PARP-Targeted Auger Therapy in p53 Mutant Colon Cancer Xenograft Mouse Models

Despite Auger electrons being highly appealing due to their short-range and high linear energy transfer to surrounding tissues, the progress in the field has been limited due to the challenge in delivering a therapeutic dose within the close proximity of cancer cell's DNA. Here, we demonstrate that the PARP inhibitor ¹²³I-MAPi is a viable agent for the systemic administration and treatment of p53 mutant cancers. Significantly, minimal off-site toxicity was observed in mice administered with up to 74 MBq of ¹²⁷I-PARPi. Taken together, these results lay the foundation for future clinical evaluation and broader preclinical investigations. By harnessing the scaffold of the PARP inhibitor Olaparib, we were able to deliver therapeutic levels of Auger radiation to the site of human colorectal cancer xenograft tumors after systemic administration. In-depth toxicity studies analyzed blood chemistry levels and markers associated with specific organ toxicity. Finally, p53^+/+ and p53^-/- human colorectal cancer cell lines were evaluated for the ability of ¹²³I-MAPi to induce tumor growth delay. Toxicity studies demonstrate that both ¹²³I-MAPi and its stable isotopologue, ¹²⁷I-PARPi, have no significant off-site toxicity when administered systemically. Analysis following ¹²³I-MAPi treatment confirmed its ability to induce DNA damage at the site of xenograft tumors when administered systemically. Finally, we demonstrate that ¹²³I-MAPi generates a therapeutic response in p53^-/-, but not p53^+/+, subcutaneous xenograft tumors in mouse models. Taken together, these results represent the first example of a PARP Auger theranostic agent capable of delivering a therapeutic dose to xenograft human colorectal cancer tumors upon systemic administration without causing significant toxicity to surrounding mouse organs. Moreover, it suggests that a PARP Auger theranostic can act as a targeted therapeutic for cancers with mutated p53 pathways. This landmark goal paves the way for clinical evaluation of ¹²³I-MAPi for pan cancer therapeutics.

PARP1: A Potential Molecular Marker to Identify Cancer During Colposcopy Procedures

Despite efforts in prevention, cervical cancer still presents with a high worldwide incidence and remains a great problem in public health, especially in low-income countries. Screening programs, such as colposcopy with Papanicolaou testing, have greatly improved mortality rates. However, the agents currently used to delineate those lesions (topical application of acetic acid or Lugol iodine) lack specificity and sometimes can lead to unnecessary biopsies or even cervical excisions. A tool to enable in vivo histology to quickly and quantitatively distinguish between tumor, dysplastic tissue, and healthy tissue would be of great clinical interest. Methods: Here, we describe the use of PARPi-FL, a fluorescent inhibitor of poly[adenosine diphosphate-ribose]polymerase 1 (PARP1), which is a nuclear enzyme that is overexpressed in cancer when compared with the normal surrounding tissues. We exploit its use as an optical imaging agent to specifically target PARP1 expression, which was demonstrated to be higher in cervical cancer than the normal surrounding tissue. Results: After topical application of PARPi-FL on freshly excised cone biopsy samples, the nuclei of tumor cells emitted a specific fluorescent signal that could be visualized using a handheld fluorescence confocal microscope. Conclusion: This approach has the potential to improve in vivo identification of tumor cells during colposcopy examination, allowing a rapid, noninvasive, and accurate histopathologic assessment.

Radiomic and radiogenomic modeling for radiotherapy: strategies, pitfalls, and challenges

The power of predictive modeling for radiotherapy outcomes has historically been limited by an inability to adequately capture patient-specific variabilities; however, next-generation platforms together with imaging technologies and powerful bioinformatic tools have facilitated strategies and provided optimism. Integrating clinical, biological, imaging, and treatment-specific data for more accurate prediction of tumor control probabilities or risk of radiation-induced side effects are high-dimensional problems whose solutions could have widespread benefits to a diverse patient population-we discuss technical approaches toward this objective. Increasing interest in the above is specifically reflected by the emergence of two nascent fields, which are distinct but complementary: radiogenomics, which broadly seeks to integrate biological risk factors together with treatment and diagnostic information to generate individualized patient risk profiles, and radiomics, which further leverages large-scale imaging correlates and extracted features for the same purpose. We review classical analytical and data-driven approaches for outcomes prediction that serve as antecedents to both radiomic and radiogenomic strategies. Discussion then focuses on uses of conventional and deep machine learning in radiomics. We further consider promising strategies for the harmonization of high-dimensional, heterogeneous multiomics datasets (panomics) and techniques for nonparametric validation of best-fit models. Strategies to overcome common pitfalls that are unique to data-intensive radiomics are also discussed.

[18F]PARPi Imaging Is Not Affected by HPV Status In Vitro

Background

Human papillomavirus- (HPV-) associated oropharyngeal squamous cell carcinomas (OPSCCs) are clinically and pathologically distinct from HPV-negative tumors. Here, we explore whether HPV affects functional biomarkers, including γH2AX, RAD51, and PARP1. Moreover, the role of [18F]PARPi as a broadly applicable imaging tool for head and neck carcinomas is investigated.

Methods

HPV-positive and HPV-negative cell lines were used to evaluate the γH2AX, RAD51, and PARP1 expression with immunoblotting and immunofluorescence. Effects of external beam ionizing radiation were investigated in vitro, and survival was investigated via colony-formation assay. [18F]PARPi uptake experiments were performed on HPV-negative and HPV-positive cell lines to quantify PARP1 expression. PARP1 IHC and γH2AX foci were quantified using patient-derived oropharyngeal tumor specimens.

Results

Differences in DNA repair were detected, showing higher RAD51 and γH2AX expression in HPV-positive cell lines. Clonogenic assays confirm HPV-positive cell lines to be significantly more radiosensitive. PARP1 expression levels were similar, irrespective of HPV status. Consequently, [18F]PARPi uptake assays demonstrated that this tracer is internalized in cell lines independently from their HPV status.

Conclusion

The HPV status, often used clinically to stratify patients, did not affect PARP1 levels, suggesting that PARP imaging can be performed in both HPV-positive and HPV-negative patients. This study confirms that the PET imaging agent [18F]PARPi could serve as a general clinical tool for oropharyngeal cancer patients.

Rapid detection of SARS-CoV-2 using a radiolabeled antibody

PURPOSE

Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus 2019 disease (COVID-19), poses a serious risk to humanity and represents a huge challenge for healthcare systems worldwide. Since the early days of the COVID-19 pandemic, it has been evident that adequate testing is an essential step in limiting and controlling the spread of SARS-CoV-2. Here, we present an accurate, inexpensive, scalable, portable, and rapid detection kit to directly detect SARS-CoV-2 in biological samples that could even be translated for population testing. We have demonstrated that our method can reliably identify viral load and could be used to reach those fractions of the population with limited access to more sophisticated and expensive tests.

PROCEDURES

The proposed SARS-CoV-2 detection kit is based on the combination of a SARS-CoV-2-targeted antibody (CR3022) that targets spike protein S1 domain on the viral surface. This antibody was radiolabeled with a long-lived isotope (Iodine-125) to allow us to detect bound antibody in samples with SARS-CoV-2. We used a series of in vitro assays to determine sensitivity and specificity and facilitate automation of the testing kit. Bound antibody was extracted from saliva samples via a centrifugation step and a semi-permeable membrane. Our kit was further validated using SARS-CoV-2 virions.

RESULTS

We were able to accomplish radiosynthesis of [¹²⁵I]I-CR3022 reliably without loss of binding. The SARS-CoV-2-sensing antibody was shown to maintain its spike S1 affinity and to bind to as low as 2.5-5 ng of spike protein. We then used beads-bound spike S1 to develop a separation kit which proved to be both easy to use and inexpensive. The kit made it possible to extract bound antibody from the saliva-like sample. We were able to validate the separation kit using intact SARS-CoV-2 virions and showed that our kit can detect a viral concentration as low as 19,700 PFU/mL (~ 9.22%TBF) and as high as 1,970,000 PFU/mL (45.04%TBF).

