Table 1 Characteristics of ¹⁶⁶Ho-EDTMP and ¹⁶⁶Ho-DOTMP. The results are expressed as the means ± standard deviations; n = 3 for each experimental point (M/M: molar/molar ratio, mbq: Megabecquerel, RCP: radiochemical purity, SA: specific activity). (^a) ¹⁶⁶Ho³⁺ (mmol) = calculated as ~ 200 Mg Ho₂O₃ × 87.28% (Ho³⁺ in Ho₂O₃)/164.9 g.mol⁻, divided by 4 (volume of ¹⁶⁶Ho³⁺ solution, 4 mL) = 0.264 mM (^b) concentration: determined as the activity of ¹⁶⁶HoCl₃ (MBq)/mL (collected range: 74,275–82,880 MBq/4.0 mL). ^*Radiochemical purity of ¹⁶⁶Ho-EDTMP/¹⁶⁶Ho-DOTMP was determined by a PC (using 20 × 200 mm strips). ^**Specific activity (MBq/mg) of ¹⁶⁶Ho: calculated as ¹⁶⁶Ho activity/200 Mg ¹⁶⁵Ho₂O₃ × 0.8728 Ho³⁺ content) = 451.44 ± 33.53. ^**Specific activity (MBq/mg) of ¹⁶⁶Ho-EDTMP: Range = 8.11–9.00. ^**Specific activity (MBq/mg) of ¹⁶⁶Ho-DOTMP: Range = 4.30–4.77. ^#166Ho/EDTMP molar ratio: calculated as = 0.0132 mmol Ho³⁺/0.264 mmol EDTMP × 99.10% (efficiency) = 0.0495. ^#166Ho/DOTMP molar ratio: calculated as 0.0132 mmol Ho³⁺/0.264 mmol DOTMP × 99.35% (efficiency) = 0.0331. The stability of ¹⁶⁶Ho-EDTMP and ¹⁶⁶DOTMP was evaluated under various conditions (Fig. S1a,b). A radiochemical purity exceeding 95% was observed at 4 °C and 24 °C in 0.9% NaCl and 0.2 M PBS and at 37 °C in 0.05% HSA after 3 days of storage.

From: Acute radiotoxicity studies and safety assessment of ¹⁶⁶Ho-EDTMP and ¹⁶⁶Ho-DOTMP for the palliative treatment of bone metastases