggest that the topical application of SERS nanoparticles in the mouse colon appears to minimize their systemic distribution, thus avoiding potential toxicity and supporting the clinical translation of Raman spectroscopy as an endoscopic imaging tool.

    View details for DOI 10.1002/smll.201002317

    View details for Web of Science ID 000294361200015

    View details for PubMedID 21608124

  • [F-18]FTC-146: A novel and highly selective PET ligand for visualizing sigma-1 receptors in living subjects 8th International Symposium on Functional Neuroreceptor Mapping of the Living Brain James, M. L., Shen, B., Zavaleta, C., Berganos, R. A., Mesangeau, C., Shaikh, J., Gambhir, S. S., Matsumoto, R. R., McCurdy, C. R., Chin, F. T. ACADEMIC PRESS INC ELSEVIER SCIENCE. 2010: S123–S124
  • [C-11]-DPA-713 and [F-18]-DPA-714 as New PET Tracers for TSPO: A Comparison with [C-11]-(R)-PK11195 in a Rat Model of Herpes Encephalitis MOLECULAR IMAGING AND BIOLOGY Doorduin, J., Klein, H. C., Dierckx, R. A., James, M., Kassiou, M., De Vries, E. F. 2009; 11 (6): 386-398


    Activation of microglia cells plays an important role in neurological diseases. Positron emission tomography (PET) with [(11)C]-(R)-PK11195 has already been used to visualize activated microglia cells in neurological diseases. However, [(11)C]-(R)-PK11195 may not possess the required sensitivity to visualize mild neuroinflammation. In this study, we evaluated the PET tracers [(11)C]-DPA-713 and [(18)F]-DPA-714 as agents for imaging of activated microglia in a rat model of herpes encephalitis.Rats were intranasally inoculated with HSV-1. On day 6 or 7 after inoculation, small animal PET studies were performed to compare [(11)C]-(R)-PK11195, [(11)C]-DPA-713, and [(18)F]-DPA-714.Uptake of [(11)C]-DPA-713 in infected brain areas was comparable to that of [(11)C]-(R)-PK11195, but [(11)C]-DPA-713 showed lower non-specific binding. Non-specific uptake of [(18)F]-DPA-714 was lower than that of [(11)C]-(R)-PK11195. In the infected brain, total [(18)F]-DPA-714 uptake was lower than that of [(11)C]-(R)-PK11195, with comparable specific uptake.[(11)C]-DPA-713 may be more suitable for visualizing mild inflammation than [(11)C]-(R)-PK11195. In addition, the fact that [(18)F]-DPA-714 is an agonist PET tracer opens new possibilities to evaluate different aspects of neuroinflammation. Therefore, both tracers warrant further investigation in animal models and in a clinical setting.

    View details for DOI 10.1007/s11307-009-0211-6

    View details for Web of Science ID 000270882900002

    View details for PubMedID 19330384

  • Initial Evaluation of C-11-DPA-713, a Novel TSPO PET Ligand, in Humans JOURNAL OF NUCLEAR MEDICINE Endres, C. J., Pomper, M. G., James, M., Uzuner, O., Hammoud, D. A., Watkins, C. C., Reynolds, A., Hilton, J., Dannals, R. F., Kassiou, M. 2009; 50 (8): 1276-1282


    Translocator protein (TSPO) is upregulated in activated microglia and thus can serve as a marker of neuroinflammation. Recently, a novel radioligand, (11)C-N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide ((11)C-DPA-713), has been described that binds to TSPO with high affinity. Here, we report the first examination of (11)C-DPA-713 in human subjects using PET.Five healthy controls were studied with PET for 90 min after a bolus injection of high-specific-activity (11)C-DPA-713. For comparison, 2 additional healthy controls were studied with (11)C-R-PK11195. Arterial blood sampling and metabolite analysis were performed to allow the accurate quantification of tracer kinetics. Tracer uptake was evaluated for several brain regions. Tissue time-activity curves were fitted using 1- and 2-tissue-compartment models, with goodness-of-fit tests showing a preference for the 2-tissue model.In the healthy brain, the average plasma-to-tissue clearance and the total volume of distribution were an order of magnitude larger than measured for (11)C-R-PK11195. Accordingly, dose-normalized time-activity curves showed that (11)C-DPA-713 gives a larger brain signal.Studies in patient populations will help determine whether (11)C-DPA-713 provides better sensitivity for evaluating increased TSPO expression. This initial study in humans shows that (11)C-DPA-713 is a promising ligand for evaluating TSPO binding with PET.

