Preparation and radiolabeling of a lyophilized (kit) formulation of DOTA-rituximab with ⁹⁰Y and ¹¹¹In for domestic radioimmunotherapy and radioscintigraphy of non-Hodgkin's lymphoma

Does the Number of Bifunctional Chelators Conjugated to a mAb Affect the Biological Activity of Its Radio-Labeled Counterpart? Discussion Using the Example of mAb against CD-20 Labeled with 90Y or 177Lu

There has been considerable interest in developing a monoclonal antibody (mAb) against-CD-20 (for example, Rituximab) modified by bifunctional chelating agents (BCA) for non-Hodgkin's lymphoma radioimmunotherapy. Therefore, many researchers have modified this monoclonal antibody by attaching different BCA moieties and evaluated their biological activities in terms of in vitro study and in vivo study in healthy and tumor xenografted rodents. This mini-perspective reviews the in vitro studies, the immunoreactivity and physiological distribution studies: organ-to-blood and the tumor-to-organ ratio of conjugates with different numbers of chelators per mAb. We set up a null hypothesis that states there is no statistical significance between the biological activity of monoclonal antibody (Rituximab) and the number of conjugated bifunctional chelators. Overall, we have concluded that there is no strong evidence for this hypothesis. However, the literature data should be questioned due to the potential lack of uniform study methodology.

A novel theranostic probe [111In]In-DO3A-NHS-nimotuzumab in glioma xenograft

Indium-111 (111In) has an appropriate half-life (T 1/2 = 67 h) and energy characteristics for cancer diagnosis via γ-ray imaging and cancer therapy with Auger electrons. The aim of our study is to evaluate the potential of [111In]In-DO3A-NHS-nimotuzumab as a theranostic agent for radioimmunoimaging (RII) and radioimmunotherapy (RIT) against human glioma xenografts in mice. We explored the chelators DO3A-NHS and DOTA-p-SCN-Bz to optimize 111In radiolabeling efficiency of nimotuzumab. The radiopharmaceuticals were purified by PD-10 mini-column and their in vitro stabilities were assessed. We investigated the biodistribution of [111In]In-DO3A-NHS-nimotuzumab as it had relatively superior labeling efficiency and stability in vitro. We conducted SPECT imaging on mice bearing glioma (U87MG) xenografts, which were injected with ∼3.7 MBq of [111In]In-DO3A-NHS-nimotuzumab. The in vivo radiotherapeutic effects of [111In]In-DO3A-NHS-nimotuzumab was analyzed via injecting a single 37 MBq dose, 2 × 18 MBq doses, or 2 × 37 MBq doses into mice bearing U87MG xenografts. The control groups were administered either 30 μg nimotuzumab or saline. The radiochemical yields of [111In]In-DO3A-NHS-nimotuzumab and [111In]In-DOTA-p-SCN-Bz-nimotuzumab were > 85% and > 75%, respectively. [111In]In-DO3A-NHS-nimotuzumab had > 95% radiochemical purity and was more stable in vitro than [111In]In-DOTA-p-SCN-Bz-nimotuzumab. Biodistribution study demonstrated that [111In]In-DO3A-NHS-nimotuzumab was highly stable in vivo. SPECT imaging disclosed that [111In]In-DO3A-NHS-nimotuzumab had excellent targeted tumor uptake and retained in tumors for 24 and 72 h. All [111In]In-DO3A-NHS-nimotuzumab treatments substantially inhibited tumor growth over the controls. The 2 × 37 MBq treatment was particularly efficacious, and presented with survival time prolonged by ≤66 days. In contrast, the survival time of the control group was only 30 days. In our study, we developed an optimized synthesis protocol for radiopharmaceutical 111In-DO3A-NHS-nimotuzumab and demonstrated that it is a promising theranostic agent. It could be highly efficacious in RII and RIT against EGFR-expressing glioma.

Encapsulation of Imatinib in Targeted KIT-5 Nanoparticles for Reducing its Cardiotoxicity and Hepatotoxicity

BACKGROUND

Using imatinib, a tyrosine kinase inhibitor drug used in lymphoblastic leukemia, has always had limitations due to its cardiotoxicity and hepatotoxicity side effects. The objective of this study is to develop a target-oriented drug carrier to minimize these adverse effects by the controlled release of the drug.

