Timothy Degrado

• PhD, Medical Physics
• Managing Director at University of Colorado

Glycogen synthase kinase‐3 α/β is involved in dysregulation of neuronal tau protein in Alzheimer's disease (AD). There is an unmet clinical need for a blood‐brain barrier (BBB) permeable positron emission tomography (PET) probe for imaging of GSK‐3α/β in the brain to understand the pathogenesis of AD. Herein, we synthesized two PET probes, [¹⁸F]F‐C...

Aberrant insulin signaling has been considered one of the risk factors for the development of Alzheimer's disease (AD) and has drawn considerable attention from the research community to further study its role in AD pathophysiology. Herein, we describe the development of an insulin-based novel positron emission tomography (PET) probe, [68Ga]Ga-NOTA...

Due to the advent of various biologics like antibodies, proteins, cells, viruses, and extracellular vesicles as biomarkers for disease diagnosis, progression, and as therapeutics, there exists a need to have a simple and ready to use radiolabeling synthon to enable noninvasive imaging trafficking studies. Previously, we reported [89Zr]zirconium-p-i...

[This corrects the article DOI: 10.3389/fnmol.2021.665686.].

Although chimeric antigen receptor T (CART)-cell therapy has been successful in treating certain hematological malignancies, wider adoption of CART-cell therapy is limited due to minimal activity in solid tumors and development of life-threatening toxicities, including cytokine release syndrome (CRS). There is a lack of a robust, clinically relevan...

Introduction Immunotherapy targeting PD-1/PD-L1 immune checkpoint inhibition (ICI) is efficacious in various solid and hematologic malignancies. However, the response rate to PD-1/PD-L1 therapy is only 15–35%. To obtain optimal clinical response to ICI therapies, a reliable assessment of tumor PD-L1 expression is needed to select appropriate patien...

Metal ion dyshomeostasis and disparate levels of biometals like zinc (Zn), copper (Cu), and selenium (Se) have been implicated as a potential causative factor for Autism Spectrum Disorder (ASD). In this study, we have enrolled 129 children (aged 2–4 years) in North America, of which 64 children had a diagnosis of ASD and 65 were controls. Hair, nai...

Introduction Radiolabeling of stem cells with a positron emitting radioisotope represents a major advancement in regenerative biotherapy enabling non-invasive imaging. To assess the value of such an approach in a clinically relevant scenario, the tolerability and therapeutic aptitude of [89Zr]zirconium-p-isothiocyanatobenzyl-desferrioxamine ([89Zr...

Four tris-bidentate catecholamide (CAM) ligands were synthesized, characterized, and evaluated as ligands for radiolabeling of gallium-68 for positron emission tomography (PET). Three of those ligands, 2,2-Glu-CAM, 3,3-Glu-CAM, and TREN-bisGlyGlu-CAM, incorporate ligand caps that contain a pendant carboxylic group for further conjugation to targeti...

Present review describes the methodological aspects and prospects of production of Positron Emission Tomography (PET) radiometals in a liquid target using low-medium energy medical cyclotrons. The main objective of this review is to delineate and discuss the critical factors involved in the liquid target production of radiometals including type of...

The effectiveness of cell-based therapies to treat liver failure is often limited by the diseased liver environment. Here we provide preclinical proof-of-concept for hepatocyte transplantation into lymph nodes as a cure for liver failure in a large-animal model with hereditary tyrosinemia type 1 (HT1), a metabolic liver disease caused by deficiency...

Background & Aims Endoplasmic reticulum to nucleus signaling 1 (ERN1, also called IRE1A) is a sensor of the unfolded protein response that is activated in livers of patients with nonalcoholic steatohepatitis (NASH). Hepatocytes release ceramide-enriched inflammatory extracellular vesicles (EVs) following activation of IRE1A. We studied the effects...

Noninvasive bioluminescence imaging (BLI) of luciferase-expressing tumor cells has advanced pre-clinical evaluation of cancer therapies. Yet despite its successes, BLI is limited by poor spatial resolution and signal penetration, making it unusable for deep tissue or large animal imaging and preventing precise anatomical localization or signal quan...

Objective: The objectives of the present work were to optimize and validate the synthesis and stability of 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid ([18F]FTHA) and 16-[18F]fluoro-4-thia-palmitic acid ([18F]FTP) under cGMP conditions for clinical applications. Methods: Benzyl-14-(R,S)-tosyloxy-6-thiaheptadecanoate and methyl 16-bromo-4-thia-...

