High-resolution microPET imaging of carcinoembryonic antigen-positive xenografts by using a copper-64-labeled engineered antibody fragment

Immuno-PET of colorectal cancer with a CEA-targeted [68 Ga]Ga-nanobody: from bench to bedside

PURPOSE

An accurate diagnosis of colorectal carcinoma (CRC) can assist physicians in developing reasonable therapeutic regimens, thereby significantly improving the patient's prognosis. Carcinoembryonic antigen (CEA)-targeted PET imaging shows great potential for this purpose. Despite showing remarkable abilities to detect primary and metastatic CRC, previously reported CEA-specific antibody radiotracers or pretargeted imaging are not suitable for clinical use due to poor pharmacokinetics and complicated imaging procedures. In contrast, radiolabeled nanobodies exhibit ideal characteristics for PET imaging, for instance, rapid clearance rates and excellent distribution profiles, allowing same-day imaging with sufficient contrast. In this study, we developed a novel CEA-targeted nanobody radiotracer, [68 Ga]Ga-HNI01, and assessed its tumor imaging ability and biodistribution profile in preclinical xenografts and patients with primary and metastatic CRC.

METHODS

The novel nanobody HNI01 was acquired by immunizing the llama with CEA proteins. [68 Ga]Ga-HNI01 was synthesized by site-specifically conjugating [68 Ga]Ga with tris(hydroxypyridinone) (THP). Small-animal PET imaging and biodistribution studies were performed in CEA-overexpressed LS174T and CEA-low-expressed HT-29 tumor models. Following successful preclinical assessment, a phase I study was conducted on 9 patients with primary and metastatic CRC. Study participants received 151.21 ± 25.25 MBq of intravenous [68 Ga]Ga-HNI01 and underwent PET/CT scans at 1 h and 2 h post injection. Patients 01-03 also underwent whole-body dynamic PET imaging within 0-40 min p.i. All patients underwent [18F]F-FDG PET/CT imaging within 1 week after [68 Ga]Ga-HNI01 imaging. Tracer distribution, pharmacokinetics, and radiation dosimetry were calculated.

RESULTS

[68 Ga]Ga-HNI01 was successfully synthesized within 10 min under mild conditions, and the radiochemical purity was more than 98% without purification. Micro-PET imaging with [68 Ga]Ga-HNI01 revealed clear visualization of LS174T tumors, while signals from HT-29 tumors were significantly lower. Biodistribution studies indicated that uptake of [68 Ga]Ga-HNI01 in LS174T and HT-29 was 8.83 ± 3.02%ID/g and 1.81 ± 0.87%ID/g, respectively, at 2 h p.i. No adverse events occurred in all clinical participants after the injection of [68 Ga]Ga-HNI01. A fast blood clearance and low background uptake were observed, and CRC lesions could be visualized with high contrast as early as 30 min after injection. [68 Ga]Ga-HNI01 PET could clearly detect metastatic lesions in the liver, lung, and pancreas and showed superior ability in detecting small metastases. A significant accumulation of radioactivity was observed in the kidney, and normal tissues physiologically expressing CEA receptors showed slight uptakes of [68 Ga]Ga-HNI01. An interesting finding was that strong uptake of [68 Ga]Ga-HNI01 was found in non-malignant colorectal tissues adjacent to the primary tumor in some patients, suggesting abnormal CEA expression in these healthy tissues.

CONCLUSION

[68 Ga]Ga-HNI01 is a novel CEA-targeted PET imaging radiotracer with excellent pharmacokinetics and favorable dosimetry profiles. [68 Ga]Ga-HNI01 PET is an effective and convenient imaging tool for detecting CRC lesions, particularly for identifying small metastases. Furthermore, its high specificity for CEA in vivo makes it an ideal tool for selecting patients for anti-CEA therapy.

Lasso peptide microcin J25 variant containing RGD motif as a PET probe for integrin a v ß 3 in tumor imaging

Microcin J25 (MccJ25), a lasso peptide, has a unique 3-D interlocked structure that provides high stability under acidic conditions, at high temperatures, and in the presence of proteases. In this study, we generated a positron emission tomography (PET) probe based on MccJ25 analog with an RGD motif and investigated their pharmacokinetics and utility for integrin α_vβ₃ imaging in tumors. The MccJ25 variant with an RGD motif in the loop region and a lysine substitution at the C-terminus (MccJ25(RGDF)GtoK) was produced in E. coli transfected with plasmid DNA containing the MccJ25 biosynthetic gene cluster (mcjABCD). [⁶⁴Cu]Cu-MccJ25(RGDF)GtoK was synthesized using the C-terminal lysine labeled with copper-64 (t_1/2 = 12.7 h) via a bifunctional chelator; it showed stability in 90% mouse plasma for 45 min. Using PET imaging for integrin α_vβ₃ positive U87MG tumor bearing mice, [⁶⁴Cu]Cu-MccJ25(RGDF)GtoK could clearly distinguish the tumor, and its accumulation was significantly higher than that of MccJ25(GIGT)GtoK without the binding motif for integrin α_vβ₃. Furthermore, MccJ25(RGDF)GtoK enabled visualization of only U87MG tumors but not MCF-7 tumors with low integrin α_vβ₃ expression in double tumor-bearing mice. In ex vivo biodistribution analysis, the integrin α_vβ₃ non-specific accumulation of [⁶⁴Cu]Cu-MccJ25(RGDF)GtoK was significantly lower in various tissues, except for the kidneys, as compared to the control probe ([⁶⁴Cu]Cu-cyclic RGD peptide). These results of the present study indicate that ⁶⁴Cu-labeling methods are appropriate for the synthesis of MccJ25-based PET probes, and [⁶⁴Cu]Cu-MccJ25 variants are useful tools for cancer molecular imaging.

ImmunoPET: harnessing antibodies for imaging immune cells

Dramatic, but uneven, progress in the development of immunotherapies for cancer has created a need for better diagnostic technologies including innovative non-invasive imaging approaches. This review discusses challenges and opportunities for molecular imaging in immuno-oncology and focuses on the unique role that antibodies can fill. ImmunoPET has been implemented for detection of immune cell subsets, activation and inhibitory biomarkers, tracking adoptively transferred cellular therapeutics, and many additional applications in preclinical models. Parallel progress in radionuclide availability and infrastructure supporting biopharmaceutical manufacturing has accelerated clinical translation. ImmunoPET is poised to provide key information on prognosis, patient selection, and monitoring immune responses to therapy in cancer and beyond.