METHODS

KIT-5 nanoparticles were functionalized with 3-aminopropyltriethoxysilane and conjugated to rituximab as the targeting agent for the CD20 positive receptors of the B-cells. Then they were loaded with imatinib and their physical properties were characterized. The cell cytotoxicity of the nanoparticles was studied by MTT assay in Ramos (CD20 positive) and Jurkat cell lines (CD20 negative) and their cellular uptake was shown by fluorescence microscope. Wistar rats received an intraperitoneal injection of 50 mg/kg of the free drug or targeted nanoparticles for 21 days. Then the level of aspartate Aminotransferase (AST), alanine Aminotransferase (ALT), Alkaline Phosphatase (ALP) and Lactate Dehydrogenase (LDH) were measured in serum of animals. The cardiotoxicity and hepatotoxicity of the drug were also studied by hematoxylin and eosin staining of the tissues.

RESULTS

The targeted nanoparticles of imatinib showed to be more cytotoxic to Ramos cells rather than Jurkat cells. The results of the biochemical analysis displayed a significant reduction in AST, ALT, ALP, and LDH levels in animals treated with targeted nanoparticles, compared to the free drug group. By comparison with the free imatinib, histopathological results represented less cardiotoxicity and hepatotoxicity in the animals, which received the drug through the current designed delivery system.

CONCLUSION

The obtained results confirmed that the rituximab targeted KIT-5 nanoparticles are promising in the controlled release of imatinib and could decrease its cardiotoxicity and hepatotoxicity side effects.

Preclinical Characterization of the Radioimmunoconjugate 111In or 90Y-FF-21101 Against a P-Cadherin-Expressing Tumor in a Mouse Xenograft Model and a Nonhuman Primate

P-cadherin is overexpressed in various cancers and can be a target for radioimmunotherapy. We investigated the preclinical pharmacokinetics and pharmacology of FF-21101, an ¹¹¹In- or ⁹⁰Y-conjugated monoclonal antibody against P-cadherin, to evaluate its clinical applications. Methods: The radiochemical purity, binding affinity, and in vitro serum stability of ¹¹¹In or ⁹⁰Y-labeled FF-21101 were evaluated. The pharmacokinetics of ¹¹¹In or ⁹⁰Y-FF-21101 were compared in normal mice. Tumor accumulation after ¹¹¹In-FF-21101 administration was investigated in mice bearing subcutaneous tumors with high (NCI-H1373), moderate (EBC-1), or no (A549) P-cadherin expression. The tumor suppression effect after a single intravenous injection of ⁹⁰Y-FF-21101 was assessed in NCI-H1373 and EBC-1 mouse xenograft models. The relationship between antibody dose and tumor accumulation was investigated in the NCI-H1373 mouse xenograft model. The absorbed radiation dose in humans after injection of ⁹⁰Y-FF-21101 was estimated using γ-camera images of cynomolgus monkeys. Results: The radiochemical purities of ¹¹¹In- and ⁹⁰Y-FF-21101 were 98.2% ± 2.5% (n = 9) and 99.3% ± 0.6% (n = 5), respectively. The dissociation constants were 1.083 nM for ¹¹¹In-FF-21101 and 1.367 nM for ⁹⁰Y-FF-21101. Both ¹¹¹In- and ⁹⁰Y-FF-21101 were stable in human serum after 96 h of incubation and exhibited similar pharmacokinetics in normal mice. The tumor accumulation of ¹¹¹In-FF-21101 was closely related to the intensity of P-cadherin expression in the cells. ⁹⁰Y-FF-21101 showed significant tumor growth inhibition, indicating that NCI-H1373 and EBC-1 recurrence was not observed after intravenous administration of 3.7 and 7.4 MBq, respectively of ⁹⁰Y-FF-21101 per animal. Tumor uptake in the mouse xenograft model and estimated absorbed radiation doses in the spleen of monkeys decreased with increasing antibody doses of ¹¹¹In-FF-21101. Conversely, the estimated absorbed radiation dose in the red marrow increased with increasing antibody dose. An antibody dose of 4.8 mg/m² was considered appropriate for humans, on the basis of efficacy and safety. The maximum tolerated administered activity of ⁹⁰Y-FF-21101 was estimated to be 2,886 MBq/human. Conclusion: FF-21101 radioimmunotherapy exhibited high antitumor affinity and antitumor efficacy in mouse xenograft models. Extrapolation of the pharmacokinetics in monkeys to humans suggests the potential for clinical application of FF-21101 for treating P-cadherin–expressing tumor.