Noninvasive dual-imaging methods that provide an early readout on tumor permissiveness to virus infection and tumor cell death could be valuable in optimizing development of oncolytic virotherapies. Here, we have used the sodium iodide symporter (NIS) and 125I radiotracer to detect infection and replicative spread of an oncolytic vesicular stomatit...

The effectiveness of cell-based therapies to treat liver failure is limited by the diseased liver environment. Herein we provide preclinical proof-of-concept for the treatment of liver failure through hepatocyte transplantation into lymph nodes in a large-animal model of hereditary tyrosinemia type 1 (HT1), a metabolic liver disease caused by defic...

Objectives: To optimize 68Ga production using a liquid cyclotron target, investigations were performed to compare production yields using different concentrations of [68Zn]Zn(NO3)2, nitric acid, and irradiation parameters. Methods: Different concentrations of [68Zn]Zn(NO3)2 (0.6 M, 1.2 M and 1.42 M) in varying normality of nitric acid (0.8-1.5 N...

Cyclotron Production of Gallium 68 for medical application: Technical guidelines

Zinc (Zn2+) is the second most abundant trace element, but is considered a micronutrient, as it is a cofactor for many enzymes and transcription factors. Whereas Zn2+ deficiency can cause cognitive immune or metabolic dysfunction and infertility, excess Zn2+ is nephrotoxic. As for other ions and solutes, Zn2+ is moved into and out of cells by speci...

The ability of heart and skeletal muscle (SM) to switch between fat and carbohydrate oxidation is of high interest in the study of metabolic diseases and exercise physiology. Positron emission tomography (PET) imaging with the glucose analog 2-[18F]fluoro-2-deoxy-glucose (18F-FDG) provides a noninvasive means to quantitate glucose metabolic rates....

Abstract Fibrogenesis is the underlying mechanism of wound healing and repair. Animal models that enable longitudinal monitoring of fibrogenesis are needed to improve traditional tissue analysis post-mortem. Here, we generated transgenic reporter rats expressing the sodium iodide symporter (NIS) driven by the rat collagen type-1 alpha-1 (Col1α1) pr...

Sodium/iodide symporter (NIS)-mediated iodide uptake in thyroid follicular cells is the basis of clinical utilization of radioiodines. The cloning of the NIS gene enabled applications of NIS as a reporter gene in both preclinical and translational research. Non-invasive NIS imaging with radioactive iodides and iodide analogs has gained much interes...

Background: Autologous hepatocyte transplantation after ex vivo gene therapy is an alternative to liver transplantation for metabolic liver disease. Here we evaluate ex vivo gene therapy followed by transplantation of single-cell or spheroid hepatocytes. Methods: Pig and mouse hepatocytes were isolated, labeled with zirconium-89 and returned to...

The human zinc transporter SLC39A2, also known as ZIP2, was shown to mediate zinc transport that could be inhibited at pH values below 7.0 and stimulated by HCO3-, suggesting a Zn2+/HCO3- cotransport mechanism (1). In contrast, recent experiments in our laboratory indicated that the functional activity of ZIP2 increases at acidic pH (2). The presen...

Noninvasive imaging of iodide uptake via the sodium/iodide symporter (NIS) has received great interest for evaluation of thyroid cancer and reporter imaging of NIS-expressing viral therapies. In this study, we investigate 18F-labeled hexafluorophosphate (HFP or PF6-) as a high-affinity iodide analog for NIS imaging. 18F-HFP was synthesized by radio...

Background: (18)F-Tetrafluoroborate ((18)F-TFB) is a promising iodide analog for PET imaging of thyroid cancer and sodium/iodide symporter (NIS) reporter activity in viral therapy applications. The aim of this study was to evaluate the safety, pharmacokinetics, biodistribution, and radiation dosimetry of high-specific activity (18)F-TFB in healthy...

Abnormalities in zinc homeostasis are indicated in many human diseases, including Alzheimer disease (AD). 63Zn-zinc citrate was developed as a positron emission tomography (PET) imaging probe of zinc transport and used in a first-in-human study in 6 healthy elderly individuals and 6 patients with clinically confirmed AD. Dynamic PET imaging of the...

We tested the hypothesis that ex vivo hepatocyte gene therapy can correct the metabolic disorder in fumarylacetoacetate hydrolase-deficient (Fah-/-) pigs, a large animalmodel of hereditary tyrosinemia type 1 (HT1). Recipient Fah-/- pigs underwent partial liver resection and hepatocyte isolation by collagenase digestion. Hepatocytes were transduced...