CONCLUSION

Here we report the development and validation of a SARS-CoV-2 detection system based on the combination of a specific radiolabeled antibody and a separation membrane. We demonstrate our system to be comparable to other SARS-CoV-2 detection kits already approved by the FDA and believe this technology could be easily deployed to countries with limited resources for the diagnosis of COVID-19. Furthermore, workflows could be easily adapted to target other antigens and therefore other types of diseases.

The anti-malarial drug atovaquone potentiates platinum-mediated cancer cell death by increasing oxidative stress

Platinum chemotherapies are highly effective cytotoxic agents but often induce resistance when used as monotherapies. Combinatorial strategies limit this risk and provide effective treatment options for many cancers. Here, we repurpose atovaquone (ATQ), a well-tolerated & FDA-approved anti-malarial agent by demonstrating that it potentiates cancer cell death of a subset of platinums. We show that ATQ in combination with carboplatin or cisplatin induces striking and repeatable concentration- and time-dependent cell death sensitization in vitro across a variety of cancer cell lines. ATQ induces mitochondrial reactive oxygen species (mROS), depleting intracellular glutathione (GSH) pools in a concentration-dependent manner. The superoxide dismutase mimetic MnTBAP rescues ATQ-induced mROS production and pre-loading cells with the GSH prodrug N-acetyl cysteine (NAC) abrogates the sensitization. Together, these findings implicate ATQ-induced oxidative stress as key mediator of the sensitizing effect. At physiologically achievable concentrations, ATQ and carboplatin furthermore synergistically delay the growth of three-dimensional avascular spheroids. Clinically, ATQ is a safe and specific inhibitor of the electron transport chain (ETC) and is concurrently being repurposed as a candidate tumor hypoxia modifier. Together, these findings suggest that ATQ is deserving of further study as a candidate platinum sensitizing agent.

Ingestion and effects of polystyrene nanoparticles in the silkworm Bombyx mori

Information on the occurrence and effects of nanoplastics in ecosystems worldwide currently represent one of the main challenges from the ecotoxicological point of view. This is particularly true for terrestrial environments, in which nanoplastics are released directly by human activities or derive from the fragmentation of larger plastic items incorrectly disposed. Since insects can represent a target for these emerging contaminants in land-based community, the aim of this study was the evaluation of ingestion of 0.5 μm polystyrene nanoplastics and their effects in silkworm (Bombyx mori) larvae, a useful and well-studied insect model. The ingestion of nanoplastics, the possible infiltration in the tissues and organ accumulation were checked by confocal microscopy, while we evaluated the effects due to the administered nanoplastics through a multi-tier approach based on insect development and behaviour assessment, as endpoints at organism level, and the measurements of some biochemical responses associated with the imbalance of the redox status (superoxide dismutase, catalase, glutathione s-transferase, reactive oxygen species evaluation, lipid peroxidation) to investigate the cellular and molecular effects. We observed the presence of microplastics in the intestinal lumen, but also inside the larvae, specifically into the midgut epithelium, the Malpighian tubules and in the haemocytes. The behavioural observations revealed a significant (p < 0.05) increase of erratic movements and chemotaxis defects, potentially reflecting negative indirect effects on B. mori survival and fitness, while neither effect on insect development nor redox status imbalance were measured, with the exception of the significant (p < 0.05) inhibition of superoxide dismutase activity.

Preclinical and first-in-human-brain-cancer applications of [18F]poly (ADP-ribose) polymerase inhibitor PET/MR

Background

We report preclinical and first-in-human-brain-cancer data using a targeted poly (ADP-ribose) polymerase 1 (PARP1) binding PET tracer, [¹⁸F]PARPi, as a diagnostic tool to differentiate between brain cancers and treatment-related changes.

Methods

We applied a glioma model in p53-deficient nestin/tv-a mice, which were injected with [¹⁸F]PARPi and then sacrificed 1 h post-injection for brain examination. We also prospectively enrolled patients with brain cancers to undergo dynamic [¹⁸F]PARPi acquisition on a dedicated positron emission tomography/magnetic resonance (PET/MR) scanner. Lesion diagnosis was established by pathology when available or by Response Assessment in Neuro-Oncology (RANO) or RANO-BM response criteria. Resected tissue also underwent PARPi-FL staining and PARP1 immunohistochemistry.

Results

In a preclinical mouse model, we illustrated that [¹⁸F]PARPi crossed the blood–brain barrier and specifically bound to PARP1 overexpressed in cancer cell nuclei. In humans, we demonstrated high [¹⁸F]PARPi uptake on PET/MR in active brain cancers and low uptake in treatment-related changes independent of blood–brain barrier disruption. Immunohistochemistry results confirmed higher PARP1 expression in cancerous than in noncancerous tissue. Specificity was also corroborated by blocking fluorescent tracer uptake with an excess unlabeled PARP inhibitor in patient cancer biospecimen.

Conclusions

Although larger studies are necessary to confirm and further explore this tracer, we describe the promising performance of [¹⁸F]PARPi as a diagnostic tool to evaluate patients with brain cancers and possible treatment-related changes.

Optical Imaging Modalities: Principles and Applications in Preclinical Research and Clinical Settings

With the ability to noninvasively image and monitor molecular processes within tumors, molecular imaging represents a fundamental tool for cancer scientists. In the current review, we describe emergent optical technologies for molecular imaging. We aim to provide the reader with an overview of the fundamental principles on which each imaging strategy is based, to introduce established and future applications, and to provide a rationale for selecting optical technologies for molecular imaging depending on disease location, biology, and anatomy. To accelerate clinical translation of imaging techniques, we also describe examples of practical applications in patients. Elevating these techniques into standard-of-care tools will transform patient stratification, disease monitoring, and response evaluation.

Improved radiosynthesis of 123I-MAPi, an auger theranostic agent

PURPOSE

123I-MAPi, a novel PARP1-targeted Auger radiotherapeutic has shown promising results in pre-clinical glioma model. Currently, 123I-MAPi is synthesized using multistep synthesis that results in modest yields and low molar activities (MA) that limits the ability to translate this technology for human studies where high doses are administered. Therefore, new methods are needed to synthesize 123I-MAPi in high activity yields (AY) and improved MA to facilitate clinical translation and multicenter trials.

MATERIALS AND METHODS

123I-MAPi was prepared in a single step via 123I-iododetannylation of the corresponding tributylstannane precursor. In vitro internalization assay, subcellular fractionation and confocal microscopy where used to evaluate the performance of 123I-MAPi in a small cell lung cancer model.

RESULTS

123I-MAPi was synthesized in a single step from the corresponding stannane precursor in AY of 45 ± 2% and MA of 11.8 ± 4.8 GBq µmol-1. In vitro in LX22 cells showed rapid internalization (5 min) with accumulation found predominantly in the membrane, nucleus and chromatin of the cell as determined by subcellular fractionation.

CONCLUSIONS

Here, we have developed an improved radiosynthesis of 123I-MAPi, an Auger theranostic agent. This process was achieved using a single step, 123I-iododestannylation reaction from the corresponding stannane precursor in good AY and MA. 123I-MAPi was evaluated in vitro in a small cell lung cancer model with high PARP expression, rapid internalization and high nuclear uptake shown.

Fluorescence labeling of a NaV1.7-targeted peptide for near-infrared nerve visualization

BACKGROUND

Accidental peripheral nerve injury during surgical intervention results in a broad spectrum of potentially debilitating side effects. Tissue distortion and poor visibility can significantly increase the risk of nerve injury with long-lasting consequences for the patient. We developed and characterized Hs1a-FL, a fluorescent near-infrared molecule for nerve visualization in the operating theater with the aim of helping physicians to visualize nerves during surgery. Hs1a was derived from the venom of the Chinese bird spider, Haplopelma schmidti, and conjugated to Cy7.5 dye. Hs1a-FL was injected intravenously in mice, and harvested nerves were imaged microscopically and with epifluorescence.