Metallic nanoparticles as drug delivery system for the treatment of cancer

INTRODUCTION

The targeted delivery of anticancer agents to tumor is a major challenge because most of the drugs show off-target effect resulting in nonspecific cell death. Multifunctionalized metallic nanoparticles (NPs) are explored as new carrier system in the era of cancer therapeutics. Researchers investigated the potential of metallic NPs to target tumor cells by active and passive mechanisms, thereby reducing off-target effects of anticancer agents. Moreover, photocatalytic activity of upconversion nanoparticles (UCNPs) and the enhanced permeation and retention (EPR) effect have also gained wide potential in cancer treatment. Recent advancement in the field of nanotechnology highlights their potency for cancer therapy.

AREAS COVERED

This review summarizes the types of gold and silver metallic NPs with targeting mechanisms and their potentiality in cancer therapy.

EXPERT OPINION

Recent advances in the field of nanotechnology for cancer therapy offer high specificity and targeting efficiency. Targeting tumor cells through mechanistic pathways using metallic NPs for the disruption/alteration of molecular profile and survival rate of the tumor cells has led to an effective approach for cancer therapeutics. This alteration in the survival rate of the tumor cells might decrease the proliferation thereby resulting in more efficient management in the treatment of cancer.

Tumor regression and immunity in combination therapy with anti-CEA chimeric antigen receptor T cells and anti-CEA-IL2 immunocytokine

Targeted immunotherapy of solid cancers with chimeric antigen receptor (CAR) T cells and immunocytokines are attractive options in that they both rely on the specificity of tumor-targeted antibodies. Since carcinoembryonic antigen (CEA) expression in both colon and breast cancers is correlated with poor prognosis, it was chosen as a model tumor target in immunocompetent CEA transgenic (CEATg) mice. A second-generation anti-CEA CAR derived from CEA-specific antibody T84.66 was used to treat murine MC38 colon or E0771 breast carcinomas transfected with CEA. Anti-CEA CAR vs. mock transduced T cells exhibited a CEA-specific cytotoxic and IFNγ dose response to both CEA transfected cell lines vs. their CEA-negative controls. Anti-CEA CAR vs. mock transduced T cells delayed the median survival of CEA transfected s.c. MC38 or orthotopic E0771 tumor-bearing CEATg mice by 2 days. With the addition of one-day prior cyclophosphamide (CY) lymphodepletion, anti-CEA CAR T cell treatment delayed the median survival of MC38/CEA and E0771/CEA tumor-bearing CEATg mice by ten and 3 days, respectively. Since CAR T cells require IL2 for survival and expansion, anti-CEA-IL2 immunocytokine (ICK) treatment was performed post CAR T cell therapy. Single ICK treatment 1 day after CY plus anti-CEA CAR T cell therapy in the MC38/CEA model, and two ICK treatments every 3 days after CY plus anti-CEA CAR T cell therapy in the E0771/CEA model were ineffective, while four ICK treatments every 3 days after CY plus anti-CEA CAR T cell therapy completely eradicated MC38/CEA tumor growth and induced tumor immunity when the mice were re-challenged with tumor. These studies show the therapeutic potential of anti-CEA CAR T cells combined with ICK to treat CEA-positive tumors.

Abbreviations: CAR: Chimeric antigen receptor, CEA: Carcinoembryonic antigen, CEACAM5, ICK: Immunocytokine, CY: Cyclophosphamide, CEATg mouse: transgenic CEA mouse, TDLN: Tumor-draining lymph node

PET/CT Imaging of Human TNFα Using [89Zr]Certolizumab Pegol in a Transgenic Preclinical Model of Rheumatoid Arthritis

PURPOSE

Tumor necrosis factor alpha (TNFα) drives inflammation and bone degradation in patients with rheumatoid arthritis (RA). Some RA patients experience a rapid clinical response to TNFα inhibitors such as certolizumab pegol (CZP) while other patients show limited to no response. Current methods for imaging RA have limited sensitivity and do not assist in the selection of patients most likely to respond to immune-mediated therapy. Herein, we developed a novel positron emission tomography (PET) radiotracer for immuno-PET imaging of TNFα in transgenic human TNFα-expressing mice.

PROCEDURES

CZP was modified with p-isothiocyanatobenzyl-deferoxamine (DFO) and radiolabeled with Zr-89. The biological activity of [⁸⁹Zr]DFO-CZP was evaluated by HPLC and binding assay using human recombinant TNFα (hTNFα). The feasibility of specific immuno-PET imaging of human TNFα was assessed in a transgenic mouse model of RA that expresses human TNFα. This model resembles the progression of RA in humans by maintaining lower levels of circulating hTNFα and exhibits chronic arthritis in the forepaw and hind paw joints. The dosimetry of [⁸⁹Zr]DFO-CZP in humans was estimated using microPET/CT imaging in Sprague Dawley rats.

RESULTS

[⁸⁹Zr]DFO-CZP was isolated with radiolabeling yields of 85 ± 6 % (n = 5) and specific activities ranging from 74 to 185 MBq/mg (n = 5). Following size exclusion purification, the radiochemical purity of [⁸⁹Zr]DFO-CZP was greater than 97 %. [⁸⁹Zr]DFO-CZP retained high immunoreactivity with more than 95 % of the radioactivity shifted into higher molecular weight complexes. Images showed increasing uptake of the tracer in forepaw and hind paw joints with disease progression. No uptake was observed in the model previously administered with an excess amount of unmodified CZP and in normal control mice, demonstrating in vivo specific uptake of [⁸⁹Zr]DFO-CZP.

CONCLUSION

The feasibility of immuno-PET imaging of human TNFα with [⁸⁹Zr]DFO-CZP has been demonstrated in a preclinical model of RA.

