Evaluation of (177)Lu-CHX-A''-DTPA-Bevacizumab as a radioimmunotherapy agent targeting VEGF expressing cancers

The Role of VEGF Receptors as Molecular Target in Nuclear Medicine for Cancer Diagnosis and Combination Therapy

Simple Summary

The rapid development of diagnostic and therapeutic methods of the cancer treatment causes that these diseases are becoming better known and the fight against them is more and more effective. Substantial contribution in this development has nuclear medicine that enables very early cancer diagnosis and early start of the so-called targeted therapy. This therapeutic concept compared to the currently used chemotherapy, causes much fewer undesirable side effects, due to targeting a specific lesion in the body. This review article discusses the possible applications of radionuclide-labelled tracers (peptides, antibodies or synthetic organic molecules) that can visualise cancer cells through pathological blood vessel system in close tumour microenvironment. Hence, at a very early step of oncological disease, targeted therapy can involve in tumour formation and growth.

Abstract

One approach to anticancer treatment is targeted anti-angiogenic therapy (AAT) based on prevention of blood vessel formation around the developing cancer cells. It is known that vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptors (VEGFRs) play a pivotal role in angiogenesis process; hence, application of angiogenesis inhibitors can be an effective approach in anticancer combination therapeutic strategies. Currently, several types of molecules have been utilised in targeted VEGF/VEGFR anticancer therapy, including human VEGF ligands themselves and their derivatives, anti-VEGF or anti-VEGFR monoclonal antibodies, VEGF binding peptides and small molecular inhibitors of VEGFR tyrosine kinases. These molecules labelled with diagnostic or therapeutic radionuclides can become, respectively, diagnostic or therapeutic receptor radiopharmaceuticals. In targeted anti-angiogenic therapy, diagnostic radioagents play a unique role, allowing the determination of the emerging tumour, to monitor the course of treatment, to predict the treatment outcomes and, first of all, to refer patients for AAT. This review provides an overview of design, synthesis and study of radiolabelled VEGF/VEGFR targeting and imaging agents to date. Additionally, we will briefly discuss their physicochemical properties and possible application in combination targeted radionuclide tumour therapy.

Preparation and preliminary bioevaluation studies of 68 Ga-NOTA-rituximab fragments as radioimmunoscintigraphic agents for non-Hodgkin lymphoma

Rituximab is used for the treatment of non-Hodgkin lymphoma (NHL). This study focuses on development of ⁶⁸ Ga-labeled rituximab fragments, (⁶⁸ Ga-NOTA-F (ab')-rituximab and ⁶⁸ Ga-NOTA-F (ab')₂ -rituximab, as PET-imaging agents for NHL. Rituximab was digested with immobilized pepsin and papain to yield F (ab')₂ and Fab fragments respectively that were characterized by size exclusion HPLC (SE-HPLC) and SDS-PAGE. They were conjugated with p-SCN-Bn-NOTA, labeled with ⁶⁸ Ga and characterized by SE-HPLC. Intact rituximab was labeled with gallium-68 for comparison. Specificity of ⁶⁸ Ga-labeled immunoconjugates was ascertained by immunoreactivity and cell binding studies in Raji cells, while biodistribution studies were performed in normal Swiss mice. Gradient SDS-PAGE under nonreducing condition showed molecular weights of F (ab')₂ -rituximab and F (ab')-rituximab as approximately 100 and 40 Kd, respectively. Radiochemical purity (RCP) of ⁶⁸ Ga-NOTA-F (ab')₂ -rituximab and ⁶⁸ Ga-NOTA-F (ab')-rituximab were 98.2 ± 0.5% and 98.8 ± 0.2% respectively with retention times of 17.1 ± 0.1 min and 19.3 ± 0.1 min in SE-HPLC. ⁶⁸ Ga-labeled rituximab fragments were stable in saline and serum up to 2-hour post preparation and exhibited specificity to CD20 antigen. Immunoreactivity of ⁶⁸ Ga-labeled immunoconjugates was greater than 80%. Clearance of the fragmented radioimmunoconjugates was predominantly through renal route. Preliminary results from this study demonstrate the potential of ⁶⁸ Ga- NOTA-F (ab')₂ -rituximab and ⁶⁸ Ga-NOTA-F (ab')-rituximab as PET imaging agents for NHL.

Evaluation of 99mTc-Labeled Bevacizumab-N-HYNIC Conjugate in Human Ovarian Tumor Xenografts

Aim: The aim of the present investigation was to examine the suitability of 99mTc-N-HYNIC-BZMB as a specific vascular endothelial growth factor (VEGF)-targeting agent. Bevacizumab is a recombinant humanized monoclonal antibody that inhibits VEGF. Methods: N-hydroxysuccinimide-2-hydrazinonicotinic acid (N-HYNIC) was conjugated to BZMB, followed by labeling with 99mTc using N-[Tris(hydroxymethyl)methyl] glycine (tricine), ethylenediamine-N,N'-diacetic acid (EDDA), and nicotinic acid as coligands. 99mTc-labeled BZMB was characterized in terms of 99mTcO4, radiocolloids, and labeled N-HYNIC-BZMB using thin-layer chromatography and HPLC. Poor metastatic SKOV-3 and high metastatic SKOV-3.ip1 human ovarian cancer cell lines were used for in vitro binding uptake of 99mTc-N-HYNIC-BZMB. Biodistribution and scintigraphy accuracy were examined in human ovarian tumor xenografts in rats and rabbits. Results: 99mTc-N-HYNIC-BZMB prepared by using a mixture of tricine and EDDA demonstrated relatively high radiochemical purity (more than 98%). In L-cysteine and serum, it exhibited a stable behavior up to 16 h. In vitro binding uptake indicated that it targets high metastatic SKOV-3.ip1 tumors. Biodistribution in human ovarian tumor xenografts in rats confirmed a significant uptake in SKOV-3.ip1 tumors (5.69% ± 1.86%, 4 h). Scintigraphic accuracy in human ovarian tumor xenografts in rabbits validated its suitability as a high metastatic SKOV-3.ip1 radiotracer. Conclusion: High radiochemical purity, stability in saline and serum, biodistribution, and scintigraphy of 99mTc-N-HYNIC-BZMB in human ovarian tumor xenografts in rats and rabbits confirmed its suitability as a potential radiotracer for imaging high metastatic SKOV-3.ip1 sites.

Preclinical evaluation of 131I-Bevacizumab - A prospective agent for radioimmunotherapy in VEGF expressing cancers

This study focuses on preparation and evaluation of ¹³¹I-bevacizumab by Iodogen method for targeting VEGF over-expressing cancers for therapy. ¹³¹I-Bevacizumab exhibited radiochemical purity of 98.0±0.7%. In vitro stability of ¹³¹I-Bevacizumab was retained at >85% in both saline and serum at 37°C upto 5 days post iodination. In vitro cell studies showed good immunoreactivity and uptake by VEGF expressing tumor cells. Uptake and retention of ¹³¹I-Bevacizumab in tumor with reduction in uptake in presence of cold Bevacizumab confirmed its specificity to VEGF.