    View details for DOI 10.2967/jnumed.109.062265

    View details for Web of Science ID 000272548100018

    View details for PubMedID 19617321

  • Comparative Evaluation of the Translocator Protein Radioligands C-11-DPA-713, F-18-DPA-714, and C-11-PK11195 in a Rat Model of Acute Neuroinflammation JOURNAL OF NUCLEAR MEDICINE Chauveau, F., Van Camp, N., Dolle, F., Kuhnast, B., Hinnen, F., Damont, A., Boutin, H., James, M., Kassiou, M., Tavitian, B. 2009; 50 (3): 468-476


    Overexpression of the translocator protein, TSPO (18 kDa), formerly known as the peripheral benzodiazepine receptor, is a hallmark of activation of cells of monocytic lineage (microglia and macrophages) during neuroinflammation. Radiolabeling of TSPO ligands enables the detection of neuroinflammatory lesions by PET. Two new radioligands, (11)C-labeled N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-alpha]pyrimidin-3-yl]acetamide (DPA-713) and (18)F-labeled N,N-diethyl-2-(2-(4-(2-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-alpha]pyrimidin-3-yl)acetamide (DPA-714), both belonging to the pyrazolopyrimidine class, were compared in vivo and in vitro using a rodent model of neuroinflammation.(11)C-DPA-713 and (18)F-DPA-714, as well as the classic radioligand (11)C-labeled (R)-N-methyl-N-(1-methylpropyl)-1-(2-chlorophenyl)isoquinoline-3-carboxamide (PK11195), were used in the same rat model, in which intrastriatal injection of (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolopropionique gave rise to a strong neuroinflammatory response. Comparative endpoints included in vitro autoradiography and in vivo imaging on a dedicated small-animal PET scanner under identical conditions.(11)C-DPA-713 and (18)F-DPA-714 could specifically localize the neuroinflammatory site with a similar signal-to-noise ratio in vitro. In vivo, (18)F-DPA-714 performed better than (11)C-DPA-713 and (11)C-PK11195, with the highest ratio of ipsilateral to contralateral uptake and the highest binding potential.(18)F-DPA-714 appears to be an attractive alternative to (11)C-PK11195 because of its increased bioavailability in brain tissue and its reduced nonspecific binding. Moreover, its labeling with (18)F, the preferred PET isotope for radiopharmaceutical chemistry, favors its dissemination and wide clinical use. (18)F-DPA-714 will be further evaluated in longitudinal studies of neuroinflammatory conditions such as are encountered in stroke or neurodegenerative diseases.

    View details for DOI 10.2967/jnumed.108.058669

    View details for Web of Science ID 000264084500027

    View details for PubMedID 19223401

  • Radiosynthesis of [F-18]DPA-714, a selective radioligand for imaging the translocator protein (18 kDa) with PET JOURNAL OF LABELLED COMPOUNDS & RADIOPHARMACEUTICALS Damont, A., Hinnen, F., Kuhnast, B., Schollhorn-Peyronneau, M., James, M., Luus, C., Tavitian, B., Kassiou, M., Dolle, F. 2008; 51 (7-8): 286-292

    View details for DOI 10.1002/jlcr.1523

    View details for Web of Science ID 000258903500002

  • DPA-714, a new translocator protein-specific ligand: Synthesis, radiofluorination, and pharmacologic characterization JOURNAL OF NUCLEAR MEDICINE James, M. L., Fulton, R. R., Vercoullie, J., Henderson, D. J., Garreau, L., Chalon, S., Dolle, F., Selleri, S., Guilloteau, D., Kassiou, M. 2008; 49 (5): 814-822


    The translocator protein (18 kDa) (TSPO), formerly known as the peripheral benzodiazepine receptor, is dramatically upregulated under pathologic conditions. Activated microglia are the main cell type expressing the TSPO at sites of central nervous system pathology. Radioligands for the TSPO can therefore measure active disease in the brain. This article details the synthesis, radiofluorination, and pharmacologic evaluation of a new TSPO-specific pyrazolopyrimidine, DPA-714.The affinity of DPA-714 for the TSPO was measured in rat kidney membranes with (3)H-PK11195. The in vitro functional activity of DPA-714 was measured in a steroidogenic assay in which the ability of DPA-714 to increase pregnenolone synthesis was measured with rat C6 glioma cells. The radiofluorination of DPA-714 was achieved by nucleophilic (18)F-fluoride displacement of the tosylate precursor. (18)F-DPA-714 was assessed in rats harboring unilateral quinolinic acid (QA) lesions. In addition, pretreatment experiments were performed with PK11195 (5 mg/kg), DPA-714 (1 mg/kg), and DPA-713 (1 mg/kg). The in vivo binding and biodistribution of (18)F-DPA-714 were determined in a baboon with PET. Experiments involving presaturation with PK11195 (1.5 mg/kg) and displacement with DPA-714 (1 mg/kg) were conducted to evaluate the specificity of radioligand binding.In vitro binding studies revealed that DPA-714 displayed a high affinity for the TSPO (dissociation constant, 7.0 nM). DPA-714 stimulated pregnenolone synthesis at levels 80% above the baseline. (18)F-DPA-714 was prepared at a 16% radiochemical yield and a specific activity of 270 GBq/mumol. In rats harboring unilateral QA lesions, an 8-fold-higher level of uptake of (18)F-DPA-714 was observed in the ipsilateral striatum than in the contralateral striatum. Uptake in the ipsilateral striatum was shown to be selective because it was inhibited to the level in the contralateral striatum in the presence of PK11195, nonlabeled DPA-714, or DPA-713. PET studies demonstrated rapid penetration and good retention of (18)F-DPA-714 in the baboon brain. Pretreatment with PK11195 effectively inhibited the uptake of (18)F-DPA-714 in the whole brain, indicating its selective binding to the TSPO. The injection of nonlabeled DPA-714 20 min after the injection of (18)F-DPA-714 resulted in radioligand washout, demonstrating the reversibility of (18)F-DPA-714 binding.(18)F-DPA-714 is a specific radioligand for the TSPO, displaying promising in vivo properties and thus warranting further investigation.