RESULTS

Hs1a-FL showed specific and stable binding to the sodium channel NaV1.7, present on the surface of human and mouse nerves. Hs1a-FL allowed epifluorescence visualization of sciatic mouse nerves with favorable nerve-to-muscle contrast.

CONCLUSIONS

Fluorescent NaV1.7-targeted tracers have the potential to be adopted clinically for the intraoperative visualization of peripheral nerves during surgery, providing guidance for the surgeon and potentially improving the standard of care.

Validation of the use of a fluorescent PARP1 inhibitor for the detection of oral, oropharyngeal and oesophageal epithelial cancers

For oral, oropharyngeal and oesophageal cancer, the early detection of tumours and of residual tumour after surgery are prognostic factors of recurrence rates and patient survival. Here, we report the validation, in animal models and a human, of the use of a previously described fluorescently labelled small-molecule inhibitor of the DNA repair enzyme poly(ADP-ribose) polymerase 1 (PARP1) for the detection of cancers of the oral cavity, pharynx and oesophagus. We show that the fluorescent contrast agent can be used to quantify the expression levels of PARP1 and to detect oral, oropharyngeal and oesophageal tumours in mice, pigs and fresh human biospecimens when delivered topically or intravenously. The fluorescent PARP1 inhibitor can also detect oral carcinoma in a patient when applied as a mouthwash, and discriminate between fresh biopsied samples of the oral tumour and the surgical resection margin with more than 95% sensitivity and specificity. The PARP1 inhibitor could serve as the basis of a rapid and sensitive assay for the early detection and for the surgical-margin assessment of epithelial cancers of the upper intestinal tract.

Targeted Brain Tumor Radiotherapy Using an Auger Emitter

PURPOSE

Glioblastoma multiforme is a highly aggressive form of brain cancer whose location, tendency to infiltrate healthy surrounding tissue, and heterogeneity significantly limit survival, with scant progress having been made in recent decades.

EXPERIMENTAL DESIGN

¹²³I-MAPi (Iodine-123 Meitner-Auger PARP1 inhibitor) is a precise therapeutic tool composed of a PARP1 inhibitor radiolabeled with an Auger- and gamma-emitting iodine isotope. Here, the PARP inhibitor, which binds to the DNA repair enzyme PARP1, specifically targets cancer cells, sparing healthy tissue, and carries a radioactive payload within reach of the cancer cells' DNA.

RESULTS

The high relative biological efficacy of Auger electrons within their short range of action is leveraged to inflict DNA damage and cell death with high precision. The gamma ray emission of ¹²³I-MAPi allows for the imaging of tumor progression and therapy response, and for patient dosimetry calculation. Here we demonstrated the efficacy and specificity of this small-molecule radiotheranostic in a complex preclinical model. In vitro and in vivo studies demonstrate high tumor uptake and a prolonged survival in mice treated with ¹²³I-MAPi when compared with vehicle controls. Different methods of drug delivery were investigated to develop this technology for clinical applications, including convection enhanced delivery and intrathecal injection.

CONCLUSIONS

Taken together, these results represent the first full characterization of an Auger-emitting PARP inhibitor which demonstrate a survival benefit in mouse models of GBM and confirm the high potential of ¹²³I-MAPi for clinical translation.

Smartphone epifluorescence microscopy for cellular imaging of fresh tissue in low-resource settings

Disease diagnosis in low-resource settings can be challenging due to the lack of equipment and trained personnel required for histologic analysis. In this paper, we have developed a smartphone-based epifluorescence microscope (SeFM) for imaging fresh tissues at sub-cellular resolution. SeFM provides similar resolution and field of view (FOV) as those used during histologic analysis. The SeFM device achieved the lateral resolution of 0.57 µm and provided microscopy images over a sample area larger than 500 µm. The material cost was low, approximately $3,000. Preliminary images of human pancreatic tumor specimens clearly visualized cellular details. Quantitative analysis showed that using an excess dose of a chemotherapy drug significantly reduced the tumor-specific fluorescence signal, confirming the specificity of the drug and the detection potential of SeFM.

TOPKi-NBD: a fluorescent small molecule for tumor imaging

PURPOSE

OTS514 is a highly specific inhibitor targeting lymphokine-activated killer T cell-originated protein kinase (TOPK). A fluorescently labeled TOPK inhibitor could be used for tumor delineation or intraoperative imaging, potentially improving patient care.

METHODS

Fluorescently labeled OTS514 was obtained by conjugating the fluorescent small molecule NBD to the TOPK inhibitor. HCT116 colorectal cancer cells were used to generate tumors in NSG mice for in vivo studies. Images were generated in vitro using confocal microscopy and ex vivo using an IVIS Spectrum.

RESULTS

OTS514 was successfully conjugated to a fluorescent sensor and validated in vitro, in vivo, and ex vivo. The labeling reaction led to TOPKi-NBD with 67% yield and 97% purity after purification. We were able to test binding properties of TOPKi-NBD to its target, TOPK, and compared them to the precursor inhibitor. EC₅₀s showed similar target affinities for TOPKi-NBD and the unlabeled OTS514. TOPKi-NBD showed specific tumor uptake after systemic administration and was microscopically detectable inside cancer cells ex vivo. Blocking controls performed with an excess of the unlabeled OTS514 confirmed specificity of the compound. Overall, the results represent a first step toward the development of a class of TOPK-specific fluorescent inhibitors for in vivo imaging and tumor delineation.

CONCLUSIONS

TOPK has the potential to be a new molecular target for cancer-specific imaging in a large variety of tumors. This could lead to broad applications in vitro and in vivo.

Fluorescence Imaging of Peripheral Nerves by a Nav1.7-Targeted Inhibitor Cystine Knot Peptide

Twenty million Americans suffer from peripheral nerve injury caused by trauma and medical disorders, resulting in a broad spectrum of potentially debilitating side effects. In one out of four cases, patients identify surgery as the root cause of their nerve injury. Particularly during tumor resections or after traumatic injuries, tissue distortion and poor visibility can challenge a surgeon's ability to precisely locate and preserve peripheral nerves. Intuitively, surgical outcomes would improve tremendously if nerves could be highlighted using an exogeneous contrast agent. In clinical practice, however, the current standard of care-visual examination and palpation-remains unchanged. To address this unmet clinical need, we explored the expression of voltage-gated sodium channel Na_v1.7 as an intraoperative marker for the peripheral nervous system. We show that expression of Na_v1.7 is high in peripheral nerves harvested from both human and mouse tissue. We further show that modification of a Na_v1.7-selective peptide, Hsp1a, can serve as a targeted vector for delivering a fluorescent sensor to the peripheral nervous system. Ex vivo, we observe a high signal-to-noise ratio for fluorescently labeled Hsp1a in both histologically prepared and fresh tissue. Using a surgical fluorescent microscope, we show in a simulated clinical scenario that the identification of mouse sciatic nerves is possible, suggesting that fluorescently labeled Hsp1a tracers could be used to discriminate nerves from their surrounding tissues in a routine clinical setting.

Source apportionment to support air quality planning: Strengths and weaknesses of existing approaches

Information on the origin of pollution constitutes an essential step of air quality management as it helps identifying measures to control air pollution. In this work, we review the most widely used source-apportionment methods for air quality management. Using theoretical and real-case datasets we study the differences among these methods and explain why they result in very different conclusions to support air quality planning. These differences are a consequence of the intrinsic assumptions that underpin the different methodologies and determine/limit their range of applicability. We show that ignoring their underlying assumptions is a risk for efficient/successful air quality management as these methods are sometimes used beyond their scope and range of applicability. The simplest approach based on increments (incremental approach) is often not suitable to support air quality planning. Contributions obtained through mass-transfer methods (receptor models or tagging approaches built in air quality models) are appropriate to support planning but only for specific pollutants. Impacts obtained via "brute-force" methods are the best suited but it is important to assess carefully their application range to make sure they reproduce correctly the prevailing chemical regimes.

