Bio

Honors & Awards


  • Place Brain Imaging Council, Young Investigators Award, SNMMI (2018)
  • ISRS Travel Award, ISRS (2015)
  • IC Trust Travel Grant, Imperial College (2015)
  • Radiochemistry Group Young Researcher's Fund, Royal Society of Chemistry (2015)

Professional Education


  • Doctor of Philosophy, Imperial College of Science, Technology & Medicine (2016)
  • Master of Science, Imperial College of Science, Technology & Medicine (2011)

Stanford Advisors


Publications

All Publications


  • Synthesis and Characterization of 9-(4-[18F]Fluoro-3-(hydroxymethyl)butyl)-2-(phenylthio)-6-oxopurine as a Novel PET Agent for Mutant Herpes Simplex Virus Type 1 Thymidine Kinase Reporter Gene Imaging. Molecular imaging and biology Fuchigami, T., Haywood, T., Gowrishankar, G., Anders, D., Namavari, M., Wardak, M., Gambhir, S. S. 2020

    Abstract

    PURPOSE: [18F]FHBG has been used as a positron emission tomography (PET) imaging tracer for the monitoring of herpes simplex virus type 1 thymidine kinase (HSV1-tk), a reporter gene for cell and gene therapy in humans. However, this tracer shows inadequate blood-brain barrier (BBB) penetration and, therefore, would be limited for accurate quantification of reporter gene expression in the brain. Here, we report the synthesis and evaluation of 9-(4-[18F]fluoro-3-(hydroxymethyl)butyl)-2(phenylthio)-6-oxopurine ([18F]FHBT) as a new PET tracer for imaging reporter gene expression of HSV1-tk and its mutant HSV1-sr39tk, with the aim of improved BBB penetration.PROCEDURES: [18F]FHBT was prepared by using a tosylate precursor and [18F]KF. The cellular uptake of [18F]FHBT was performed in HSV1-sr39tk-positive (+) or HSV1-sr39tk-negative (-) MDA-MB-231 breast cancer cells. The specificity of [18F]FHBT to assess HSV1-sr39tk expression was evaluated by in vitro blocking studies using 1mM of ganciclovir (GCV). Penetration of [18F]FHBT and [18F]FHBG across the BBB was assessed by dynamic PET imaging studies in normal mice.RESULTS: The tosylate precursor reacted with [18F]KF using Kryptofix2.2.2 followed by deprotection to give [18F]FHBT in 10% radiochemical yield (decay-corrected). The uptake of [18F]FHBT in HSV1-sr39tk (+) cells was significantly higher than that of HSV1-sr39tk (-) cells. In the presence of GCV (1mM), the uptake of [18F]FHBT was significantly decreased, indicating that [18F]FHBT serves as a selective substrate of HSV1-sr39TK. PET images and time-activity curves of [18F]FHBT in the brain regions showed similar initial brain uptakes (~12.75min) as [18F]FHBG (P>0.855). Slower washout of [18F]FHBT was observed at the later time points (17.75 - 57.75 min, P >0.207).CONCLUSIONS: Although [18F]FHBT showed no statistically significant improvement of BBB permeability compared with [18F]FHBG, we have demonstrated that the 2-(phenylthio)-6-oxopurine backbone can serve as a novel scaffold for developing HSV1-tk/HSV1-sr39tk reporter gene imaging agents for additional research in the future.

    View details for DOI 10.1007/s11307-020-01517-5

    View details for PubMedID 32691392

  • Molecular Imaging of Infective Endocarditis With 6''-[18F]Fluoromaltotriose Positron Emission Tomography-Computed Tomography. Circulation Wardak, M., Gowrishankar, G., Zhao, X., Liu, Y., Chang, E., Namavari, M., Haywood, T., Gabr, M. T., Neofytou, E., Chour, T., Qin, X., Vilches-Moure, J. G., Hardy, J., Contag, C. H., McConnell, M. V., Wu, J. C., Gambhir, S. S. 2020; 141 (21): 1729?31

    View details for DOI 10.1161/CIRCULATIONAHA.119.043924

    View details for PubMedID 32453662

  • Human biodistribution and radiation dosimetry of [18F]DASA-23, a PET probe targeting pyruvate kinase M2. European journal of nuclear medicine and molecular imaging Beinat, C., Patel, C. B., Haywood, T., Shen, B., Naya, L., Gandhi, H., Holley, D., Khalighi, M., Iagaru, A., Davidzon, G., Gambhir, S. S. 2020