    View details for DOI 10.2967/jnumed.107.046151

    View details for Web of Science ID 000255809100033

    View details for PubMedID 18413395

  • C-11-DPA-713: A novel peripheral benzodiazepine receptor PET ligand for in vivo imaging of neuroinflammation JOURNAL OF NUCLEAR MEDICINE Boutin, H., Chauveau, F., Thominiaux, C., Gregoire, M., James, M. L., Trebossen, R., Hantraye, P., Dolle, F., Tavitian, B., Kassiou, M. 2007; 48 (4): 573-581


    The induction of neuroinflammatory processes, characterized by upregulation of the peripheral benzodiazepine receptor (PBR) expressed by microglial cells, is well correlated with neurodegenerative diseases and with acute neuronal loss. The continually increasing incidence of neurodegenerative diseases in developed countries has become a major health problem, for which the development of diagnostic and follow-up tools is required. Here we investigated a new PBR ligand suitable for PET to monitor neuroinflammatory processes as an indirect hallmark of neurodegeneration.We compared PK11195, the reference compound for PBR binding sites, with the new ligand DPA-713 (N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl]acetamide), using a small-animal dedicated PET camera in a model of neuroinflammation in rats. Seven days after intrastriatal injection of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), a PET scan was performed using (11)C-PK11195 or (11)C-DPA-713. Immunohistochemistry for neuronal (NeuN), astrocyte (glial fibrillary acidic protein), and microglial (CD11) specific markers as well as (3)H-PK11195 autoradiographic studies were then correlated with the imaging data.Seven days after a unilateral injection of AMPA in the striatum, (11)C-DPA-713 exhibits a better contrast between healthy and damaged brain parenchyma than (11)C-PK11195 (2.5-fold +/- 0.14 increase vs. 1.6-fold +/- 0.05 increase, respectively). (11)C-DPA-713 and (11)C-PK11195 exhibit similar brain uptake in the ipsilateral side, whereas, in the contralateral side, (11)C-DPA-713 uptake was significantly lower than (11)C-PK11195. Modeling of the data using the simplified reference tissue model shows that the binding potential was significantly higher for (11)C-DPA-713 than for (11)C-PK11195.(11)C-DPA-713 displays a higher signal-to-noise ratio than (11)C-PK11195 because of a lower level of unspecific binding that is likely related to the lower lipophilicity of (11)C-DPA-713. Although further studies in humans are required, (11)C-DPA-713 represents a suitable alternative to (11)C-PK11195 for PET of PBR as a tracer of neuroinflammatory processes induced by neuronal stress.

    View details for DOI 10.2967/jnumed.106.036764

    View details for Web of Science ID 000245647000020

    View details for PubMedID 17401094

  • Development of Ligands for the Peripheral Benzodiazepine Receptor CURRENT MEDICINAL CHEMISTRY James, M. L., Selleri, S., Kassiou, M. 2006; 13 (17): 1991-2001