An 89Zr-HDL PET Tracer Monitors Response to a CSF1R Inhibitor

The immune function within the tumor microenvironment has become a prominent therapeutic target, with tumor-associated macrophages (TAMs) playing a critical role in immune suppression. We propose an ⁸⁹Zr-labeled high-density lipoprotein (⁸⁹Zr-HDL) nanotracer as a means of monitoring response to immunotherapy. Methods: Female MMTV-PyMT mice were treated with pexidartinib, a colony-stimulating factor 1 receptor (CSF1R) inhibitor, to reduce TAM density. The accumulation of ⁸⁹Zr-HDL within the tumor was assessed using PET/CT imaging and autoradiography, whereas TAM burden was determined using immunofluorescence. Results: A significant reduction in ⁸⁹Zr-HDL accumulation was observed in PET/CT images, with 2.9% ± 0.3% and 3.7% ± 0.2% injected dose/g for the pexidartinib- and vehicle-treated mice, respectively. This reduction was corroborated ex vivo and correlated with decreased TAM density. Conclusion: These results support the potential use of ⁸⁹Zr-HDL nanoparticles as a PET tracer to quickly monitor the response to CSF1R inhibitors and other therapeutic strategies targeting TAMs.

[18F]FE-OTS964: a Small Molecule Targeting TOPK for In Vivo PET Imaging in a Glioblastoma Xenograft Model

PURPOSE

Lymphokine-activated killer T cell-originated protein kinase (TOPK) is a fairly new cancer biomarker with great potential for clinical applications. The labeling of a TOPK inhibitor with F-18 can be exploited for positron emission tomography (PET) imaging allowing more accurate patient identification, stratification, and disease monitoring.

PROCEDURES

[18F]FE-OTS964 was produced starting from OTS964, a preclinical drug which specifically binds to TOPK, and using a two-step procedure with [18F]fluoroethyl p-toluenesulfonate as a prosthetic group. Tumors were generated in NSG mice by subcutaneous injection of U87 glioblastoma cells. Animals were injected with [18F]FE-OTS964 and PET imaging and ex vivo biodistribution analysis was carried out.

RESULTS

[18F]FE-OTS964 was successfully synthesized and validated in vivo as a PET imaging agent. The labeling reaction led to 15.1 ± 7.5 % radiochemical yield, 99 % radiochemical purity, and high specific activity. Chemical identity of the radiotracer was confirmed by co-elution on an analytical HPLC with a cold-labeled standard. In vivo PET imaging and biodistribution analysis showed tumor uptake of 3.06 ± 0.30 %ID/cc, which was reduced in animals co-injected with excess blocking dose of OTS541 to 1.40 ± 0.42 %ID/cc.

CONCLUSIONS

[18F]FE-OTS964 is the first TOPK inhibitor for imaging purposes and may prove useful in the continued investigation of the pharmacology of TOPK inhibitors and the biology of TOPK in cancer patients.

Nanoemulsion-Based Delivery of Fluorescent PARP Inhibitors in Mouse Models of Small Cell Lung Cancer

The preclinical potential of many diagnostic and therapeutic small molecules is limited by their rapid washout kinetics and consequently modest pharmacological performances. In several cases, these could be improved by loading the small molecules into nanoparticulates, improving blood half-life, in vivo uptake and overall pharmacodynamics. In this study, we report a nanoemulsion (NE) encapsulated form of PARPi-FL. As a proof of concept, we used PARPi-FL, which is a fluorescently labeled sensor for olaparib, a FDA-approved small molecule inhibitor of the nuclear enzyme poly(ADP-ribose)polymerase 1 (PARP1). Encapsulated PARPi-FL showed increased blood half-life, and delineated subcutaneous xenografts of small cell lung cancer (SCLC), a fast-progressing disease where efficient treatment options remain an unmet clinical need. Our study demonstrates an effective method for expanding the circulation time of a fluorescent PARP inhibitor, highlighting the pharmacokinetic benefits of nanoemulsions as nanocarriers and confirming the value of PARPi-FL as an imaging agent targeting PARP1 in small cell lung cancer.

T-LAK cell-originated protein kinase (TOPK): an emerging target for cancer-specific therapeutics

'Targeted' or 'biological' cancer treatments rely on differential gene expression between normal tissue and cancer, and genetic changes that render tumour cells especially sensitive to the agent being applied. Problems exist with the application of many agents as a result of damage to local tissues, tumour evolution and treatment resistance, or through systemic toxicity. Hence, there is a therapeutic need to uncover specific clinical targets which enhance the efficacy of cancer treatment whilst minimising the risk to healthy tissues. T-LAK cell-originated protein kinase (TOPK) is a MAPKK-like kinase which plays a role in cell cycle regulation and mitotic progression. As a consequence, TOPK expression is minimal in differentiated cells, although its overexpression is a pathophysiological feature of many tumours. Hence, TOPK has garnered interest as a cancer-specific biomarker and biochemical target with the potential to enhance cancer therapy whilst causing minimal harm to normal tissues. Small molecule inhibitors of TOPK have produced encouraging results as a stand-alone treatment in vitro and in vivo, and are expected to advance into clinical trials in the near future. In this review, we present the current literature pertaining to TOPK as a potential clinical target and describe the progress made in uncovering its role in tumour development. Firstly, we describe the functional role of TOPK as a pro-oncogenic kinase, followed by a discussion of its potential as a target for the treatment of cancers with high-TOPK expression. Next, we provide an overview of the current preclinical progress in TOPK inhibitor discovery and development, with respect to future adaptation for clinical use.

CDK1 inhibition sensitizes normal cells to DNA damage in a cell cycle dependent manner

Cyclin-dependent kinase 1 (CDK1) orchestrates the transition from the G2 phase into mitosis and as cancer cells often display enhanced CDK1 activity, it has been proposed as a tumor specific anti-cancer target. Here we show that the effects of CDK1 inhibition are not restricted to tumor cells but can also reduce viability in non-cancer cells and sensitize them to radiation in a cell cycle dependent manner. Radiosensitization by the specific CDK1 inhibitor, RO-3306, was determined by colony formation assays in three tumor lines (HeLa, T24, SQ20B) and three non-cancer lines (HFL1, MRC-5, RPE). Initial results showed that CDK1 inhibition radiosensitized tumor cells, but did not sensitize normal fibroblasts and epithelial cells in colony formation assays despite effective inhibition of CDK1 signaling. Further investigation showed that normal cells were less sensitive to CDK1 inhibition because they remained predominantly in G1 for a prolonged period when plated in colony formation assays. In contrast, inhibiting CDK1 a day after plating, when the cells were going through G2/M phase, reduced their clonogenic survival both with and without radiation. Our finding that inhibition of CDK1 can damage normal cells in a cell cycle dependent manner indicates that targeting CDK1 in cancer patients may lead to toxicity in normal proliferating cells. Furthermore, our finding that cell cycle progression becomes easily stalled in non-cancer cells under normal culture conditions has general implications for testing anti-cancer agents in these cells.

TOPK modulates tumour-specific radiosensitivity and correlates with recurrence after prostate radiotherapy

BACKGROUND

Tumour-specific radiosensitising treatments may enhance the efficacy of radiotherapy without exacerbating side effects. In this study we determined the radiation response following depletion or inhibition of TOPK, a mitogen-activated protein kinase kinase family Ser/Thr protein kinase that is upregulated in many cancers.

METHODS

Radiation response was studied in a wide range of cancer cell lines and normal cells using colony formation assays. The effect on cell cycle progression was assessed and the relationship between TOPK expression and therapeutic efficacy was studied in a cohort of 128 prostate cancer patients treated with radical radiotherapy.

RESULTS

TOPK knockdown did not alter radiation response in normal tissues, but significantly enhanced radiosensitivity in cancer cells. This result was recapitulated in TOPK knockout cells and with the TOPK inhibitor, OTS964. TOPK depletion altered the G1/S transition and G2/M arrest in response to radiation. Furthermore, TOPK depletion increased chromosomal aberrations, multinucleation and apoptotic cell death after irradiation. These results suggest a possible role for TOPK in the radiation-induced DNA damage checkpoints. These findings have clinical relevance, as elevated TOPK protein expression was associated with poorer clinical outcomes in prostate cancer patients treated with radical radiotherapy.