    Abstract

    To assess the safety, biodistribution, and radiation dosimetry of the novel positron emission tomography (PET) radiopharmaceutical 1-((2-fluoro-6-[[18F]]fluorophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine ([18F]DASA-23) in healthy volunteers.We recruited 5 healthy volunteers who provided a written informed consent. Volunteers were injected with 295.0??8.2MBq of [18F]DASA-23 intravenously. Immediately following injection, a dynamic scan of the brain was acquired for 15min. This was followed by serial whole-body PET/MRI scans acquired up to 3h post-injection. Blood samples were collected at regular intervals, and vital signs monitored pre- and post-radiotracer administration. Regions of interest were drawn around multiple organs, time-activity curves were calculated, and organ uptake and dosimetry were estimated with OLINDA/EXM (version 1.1) software.All subjects tolerated the PET/MRI examination, without adverse reactions to [18F]DASA-23. [18F]DASA-23 passively crossed the blood-brain barrier, followed by rapid clearance from the brain. High accumulation of [18F]DASA-23 was noted in organs such as the gallbladder, liver, small intestine, and urinary bladder, suggesting hepatobiliary and urinary clearance. The effective dose of [18F]DASA-23 was 23.5??5.8?Sv/MBq.We successfully completed a pilot first-in-human study of [18F]DASA-23. Our results indicate that [18F]DASA-23 can be used safely in humans to evaluate pyruvate kinase M2 levels. Ongoing studies are evaluating the ability of [18F]DASA-23 to visualize intracranial malignancies, NCT03539731.ClinicalTrials.gov, NCT03539731 (registered 28 May 2018).

    View details for DOI 10.1007/s00259-020-04687-0

    View details for PubMedID 31938892

  • Maltotriose-based probes for fluorescence and photoacoustic imaging of bacterial infections. Nature communications Zlitni, A., Gowrishankar, G., Steinberg, I., Haywood, T., Sam Gambhir, S. 2020; 11 (1): 1250

    Abstract

    Currently, there are no non-invasive tools to accurately diagnose wound and surgical site infections before they become systemic or cause significant anatomical damage. Fluorescence and photoacoustic imaging are cost-effective imaging modalities that can be used to noninvasively diagnose bacterial infections when paired with a molecularly targeted infection imaging agent. Here, we develop a fluorescent derivative of maltotriose (Cy7-1-maltotriose), which is shown to be taken up in a variety of gram-positive and gram-negative bacterial strains in vitro. In vivo fluorescence and photoacoustic imaging studies highlight the ability of this probe to detect infection, assess infection burden, and visualize the effectiveness of antibiotic treatment in E. coli-induced myositis and a clinically relevant S. aureus wound infection murine model. In addition, we show that maltotriose is an ideal scaffold for infection imaging agents encompassing better pharmacokinetic properties and in vivo stability than other maltodextrins (e.g. maltohexose).

    View details for DOI 10.1038/s41467-020-14985-8

    View details for PubMedID 32144257

  • New synthesis of 6''-[18 F]fluoromaltotriose for positron emission tomography (PET) imaging of bacterial infection. Journal of labelled compounds & radiopharmaceuticals Gabr, M. T., Haywood, T., Gowrishankar, G., Srinivasan, A., Gambhir, S. S. 2020

    Abstract

    6''-[18 F]fluoromaltotriose is a positron emission tomography (PET) tracer that can differentiate between bacterial infection and inflammation in vivo. Bacteria-specific uptake of 6''-[18 F]fluoromaltotriose is attributed to the targeting of maltodextrin transporter in bacteria that is absent in mammalian cells. Herein, we report a new synthesis of 6''-[18 F]fluoromaltotriose as a key step for its clinical translation. In comparison to the previously reported synthesis, the new synthesis features unambiguous assignment of the fluorine-18 position on the maltotriose unit. The new method utilizes direct fluorination of 2'',3'',4''-tri-O-acetyl-6''-O-trifyl-?-D-glucopyranosyl-(1-4)-O-2',3',6'-tri-O-acetyl-?-D-glucopyranosyl-(1-4)-1,2,3,6-tetra-O-acetyl-D-glucopyranose followed by basic hydrolysis. Radiolabeling of the new maltotriose triflate precursor proceeds using a single HPLC purification step, which results in shorter reaction time in comparison to the previously reported synthesis. Successful synthesis of 6''-[18 F]fluoromaltotriose has been achieved in 3.5 0.3% radiochemical yield (decay corrected, n=7) and radiochemical purity above 95%. The efficient radiosynthesis of 6''-[18 F]fluoromaltotriose would be critical in advancing this PET tracer into clinical trials for imaging bacterial infections.