    The peripheral benzodiazepine receptor (PBR) initially characterised as a high affinity binding site for diazepam, is densely distributed in most peripheral organs whilst only moderately expressed in the healthy brain. The predominant cell type expressing the PBR at regions of central nervous system (CNS) pathology are activated microglial cells. Under neuroinflammatory conditions there is an over-expression of PBR binding sites indicating that measurements of PBR density can act as a useful index of brain disease activity. The PBR is now considered a significant therapeutic and diagnostic target which has provided the impetus for PBR ligand development. There are several classes of PBR ligands available including benzodiazepines (Ro5-4864), isoquinoline carboxamides (PK 11195), indoleacetamides (FGIN-1-27), phenoxyphenyl-acetamides (DAA1106) and pyrazolopyrimidines (DPA-713). Subsequent conformationally restrained isoquinoline and indoleacetamide analogues have been synthesised in an attempt to yield PBR ligands with superior affinity and brain kinetics. Even though the PBR has been linked to a number of biochemical processes, including cell proliferation, apoptosis, steroidogenesis, porphyrin transport and immunomodulation, its exact physiological role is yet to be deciphered. Selective PBR ligands with favourable in vivo binding properties and kinetics is required to gain a more complete understanding on the normal functioning of the PBR and the chemical pathways underlying several pathological conditions. Novel PBR ligands with unique binding properties and functional activity may also generate information on the localisation of the PBR and the possibility of PBR subtypes. This review highlights the main classes of PBR ligands to date. In addition the biological activity and therapeutic potential of certain PBR ligands is discussed.

    View details for Web of Science ID 000207523900003

    View details for PubMedID 16842193

  • Improved synthesis of the peripheral benzodiazepine receptor ligand [C-11]DPA-713 using [C-11]methyl triflate APPLIED RADIATION AND ISOTOPES Thominiaux, C., Dolle, F., James, M. L., Bramoulle, Y., Boutin, H., Besret, L., Gregoire, M. C., Valette, H., Bottlaender, M., Tavitian, B., Hantraye, P., Selleri, S., Kassiou, M. 2006; 64 (5): 570-573


    Recently, the pyrazolopyrimidine, [11C] N,N-Diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl]acetamide (DPA-713) has been reported as a new promising marker for the study of peripheral benzodiazepine receptors with positron emission tomography. In the present study, DPA-713 has been labelled from the corresponding nor-analogue using [11C]methyl triflate (CH3OTf). Conditions for HPLC were also modified to include physiological saline (aq. 0.9% NaCl)/ethanol:60/40 as mobile phase making it suitable for injection. The total time of radiosynthesis, including HPLC purification, was 18-20 min. This reported synthesis of [11C]DPA-713, using [11C]CH3OTf, resulted in an improved radiochemical yield (30-38%) compared to [11C]methyl iodide (CH3I) (9) with a simpler purification method. This ultimately enhances the potential of [11C]DPA-713 for further pharmacological and clinical evaluation. These improvements make this radioligand more suitable for automated synthesis which is of benefit where multi-dose preparations and repeated syntheses of radioligand are required.

    View details for DOI 10.1016/j.apradiso.2005.12.003

    View details for Web of Science ID 000237041800009

    View details for PubMedID 16427784

  • Synthesis and in vivo evaluation of a novel peripheral benzodiazepine receptor PET radioligand BIOORGANIC & MEDICINAL CHEMISTRY James, M. L., Fulton, R. R., Henderson, D. J., Eberl, S., Melkle, S. R., Thomson, S., Allan, R. D., Dolle, F., Fulham, M. J., Kassiou, M. 2005; 13 (22): 6188-6194


    The novel pyrazolopyrimidine ligand, N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide 1 (DPA-713), has been reported as a potent ligand for the peripheral benzodiazepine receptor (PBR) displaying an affinity of K(i)=4.7 nM. In this study, 1 was successfully synthesised and demethylated to form the phenolic derivative 6 as precursor for labelling with carbon-11 (t(1/2) = 20.4 min). [11C]1 was prepared by O-alkylation of 6 with [11C]methyl iodide. The radiochemical yield of [(11)C]1 was 9% (non-decay corrected) with a specific activity of 36 GBq/micromol at the end of synthesis. The average time of synthesis including formulation was 13.2 min with a radiochemical purity >98%. In vivo assessment of [11C]1 was performed in a healthy Papio hamadryas baboon using positron emission tomography (PET). Following iv administration of [11C]1, significant accumulation was observed in the baboon brain and peripheral organs. In the brain, the radioactivity peaked at 20 min and remained constant for the duration of the imaging experiment. Pre-treatment with the PBR-specific ligand, PK 11195 (5 mg/kg), effectively reduced the binding of [11C]1 at 60 min by 70% in the whole brain, whereas pre-treatment with the central benzodiazepine receptor ligand, flumazenil (1mg/kg), had no inhibitory effect on [11C]1 uptake. These results indicate that accumulation of [11C]1 in the baboon represents selective binding to the PBR. These exceptional in vivo binding properties suggest that [11C]1 may be useful for imaging the PBR in disease states. Furthermore, [11C]1 represents the first ligand of its pharmacological class to be labelled for PET studies and therefore has the potential to generate new information on the pathological role of the PBR in vivo.

    View details for DOI 10.1016/j.bmc.2005.06.030

    View details for Web of Science ID 000232733000012

    View details for PubMedID 16039131