Radiochemistry, Production Processes, Labeling Methods, and ImmunoPET Imaging Pharmaceuticals of Iodine-124

Target-specific biomolecules, monoclonal antibodies (mAb), proteins, and protein fragments are known to have high specificity and affinity for receptors associated with tumors and other pathological conditions. However, the large biomolecules have relatively intermediate to long circulation half-lives (>day) and tumor localization times. Combining superior target specificity of mAbs and high sensitivity and resolution of the PET (Positron Emission Tomography) imaging technique has created a paradigm-shifting imaging modality, ImmunoPET. In addition to metallic PET radionuclides, 124I is an attractive radionuclide for radiolabeling of mAbs as potential immunoPET imaging pharmaceuticals due to its physical properties (decay characteristics and half-life), easy and routine production by cyclotrons, and well-established methodologies for radioiodination. The objective of this report is to provide a comprehensive review of the physical properties of iodine and iodine radionuclides, production processes of 124I, various 124I-labeling methodologies for large biomolecules, mAbs, and the development of 124I-labeled immunoPET imaging pharmaceuticals for various cancer targets in preclinical and clinical environments. A summary of several production processes, including 123Te(d,n)124I, 124Te(d,2n)124I, 121Sb(α,n)124I, 123Sb(α,3n)124I, 123Sb(3He,2n)124I, natSb(α, xn)124I, natSb(3He,n)124I reactions, a detailed overview of the 124Te(p,n)124I reaction (including target selection, preparation, processing, and recovery of 124I), and a fully automated process that can be scaled up for GMP (Good Manufacturing Practices) production of large quantities of 124I is provided. Direct, using inorganic and organic oxidizing agents and enzyme catalysis, and indirect, using prosthetic groups, 124I-labeling techniques have been discussed. Significant research has been conducted, in more than the last two decades, in the development of 124I-labeled immunoPET imaging pharmaceuticals for target-specific cancer detection. Details of preclinical and clinical evaluations of the potential 124I-labeled immunoPET imaging pharmaceuticals are described here.

Copper-64-immunoPET imaging: bench to bedside

Positron emission tomography (PET) is a growing non-invasive diagnostic and molecular imaging tool in nuclear medicine, that is used to identify several diseases including cancer. The immunoPET probe is made up of monoclonal antibodies (mAbs) or its fragments or similar molecules that tagged with positron radioisotopes (⁶⁸Ga, ⁶⁴Cu, ⁸⁹Zr) bound together by a bifunctional chelator (BFC). This probe is designed to identify a specific disease. Currently, several immunoPET probes are being developed for preclinical as well as for clinical applications. These studies are showing promising results, both in preclinical and patients, using mostly ⁶⁴Cu, ⁸⁹Zr isotopes. This review elucidates the ⁶⁴Cu based immunoPET applications, their pipelines and the emerging scope of this technique within the nuclear medicine and molecular imaging clinics from bench to bedside. Recently, immunoPET research have sharply increased especially after a big surge in approval of oncology antibodies by the FDA for immune checkpoint-blockade cancer immunotherapies. Currently, preclinical to clinical translations of immunoPET has several challenges, including designing probes, choice of radioisotopes, selection of stable BFC, and size of antibody and its tracer kinetics. All these obstacles will be addressed eventually by improving PET scanner sensitivity, designing appropriate size of imaging probe, and combining immunoPET with specific targeting antibodies. These improvements should contribute to the immunoPET becoming more applicable in clinics, which, in turn, will provide critical information for correct patient selection, for right dosing, and for the right time/staging of treatment.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

Synthesis and Cytotoxicity Evaluation of DOTA-Conjugates of Ursolic Acid

In this study, we report the synthesis of several amine-spacered conjugates of ursolic acid (UA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Thus, a total of 11 UA-DOTA conjugates were prepared holding various oligo-methylene diamine spacers as well as different substituents at the acetate units of DOTA including tert-butyl, benzyl, and allyl esters. Furthermore, three synthetic approaches were compared for the ethylenediamine-spacered conjugate 29 regarding reaction steps, yields, and precursor availability. The prepared conjugates were investigated regarding cytotoxicity using SRB assays and a set of human tumor cell lines. The highest cytotoxicity was observed for piperazinyl spacered compound 22. Thereby, EC50 values of 1.5 µM (for A375 melanoma) and 1.7 µM (for A2780 ovarian carcinoma) were determined. Conjugates 22 and 24 were selected for further cytotoxicity investigations including fluorescence microscopy, annexin V assays and cell cycle analysis.

Antibody Fragment and Affibody ImmunoPET Imaging Agents: Radiolabelling Strategies and Applications

Antibodies have long been recognised as potent vectors for carrying diagnostic medical radionuclides, contrast agents and optical probes to diseased tissue for imaging. The area of ImmunoPET combines the use of positron emission tomography (PET) imaging with antibodies to improve the diagnosis, staging and monitoring of diseases. Recent developments in antibody engineering and PET radiochemistry have led to a new wave of experimental ImmunoPET imaging agents that are based on a range of antibody fragments and affibodies. In contrast to full antibodies, engineered affibody proteins and antibody fragments such as minibodies, diabodies, single-chain variable region fragments (scFvs), and nanobodies are much smaller but retain the essential specificities and affinities of full antibodies in addition to more desirable pharmacokinetics for imaging. Herein, recent key developments in the PET radiolabelling strategies of antibody fragments and related affibody molecules are highlighted, along with the main PET imaging applications of overexpressed antigen-associated tumours and immune cells.

Overcoming the Blood-Brain Barrier: The Role of Nanomaterials in Treating Neurological Diseases

Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood-brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial-based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease-targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial-mediated treatment of neurological diseases.

Multimodal assessment of SERS nanoparticle biodistribution post ingestion reveals new potential for clinical translation of Raman imaging

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 64Cu 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.

Quantitative Examination of the Active Targeting Effect: The Key Factor for Maximal Tumor Accumulation and Retention of Short-Circulated Biopolymeric Nanocarriers

Targeted and nontargeted biopolymeric nanoparticles with identical hydrodynamic sizes and surface charges were quantitatively examined in terms of the pharmacokinetic and biodistribution differences in detail. In adding cancer cell targeting folate molecules to the surface of the heparin nanocarriers, the amount of drug delivered to the tumor is doubled, and tumor growth inhibition is significantly enhanced. The folate-targeted heparin particles offered similar therapeutic potentials compared to their synthetic long-circulating analogues, thus presenting a viable alternative for drug-delivery vehicle construction using biological polymers, which are easier for the body to eliminate.

