Biodistribution and pharmacokinetics of [89Zr]-anti-VEGF mAbs using PET in glioblastoma rat models

INTRODUCTION

Glioblastomas present intensive angiogenesis, thus anti-Vascular Endothelial Growth Factor (VEGF) antibodies (mAbs) have been proposed as promising therapies. However, the results of clinical trials reported moderate toxicity and limited effectiveness. This study evaluates the in vivo pharmacokinetics and biodistribution of these mAbs in a growing model of glioblastoma in rats using Positron Emission Tomography (PET).

MATERIAL

&Methods: mAbs were radiolabeled with zirconium-89. Four days after the model induction, animals were injected with 2.33 ± 1.3 MBq of [89Zr]-DFO-bevacizumab (n = 8) or 2.35 ± 0.26 MBq of [89Zr]-DFO-aflibercept (n = 6). PETs were performed at 0H, 48H, 168H, 240H, and 336H post-injection. Tumor induction was confirmed using [18F]-Fluorodeoxyglucose-PET and immunohistochemistry. Radiotracer uptake was estimated in all pre-defined Volumes-of-Interest.

RESULTS

Anti-VEGF mAbs showed 100 % Radiochemical-Purity. [89Zr]-DFO-bevacizumab showed a significantly higher bioavailability in whole-blood. A significant increase in the tumor uptake was detectable at 168H PET with [89Zr]-DFO-bevacizumab meanwhile with [89Zr]-DFO-aflibercept it was only detectable at 336H. [89Zr]-DFO-bevacizumab tumor uptake was significantly higher than that of [89Zr]-DFO-aflibercept in all the scans. Tumor induction was confirmed in all animal models.

CONCLUSION

MAbs detect VEGF-expression in glioblastoma models. Tumors were earlier targeted by Bevacizumab. The lower blood availability of aflibercept resulted in a lower tumor uptake than bevacizumab in all the scans.

Abstract 2020: Derived from a platform of innovative therapeutic molecular clusters (TMC), Ag5 is a highly potent and differentiated molecule that promises to be efficacious in hard-to-treat solid cancers

Bioenergetics of cancer results in an increased oxidation state and toxic by-products such as reactive oxygen species (ROS). ROS-mediated thiol oxidation of specific sensory proteins triggers the antioxidant response in order to decrease ROS levels and to trigger apoptosis when the oxidative stress cannot be overcome. This metabolic reprogramming has been implicated in refractory and relapsed disease and shaping of the microenvironment in solid cancers. Two redundant antioxidant pathways counteract ROS-mediated oxidation: the Glutathione (GSH)- and Thioredoxin (Trx)-dependent pathways. An effective way to treat tumors is to irreversibly block both pathways simultaneously. Experimental and therapeutic experience has shown that blocking only one is insufficient because one active pathway is enough for tumor survival, a reason why inhibitors of these pathways have shown limited success in the clinic. The TMC Ag5 irreversibly blocks both the GSH and Trx-dependent pathways, making it a highly active therapeutic agent. We present here for the first time a novel and innovative approach targeting tumor pathophysiology and increased REDOX state. Ag5 contains five silver atoms arranged in a specific conformation. Extensive biophysical and cell-based analyses demonstrate its catalytic activity and stability. Ag5 selectively kills high ROS cells by catalyzing the ROS-dependent oxidation of thiol groups of thioredoxins, peroxiredoxins and targets of the glutathione pathway in cells generating high ROS. As a consequence, Ag5 will preferentially kill cancer cells, but will spare normal cells due to their REDOX homeostasis. We characterized Ag5 efficacy with a range of in vitro assays and found it to be potent against a panel of established cancer cell lines derived from solid cancers with an IC50 in the low nM range. Ag5 sensitivity was correlated with high ROS levels, especially mitochondrial superoxide as measured by DHE or MitoSOX. The investigation of specific antioxidant target proteins (e.g. mitochondrial PRX3), and the use of agents that influence the REDOX state including DTT, BSO, NAC or erastin, supported the postulated mechanism of action. Furthermore, we were able to demonstrate concentration dependent cell cycle arrest, mitochondrial swelling, and induction of apoptosis by TUNEL staining, caspase activation and PARP cleavage. In addition, Ag5 was shown to be effective in reducing tumor growth in KRAS-mutated NSCLC and other relevant cell lines in vivo. Finally, Ag5 was safely administered without any clinical observations of toxicity in mouse and rat studies. In summary, Ag5 is a novel and innovative therapeutic candidate that was shown to be safe and effective in preclinical studies, and has the promise to address the unmet medical need in a range of solid cancers that currently have no effective treatment.

