Preparation of a radiolabeled GnRH-I analogue derivative with 111 In as a new anti-proliferative agent

The new GnRH-Ιanalogue developed in this paper was based on the D-Trp⁶ -GnRH-Ι-scaffold, and its potency was increased by the replacement Gly-NH₂ by NH-NH₂ binding to the Gly at position 10. Triptorelin-Hydrazide analogue was synthesized using solid phase. For ¹¹¹ In labeling, synthesized peptide was followed by conjugation with DOTA using pSCN-Bn-DOTA. The conjugated Triptorelin-Hydrazide was labeled with 500-550 MBq of ¹¹¹ In-chloride (in 0.2 M HCl). At optimized conditions after labeling, radio-chromatography showed radiochemical purity of approximately equal to 98% (RTLC) and greater than 95% (HPLC). The serum stability of the tracer was determined up to 24 hr. Binding affinities of Triptorelin-Hydrazide analogue were determined in a binding assay for both human and rat GnRH receptors. For in vivo studies, ¹¹¹ In-peptide was injected intravenously via the tail vein into rats and significant ovaries uptake consist with reported GnRH receptor mappings. In vitro radioligand binding assays performed with GnRHR-expressing human cell lines using ¹²⁵ I-Triptorelin as the standard radioligand. The quantities of internalization efficiency and receptor affinity of the new radioligand were IC₅₀  = 0.20 ± 0.04 nM vs 0.13 ± 0.08 nM for Triptorelin and internalization: 3.5 ± 0.9% at 1 hr and 12.8 ± 1.8% at 4 hr of the internal reference.

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.

Optimized production, quality control, biological evaluation and PET/CT imaging of 68Ga-PSMA-617 in breast adenocarcinoma model

Optimized production, quality control and preclinical evaluation of 68Ga-PSMA-617 as a PET radiotracer for PSMA-positive malignancies as well as successful application in imaging of breast adenocarcinomas are reported. 68Ga-PSMA-617 radiolabeling and QC optimization, stability, log P, biodistribution in breast adenocarcinomas-bearing mice (direct and blockade studies) and also PET/CT imaging was performed. 68Ga-PSMA-617 complex was prepared in high radiochemical purity (>96%, ITLC, HPLC) and specific activity of 300–310 GBq/mM at 95 °C using 2–4 micrograms of the peptide in 10 min followed by solid phase purification. The tracer was stable in serum and final formulation for at least 120 min. The log P was −1.98. Western blot test on the tumor cell homogenates demonstrated distinct existence of the PSMA on the surface. The biodistribution of the tracer demonstrated specific kidney and tumor significant uptake using blocking study. Significant tumor:blood and tumor:muscle ratio uptake observed at 30 min post-injection (2.69 and 19.1, respectively). A reduction of 40–80% off tumor uptake in the study time period observed using blocking test. 68Ga-PSMA-617 can be proposing a possible tracer for PET imaging of breast adenocarcinomas and other breast malignancies.