New synthesis of phenyl-isothiocyanate C-functionalised cyclams. Bioconjugation and (64)Cu phenotypic PET imaging studies of multiple myeloma with the te2a derivative

Azamacrocyclic bifunctional chelating agents (BCAs) are essential for the development of radiopharmaceuticals in nuclear medicine and we wish to prove that their bioconjugation by a function present on a carbon atom of the macrocyclic skeleton is a solution of choice to maintain their in vivo inertness. Based on our very recent methodology using a bisaminal template and selective N-alkylation approach, a new synthesis of conjugable C-functionalised teta, te2a and cb-te2a has been developed. These chelators have indeed a growing interest in nuclear medicine for positron emission tomography (PET) and radioimmunotherapy (RIT) where they show in several cases better complexation properties than dota or dota-like macrocycles, especially with (64)Cu or (67)Cu radioisotopes. Chelators are bearing an isothiocyanate grafting function introduced by C-alkylation to avoid as much as possible a critical decrease of their chelating properties. The synthesis is very efficient and yields the targeted ligands, teta-Ph-NCS, te2a-Ph-NCS and cb-te2a-Ph-NCS without fastidious work-up and could be easily extended to other cyclam based-BCAs. The newly synthetised te2a-Ph-NCS has been conjugated to an anti mCD138 monoclonal antibody (mAb) to evaluate its in vivo behavior and potentiality as BCA and to explore a first attempt of PET-phenotypic imaging in multiple myeloma (MM). Mass spectrometry analysis of the immunoconjugate showed that up to 4 chelates were conjugated per 9E7.4 mAb. The radiolabeling yield and specific activity post-purification of the bioconjugate 9E7.4-CSN-Ph-te2a were 95 ± 2.8% and 188 ± 27 MBq mg(-1) respectively and the immunoreactivity of (64)Cu-9E7.4-CSN-Ph-te2a was 81 ± 7%. Animal experiments were carried out on 5T33-Luc(+) tumor bearing mice, either in subcutaneous or orthotopic. To achieve PET imaging, mice were injected with (64)Cu-9E7.4-CNS-Ph-te2a and acquisitions were conducted 2 and 20 h post-injection (PI). A millimetric bone uptake was localised in a sacroiliac of a MM orthotopic tumor. Nonspecific uptakes were observed at 2 h PI but, unlike for the tumor, a significant decrease was observed at 20 h PI which improves the contrast of the images.

Dual PET and Near-Infrared Fluorescence Imaging Probes as Tools for Imaging in Oncology

OBJECTIVE

The purpose of this article is to summarize advances in PET fluorescence resolution, agent design, and preclinical imaging that make a growing case for clinical PET fluorescence imaging.

CONCLUSION

Existing SPECT, PET, fluorescence, and MRI contrast imaging techniques are already deeply integrated into the management of cancer, from initial diagnosis to the observation and management of metastases. Combined positron-emitting fluorescent contrast agents can convey new or substantial benefits that improve on these proven clinical contrast agents.

New Dioxaborolane Chemistry Enables [(18)F]-Positron-Emitting, Fluorescent [(18)F]-Multimodality Biomolecule Generation from the Solid Phase

New protecting group chemistry is used to greatly simplify imaging probe production. Temperature and organic solvent-sensitive biomolecules are covalently attached to a biotin-bearing dioxaborolane, which facilitates antibody immobilization on a streptavidin-agarose solid-phase support. Treatment with aqueous fluoride triggers fluoride-labeled antibody release from the solid phase, separated from unlabeled antibody, and creates [(18)F]-trifluoroborate-antibody for positron emission tomography and near-infrared fluorescent (PET/NIRF) multimodality imaging. This dioxaborolane-fluoride reaction is bioorthogonal, does not inhibit antigen binding, and increases [(18)F]-specific activity relative to solution-based radiosyntheses. Two applications are investigated: an anti-epithelial cell adhesion molecule (EpCAM) monoclonal antibody (mAb) that labels prostate tumors and Cetuximab, an anti-epidermal growth factor receptor (EGFR) mAb (FDA approved) that labels lung adenocarcinoma tumors. Colocalized, tumor-specific NIRF and PET imaging confirm utility of the new technology. The described chemistry should allow labeling of many commercial systems, diabodies, nanoparticles, and small molecules for dual modality imaging of many diseases.

Multifunctional quantum dots-based cancer diagnostics and stem cell therapeutics for regenerative medicine

A field of recent diagnostics and therapeutics has been advanced with quantum dots (QDs). QDs have developed into new formats of biomolecular sensing to push the limits of detection in biology and medicine. QDs can be also utilized as bio-probes or labels for biological imaging of living cells and tissues. More recently, QDs has been demonstrated to construct a multifunctional nanoplatform, where the QDs serve not only as an imaging agent, but also a nanoscaffold for diagnostic and therapeutic modalities. This review highlights the promising applications of multi-functionalized QDs as advanced nanosensors for diagnosing cancer and as innovative fluorescence probes for in vitro or in vivo stem cell imaging in regenerative medicine.

Bifunctional (64)Cu-labelled macrobicyclic cage amine isothiocyanates for immuno-positron emission tomography

New macrobicyclic cage amine or "sarcophagine" (sar) bifunctional chelators have been synthesised that form copper complexes of exceptional in vivo stability and incorporate isothiocyanate (-NCS) functional groups for conjugation to an antibody. The chelators were synthesised from the methyl-capped complex [Mg(II)(CH3)(NH2)sar](2+). Coordination of Mg(II) within the cavity of the cage amine ligand protects the secondary amine atoms from reacting with the -NCS functional groups. Two different [Mg(II)(NCS-sar)](2+) derivatives were conjugated to the HER2/neu-targeting antibody trastuzumab and the progress of the reaction monitored by electrospray mass spectrometry. The Mg(II) ion was removed from the immunoconjugates under mild conditions (0.1 M citrate buffer, pH 6). Labelling of the (CH3)(p-NCS-Ph)sar-trastuzumab conjugate with (64)Cu(II), a radioisotope suitable for positron emission tomography (PET), was fast (∼5 min) and easily performed at room temperature with high radiochemical purity (>95%). Biodistribution and PET imaging studies in vivo showed that (64)Cu-labelled (CH3)(p-NCS-Ph)sar-trastuzumab maintained high stability under physiological conditions with high and selective uptake in a HER2-positive cancer cell line. The stability of the copper complex and the 12.7 h half-life of the radioisotope allows clear visualisation of tumours out to 48 h.

