Preparation, quality control and biodistribution assessment of 153Sm-BPAMD as a novel agent for bone pain palliation therapy

Preliminary dosimetric evaluation of 90Y-BPAMD as a potential agent for bone marrow ablative therapy

Aim

Bone-seeking radiopharmaceuticals are potential therapeutic tools for bone marrow ablation in patients with multiple myeloma. In this procedure, estimation of radiation absorbed dose received by the target and non-target organs is one of the most important parameters that should be undertaken. This research revolves around the absorbed dose to human organs after 90Y-BPAMD injection.

Materials and methods

90Y-(4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid (90Y-BPAMD) complex was successfully prepared under optimised conditions. The human absorbed dose of the complex was estimated based on the biodistribution data on rats using the radiation-absorbed dose-assessment resource method. The target to non-target absorbed dose ratios for the complex was compared with the ratios for 166Ho-DOTMP, as the main radiopharmaceutical for bone marrow ablation.

Results

As expected, the highest amounts of absorbed dose were observed in the bone surface and the bone marrow with 2·52 and 2·29 mGy/MBq, respectively. The red marrow to the most organ absorbed dose ratios for 90Y-BPAMD are much higher than the ratios for 166Ho-DOTMP.

Findings

90Y-BPAMD has interesting characteristics compared with 166Ho-DOTMP and can be considered as a high potential agent for bone marrow ablative therapy of the patient with multiple myeloma.

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.

Pharmaceutical and clinical development of phosphonate-based radiopharmaceuticals for the targeted treatment of bone metastases

Therapeutic phosphonate-based radiopharmaceuticals radiolabeled with beta, alpha and conversion electron emitting radioisotopes have been investigated for the targeted treatment of painful bone metastases for >35years. We performed a systematic literature search and focused on the pharmaceutical development, preclinical research and early human studies of these radiopharmaceuticals. The characteristics of an ideal bone-targeting therapeutic radiopharmaceutical are presented and compliance with these criteria by the compounds discussed is verified. The importance of both composition and preparation conditions for the stability and biodistribution of several agents is discussed. Very few studies have described the characterization of these products, although knowledge on the molecular structure is important with respect to in vivo behavior. This review discusses a total of 91 phosphonate-based therapeutic radiopharmaceuticals, of which only six agents have progressed to clinical use. Extensive clinical studies have only been described for (186)Re-HEDP, (188)Re-HEDP and (153)Sm-EDTMP. Of these, (153)Sm-EDTMP represents the only compound with worldwide marketing authorization. (177)Lu-EDTMP has recently received approval for clinical use in India. This review illustrates that a thorough understanding of the radiochemistry of these agents is required to design simple and robust preparation and quality control methods, which are needed to fully exploit the potential benefits of these theranostic radiopharmaceuticals. Extensive biodistribution and dosimetry studies are indispensable to provide the portfolios that are required for assessment before human administration is possible. Use of the existing knowledge collected in this review should guide future research efforts and may lead to the approval of new promising agents.

Human absorbed dose estimation for a new (175)Yb-phosphonate based on rats data: Comparison with similar bone pain palliation agents

In this work, the absorbed dose to human organs for (175)Yb-BPAMD was evaluated based on the biodistribution studies in rats. The results showed that the bone surface would receive the highest absorbed dose after injection of (175)Yb-BPAMD with 13.32mGy/MBq, while the other organs receive insignificant absorbed dose. Also, the comparison of (175)Yb-BPAMD with other therapeutic phosphonate complexes demonstrated noticeable characteristics for this new agent. Generally, based on the obtained results, (175)Yb-BPAMD can be considered as a promising agent for bone pain palliative therapy in near future.