Impact of DOTA-Chelators on the Antitumor Activity of 177Lu-DOTA-Rituximab Preparations in Lymphoma Tumor-Bearing Mice

Background: This work aimed to evaluate the influence of two chelators: DOTA(SCN) and DOTA(NHS) on radioimmunotherapy using ¹⁷⁷Lu-DOTA-Rituximab preparations in murine lymphoma xenograft models. Subsequently, based on animal data, the organ radiation-absorbed doses were extrapolated to humans (adult male). Materials and Methods: Therapeutic efficacy of ¹⁷⁷Lu-DOTA-Rituximab was evaluated in male nude mice bearing either Raji (B lymphocyte, CD20⁺) and Jurkat (T lymphocyte, CD20) xenografts, utilizing an anti-CD20 antibody-Rituximab conjugate with either DOTA(SCN) or DOTA(NHS). The DOTA-Rituximab conjugates were prepared in the form of freeze-dried kits. Results: All radioimmunoconjugates were obtained with high radiolabeling yield (radiochemical purity, RCP > 95%) and specific activity of ca. 0.5 GBq/mg. Therapeutic effects of ¹⁷⁷Lu-DOTA-Rituximab were observed in animals regardless whether DOTA(SCN) or DOTA(NHS) were used for conjugation. Importantly, therapy involving ¹⁷⁷Lu-DOTA-Rituximab was more effective than use of Rituximab alone. Conclusions: The degree of antitumor efficacy was dependent on the type of applied bifunctional chelators conjugated to mAb. However, this difference was not statistically significant. Dosimetry calculations showed that the absorbed radiation doses extrapolated to humans were very low for osteogenic cells regardless of the conjugates. Organs like the liver and spleen, treated with ¹⁷⁷Lu-DOTA(SCN)-Rituximab, showed similar radiation absorbed doses when compared with ¹⁷⁷Lu-DOTA(NHS)-Rituximab.

Influence of DOTA Chelators on Radiochemical Purity and Biodistribution of 177Lu- and 90Y-Rituximab in Xenografted Mice

This work presents a comparative biological evaluation of ⁹⁰Y- and ¹⁷⁷Lu- labelled DOTA-SCN and DOTA-NHS conjugated to Rituximab in tumour-bearing mice. Two DOTA derivatives, p-SCN-Bn-DOTA and DOTA-NHS-ester were conjugated to Rituximab and then freeze-dried kit formulations were prepared, as previously described (1). Tissue distribution was investigated in tumour-bearing (Raji s.c.) male Rj: NMRI-Foxn1^nu/Foxn1^nu mice at different time points after administration of ¹⁷⁷Lu-DOTA-Rituximab or ⁹⁰Y-DOTA-Rituximab (6 MBq/10 μg per mouse). In addition, tumour images were acquired with a PhotonIMAGER^TM after injection of ⁹⁰Y-DOTA (SCN)-Rituximab. All radioimmunoconjugates were obtained with high radiolabelling yield (RCP > 98%) and specific activity of ca. 0.6 GBq/mg. The conjugates were stable in human serum and in 0.9% NaCl; however, progressive aggregation was observed with time, in particular for DOTA -(SCN) conjugates. Both ¹⁷⁷Lu- and ⁹⁰Y-DOTA -(SCN)-Rituximab revealed slow blood clearance. The maximum tumour uptake was found 72 h after injection of ¹⁷⁷Lu-DOTA -(SCN)-Rituximab (9.3 ID/g). A high radioactivity uptake was observed in liver and spleen, confirming the hepatobiliary excretion route. The results obtained by the radioactive optical imaging harmonize with those from the biodistribution study.