Applications of in vivo imaging in the evaluation of the pathophysiology of viral and bacterial infections and in development of countermeasures to BSL3/4 pathogens

While preclinical and clinical imaging have been applied to drug discovery/development and characterization of disease pathology, few examples exist where imaging has been used to evaluate infectious agents or countermeasures to biosafety level (BSL)3/4 threat agents. Viruses engineered with reporter constructs, i.e., enzymes and receptors, which are amenable to detection by positron emission tomography (PET), single photon emission tomography (SPECT), or magnetic resonance imaging (MRI) have been used to evaluate the biodistribution of viruses containing specific therapeutic or gene transfer payloads. Bioluminescence and nuclear approaches involving engineered reporters, direct labeling of bacteria with radiotracers, or tracking bacteria through their constitutively expressed thymidine kinase have been utilized to characterize viral and bacterial pathogens post-infection. Most PET, SPECT, CT, or MRI approaches have focused on evaluating host responses to the pathogens such as inflammation, brain neurochemistry, and structural changes and on assessing the biodistribution of radiolabeled drugs. Imaging has the potential when applied preclinically to the development of countermeasures against BSL3/4 threat agents to address the following: (1) presence, biodistribution, and time course of infection in the presence or absence of drug; (2) binding of the therapeutic to the target; and (3) expression of a pharmacologic effect either related to drug mechanism, efficacy, or safety. Preclinical imaging could potentially provide real-time dynamic tools to characterize the pathogen and animal model and for developing countermeasures under the U.S. FDA Animal Rule provision with high confidence of success and clinical benefit.

New trends in guided nanotherapies for digestive cancers: A systematic review

Digestive tract tumors are among the most common and deadliest malignancies worldwide, mainly due to late diagnosis and lack of efficient therapeutics. Current treatments essentially rely on surgery associated with (neo)adjuvant chemotherapy agents. Despite an upfront response, conventional drugs often fail to eliminate highly aggressive clones endowed with chemoresistant properties, which are responsible for tumor recurrence and disease dissemination. Synthetic drugs also present severe adverse systemic effects, hampering the administration of biologically effective dosages. Nanoencapsulation of chemotherapeutic agents within biocompatible polymeric or lipid matrices holds great potential to improve the pharmacokinetics and efficacy of conventional chemotherapy while reducing systemic toxicity. Tagging nanoparticle surfaces with specific ligands for cancer cells, namely monoclonal antibodies or antibody fragments, has provided means to target more aggressive clones, further improving the selectivity and efficacy of nanodelivery vehicles. In fact, over the past twenty years, significant research has translated into a wide array of guided nanoparticles, providing the molecular background for a new generation of intelligent and more effective anti-cancer agents. Attempting to bring awareness among the medical community to emerging targeted nanopharmaceuticals and foster advances in the field, we have conducted a systematic review about this matter. Emphasis was set on ongoing preclinical and clinical trials for liver, colorectal, gastric and pancreatic cancers. To the best of our knowledge this is the first systematic and integrated overview on this field. Using a specific query, 433 abstracts were gathered and narrowed to 47 manuscripts when matched against inclusion/exclusion criteria. All studies showed that active targeting improves the effectiveness of the nanodrugs alone, while lowering its side effects. The main focus has been on hepatocarcinomas, mainly by exploring glycans as homing molecules. Other ligands such as peptides/small proteins and antibodies/antibody fragments, with affinity to either tumor vasculature or tumor cells, have also been widely and successfully applied to guide nanodrugs to gastrointestinal carcinomas. Conversely, few solutions have been presented for pancreatic tumors. To this date only three nanocomplexes have progressed beyond pre-clinical stages: i) PK2, a galactosamine-functionalized polymeric-DOX formulation for hepatocarcinomas; ii) MCC-465, an anti-(myosin heavy chain a) immunoliposome for advanced stage metastatic solid tumors; and iii) MBP-426, a transferrin-liposome-oxaliplatin conjugate, also for advanced stage tumors. Still, none has been approved for clinical use. However, based on the high amount of pre-clinical studies showing enthusiastic results, the number of clinical trials is expected to increase in the near future. A more profound understanding about the molecular nature of chemoresistant clones and cancer stem cell biology will also contribute to boost the field of guided nanopharmacology towards more effective solutions.

Click-chemistry strategy for labeling antibodies with copper-64 via a cross-bridged tetraazamacrocyclic chelator scaffold

We report a click-chemistry based modular strategy for antibody labeling with (64)Cu (t1/2 = 12.7 h; β(+) 0.656 MeV, 17.4%; β(-) 0.573 MeV, 39%; EC 43%) under ambient condition utilizing a cross-bridged tetraazamacrocyclic (CB-TE2A) analogue, which otherwise requires harsh conditions that make the CB-TE2A analogues under-utilized for protein labeling despite the fact that they form kinetically inert copper complexes with high in vivo stability. Our strategy involves prelabeling a CB-TE2A based scaffold (CB-TE2A-1C) with (64)Cu and its subsequent reaction with an antibody via the tetrazine-norbornene mediated click chemistry. The effectiveness of this strategy was demonstrated by labeling two monoclonal antibodies, an anti-PSMA antibody (YPSMA-1) and a chimeric anti-phosphatidylserine antibody (Bavituximab). The immunoreactivity of the antibodies remained unchanged after the tetrazine modification and click-chemistry (64)Cu labeling. To further demonstrate the practicality of the modular (64)Cu labeling strategy, we tested positron emission tomography (PET) imaging of tumor with the (64)Cu-labeled bavituximab in a mouse xenograft model. The tumor visualization and uptake of the labeled antibody exhibited the versatility of the click-chemistry strategy.

Nanoparticle ligand presentation for targeting solid tumors

Among the many scientific advances to come from the study of nanoscience, the development of ligand-targeted nanoparticles to eliminate solid tumors is predicted to have a major impact on human health. There are many reports describing novel designs and testing of targeted nanoparticles to treat cancer. While the principles of the technology are well demonstrated in controlled lab experiments, there are still many hurdles to overcome for the science to mature into truly efficacious targeted nanoparticles that join the arsenal of agents currently used to treat cancer in humans. One of these hurdles is overcoming unwanted biodistribution to the liver while maximizing delivery to the tumor. This almost certainly requires advances in both nanoparticle stealth technology and targeting. Currently, it continues to be a challenge to control the loading of ligands onto polyethylene glycol (PEG) to achieve maximal targeting. Nanoparticle cellular uptake and subcellular targeting of genes and siRNA also remain a challenge. This review examines the types of ligands that have been most often used to target nanoparticles to solid tumors. As the science matures over the coming decade, careful control over ligand presentation on nanoparticles of precise size, shape, and charge will likely play a major role in achieving success.