    View details for DOI 10.1002/jlcr.3868

    View details for PubMedID 32602175

  • Evaluation of integrin alphavbeta6 cystine knot PET tracers to detect cancer and idiopathic pulmonary fibrosis. Nature communications Kimura, R. H., Wang, L., Shen, B., Huo, L., Tummers, W., Filipp, F. V., Guo, H. H., Haywood, T., Abou-Elkacem, L., Baratto, L., Habte, F., Devulapally, R., Witney, T. H., Cheng, Y., Tikole, S., Chakraborti, S., Nix, J., Bonagura, C. A., Hatami, N., Mooney, J. J., Desai, T., Turner, S., Gaster, R. S., Otte, A., Visser, B. C., Poultsides, G. A., Norton, J., Park, W., Stolowitz, M., Lau, K., Yang, E., Natarajan, A., Ilovich, O., Srinivas, S., Srinivasan, A., Paulmurugan, R., Willmann, J., Chin, F. T., Cheng, Z., Iagaru, A., Li, F., Gambhir, S. S. 2019; 10 (1): 4673

    Abstract

    Advances in precision molecular imaging promise to transform our ability to detect, diagnose and treat disease. Here, we describe the engineering and validation of a new cystine knot peptide (knottin) that selectively recognizes human integrin alphavbeta6 with single-digit nanomolar affinity. We solve its 3D structure by NMR and x-ray crystallography and validate leads with 3 different radiolabels in pre-clinical models of cancer. We evaluate the lead tracer's safety, biodistribution and pharmacokinetics in healthy human volunteers, and show its ability to detect multiple cancers (pancreatic, cervical and lung) in patients at two study locations. Additionally, we demonstrate that the knottin PET tracers can also detect fibrotic lung disease in idiopathic pulmonary fibrosis patients. Our results indicate that these cystine knot PET tracers may have potential utility in multiple disease states that are associated with upregulation of integrin alphavbeta6.

    View details for DOI 10.1038/s41467-019-11863-w

    View details for PubMedID 31611594

  • Identifying Hypoperfusion in Moyamoya Disease With Arterial Spin Labeling and an [O-15]-Water Positron Emission Tomography/Magnetic Resonance Imaging Normative Database STROKE Fan, A. P., Khalighi, M. M., Guo, J., Ishii, Y., Rosenberg, J., Wardak, M., Park, J., Shen, B., Holley, D., Gandhi, H., Haywood, T., Singh, P., Steinberg, G. K., Chin, F. T., Zaharchuk, G. 2019; 50 (2): 373?80
  • Positron emission tomography reporter gene strategy for use in the central nervous system PNAS Haywood, T., Beinat, C., Gowrishankar, G., Patel, C. B., Alam, I. S., Murty, S., Gambhir, S. S. 2019

    View details for DOI 10.1073/pnas.1901645116

  • The characterization of 18F-hGTS13 for molecular imaging of xC- transporter activity with positron emission tomography. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Beinat, C., Gowrishankar, G., Shen, B., Alam, I. S., Robinson, E., Haywood, T., Patel, C. B., Azevedo, E. C., Castillo, J., Ilovich, O., Koglin, N., Schmitt-Willich, H., Berndt, M., Mueller, A., Zerna, M., Srinivasan, A., Gambhir, S. S. 2019

    Abstract

    Purpose: The aim of this study was development of an improved positron emission tomography (PET) radiotracer for measuring xC- activity with increased tumor uptake and reduced uptake in inflammatory cells compared to (S)-4-(3-18F-Fluoropropyl)-L-glutamic acid (18F-FSPG). Experimental design: A racemic glutamate derivative, 18F-hGTS13 was evaluated in cell culture and animal tumor models. 18F-hGTS13 was separated into C5-epimers and the corresponding 18F-hGTS13-isomer1 and 18F-hGTS13-isomer2 evaluated in H460 tumor bearing rats. Preliminary studies investigate the cellular uptake of 18F-hGTS13-isomer2 in multiple immune cell populations and states. Results:18F-hGTS13 demonstrated excellent H460 tumor visualization with high tumor-to-background ratios, confirmed by ex vivo biodistribution studies. Tumor associated radioactivity of 18F-hGTS13 (7.50.9%ID/g, n = 3) was significantly higher than with 18F-FSPG (4.60.7%ID/g, n = 3, P = 0.01). 18F-hGTS13-isomer2 exhibited excellent H460 tumor visualization (6.31.1%ID/g, n-3), and significantly reduced uptake in multiple immune cell populations relative to 18F-FSPG. 18F-hGTS13-isomer2 exhibited increased liver uptake relative to 18F-FSPG (4.60.8%ID/g vs. 0.70.01%ID/g) limiting its application in hepatocellular carcinoma. Conclusion:18F-hGTS13-isomer2 is a new PET radiotracer for molecular imaging of xC- activity which may provide information regarding tumor oxidation states. 18F-hGTS13-isomer2 has potential for clinical translation for imaging cancers of the thorax due to the low background signal in healthy tissue.