CONCLUSIONS

This study demonstrates that TOPK disruption may cause tumour-specific radiosensitisation in multiple different tumour types.

The anti-malarial atovaquone increases radiosensitivity by alleviating tumour hypoxia

Tumour hypoxia renders cancer cells resistant to cancer therapy, resulting in markedly worse clinical outcomes. To find clinical candidate compounds that reduce hypoxia in tumours, we conduct a high-throughput screen for oxygen consumption rate (OCR) reduction and identify a number of drugs with this property. For this study we focus on the anti-malarial, atovaquone. Atovaquone rapidly decreases the OCR by more than 80% in a wide range of cancer cell lines at pharmacological concentrations. In addition, atovaquone eradicates hypoxia in FaDu, HCT116 and H1299 spheroids. Similarly, it reduces hypoxia in FaDu and HCT116 xenografts in nude mice, and causes a significant tumour growth delay when combined with radiation. Atovaquone is a ubiquinone analogue, and decreases the OCR by inhibiting mitochondrial complex III. We are now undertaking clinical studies to assess whether atovaquone reduces tumour hypoxia in patients, thereby increasing the efficacy of radiotherapy.

A role for human homologous recombination factors in suppressing microhomology-mediated end joining

DNA double-strand breaks (DSBs) are toxic lesions, which if improperly repaired can result in cell death or genomic instability. DSB repair is usually facilitated by the classical non-homologous end joining (C-NHEJ), or homologous recombination (HR) pathways. However, a mutagenic alternative NHEJ pathway, microhomology-mediated end joining (MMEJ), can also be deployed. While MMEJ is suppressed by C-NHEJ, the relationship between HR and MMEJ is less clear. Here, we describe a role for HR genes in suppressing MMEJ in human cells. By monitoring DSB mis-repair using a sensitive HPRT assay, we found that depletion of HR proteins, including BRCA2, BRCA1 or RPA, resulted in a distinct mutational signature associated with significant increases in break-induced mutation frequencies, deletion lengths and the annealing of short regions of microhomology (2-6 bp) across the break-site. This signature was dependent on CtIP, MRE11, POLQ and PARP, and thus indicative of MMEJ. In contrast to CtIP or MRE11, depletion of BRCA1 resulted in increased partial resection and MMEJ, thus revealing a functional distinction between these early acting HR factors. Together these findings indicate that HR factors suppress mutagenic MMEJ following DSB resection.

The Benefits of High Relaxivity for Brain Tumor Imaging: Results of a Multicenter Intraindividual Crossover Comparison of Gadobenate Dimeglumine with Gadoterate Meglumine (The BENEFIT Study)

BACKGROUND AND PURPOSE

Gadobenate dimeglumine (MultiHance) has higher r1 relaxivity than gadoterate meglumine (Dotarem) which may permit the use of lower doses for MR imaging applications. Our aim was to compare 0.1- and 0.05-mmol/kg body weight gadobenate with 0.1-mmol/kg body weight gadoterate for MR imaging assessment of brain tumors.

MATERIALS AND METHODS

We performed crossover, intraindividual comparison of 0.1-mmol/kg gadobenate with 0.1-mmol/kg gadoterate (Arm 1) and 0.05-mmol/kg gadobenate with 0.1-mmol/kg gadoterate (Arm 2). Adult patients with suspected or known brain tumors were randomized to Arm 1 (70 patients) or Arm 2 (107 patients) and underwent 2 identical examinations at 1.5 T. The agents were injected in randomized-sequence order, and the 2 examinations were separated by 2-14 days. MR imaging scanners, imaging sequences (T1-weighted spin-echo and T1-weighted high-resolution gradient-echo), and acquisition timing were identical for the 2 examinations. Three blinded readers evaluated images for diagnostic information (degree of definition of lesion extent, lesion border delineation, visualization of lesion internal morphology, contrast enhancement) and quantitatively for percentage lesion enhancement and lesion-to-background ratio. Safety assessments were performed.

RESULTS

In Arm 1, a highly significant superiority (P < .002) of 0.1-mmol/kg gadobenate was demonstrated by all readers for all end points. In Arm 2, no significant differences (P > .1) were observed for any reader and any end point, with the exception of percentage enhancement for reader 2 (P < .05) in favor of 0.05-mmol/kg gadobenate. Study agent-related adverse events were reported by 2/169 (1.2%) patients after gadobenate and by 5/175 (2.9%) patients after gadoterate.

CONCLUSIONS

Significantly superior morphologic information and contrast enhancement are demonstrated on brain MR imaging with 0.1-mmol/kg gadobenate compared with 0.1-mmol/kg gadoterate. No meaningful differences were recorded between 0.05-mmol/kg gadobenate and 0.1-mmol/kg gadoterate.

Compensatory biliary and urinary excretion of gadobenate ion after administration of gadobenate dimeglumine (MultiHance(®)) in cases of impaired hepatic or renal function: a mechanism that may aid in the prevention of nephrogenic systemic fibrosis?

Objective:

To determine whether increased elimination of gadobenate ion via the hepatobiliary pathway might compensate for reduced/absent elimination via the urinary pathway in the event of compromised renal function, as a possible protective mechanism against nephrogenic systemic fibrosis (NSF).

Methods:

15 male Crl:CD^® R(SD)Br rats (Charles River Italia, Como, Italy) randomized to three treatment groups: (1) animals with occluded bile ducts, (2) animals with occluded renal vessels and (3) control animals, each received 0.25 mmol kg⁻¹ of bodyweight of gadobenate dimeglumine (MultiHance^®; Bracco Imaging SpA, Milan, Italy). Urine and bile were collected from 0−30, 30−60, 60−120, 120−240 and 240−480 min after gadobenate dimeglumine administration prior to exsanguination. Determinations of gadobenate ion in blood, bile and urine were performed by high-performance liquid chromatography. Gadolinium (Gd³⁺) levels in excised liver and kidneys were determined by X-ray fluorescence.

Results:

The recovery of gadobenate ion in the urine of rats with bile duct occlusion was significantly higher than that in the urine of normal rats (89.1 ± 4.2% vs 60.6 ± 2.8%; p < 0.0001). Conversely, mean recovery in the bile of rats with renal vessel occlusion was significantly higher than that in the bile of normal rats (96.16 ± 0.55% vs 33.5 ± 4.7%; p < 0.0001). Gadobenate ion was not quantifiable in any group 8 h post-injection.

Conclusion:

Compensatory elimination may be an effective means to overcome compromised renal or hepatobiliary elimination.

Advances in knowledge:

The absence of NSF in at-risk patients administered with gadobenate dimeglumine may in part reflect greater Gd³⁺ elimination via the hepatobiliary route.

Are there differences between macrocyclic gadolinium contrast agents for brain tumor imaging? Results of a multicenter intraindividual crossover comparison of gadobutrol with gadoteridol (the TRUTH study)

BACKGROUND AND PURPOSE

Gadobutrol (Gadavist) and gadoteridol (ProHance) have similar macrocyclic molecular structures, but gadobutrol is formulated at a 2-fold higher (1 mol/L versus 0.5 mol/L) concentration. We sought to determine whether this difference impacts morphologic contrast-enhanced MR imaging.

MATERIALS AND METHODS

Two hundred twenty-nine adult patients with suspected or known brain tumors underwent two 1.5T MR imaging examinations with gadoteridol or gadobutrol administered in randomized order at a dose of 0.1 mmol/kg of body weight. Imaging sequences and T1 postinjection timing were identical for both examinations. Three blinded readers evaluated images qualitatively and quantitatively for lesion detection and for accuracy in characterization of histologically confirmed brain tumors. Data were analyzed by using the Wilcoxon signed rank test, the McNemar test, and a mixed model.