Radioimmunoimaging of liver metastases with PET using a 64Cu-labeled CEA antibody in transgenic mice

Purpose

Colorectal cancer is one of the most common forms of cancer, and the development of novel tools for detection and efficient treatment of metastases is needed. One promising approach is the use of radiolabeled antibodies for positron emission tomography (PET) imaging and radioimmunotherapy. Since carcinoembryonic antigen (CEA) is an important target in colorectal cancer, the CEA-specific M5A antibody has been extensively studied in subcutaneous xenograft models; however, the M5A antibody has not yet been tested in advanced models of liver metastases. The aim of this study was to investigate the ⁶⁴Cu-DOTA-labeled M5A antibody using PET in mice bearing CEA-positive liver metastases.

Procedures

Mice were injected intrasplenically with CEA-positive C15A.3 or CEA-negative MC38 cells and underwent micro-computed tomography (micro-CT) to monitor the development of liver metastases. After metastases were detected, PET/MRI scans were performed with ⁶⁴Cu-DOTA-labeled M5A antibodies. H&E staining, immunohistology, and autoradiography were performed to confirm the micro-CT and PET/MRI findings.

Results

PET/MRI showed that M5A uptake was highest in CEA-positive metastases. The %ID/cm³ (16.5%±6.3%) was significantly increased compared to healthy liver tissue (8.6%±0.9%) and to CEA-negative metastases (5.5%±0.6%). The tumor-to-liver ratio of C15A.3 metastases and healthy liver tissue was 1.9±0.7. Autoradiography and immunostaining confirmed the micro-CT and PET/MRI findings.

Conclusion

We show here that the ⁶⁴Cu-DOTA-labeled M5A antibody imaged by PET can detect CEA positive liver metastases and is therefore a potential tool for staging cancer, stratifying the patients or radioimmunotherapy.

Noninvasive Imaging of PSMA in prostate tumors with (89)Zr-Labeled huJ591 engineered antibody fragments: the faster alternatives

Engineered antibody fragments offer faster delivery with retained tumor specificity and rapid clearance from nontumor tissues. Here, we demonstrate that positron emission tomography (PET) based detection of prostate specific membrane antigen (PSMA) in prostatic tumor models using engineered bivalent antibodies built on single chain fragments (scFv) derived from the intact antibody, huJ591, offers similar tumor delineating properties but with the advantage of rapid targeting and imaging. (89)Zr-radiolabeled huJ591 scFv (dimeric scFv-CH3; (89)Zr-Mb) and cysteine diabodies (dimeric scFv; (89)Zr-Cys-Db) demonstrated internalization and similar Kds (∼2 nM) compared to (89)Zr-huJ591 in PSMA(+) cells. Tissue distribution assays established the specificities of both (89)Zr-Mb and (89)Zr-Cys-Db for PSMA(+) xenografts (6.2 ± 2.5% ID/g and 10.2 ± 3.4% ID/g at 12 h p.i. respectively), while minimal accumulation in PSMA(-) tumors was observed. From the PET images, (89)Zr-Mb and (89)Zr-Cys-Db exhibited faster blood clearance than the parent huJ591 while tumor-to-muscle ratios for all probes show comparable values across all time points. Ex vivo autoradiography and histology assessed the distribution of the probes within the tumor. Imaging PSMA-expressing prostate tumors with smaller antibody fragments offers rapid tumor accumulation and accelerated clearance; hence, shortened wait periods between tracer administration and high-contrast tumor imaging and lower dose-related toxicity are potentially realized.

Anti-CEA antibody fragments labeled with [(18)F]AlF for PET imaging of CEA-expressing tumors

A facile and rapid method to label peptides with (18)F based on chelation of [(18)F]AlF has been developed recently. Since this method requires heating to 100 °C, it cannot be used to label heat-sensitive proteins. Here, we used a two-step procedure to prepare (18)F-labeled heat-labile proteins using the [(18)F]AlF method based on hot maleimide conjugation. 1,4,7-Triazacyclononae-1,4-diacetate (NODA) containing a methyl phenylacetic acid group (MPA) functionalized with N-(2-aminoethyl)maleimide (EM) was used as a ligand which was labeled with [(18)F]AlF and then conjugated to the humanized anti-CEA antibody derivatives hMN-14-Fab', hMN-14-(scFv)2 (diabody), and a Dock-and-Lock engineered dimeric fragment hMN-14 Fab-AD2 at room temperature. The in vivo tumor targeting characteristics of the (18)F-labeled antibody derivatives were determined by PET imaging of mice with s.c. xenografts. NODA-MPAEM was radiolabeled with [(18)F]AlF at a specific activity of 29-39 MBq/nmol and a labeling efficiency of 94 ± 2%. The labeling efficiencies of the maleimide conjugation ranged from 70% to 77%, resulting in [(18)F]AlF-labeled hMN14-Fab', hMN14-Fab-AD2, or hMN14-diabody with a specific activity of 15-17 MBq/nmol. The radiolabeled conjugates were purified by gel filtration. For biodistribution and microPET imaging, antibody fragments were injected intravenously into BALB/c nude mice with s.c. CEA-expressing LS174T xenografts (right flank) and CEA-negative SK-RC-52 xenografts (left flank). All [(18)F]AlF-labeled conjugates showed specific uptake in the LS174T xenografts with a maximal tumor uptake of 4.73% ID/g at 4 h after injection. Uptake in CEA-negative SK-RC-52 xenografts was significantly lower. Tumors were clearly visualized on microPET images. Using a [(18)F]AlF-labeled maleimide functionalized chelator, antibody fragments could be radiofluorinated within 4 h at high specific activity. Here, we translated this method to preclinical PET imaging studies and showed feasibility of [(18)F]AlF-fluorinated hMN-14-Fab', [(18)F]AlF-hMN-14-Fab-AD2, and [(18)F]AlF-hMN-14-diabody for microPET imaging of CEA-expressing colonic cancer.

Engineered antibody fragments for immuno-PET imaging of endogenous CD8+ T cells in vivo

The noninvasive detection and quantification of CD8(+) T cells in vivo are important for both the detection and staging of CD8(+) lymphomas and for the monitoring of successful cancer immunotherapies, such as adoptive cell transfer and antibody-based immunotherapeutics. Here, antibody fragments are constructed to target murine CD8 to obtain rapid, high-contrast immuno-positron emission tomography (immuno-PET) images for the detection of CD8 expression in vivo. The variable regions of two anti-murine CD8-depleting antibodies (clones 2.43 and YTS169.4.2.1) were sequenced and reformatted into minibody (Mb) fragments (scFv-CH3). After production and purification, the Mbs retained their antigen specificity and bound primary CD8(+) T cells from the thymus, spleen, lymph nodes, and peripheral blood. Importantly, engineering of the parental antibodies into Mbs abolished the ability to deplete CD8(+) T cells in vivo. The Mbs were subsequently conjugated to S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid for (64)Cu radiolabeling. The radiotracers were injected i.v. into antigen-positive, antigen-negative, immunodeficient, antigen-blocked, and antigen-depleted mice to evaluate specificity of uptake in lymphoid tissues by immuno-PET imaging and ex vivo biodistribution. Both (64)Cu-radiolabeled Mbs produced high-contrast immuno-PET images 4 h postinjection and showed specific uptake in the spleen and lymph nodes of antigen-positive mice.