    View details for DOI 10.2967/jnumed.119.225870

    View details for PubMedID 31171595

  • Ammonium [C-11]thiocyanate: revised preparation and reactivity studies of a versatile nucleophile for carbon-11 radiolabelling MEDCHEMCOMM Haywood, T., Cesarec, S., Kealey, S., Plisson, C., Miller, P. W. 2018; 9 (8): 1311?14

    Abstract

    Herein we report the preparation of ammonium [11C]thiocyanate via the reaction of [11C]CS2 with ammonia. The [11C]SCN- ion is demonstrated as a potent nucleophile that can be used to readily generate a range of 11C-labelled thiocyanate molecules in high conversions. Furthermore, novel 11C-labelled thiazolone molecules can be easily prepared from the intermediate ?-thiocyanatophenones via an acid mediated cyclisation reaction.

    View details for DOI 10.1039/c7md00425g

    View details for Web of Science ID 000442751800007

    View details for PubMedID 30151085

    View details for PubMedCentralID PMC6096773

  • A novel synthesis of 6''-[18 F]-fluoromaltotriose as a PET tracer for imaging bacterial infection. Journal of labelled compounds & radiopharmaceuticals Namavari, M., Gowrishankar, G., Srinivasan, A., Gambhir, S. S. 2018

    Abstract

    The aim of this study was to develop a positron emission tomography (PET) tracer to visualize and monitor therapeutic response to bacterial infections. In our continued efforts to find maltose based PET tracers that can image bacterial infections, we have designed and prepared 6''-[18 F]fluoromaltotriose as a second generation PET imaging tracer targeting the maltodextrin transporter of bacteria. We have developed methods to synthesize 6''-deoxy-6''-[18 F]fluoro-?-D-glucopyranosyl-(1-4)-O-?-D-glucopyranosyl-(1-4)-O-D-glucopyranose (6''-[18 F]-fluoromaltotriose) as a bacterial infection PET imaging agent. 6''-[18 F]fluoromaltotriose was prepared from precursor, 2'',3'',4''-tri-O-acetyl-6''-O-nosyl-?-D-glucopyranosyl-(1-4)-O-2',3',6'-tri-O-acetyl-?-D-glucopyranosyl-(1-4)-1,2,3,6-tetra-O-acetyl-D-glucopyranose (per-O-acetyl-6''-O-nosyl-maltotriose 4). This method utilizes the reaction between precursor 4 and anhydrous [18 F]KF/Kryptofix 2.2.2 in Dimethylformamide (DMF) at 85o C for 10 minutes to yield per-O-acetyl-6''-deoxy-6-'' [18 F]-fluoromaltotriose (7). Successive acidic and basic hydrolysis of the acetyl protecting groups in 7 produced 6''-[18 F]fluoromaltotriose (8). Also, cold 6''- [19 F]fluoromaltotriose was prepared from per-O-acetyl-6''-hydroxymaltotriose via a DAST reaction followed by a basic hydrolysis. A successful synthesis of 6''-[18 F]-fluoromaltotriose has been accomplished in 81.2 % radiochemical yield (decay corrected). Total synthesis time was 120 min. Serum stability of 6''-[18 F]fluoromaltotriose at 37o C indicated that 6''-[18 F]-fluoromaltotriose remained intact up to 2 h. In conclusion, we have successfully synthesized 6''-[18 F]-fluoromaltotriose via direct fluorination of an appropriate precursor of a protected maltotriose.

