Thulium‐170 [T1/2 = 128.4 days, Eβ(max) = 968 keV, Eγ = 84 keV (3.26%)] has radionuclidic properties suitable for use in therapy. 170Tm can be produced by a relatively feasible route involving thermal neutron bombardment on natural Tm(NO3)3 (100% 169Tm) in medium flux research reactors. The combination of beta‐particle emission of Tm‐170 with therapeutic properties of C225 monoclonal antibody (cetuximab) as well as optimization studies for future Tm‐167 labeling was targeted in this study. Conjugated cetuximab was obtained by the addition of 0.5 ml of a cetuximab pharmaceutical solution (1 mg, in phosphate buffer, pH 7.8) to a glass tube pre‐coated with in situ prepared 1,4,7,10‐tetraazacyclododecane‐N,N,N,N‐tetraacetic acid mono‐(N‐hydroxysuccinimidyl) ester (DOTA‐NHS) (~5 mg) at 25°C. Cetuximab was labeled with 170Tm‐Thulium chloride (100 MBq) after conjugation with DOTA‐NHS in 2–3 h (radiochemical purity >99%, instant thin‐layer chromatography, specific activity = 77–385 TBq/mmol). Biodistribution studies in wild‐type rats for free Tm‐170 and the radioimmunoconjugate were performed to determine the distribution up to 72 h. A comparative time‐frame study was performed for critical organs for both radiochemical species. The major organs of accumulation were shown to be the lung, liver, and spleen, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

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177Lu-ethylenediaminetetramethylene phosphonic acid (EDTMP) is presently suggested as an excellent bone seeking radionuclide for developing metastatic bone pain (MBP) palliation agent owing to its suitable nuclear decay characteristics. To find the exact dosage and its efficiency, this clinical study was performed on the human being, using 177Lu-EDTMP for MBP palliation. 177Lu-EDTMP was prepared by Iran, atomic energy organization. Thirty consecutive patients with determined tumors, incontrollable MBP, and positive bone scan at 4 weeks before the beginning of the study participated in this study in the nuclear medicine ward. 177Lu-EDTMP in the form of sterile slow IV injection was administered with a dose of 29.6 MBq/kg. Short form of brief pain inventory questionnaire was used to evaluate the efficiency of the intervention. Questionnaires were filled out by an expert nuclear physician every 2 weeks while the cell blood count was also checked every 2 weeks up to 12 weeks for evaluation of bone marrow suppression and hematological toxicity. Furthermore, whole body scan was done at days 1, 3, and 7. Twenty-five patients showed a significant pain relief since 2 weeks after the injection, and continued until the end of the follow up period (12 weeks). There were no significant early complications such as bone marrow suppression, hematological toxicity, and no systemic adverse effects. No complication was observed in renal function. Twenty one patients showed flare phenomenon that was started after the 12.2 ± 1.78 h lasting for 38.4 ± 23.08. Sixteen patients (53%) were completely treated; nine patients (30%) showed a partial response, and five patients (17%) had no response to treatment. Total response to treatment was achieved in 25 patients (83%). At the end of the evaluation, no bone marrow suppression or hematologic toxicity was observed. 177Lu-EDTMP has shown suitable physical and biological properties with good results in long term bone pain relief for patients with bone metastasis.

166Ho-EDTMP is a major therapeutic agent which is widely used in bone palliation therapy. In this study, a 166Ho-EDTMP complex was prepared successfully using an in-house synthesized EDTMP ligand and 166HoCl3. Ho-166 chloride was obtained by thermal neutron irradiation (1 × 1013 ncm−2s−1) of natural Ho(NO3)3 samples (specific activity = 3–5 GBq/mg), dissolved in acidic media. The radiochemical purity of 166Ho-EDTMP was checked by ITLC (>99%) and stability studies in presence of human serum and final preparation were performed. The biodistribution of 166Ho-EDTMP and 166HoCl3 in wild-type rats was checked by scarification. SPECT imaging of 166Ho-EDTMP was also performed in wild-type rats. A comparative accumulation study for 166Ho-EDTMP and 166HoCl3 was performed for vital organs up to 48h. Significant bone accumulation (>70%) of the tracer in 48h was observed.

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