Methods: An automated synthesis of(18)F-TFB was developed whereby cyclotron-produced(18)F-fluoride was trapped on a quaternary methyl ammonium anion exchange (QMA) cartridge, then allowed to react with BF3freshly pre-formulated in petroleum ether / tetrahydrofuran (THF) (50:1). The resultant(18)F-TFB product was retained on the QMA cartridge. Afte...

Myocardial fuel selection is a key feature of the health and function of the heart, with clear links between myocardial function and fuel selection and important impacts of fuel selection on ischemia tolerance. Radiopharmaceuticals provide uniquely valuable tools for in vivo, non-invasive assessment of these aspects of cardiac function and metaboli...

Glycogen synthase kinase-3 (GSK-3) is associated with various key biological processes, including glucose regulation, apoptosis, protein synthesis, cell signaling, cellular transport, gene transcription, proliferation, and intracellular communication. Accordingly, GSK-3 has been implicated in a wide variety of diseases and specifically targeted for...

Altered myocardial fuel selection likely underlies cardiac disease risk in diabetes, affecting oxygen demand and myocardial metabolic flexibility. We investigated myocardial fuel selection and metabolic flexibility in human Type 2 Diabetes (T2DM), using positron emission tomography to measure rates of myocardial fatty acid oxidation (16-(18)F-fluor...

With the recent growth of interest in cell-based therapies and radiolabeled cell products, there is a need to develop more robust cell labeling and imaging methods for in vivo tracking of living cells. This study describes evaluation of a novel cell labeling approach with the positron emission tomography (PET) isotope (89)Zr (T 1/2 = 78.4 h). (89)Z...

Purpose: To determine if adventitial transplantation of human adipose tissue-derived mesenchymal stem cells (MSCs) to the outflow vein of B6.Cg-Foxn1(nu)/J mice with arteriovenous fistula (AVF) at the time of creation would reduce monocyte chemoattractant protein-1 (Mcp-1) gene expression and venous neointimal hyperplasia. The second aim was to tr...

Objective: The objectives of the present work were to improve the cyclotron production yield of (89)Zr using a solution target, develop a practical synthesis of the hydroxamate resin used to process the target, and develop a biocompatible medium for (89)Zr elution from the hydroxamate resin. Methods: A new solution target (BMLT-2) with enhanced...

Fluorine-18 (18F, T1/2 = 109.7 min) is a positron-emitting isotope that has found extensive application as a radiolabel for positron emission tomography (PET). Although gaseous 11C-CO2 and 11C-CH4 are practically transported from cyclotron to radiochemistry processes, 18F-fluoride is routinely transported in aqueous solution because it is commonly...

Osteosarcoma (OS) is the most common primary bone tumor affecting children and young adults, and development of metastatic disease is associated with poor prognosis. The purpose of this study was to evaluate the antitumor efficacy of virotherapy with engineered measles virus (MV) vaccine strains in the treatment of OS. Cell lines derived from pedia...

Unlabelled: Abnormalities of zinc homeostasis are indicated in many human diseases. A noninvasive imaging method for monitoring zinc in the body would be useful to understand zinc dynamics in health and disease. To provide a PET imaging agent for zinc, we have investigated production of (63)Zn (half-life, 38.5 min) via the (63)Cu(p,n)(63)Zn reacti...

N-acylethanolamines are lipid signaling molecules found throughout the plant and animal kingdoms. The best-known mammalian compound of this class is anandamide, N-arachidonoylethanolamine, one of the endogenous ligands of cannabinoid CB1 and CB2 receptors. Signaling by N-acylethanolamines is terminated by release of the ethanolamine moiety by hydro...

The objective of the present work is to extend the applicability of the solution target approach to the production of (68)Ga using a low energy cyclotron. Since the developed method does not require solid target infrastructure, it offers a convenient alternative to (68)Ge/(68)Ga generators for the routine production of (68)Ga. A new solution target...

The existing solid target production method of radiometals requires high capital and operational expenditures, which limit the production of radiometals to the small fraction of cyclotron facilities that are equipped with solid target systems. Our objective is to develop a robust solution target method, which can be applicable to a wide array of ra...

Background : Zn is implicated as having a role in the formation of calcium oxalate (CaOx) kidney stones. Our studies indicate that Slc39a10 (Zip10) may be important in this process. Zip10 has identifiable sequences in human, dog and fly ( Drosophila ). As we are interested in a translational model of kidney stones, we examined Zip10 from all 3 spec...

