Nucl Med Mol Imaging (2011) 45:87–92 DOI 10.1007/s13139-010-0048-6

ORIGINAL ARTICLE

Development of 166Ho-phytate Complex for Radiosynovectomy Amir R. Jalilian & Akbar Anvari & Ali Bahrami-Samani & Mohammad Mazidi & Mohammad Ghannadi-Maragheh

Received: 25 May 2010 / Revised: 29 June 2010 / Accepted: 29 July 2010 / Published online: 17 February 2011 # Korean Society of Nuclear Medicine 2011

Abstract Background 66Ho-chloride was obtained by bombardment of natural Ho(NO3)3 dissolved in acidic media using thermal neutron flux (4-5×1013 n.cm-2.s-1). Methods 166Ho-holmium chloride (185 MBq) was used successfully for preparation of 166Ho-phytate complex with high radiochemical purity (>99.9 %, ITLC, MeOH: H2O: acetic acid, 4: 4: 2, as mobile phase). The complex stability and viscosity were checked in the final solution up to 2 days. The prepared complex solution (60 μCi/100 μl) was injected intraarticularly to male rat knee joints. Leakage of radioactivity from the injection site and its distribution in organs were investigated up to 2 days. Results Approximately all of the injected dose had remained in the injection site 2 days after injection. Conclusion The complex was proved to be a feasible agent for cavital radiotherapy in oncology and rheumatology. Keywords Phytate . Radiosynovectomy . Holmium-166 . Biodistribution . SPECT

Introduction With the aging of the human population around the world, the need for the management of diseases of the elderly, A. R. Jalilian (*) : A. Bahrami-Samani : M. Mazidi : M. Ghannadi-Maragheh Radiopharmaceutical Research and Development Laboratory (RRDL), Nuclear Science and Technology Research Institute (NSTRI), Tehran, Iran 14155-1339 e-mail: [email protected] A. Anvari Faculty of Nuclear Engineering, Shahid Beheshti University, P.O. Box: 19839-63113, Tehran, Iran

such as rheumatoid arthritis and other joint problems, has emerged. Also the majority of diseases can cause arthropathy, such as spondylarthropathy, Lyme disease, Behcet's disease, persistent synovial effusion, hemophilic arthritis, calcium pyrophosphate dihydrate (CPPD) arthritis, pigmented villonodular synovitis (PVNS), persistent effusion after joint prosthesis, undifferentiated arthritis, etc., leading to pain, inflammation and also immobility of patients [1]. Radiosynovectomy (RSV) has been proposed as a potent palliative therapy around the world for the last 2 decades [1], and several radiopharmaceuticals have been developed for RSV, including 166Ho-macroaggregates [2] and Ho-166 phytate complex [3]. Many beta-emitters such as 153Sm, 177Lu and 166Ho can be produced in reasonable amounts using (n, gamma) reactions, and holmium-166 (Eβ− max=1.84 MeV, T1/2 = 26.8 h) is one of the most interesting radionuclides for the development of therapeutic radiopharmaceuticals such as 166 Ho-DOTMP for bone palliation therapy [4], 166HoDTPA in endovascular beta irradiation therapy [5], 166Hooxine-lipiodol in liver cancer therapy [6] and also 166Ho patches in the treatment of skin cancers [7]. In this research, 166Ho-phytate complex production is described in detail, followed by the determination of complex radiochemical purity, stability and biodistribution (after intraarticular injection) in wild-type male rats.

Materials and Methods Production of 166Ho was performed at the Tehran Research Reactor (TRR) using a natHo (n, gamma)166Ho nuclear reaction. Natural holmium nitrate with purity >99.99% was obtained from Aldrich Co. Phytate complex was prepared

88

Nucl Med Mol Imaging (2011) 45:87–92

using a commercial phytate kit (Kavoshyar Co., Tehran, Iran, stannous chloride free). Chromatography paper, Whatman no. 1, was obtained from Whatman (Maidstone, UK). Radiochromatography was performed by using a bioscan AR-2000 radio TLC scanner instrument (Bioscan, Washington, DC). A high-purity germanium (HPGe) detector coupled with a Canberra™ (model GC1020-7500SL) multichannel analyzer and a dose calibrator ISOMED 1010 (Dresden, Germany) were used for counting distributed activity in rat organs. All other chemical reagents were purchased from Merck (Darmstadt, Germany). Calculations were based on the 81-keV peak for 166Ho. All values were expressed as mean ± standard deviation (mean ± SD), and the data were compared using Student’s t-test. Statistical significance was defined as P