Positron emission tomography imaging of endometrial cancer using engineered anti-EMP2 antibody fragments

Purpose

As imaging of the cell surface tetraspan protein epithelial membrane protein-2 (EMP2) expression in malignant tumors may provide important prognostic and predictive diagnostic information, the goal of this study is to determine if antibody fragments to EMP2 may be useful for imaging EMP2 positive tumors.

Procedures

The normal tissue distribution of EMP2 protein expression was evaluated by immunohistochemistry and found to be discretely expressed in both mouse and human tissues. To detect EMP2 in tumors, a recombinant human anti-EMP2 minibody (scFv-hinge-C_H3 dimer; 80 kDa) was designed to recognize a common epitope in mice and humans and characterized. In human tumor cell lines, the antibody binding induced EMP2 internalization and degradation, prompting the need for a residualizing imaging strategy. Following conjugation to DOTA (1,4,7,10-tetraazacyclododecane-N,N′,N′,N′″-tetraacetic acid), the minibody was radiolabeled with ⁶⁴Cu (t_1/2 = 12.7 h) and evaluated in mice as a positron emission tomography (PET) imaging agent for human EMP2-expressing endometrial tumor xenografts.

Results

The residualizing agent, ⁶⁴Cu-DOTA anti-EMP2 minibody, achieved high uptake in endometrial cancer xenografts overexpressing EMP2 (10.2 ± 2.6, percent injected dose per gram (%ID/g) ± SD) with moderate uptake in wild-type HEC1A tumors (6.0 ± 0.1). In both cases, precise tumor delineation was observed from the PET images. In contrast, low uptake was observed with anti-EMP2 minibodies in EMP2-negative tumors (1.9 ± 0.5).

Conclusions

This new immune-PET agent may be useful for preclinical assessment of anti-EMP2 targeting in vivo. It may also have value for imaging of tumor localization and therapeutic response in patients with EMP2-positive malignancies.

Aptamer imaging with Cu-64 labeled AS1411: preliminary assessment in lung cancer

INTRODUCTION

AS1411 is a 26-base guanine-rich oligonucleotide aptamer shown binding to surface nucleolin, a protein over-expressed in multiple cancer cells, thus AS1411 labeled with a PET isotope can be explored as a potential diagnostic imaging agent. Our objective was to perform preliminary biological characterization of (64)Cu-labeled AS1411 in vitro and in vivo.

METHODS

Four chelators (DOTA, CB-TE2A, DOTA-Bn and NOTA-Bn) were selected to label AS1411 with Cu-64. 185kBq (5μCi) of each tracer was incubated in each well with H460 cells at 37°C for 1, 3, 6, 12, 24 and 48h, respectively (n=4). For microPET/CT imaging, 7.4MBq (200μCi) of AS1411 labeled with either (64)Cu-DOTA or (64)Cu-CB-TE2A was I.V. injected and multiple scans were obtained at 1, 3, 6 and 24h post injection. Afterward in vivo biodistribution studies were performed.

RESULTS

Percent uptake of (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was significantly higher than that of (64)Cu-DOTA-Bn-AS1411 and (64)Cu-NOTA-Bn-AS1411. About 90% of uptake for (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was internalized into cells within 3h and the internalization process was completed before 24h. Both tracers demonstrated reasonable in vivo stability and high binding affinity to the cells. MicroPET imaging with (64)Cu-CB-TE2A-AS1411 showed clear tumor uptake at both legs from 1 to 24h post injection, whereas both tumors were undetectable for up to 24h with (64)Cu-DOTA-AS1411. In addition, (64)Cu-CB-TE2A-AS1411 had faster in vivo pharmacokinetics than (64)Cu-DOTA-AS1411 with lower liver uptake and higher tumor to background contrast.

CONCLUSION

CB-TE2A is a preferred chelator with higher tumor-to-background ratio, lower liver uptake and faster clearance than DOTA. Aptamer imaging with (64)Cu-CB-TE2A-AS1411 may be feasible for detecting lung cancer, if an appropriate chelator can be identified and further validation can be performed with a known control oligonucleotide. It may also be used as a companion diagnostic imaging agent for AS1411 in the treatment of cancer.

Applying PET to broaden the diagnostic utility of the clinically validated CA19.9 serum biomarker for oncology

Despite their considerable advantages, many circulating biomarkers have well-documented limitations. One prominent shortcoming in oncology is a high frequency of false-positive indications for malignant disease in upfront diagnosis. Because one common cause of false positivism is biomarker production from benign disorders in unrelated host tissues, we hypothesized that probing the sites of biomarker secretion with an imaging tool could be a broadly useful strategy to deconvolute the meaning of foreboding but inconclusive circulating biomarker levels.

METHODS

In preparation to address this hypothesis clinically, we developed (89)Zr-5B1, a fully human, antibody-based radiotracer targeting tumor-associated CA19.9 in the preclinical setting.

RESULTS

(89)Zr-5B1 localized to multiple tumor models representing diseases with undetectable and supraphysiologic serum CA19.9 levels. Among these, (89)Zr-5B1 detected orthotopic models of pancreatic ductal adenocarcinoma, an elusive cancer for which the serum assay is measured in humans but with limited specificity in part because of the frequency of CA19.9 secretion from benign hepatic pathologies.

CONCLUSION

In this report, a general strategy to supplement some of the shortcomings of otherwise highly useful circulating biomarkers with immunoPET is described. To expedite the clinical validation of this model, a human monoclonal antibody to CA19.9 (a highly visible but partially flawed serum biomarker for several cancers) was radiolabeled and evaluated, and the compelling preclinical evidence suggests that the radiotracer may enhance the fidelity of diagnosis and staging of pancreatic ductal adenocarcinoma, a notoriously occult cancer.