RESULTS

Two hundred nine patients successfully completed both examinations. No reader noted a significant qualitative or quantitative difference in lesion enhancement, extent, delineation, or internal morphology (P values = .69-1.00). One hundred thirty-nine patients had at least 1 histologically confirmed brain lesion. Two readers found no difference in the detection of patients with lesions (133/139 versus 135/139, P = .317; 137/139 versus 136/139, P = .564), while 1 reader found minimal differences in favor of gadoteridol (136/139 versus 132/139, P = .046). Similar findings were noted for the number of lesions detected and characterization of tumors (malignant/benign). Three-reader agreement for characterization was similar for gadobutrol (66.4% [κ = 0.43]) versus gadoteridol (70.3% [κ = 0.45]). There were no significant differences in the incidence of adverse events (P = .199).

CONCLUSIONS

Gadoteridol and gadobutrol at 0.1 mmol/kg of body weight provide similar information for visualization and diagnosis of brain lesions. The 2-fold higher gadolinium concentration of gadobutrol provides no benefit for routine morphologic imaging.

Use of the γ-H2AX assay to investigate DNA repair dynamics following multiple radiation exposures

Radiation therapy is one of the most common and effective strategies used to treat cancer. The irradiation is usually performed with a fractionated scheme, where the dose required to kill tumour cells is given in several sessions, spaced by specific time intervals, to allow healthy tissue recovery. In this work, we examined the DNA repair dynamics of cells exposed to radiation delivered in fractions, by assessing the response of histone-2AX (H2AX) phosphorylation (γ-H2AX), a marker of DNA double strand breaks. γ-H2AX foci induction and disappearance were monitored following split dose irradiation experiments in which time interval between exposure and dose were varied. Experimental data have been coupled to an analytical theoretical model, in order to quantify key parameters involved in the foci induction process. Induction of γ-H2AX foci was found to be affected by the initial radiation exposure with a smaller number of foci induced by subsequent exposures. This was compared to chromatin relaxation and cell survival. The time needed for full recovery of γ-H2AX foci induction was quantified (12 hours) and the 1:1 relationship between radiation induced DNA double strand breaks and foci numbers was critically assessed in the multiple irradiation scenarios.

Use of the γ-H2AX assay to investigate DNA repair dynamics following multiple radiation exposures

Radiation therapy is one of the most common and effective strategies used to treat cancer. The irradiation is usually performed with a fractionated scheme, where the dose required to kill tumour cells is given in several sessions, spaced by specific time intervals, to allow healthy tissue recovery. In this work, we examined the DNA repair dynamics of cells exposed to radiation delivered in fractions, by assessing the response of histone-2AX (H2AX) phosphorylation (γ-H2AX), a marker of DNA double strand breaks. γ-H2AX foci induction and disappearance were monitored following split dose irradiation experiments in which time interval between exposure and dose were varied. Experimental data have been coupled to an analytical theoretical model, in order to quantify key parameters involved in the foci induction process. Induction of γ-H2AX foci was found to be affected by the initial radiation exposure with a smaller number of foci induced by subsequent exposures. This was compared to chromatin relaxation and cell survival. The time needed for full recovery of γ-H2AX foci induction was quantified (12 hours) and the 1:1 relationship between radiation induced DNA double strand breaks and foci numbers was critically assessed in the multiple irradiation scenarios.

Serological survey of leptospiral infection in kennelled dogs in Italy

Two hundred and forty-five dogs were examined serologically for the presence of antibodies against different serovars of Leptospira interrogans. The dogs belonged to five different groups: group 1 was composed of clinically healthy pet dogs referred for a regular veterinary check-up visit or for vaccination; group 2 was composed of stray dogs; and groups 3, 4 and 5 were composed of dogs maintained in three different kennels which had varying standards of hygiene. Seventy-two out of the 245 dogs examined were seropositive for leptospirosis. In group 1, there were 3-4 per cent seropositive dogs; in group 2, 30.3 per cent; in group 3, 13.8 per cent; in group 4, 38.6 per cent; and in group 5, 49.2 per cent. This study demonstrates that leptospiral infection is common in dogs housed in kennels, despite most of them being vaccinated, and that crowding of animals into unsanitary quarters is associated with a high prevalence of infection. The most common infecting serovars found were bratislava and grippotyphosa, confirming recent observations that demonstrate a significant change in the epidemiology of canine leptospirosis.

Magnetic resonance imaging of metastatic disease to the brain with gadobenate dimeglumine

Seventy-four patients with one to eight proven intraaxial brain metastases received a total cumulative dose of 0.2 mmol/kg bodyweight gadobenate dimeglumine, administered as sequential injections of 0.05, 0.05 and 0.1 m mol/kg over a 20-min period. MR imaging was performed before the first administration (T2- and T1-weighted sequences) and after each injection of contrast agent (T1-weighted sequences only). Quantitative assessment of images revealed significant (P <0.01) dose-related increases in lesion-to-brain (L/B) ratio and percent enhancement of lesion signal intensity. Qualitative assessment by two independent, blinded assessors revealed additional lesions in 22%, 25% and 38% (assessor 1) and 29%, 32% and 34% (assessor 2) of patients after each cumulative dose when compared with combined T1- and T2-weighted pre-contrast images. Significantly more lesions (P < 0.01) were noted by both assessors after the first injection and by one assessor after each subsequent injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted in 12%, 16% and 28% of patients by assessor 1 following each dose and in 24%, 27% and 30% of patients by assessor 2. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced MRI. For patients with one lesion observed after an initial dose of 0.05 mmol/kg, additional lesions were noted by assessors 1 and 2 in 9.1% and 11.8% of patients, respectively, after a cumulative dose of 0.1 mmol/kg and in a further 9.1% and 5.9% of patients, respectively, after a cumulative dose of 0.2 mmol/kg. No safety concerns were apparent.

Gadobenate dimeglumine-enhanced magnetic resonance imaging of intracranial metastases: effect of dose on lesion detection and delineation

Seventy-four patients with one to eight proven intraaxial metastatic lesions to the brain received a total gadobenate dimeglumine dose of 0.3 mmol/kg of body weight, administered as three sequential bolus injections of 0.1 mmol/kg, at 10-minute intervals over a 20-minute period. Quantitative and qualitative assessments of efficacy were performed after each injection and a full evaluation of safety was conducted. Cumulative dosing produced significant (P < 0.01) dose-related increases in lesion-to-brain (L/B) ratio and lesion signal intensity (SI) enhancement. Two independent, blinded assessors noted additional lesions, compared to unenhanced images in 31% and 33%, 49% and 42%, and 50% and 48% of patients after each cumulative dose, respectively. Significantly more lesions were noted after the first injection, compared to unenhanced images (P = 0.002 and P < 0.001; assessors 1 and 2, respectively), and after a second injection, compared to the first (P < 0.001 and P = 0.039; assessors 1 and 2, respectively). Neither assessor noted significantly more lesions after the third injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted by assessors 1 and 2 for 27% and 26%, 48% and 35%, and 42% and 41% of patients, respectively, following each injection. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced magnetic resonance imaging (MRI). For patients with one lesion observed after 0.1 mmol/kg of gadobenate dimeglumine, additional lesions were noted for 24% and 17% of patients (assessors 1 and 2, respectively) following a second 0.1 mmol/kg injection. Only assessor 2 noted additional lesions following the third 0.1 mmol/kg injection. The findings of on-site investigators concurred with those of the two off-site assessors. No safety concerns were apparent.