In-vivo imaging of regional fatty acid oxidation (FAO) rates would have considerable potential for evaluation of mammalian diseases. We have synthesize and evaluated (18)F-labeled thia fatty acid analogs as metabolically trapped FAO probes to understand the effect of chain length, degree of unsaturation and placement of the thia-substituent on myoc...

A Case-Based Approach to PET/CT in Oncology describes the role of PET/CT in the diagnosis, staging and monitoring of treatment response in today's practice of oncology. It provides a detailed analysis of over 100 cases occurring in daily clinical practice, emphasizing the central role that PET imaging plays in the care of cancer patients. The text...

The introduction of tracer kinetic modeling techniques in conjunction with nuclear imaging has allowed the assessment of physiologic processes in the myocardium in a noninvasive and quantitative manner. Alongside the development of novel radiopharmaceuticals for both positron emission tomography and single photon emission computed tomography is the...

Choline kinase catalyzes the phosphorylation of choline, the first step of phospholipid synthesis. Increased phosphorylation of choline is a hallmark characteristic of the malignant phenotype in a variety of neoplasms. However, in hypoxic cancer cells, choline phosphorylation is decreased. To understand the mechanism behind this altered metabolic s...

Microwave reactors remain largely underutilized in the field of positron emission tomography (PET) chemistry. This is particularly unfortunate since microwave synthesis elegantly addresses two of the most critical issues of PET radiochemistry with short-lived radionuclides: reaction rate and side-product formation. In this study, we investigate the...

Hypoxic microenvironment and overexpression of choline kinase alpha (ChKa) have been associated with tumor malignancy, but the regulation of ChKa expression in hypoxic conditions is poorly understood. In this study, the effects of chronic hypoxia on choline metabolism and ChKa expression were examined in prostate cancer cell line, PC-3. Chronic hyp...

Myocardial fatty acid oxidation (FAO) imaging is a noninvasive technique that can measure FAO rates in tissues for research applications in animals and humans, as well as clinical applications in managing patients with metabolic disorders. FAO imaging has great potential in diagnosis and monitoring of patients with ischemic heart disease, cardiomyo...

Fatty acid oxidation (FAO) is a major energy-providing process with important implications in cardiovascular, oncologic, neurologic, and metabolic diseases. A novel 4-thia oleate analog, 18-(18)F-fluoro-4-thia-oleate ((18)F-FTO), was evaluated in relationship to the previously developed palmitate analog 16-(18)F-fluoro-4-thia-palmitate ((18)F-FTP)...

Conventional imaging (CI) is known to have limitations with respect to staging of patients with primary or relapsed prostate cancer. Positron emission tomography/computed tomography (PET/CT) with (18)F-flurodeoxyglucose (FDG) is also often suboptimal because of low tracer avidity, but (18)F-fluorocholine (FCH) appears to be a promising alternative...

The bubble point test is the de facto standard for postproduction filter membrane integrity test in the radiopharmaceutical community. However, the bubble point test depends on a subjective visual assessment of bubbling rate that can be obscured by significant diffusive gas flows below the manufacturer's prescribed bubble point. To provide a more o...

We are evaluating PCT imaging in conjunction with NIR dye labeled Herceptin antibody for noninvasive assessment of HER2 expression in tumors. Herceptin was labeled with Alexa Fluor-750 amine reactive dye for characterization of photoacoustic and fluorescence signals. Measurements were performed in solution and after incubation in cultured cell line...

[(18)F]Fluorocholine ([(18)F]FCH) was developed as an analog of [(11)C]choline for tumor imaging; however, its metabolic handling remains ill defined. In this study, the metabolism of [(18)F]FCH is evaluated in cultured 9L glioma cells and Fisher 344 rats bearing 9L glioma tumors. 9L glioma cells were incubated with [(18)F]FCH and [(14)C]choline un...

The choline transporter and choline kinase enzyme frequently are overexpressed in malignancy. Therefore, positron-emitter-labeled compounds derived from choline have the potential to serve as oncologic probes for positron emission tomography. The fluorine-18 ((18)F)-labeled choline derivative fluorocholine (FCH) in particular has demonstrated poten...

The high-affinity choline transporter (CHT1) system is an attractive target for the development of positron emission tomography (PET) biomarkers to probe brain, cardiac, and cancer diseases. An efficient and convenient synthesis of new radiolabeled CHT1 inhibitors [(11)C]hemicholinium-3 and [(18)F]hemicholinium-3 by solid-phase extraction (SPE) tec...