Citation Format: Vanesa Porto, Carmen Carneiro, Erea Borrajo, Blanca Dominguez, J M. Devida, L J. Giovanetti, F G. Requejo, G Barone, Angela Turrero, David Buceta, Arturo Lopez, Anxo Vidal, Martin Treder, Fernando Dominguez. Derived from a platform of innovative therapeutic molecular clusters (TMC), Ag5 is a highly potent and differentiated molecule that promises to be efficacious in hard-to-treat solid cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2020.

Elevated Autoantibodies in Subacute Human Spinal Cord Injury Are Naturally Occurring Antibodies

Spinal cord injury (SCI) results in long-term neurological and systemic consequences, including antibody-mediated autoimmunity, which has been related to impaired functional recovery. Here we show that autoantibodies that increase at the subacute phase of human SCI, 1 month after lesion, are already present in healthy subjects and directed against non-native proteins rarely present in the normal spinal cord. The increase of these autoantibodies is a fast phenomenon–their levels are already elevated before 5 days after lesion–characteristic of secondary immune responses, further supporting their origin as natural antibodies. By proteomics studies we have identified that the increased autoantibodies are directed against 16 different nervous system and systemic self-antigens related to changes known to occur after SCI, including alterations in neural cell cytoskeleton, metabolism and bone remodeling. Overall, in the context of previous studies, our results offer an explanation to why autoimmunity develops after SCI and identify novel targets involved in SCI pathology that warrant further investigation.

[Quality assessment in single-slice spiral brain CT examinations of patients with cerebrovascular accident]

OBJECTIVES

Our objective was to apply quality criteria proposed by the European Commission (EC) Guidelines to the brain CT examinations for cerebrovascular accident (CVA) diagnosis at single-slice spiral CT scanners from five different hospitals in the Madrid area.

MATERIAL AND METHODS

A sample of 100 brain CT examinations was collected and independently reviewed by five radiologists, to determine the degree of fulfilment of image quality criteria. Dose measurements were performed to estimate the values of the CT dose indexes (CTDIw, CTDIair), the dose length product (DLP), and the effective dose (E).

RESULTS

Once the McNemar test was applied to the sample, the number of observers' readings was reduced to three. The quality criteria were, in general, fulfilled, since mean values of image quality score between 80% and 92% were deduced, with variation coefficients per centre in the range of 0.07-0.1. However, both visualization criteria 1.1.2 and 1.1.3 exhibited similar ranges of fulfilment (38% - 94%). The good compliance with critical reproduction criteria in the study reflected the capability of these CT scanners to create images of adequate quality, although optimisation should be achieved in some of the centres. Concerning radiation exposure, the mean values per centre of the dose quantities were in the range of 42-64 mGy for the weighted CTDI (CTDIw), 423-744 mGy x cm for DLP, and 1.1-1.9 mSv for E.

CONCLUSIONS

The mean values at three centres were close to but above the reference value proposed by the EC Guidelines for CTDIw (60 mGy), and lower than the corresponding reference level for DLP (1050 mGy x cm). Dose optimisation techniques focused on the adjustment of the CTDIw-related examination parameters were proposed.

Image quality and dose evaluation in spiral chest CT examinations of patients with lung carcinoma

A study was undertaken to assess the quality of general chest CT examinations for indication of lung carcinoma according to the criteria proposed in the European Commission (EC) Guidelines, and to investigate their usefulness in the optimization of this practice. The criteria were evaluated for a sample of 100 examinations from five radiology departments in the Madrid area featuring single slice helical CT scanners with special emphasis on radiation dose and image quality. To determine the degree of compliance with the image criteria considered, the examinations were independently evaluated twice by five radiologists from the participating centres. A subsequent selection of the observers was made according to the consistency and independence of their readings. Dose measurements carried out in parallel supplied data to estimate the values of the CT dose indices (CTDI), dose-length product (DLP) and effective dose (E). The results show good compliance with the image criteria used - between 93% and 98% on average at the different sites, with variable degrees of internal deviation. 10 out of a total of 16 criteria proposed in the EC guidelines were met by practically all the examinations in the sample. The average weighted CTDI (CTDI(w)) values per site were in the range of 13-19 mGy; those of DLP were between 263 mGy cm and 577 mGy cm, and those of effective dose between 4 mSv and 9 mSv. The highest mean DLP value was below but close to the reference value proposed in the EC Document (650 mGy cm). In general, a weak correlation or no correlation at all was found between image quality scores and patient dose (DLP).