Safety assessment of gadobenate dimeglumine (MultiHance): extended clinical experience from phase I studies to post-marketing surveillance

Clinical trials completed by September 2000 on gadobenate dimeglumine (Gd-BOPTA; MultiHance) included 2540 adult and pediatric subjects that were administered this agent. For adult patient volunteers, the overall incidence of adverse events (AEs) was 19.8%, although marked study- and indication-related differences were apparent. Events potentially related to Gd-BOPTA administration were reported for 15.1% of adult patients. The vast majority of AEs were non-serious, mild, transient, and self-resolving. Headache, injection site reaction, nausea, taste perversion, and vasodilation were the most common AEs, reported with a frequency of between 1.0% and 2.6%. Serious AEs potentially related to Gd-BOPTA were reported for five (0.2%) patients overall. Controlled studies revealed no differences between Gd-BOPTA and other gadolinium chelates or placebo in the incidence and type of AEs. Similarly, no differences with respect to adult patients and/or comparator were noted in studies on pediatric subjects and subjects with renal or liver insufficiency. Post-marketing surveillance of approximately 100000 doses revealed an overall AE incidence of < 0.03% with serious AEs reported for < 0.005% of patients.

Evaluation of the accuracy of gadobenate dimeglumine-enhanced MR imaging in the detection and characterization of focal liver lesions

OBJECTIVE

We evaluated the extent to which hepatic lesion characterization and detection is improved by using gadobenate dimeglumine for enhancement of MR images.

MATERIALS AND METHODS

Eighty-six patients were imaged before gadobenate dimeglumine administration, immediately after the 2 mL/sec bolus administration of a 0.05 mmol/kg dose (dynamic imaging), and at 60-120 min after the IV infusion at 10 mL/min of a further 0.05 nmol/kg dose (delayed imaging). The accuracy for lesion characterization was assessed for a total of 107 lesions. Sensitivity for lesion detection was assessed for a total of 149 lesions detected on either intra-operative sonography, iodized oil CT, CT during arterial portography, or follow-up contrast-enhanced CT as the gold standard.

RESULTS

The accuracy in differentiating benign from malignant liver lesions increased from 75% and 82% (the findings of two observers) on unenhanced images alone, to 89% and 80% on dynamic images alone (p<0.001, p = 0.8), and to 90.7% when combining the unenhanced and dynamic image sets (p<0.001, p = 0.023). Delayed images did not further improve accuracy (90% and 91%; p = 0.002, p< 0.05). A similar trend was apparent in terms of accuracy for specific diagnosis: values ranged from 49% and 62% on unenhanced images alone, to 76% and 70% on combined unenhanced and dynamic images (p<0.001, p = 0.06), and to 75% and 70% on inclusion of delayed images (p<0.001, p = 0.12). The sensitivity for lesion detection increased from 77% and 81% on unenhanced images alone, to 87% and 85% on combined unenhanced and dynamic images (p = 0.001, p = 0.267), and to 92% and 89% when all images were considered (p<0.001, p = 0.01).

CONCLUSION

Contrast-enhanced dynamic MR imaging with gadobenate dimeglumine significantly increases sensitivity and accuracy over unenhanced imaging for the characterization of focal hepatic lesions, and delayed MR imaging contributes to the improved detection of lesions.

Focal liver lesions: evaluation of the efficacy of gadobenate dimeglumine in MR imaging--a multicenter phase III clinical study

PURPOSE

To evaluate gadobenate dimeglumine (Gd-BOPTA) for dynamic and delayed magnetic resonance (MR) imaging of focal liver lesions.

MATERIALS AND METHODS

In 126 of 214 patients, MR imaging was performed before Gd-BOPTA administration, immediately after bolus administration of a 0.05- mmol/kg dose of Gd-BOPTA, and 60-120 minutes after an additional intravenously infused 0.05-mmol/kg dose. In 88 patients, imaging was performed before and 60-120 minutes after a single, intravenously infused 0.1-mmol/kg dose. T1- and T2-weighted spin-echo and T1-weighted gradient-echo images were acquired. On-site and blinded off-site reviewers prospectively evaluated all images. Intraoperative ultrasonography, computed tomography (CT) during arterial portography, and/or CT with iodized oil served as the reference methods in 110 patients.

RESULTS

Significantly more lesions were detected on combined pre- and postcontrast images compared with on precontrast images alone (P <. 01). All reviewers reported a decreased mean size of the smallest detected lesion and improved lesion conspicuity on postcontrast images. All on-site reviewers and two off-site reviewers reported increased overall diagnostic confidence (P <.01). Additional lesion characterization information was provided on up to 109 (59%) of 184 delayed images and for up to 50 (42%) of 118 patients in whom dynamic images were assessed. Gd-BOPTA would have helped change the diagnosis in 99 (47%) of 209 cases and affected patient treatment in 408 (23%) of 209 cases.

CONCLUSION

Gd-BOPTA increases liver lesion conspicuity and detectability and aids in the characterization of lesions.

Hepatocellular carcinoma: correlation between gadobenate dimeglumine-enhanced MRI and pathologic findings

RATIONALE AND OBJECTIVES

To correlate the appearance of hepatocellular carcinoma on delayed (60 minutes) postcontrast T1-weighted gradient echo images with the mode of action of gadobenate dimeglumine (Gd-BOPTA) and the anatomic and pathologic characteristics of the lesions.

METHODS

A total of 34 patients with hepatocellular carcinoma and varying degrees of diffuse liver disease were studied. T2-weighted spin echo and T1-weighted spin echo and gradient echo images were acquired before and 60 minutes after the intravenous administration of 0.1 mmol/kg Gd-BOPTA. Qualitative and quantitative evaluations of the images were performed and correlated with histologic findings. The quantitative evaluation, performed on T1-weighted gradient echo images, looked at the percentage increase of liver enhancement after Gd-BOPTA administration, the lesion-to-liver contrast/noise (C/N) ratio before and after Gd-BOPTA administration, and the C/N variation after Gd-BOPTA administration. Qualitative assessment considered the morphologic features of the lesions as well as the visual variation of contrast before and after Gd-BOPTA administration. Finally, a histologic evaluation was made of the degree of differentiation of the lesions and of the presence of fatty metaplasia, necrosis, bile, or intratumoral peliosis.

RESULTS

Among the parameters affecting lesion identification were the extent of liver function, degree of vascularization, residual functionality of the tumor cells, and characteristics of the neoplastic tissue. Positive correlations (Spearman coefficients = 0.359 and 0.393, respectively) were observed precontrast between the degree of liver failure and the amount of contrast noise, and postcontrast between the amount of intralesional fatty metaplasia and the extent to which lesion conspicuity worsened after Gd-BOPTA administration. An inverse correlation (Spearman coefficient = -0.330) was observed between the degree of lesion differentiation and the visible appearance after Gd-BOPTA administration, with well-differentiated lesions tending toward worsened conspicuity postcontrast. A statistically significant difference (P = 0.001) was observed in the mean precontrast C/N ratio for lesions later showing unchanged conspicuity and worse conspicuity on postcontrast images, respectively. Marked variation (P = 0.019) was also observed between Child A and B cirrhotic patients for the degree of hepatic enhancement on postcontrast images.

CONCLUSIONS

The results suggest that liver parenchyma signal intensity is influenced by the extent to which liver function is compromised, that residual hepatocytic functionality permits Gd-BOPTA uptake by certain lesions and that this uptake might subsequently impair the observed C/N ratio on delayed images, and that the worsening of lesion conspicuity on postcontrast images is influenced also by high quantities of intralesional fatty metaplasia.

MultiHance in the dynamic phase of contrast enhancement: a pictorial assessment

The present article demonstrates pictorially the use of MultiHance (gadobenate dimeglumine, Gd-BOPTA) in dynamic magnetic resonance imaging and is aimed at ensuring that the product is not misconceived as solely a hepatobiliary agent for use in delayed, static magnetic resonance imaging for the improved detection of focal liver lesions. The enhancement patterns of three malignant (hepatocellular carcinoma, cholangiocarcinoma and metastasis) and three benign (hemangioma, focal nodular hyperplasia and adenoma) lesion types are demonstrated. Each was imaged during the dynamic phase of contrast enhancement immediately following the intravenous bolus administration of 0.05 mmol/kg MultiHance. The article demonstrates that the enhancement patterns observed for these relatively common lesions are similar to those reported in the literature after the intravenous bolus administration of conventional, non-specific 'extracellular fluid' contrast agents, and concludes by inferring that MultiHance behaves in the liver as a conventional gadolinium-based agent in the first minutes after administration.