The ubiquitous DOTA and its derivatives: the impact of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid on biomedical imaging

Over the last twenty-five years 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) has made a significant impact on the field of diagnostic imaging. DOTA is not the only metal chelate in use in medical diagnostics, but it is the only one to significantly impact on all of the major imaging modalities Magnetic Resonance (MR), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Fluorescence imaging. This crossover of modalities has been possible due to the versatility of DOTA firstly, to complex a variety of metal ions and secondly, the ease with which it can be modified for different disease states. This has driven research over the last two decades into the chemistry of DOTA and the modification of the substituent pendant arms of this macrocycle to create functional, targeted and dual-modal imaging agents. The primary use of DOTA has been with the lanthanide series of metals, gadolinium for MRI, europium and terbium for fluorescence and neodymium for near infra-red imaging. There are now many research groups dedicated to the use of lanthanides with DOTA although other chelates such as DTPA and NOTA are being increasingly employed. The ease with which DOTA can be conjugated to peptides has given rise to targeted imaging agents seen in the PET, SPECT and radiotherapy fields. These modalities use a variety of radiometals that complex with DOTA, e.g.(64)Cu and (68)Ga which are used in clinical PET scans, (111)In, and (90)Y for SPECT and radiotherapy. In this article, we will demonstrate the remarkable versatility of DOTA, how it has crossed the imaging modality boundaries and how it has been successfully transferred into the clinic.

Positron emission tomography of 64Cu-DOTA-Rituximab in a transgenic mouse model expressing human CD20 for clinical translation to image NHL

PURPOSE

This study aims to evaluate (64)Cu-DOTA-rituximab (PETRIT) in a preclinical transgenic mouse model expressing human CD20 for potential clinical translation.

PROCEDURES

(64)Cu was chelated to DOTA-rituximab. Multiple radiolabeling, quality assurance, and imaging experiments were performed. The human CD20 antigen was expressed in B cells of transgenic mice (CD20TM). The mice groups studied were: (a) control (nude mice, n = 3) that received 7.4 MBq/dose, (b) with pre-dose (CD20TM, n = 6) received 2 mg/kg pre-dose of cold rituximab prior to PETRIT of 7.4 MBq/dose, and (c) without pre-dose (CD20TM, n = 6) PETRIT alone received 7.4 MBq/dose. Small animal PET was used to image mice at various time points (0, 1, 2, 4, 24, 48, and 72 h). The OLINDA/EXM software was used to determine the human equivalent dose for individual organs.

RESULTS

PETRIT was obtained with a specific activity of 545 ± 38.91 MBq/nmole, radiochemical purity >95%, and immunoreactivity >75%. At 24 h, spleenic uptake of PETRIT%ID/g (mean ± STD) with and without pre-dose was 1.76 ± 0.43% and 16.5 ± 0.45%, respectively (P value = 0.01). Liver uptake with and without pre-dose was 0.41 ± 0.51% and 0.52 ± 0.17% (P value = 0.86), respectively. The human equivalents of highest dose organs with and without pre-dose are osteogenic cells at 30.8 ± 0.4 μSv/MBq and the spleen at 99 ± 4 μSv/MBq, respectively.

CONCLUSIONS

PET imaging with PETRIT in huCD20 transgenic mice provided human dosimetry data for eventual applications in non-Hodgkins lymphoma patients.

Tumor-targeting multifunctional micelles for imaging and chemotherapy of advanced bladder cancer

AIM

This work aimed to determine if the treatment outcomes of bladder cancer could be improved by targeting micelles that are decorated with bladder cancer-specific ligands on the surface and loaded with the chemotherapeutic drug paclitaxel.

MATERIALS & METHODS

Targeting efficacy and specificity was determined with cell lines. An in vivo targeting and anti-tumor efficacy study was conducted in mice carrying patient-derived xenografts.

RESULTS & DISCUSSION

Targeting micelles were more efficient than nontargeting micelles in delivering the drug load into bladder cancer cells both in vitro and in vivo (p < 0.05). The micelle formulation of paclitaxel was less toxic than free paclitaxel in Cremophor(®) (Sigma, MO, USA) and allowed administration of three-times the maximum tolerated dose without increasing the toxicity. Targeting micelles were more effective than the nontargeting micelles in controlling cancer growth (p = 0.0002) and prolonging overall survival (p = 0.002).

CONCLUSION

Targeting micelles loaded with paclitaxel offer strong potential for clinical applications in treating bladder cancer.

Odyssey of a cancer nanoparticle: from injection site to site of action

No chemotherapeutic drug can be effective until it is delivered to its target site. Nano-sized drug carriers are designed to transport therapeutic or diagnostic materials from the point of administration to the drug's site of action. This task requires the nanoparticle carrying the drug to complete a journey from the injection site to the site of action. The journey begins with the injection of the drug carrier into the bloodstream and continues through stages of circulation, extravasation, accumulation, distribution, endocytosis, endosomal escape, intracellular localization and-finally-action. Effective nanoparticle design should consider all of these stages to maximize drug delivery to the entire tumor and effectiveness of the treatment.

(111)In- and (203)Pb-Labeled Cyclic RGD Peptide Conjugate as an α(v)β(3) Integrin-Binding Radiotracer

Methodology for site-specific modification and chelate conjugation of a cyclic RGD (cRGD) peptide for the preparation of a radiotracer molecular imaging agent suitable for detecting α(v)β(3) integrin is described. The method involves functionalizing the peptide with an aldehyde moiety and conjugation to a 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid (DOTA) derivative that possesses an aldehyde reactive aminooxy group. The binding assay of the (111)In-labeled peptide conjugate with α(v)β(3) integrin showed 60% bound when four equivalents of the integrin was added, a reasonable binding affinity for a mono-valent modified RGD peptide.

A critical review of lipid-based nanoparticles for taxane delivery

Nano-based delivery systems have attracted a great deal of attention in the past two decades as a strategy to overcome the low therapeutic index of conventional anticancer drugs and delivery barriers in solid tumors. Myriads of preclinical studies have been focused on developing nano-based formulations to effectively deliver taxanes, one of the most important and most prescribed anticancer drug types in the clinic. Given the hydrophobic property of taxanes, lipid-based NPs, serve as a viable alternative delivery system. This critical review will provide an overview and perspective of the advancement of lipid-based nanoparticles for taxane delivery. Currently available formulations of taxanes and their drawbacks as well as criteria for idea taxane delivery system will be discussed.