    View details for PubMedID 29314161

  • The Utility of [18F]DASA-23 for Molecular Imaging of Prostate Cancer with Positron Emission Tomography. Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging Beinat, C., Haywood, T., Chen, Y. S., Patel, C. B., Alam, I. S., Murty, S., Gambhir, S. S. 2018

    Abstract

    There is a strong, unmet need for superior positron emission tomography (PET) imaging agents that are able to measure biochemical processes specific to prostate cancer. Pyruvate kinase M2 (PKM2) catalyzes the concluding step in glycolysis and is a key regulator of tumor growth and metabolism. Elevation of PKM2 expression was detected in Gleason 8-10 tumors compared to Gleason 6-7 carcinomas, indicating that PKM2 may potentially be a marker of aggressive prostate cancer. We have recently reported the development of a PKM2-specific radiopharmaceutical [18F]DASA-23 and herein describe its evaluation in cell culture and preclinical models of prostate cancer.The cellular uptake of [18F]DASA-23 was evaluated in a panel of prostate cancer cell lines and compared to that of [18F]FDG. The specificity of [18F]DASA-23 to measure PKM2 levels in cell culture was additionally confirmed through the use of PKM2-specific siRNA. PET imaging studies were then completed utilizing subcutaneous prostate cancer xenografts using either PC3 or DU145 cells in mice.[18F]DASA-23 uptake values over 60-min incubation period in PC3, LnCAP, and DU145 respectively were 23.4??4.5, 18.0??2.1, and 53.1??4.6% tracer/mg protein. Transient reduction in PKM2 protein expression with siRNA resulted in a 50.1% reduction in radiotracer uptake in DU145 cells. Small animal PET imaging revealed 0.86??0.13 and 1.6??0.2%ID/g at 30min post injection of radioactivity in DU145 and PC3 subcutaneous tumor bearing mice respectively.Herein, we evaluated a F-18-labeled PKM2-specific radiotracer, [18F]DASA-23, for the molecular imaging of prostate cancer with PET. [18F]DASA-23 revealed rapid and extensive uptake levels in cellular uptake studies of prostate cancer cells; however, there was only modest tumor uptake when evaluated in mouse subcutaneous tumor models.

    View details for PubMedID 29736561

  • Long-Delay Arterial Spin Labeling Provides More Accurate Cerebral Blood Flow Measurements in Moyamoya Patients: A Simultaneous Positron Emission Tomography/MRI Study. Stroke Fan, A. P., Guo, J., Khalighi, M. M., Gulaka, P. K., Shen, B., Park, J. H., Gandhi, H., Holley, D., Rutledge, O., Singh, P., Haywood, T., Steinberg, G. K., Chin, F. T., Zaharchuk, G. 2017; 48 (9): 2441?49

    Abstract

    Arterial spin labeling (ASL) MRI is a promising, noninvasive technique to image cerebral blood flow (CBF) but is difficult to use in cerebrovascular patients with abnormal, long arterial transit times through collateral pathways. To be clinically adopted, ASL must first be optimized and validated against a reference standard in these challenging patient cases.We compared standard-delay ASL (post-label delay=2.025 seconds), multidelay ASL (post-label delay=0.7-3.0 seconds), and long-label long-delay ASL acquisitions (post-label delay=4.0 seconds) against simultaneous [15O]-positron emission tomography (PET) CBF maps in 15 Moyamoya patients on a hybrid PET/MRI scanner. Dynamic susceptibility contrast was performed in each patient to identify areas of mild, moderate, and severe time-to-maximum (Tmax) delays. Relative CBF measurements by each ASL scan in 20 cortical regions were compared with the PET reference standard, and correlations were calculated for areas with moderate and severe Tmax delays.Standard-delay ASL underestimated relative CBF by 20% in areas of severe Tmax delays, particularly in anterior and middle territories commonly affected by Moyamoya disease (P<0.001). Arterial transit times correction by multidelay acquisitions led to improved consistency with PET, but still underestimated CBF in the presence of long transit delays (P=0.02). Long-label long-delay ASL scans showed the strongest correlation relative to PET, and there was no difference in mean relative CBF between the modalities, even in areas of severe delays.Post-label delay times of ?4 seconds are needed and may be combined with multidelay strategies for robust ASL assessment of CBF in Moyamoya disease.

    View details for PubMedID 28765286

  • Carbon-11 Radiolabelling of Organosulfur Compounds: C-11 Synthesis of the Progesterone Receptor Agonist Tanaproget CHEMISTRY-A EUROPEAN JOURNAL Haywood, T., Kealey, S., Sanchez-Cabezas, S., Hall, J. J., Allott, L., Smith, G., Plisson, C., Miller, P. W. 2015; 21 (25): 9034-9038
  • Microfluidic Hydrogenation Reactions by using a Channel-Supported Rhodium Catalyst CHEMCATCHEM Haywood, T., Miller, P. W. 2014; 6 (5): 1199-1203

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