MultiHance in the assessment of intracranial tumors: results of phase II clinical studies

PURPOSE

To assess preliminarily the efficacy of 0.1 and 0.2 mmol/kg doses of MultiHance for contrast-enhanced magnetic resonance imaging of brain tumors.

METHODS

Patients were imaged pre-dose using proton density (PD), T2-weighted and T1-weighted spin-echo sequences, and post-dose by repetition of the T1-weighted sequences at 0-15, 15-30, 30-45 and 45-60 min after the completion of MultiHance administration. Qualitative efficacy assessments of the image sets were performed by two blinded neuroradiologists in terms of the level of diagnostic information, the type of additional information provided by post-contrast images, the best post-contrast image set in terms of diagnostic information, the radiological utility of MultiHance, and the detectability of brain metastases. Extensive safety and tolerability controls were performed at 3 and 24 h post-contrast.

RESULTS

Additional diagnostic information was available on MultiHance-enhanced images as compared to pre-contrast images for 58.678.9% of patients administered 0.1 mmol/kg MultiHance and 66.1-74.6% of patients administered 0.2 mmol/kg MultiHance. Generally, the early (0 to 30 min) post-contrast image sets were preferred, with a clear superiority at the 15-30 min post-dose time point. In a subgroup of 21 patients with brain metastases, a higher number of lesions was detected in 55.6-66.7% of the cases with 0.1 mmol/kg MultiHance and in 58.3% of the cases with 0.2 mmol/kg MultiHance. Overall, the usefulness of MultiHance was judged as good to excellent in 91.4% of the patients at both dose levels. A total of 12 of 120 patients (10%) reported 15 transient, self-resolving adverse events of mild-to-moderate intensity. No difference between doses was observed in the incidence of adverse events and no laboratory, ECG or vital signs abnormalities were reported.

CONCLUSION

MultiHance is a safe and effective contrast agent for magnetic resonance assessment of brain tumors when administered intravenously at doses up to 0.2 mmol/kg.

Clinical utility and safety of MultiHance in magnetic resonance imaging of liver cancer: results of multicenter studies in Europe and the USA

MultiHance (gadobenate dimeglumine; Gd-BOPTA, Bracco SpA, Milano, Italy) is a novel gadolinium-based contrast agent which has recently been made commercially available in Europe for magnetic resonance imaging of the liver. It combines the properties of a conventional extracellular fluid contrast agent with those of a liver-specific agent and has been shown in numerous clinical trials to improve the impact of magnetic resonance imaging for both the detection and characterization of focal liver masses. The present article briefly summarizes the safety and efficacy results of Phase I, II and III clinical studies carried out in almost 800 patient and non-patient volunteers in both Europe and the USA.

Safety, tolerance, biodistribution, and MR imaging enhancement of the liver with gadobenate dimeglumine: results of clinical pharmacologic and pilot imaging studies in nonpatient and patient volunteers

PURPOSE

The purpose of this study was to assess safety, tolerance, biodistribution, and magnetic resonance (MR) imaging enhancement of the liver with gadobenate dimeglumine.

MATERIALS AND METHODS

Phase I single-blind studies were performed in 53 healthy volunteers, of whom 39 received gadobenate dimeglumine and 14 placebo. Another 106 patients with focal liver disease received gadobenate dimeglumine in parallel-group, open-label, phase II studies. The imaging potential of gadobenate dimeglumine was assessed in all 106 patients plus 11 healthy volunteers, whereas pharmacokinetics were determined for 42 healthy volunteers. Safety was assessed for all subjects enrolled in the study. Imaging protocols for healthy volunteers were similar to those for patients and comprised predose T2-weighted sequences and pre- and postinjection T1-weighted spin-echo and gradient-echo sequences.

RESULTS

Gadobenate dimeglumine was safe and well tolerated in healthy volunteers and patients, with pharmacokinetics described adequately as a distribution phase and an elimination phase. Most of the injected dose of gadobenate was excreted unchanged in urine within 24 hours, although a fraction corresponding to 0.6%-4.0% of the injected dose was eliminated with the bile and recovered in the feces. The gadobenate dimeglumine-enhanced signal intensity of liver parenchyma was dose-related and constant for 120 minutes. Gadobenate dimeglumine-enhanced MR imaging was superior to nonenhanced MR imaging in more than 50% of patient studies, with more lesions seen in 26%-38% of patients and smaller lesions in 21%-33% of patients. In general, image sets acquired 40-180 minutes after administration of a dose were preferred, whereas images acquired during the dynamic phase after administration were typical of those obtained with extracellular fluid contrast agents.

CONCLUSION

Gadobenate dimeglumine is a safe and efficacious MR imaging contrast agent suitable for both delayed and dynamic imaging of the liver.

Delayed MR imaging of hepatocellular carcinoma enhanced by gadobenate dimeglumine (Gd-BOPTA)

The purpose of this study was to determine the efficacy of gadobenate dimeglumine (Gd-BOPTA)-enhanced magnetic resonance (MR) imaging for evaluation of hepatocellular carcinoma HCC. MR images were obtained in 14 patients with 31 HCC nodules as a part of a phase III clinical trial. T1- and T2-weighted images were obtained before and after iv administration of 0.1 mmol/kg of Gd-BOPTA. Two blinded readers evaluated pre- and delayed postcontrast images separately for detection of tumor nodules. Quantitative measurements of signal-to-noise (SNR) and tumor/liver contrast-to-noise (CNR) ratios were also performed. A signal/intensity ratio was calculated. Tumor enhancement was correlated with histologic findings. Consensus agreement of precontrast T1- and T2-weighted images revealed 23/31 HCC nodules in 14 patients; postcontrast T1-weighted images demonstrated 24/31 HCC nodules in the same number of patients. Combining both pre- and postcontrast images, 27/31 lesions were detected. Four patients had four well-differentiated HCC nodules detected only on postcontrast images, while three well-differentiated lesions in two patients were only seen on precontrast images. Quantitative evaluation showed an SNR ratio increase in both liver parenchyma and HCC nodules, as well as a significant increase in the absolute CNR ratio on postcontrast T1-weighted gradient-recalled images (P < 0.05). Well-differentiated HCC lesions showed a greater enhancement than poorly differentiated HCC lesions.

Gadobenate dimeglumine (BOPTA) enhanced MR imaging: patterns of enhancement in normal liver and cirrhosis

To determine whether gadobenate dimeglumine (BOPTA) will adequately enhance cirrhotic liver parenchyma, and to document the enhancement patterns in cirrhosis, 14 cirrhotic and 20 non-cirrhotic patients were evaluated before and 60-120 minutes after gadolinium-BOPTA. Proof of liver cirrhosis was biopsy (6), surgical resection (3), and clinical follow-up (5). Enhancement effects were compared quantitatively by determining the liver signal-to-noise ratio (SNR) and signal enhancement in both populations. Qualitatively assessment of the liver enhancement was performed and classified as homogeneous or heterogeneous. Quantitative analysis: cirrhotic liver parenchyma presented a higher increase in SNR values, relative to non-cirrhotic liver parenchyma, on postcontrast images. Likewise the signal enhancement of cirrhotic liver parenchyma was superior to non-cirrhotic liver on T1-weighted SE images (P = .02) and in-phase GRE images (P < .001). There was no statistical difference on out-of-phase GRE images. Qualitative analysis: on T1-weighted SE postcontrast images, cirrhotic liver parenchyma showed a homogeneous enhancement in 7 patients and heterogeneous in 7. Whereas on GRE images, cirrhotic parenchyma showed heterogeneous enhancement in 9 patients and homogeneous in 5 patients. The heterogeneous enhancement was due to the presence of hypointense nodules in 7 patients and hyperintense nodules in 2 patients. In conclusion, our study has shown that the hepatobiliary contrast agent Gd-BOPTA is effective in the cirrhotic liver, demonstrating an increased liver enhancement compared with non-cirrhotic patients.