Production and Clinical Applications of Radiopharmaceuticals and Medical Radioisotopes in Iran

During past 3 decades, nuclear medicine has flourished as vibrant and independent medical specialty in Iran. Since that time, more than 200 nuclear physicians have been trained and now practicing in nearly 158 centers throughout the country. In the same period, Tc-99m generators and variety of cold kits for conventional nuclear medicine were locally produced for the first time. Local production has continued to mature in robust manner while fulfilling international standards. To meet the ever-growing demand at the national level and with international achievements in mind, work for production of other Tc-99m-based peptides such as ubiquicidin, bombesin, octreotide, and more recently a kit formulation for Tc-99m TRODAT-1 for clinical use was introduced. Other than the Tehran Research Reactor, the oldest facility active in production of medical radioisotopes, there is one commercial and three hospital-based cyclotrons currently operational in the country. I-131 has been one of the oldest radioisotope produced in Iran and traditionally used for treatment of thyrotoxicosis and differentiated thyroid carcinoma. Since 2009, (131)I-meta-iodobenzylguanidine has been locally available for diagnostic applications. Gallium-67 citrate, thallium-201 thallous chloride, and Indium-111 in the form of DTPA and Oxine are among the early cyclotron-produced tracers available in Iran for about 2 decades. Rb-81/Kr-81m generator has been available for pulmonary ventilation studies since 1996. Experimental production of PET radiopharmaceuticals began in 1998. This work has culminated with development and optimization of the high-scale production line of (18)F-FDG shortly after installation of PET/CT scanner in 2012. In the field of therapy, other than the use of old timers such as I-131 and different forms of P-32, there has been quite a significant advancement in production and application of therapeutic radiopharmaceuticals in recent years. Application of (131)I-meta-iodobenzylguanidine for treatment of neuroblastoma, pheochromocytoma, and other neuroendocrine tumors has been steadily increasing in major academic university hospitals. Also (153)Sm-EDTMP, (177)Lu-EDTMP, (90)Y-citrate, (90)Y-hydroxyapatite colloid, (188/186)Re-sulfur colloid, and (188/186)Re-HEDP have been locally developed and now routinely available for bone pain palliation and radiosynovectomy. Cu-64 has been available to the nuclear medicine community for some time. With recent reports in diagnostic and therapeutic applications of this agent especially in the field of oncology, we anticipate an expansion in production and availability. The initiation of the production line for gallium-68 generator is one of the latest exciting developments. We are proud that Iran would be joining the club of few nations with production lines for this type of generator. There are also quite a number of SPECT and PET tracers at research and preclinical stage of development preliminarily introduced for possible future clinical applications. Availability of fluorine-18 tracers and gallium-68 generators would no doubt allow rapid dissemination of PET/CT practices in various parts of our large country even far from a cyclotron facility. Also, local production and availability of therapeutic radiopharmaceuticals are going to open exciting horizons in the field of nuclear medicine therapy. Given the available manpower, local infrastructure of SPECT imaging, and rapidly growing population, the production of Tc-99m generators and cold kit would continue to flourish in Iran.

Physicochemical Evaluation of Lyophilized Formulation of p-SCN-Bn-DOTA- and p-SCN-Bn-DTPA-rituximab for NHL Radio Immunotherapy

Radioimmunotherapy (RIT) of Non-Hodgkin's lymphoma (NHL) is said to be more advantageous compared to unlabelled therapeutic antibodies. To this date, radiolabelled murine anti-CD20 mAbs, Zevalin^® and Bexxar^® have been approved for imaging and therapy. A preparation containing rituximab, chimeric mAb radio immunoconjugate suitable for Lu-177 labeling, could provide better imaging and therapeutic profile at the same time. This study was conducted to evaluate prepared lyophilized formulations of two rituximab immune conjugates, intended for immediate Lu-177 labeling, for imaging and therapy. The characterization of the conjugates and demonstration of the integrity of the protein and purity after conjugation and lyophilization was performed by SDS-PAGE, FT-IR and MALDI-TOF-MS. The results showed preserved antibody structure and average of 6.1 p-SCN-Bn-DOTA and 8.8 p-SCN-Bn-DTPA groups per antibody molecule which is suitable for successful labeling. These results support the possibility of developing a "ready-to-label" rituximab immune conjugates for NHL imaging/therapy.