It is well documented that photoacoustic imaging has the capability to differentiate tissue based on the spectral characteristics of tissue in the optical regime. The imaging depth in tissue exceeds standard optical imaging techniques, and systems can be designed to achieve excellent spatial resolution. A natural extension of imaging the intrinsic...

[(11)C]Hemicholinium-15 ([(11)C]HC-15) and [(18)F]hemicholinium-15 ([(18)F]HC-15) have been synthesized as new potential PET tracers for the heart high-affinity choline uptake (HACU) system. [(11)C]HC-15 was prepared by N-[(11)C]methylation of the appropriate precursor, 4-methyl-2-phenyl-morpholin-2-ol, using [(11)C]CH(3)OTf in 55-70% radiochemical...

Choline, acetate and glucose ([2-(18)F]fluoro-2-deoxyglucose, [(18)F]FDG) analogs are under investigation as positron emission tomography (PET) tracers for the imaging of prostate cancer; however, their response to tumor hypoxia has not been clarified. The uptake of [methyl-(3)H]choline, [1-(14)C]acetate and [(18)F]FDG was monitored in androgen-ind...

Abnormalities of choline processing in cancer cells have been used as a basis for imaging of cancer with positron emission tomography and magnetic resonance spectroscopy. In this study, the transport mechanism for choline was investigated in cultured PC-3 prostate cancer cells. Furthermore, tritiated hemicholinium 3 (HC-3), a well-known inhibitor o...

Nuclear Factor kappa B (NFkappaB) is a eukaryotic transcription factor that is constitutively active in human cancers and can be inhibited by the naturally occurring sesquiterpene lactone, parthenolide (P). The in vitro effects of P were assessed using the androgen independent cell line, CWR22Rv1, and human umbilical endothelial cells (HUVECs). The...

Fatty acid oxidation (FAO) is the predominant energy-producing pathway in the healthy heart. Abnormalities in FAO are associated with many ischemic and nonischemic disease states. The aim of the present study was to further validate 16-[(18)F]-fluoro-4-thia-palmitate ((18)F-FTP) as a metabolically trapped FAO probe in the isolated perfused rat hear...

Acetylene is a versatile synthon organic chemistry. The complexity and difficulty of synthesis of [(11)C]acetylene has limited its use as a labeling intermediate for PET radiotracers. A new method for production of [(11)C]acetylene has been developed in our laboratory that simplifies the synthesis procedure allowing for easy automation and implemen...

PET imaging in the pelvis with dual planar detectors has been investigated. The scanner consisted of two 20 cm (transaxial)times15 cm (axial) planar detectors with 3times3times10 mm³ LGSO elements mounted on a rotating gantry with adjustable detector radii. A 36 cmtimes21 cm oval phantom, 40 cm long, with a centered 2.2 cm sphere and 1.3...

An improved synthesis of [C]raclopride is reported. The precursor desmethyl‐raclopride was synthesized from 3,5‐dichloro‐2,6‐dimethoxybenzoic acid and (S)‐(−)‐2‐aminoethyl‐1‐ethylpyrrolidine via a straightforward, four‐step synthetic approach with 29% overall chemical yield. [C]Raclopride was prepared by O‐[C]methylation of the precursor with [C]me...

Background: Both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have been used in preclinical studies to induce new blood vessel growth in ischemic cardiac muscle with promising results. However, clinical trials have been much less convincing and further work is needed. This study expands on prior work by compa...

Prior experimental and clinical studies have drawn disparate conclusions regarding the effects of transmyocardial laser revascularization (TMR) on regional cardiac innervation in the treated regions. Regional afferent denervation has been proposed as a potential mechanism of action of the procedure, although this as yet remains unproven. The purpos...

(2R)-2-[[4-(6-fluorohex-1-ynyl)phenyl]sulfonylamino]-3-methylbutyric acid [(11)C]methyl ester ([(11)C]FMAME), a novel carbon-11 labeled matrix metalloproteinase (MMP) inhibitor, has been synthesized for evaluation as new potential positron emission tomography (PET) cancer biomarker. [(11)C]FMAME was prepared by appropriate precursor (2R)-2-[[4-(6-f...

While several studies are available on the immediate effects of marijuana and its active ingredient tetrahydrocannabinol (THC) on regional cerebral blood flow (rCBF), we examined the effects of intravenous infusion of THC on rCBF and behavior over a 120-min. period using positron emission tomography. Indices of rCBF, intoxication and physiology wer...