Radiolabeling of NM600 with 86/90Y

As described elsewhere (37 (link)), NM600 was radiolabeled with ⁸⁶YCl₃ as no-carrier-added formulation to obtain [⁸⁶Y]Y-DOTA-NM600 (hereafter simplified to ⁸⁶Y-NM600) for positron emission tomography (PET) imaging and dosimetry; for therapeutic treatments, NM600 was radiolabeled with 90YCl₃ to obtain ⁹⁰Y-DOTA-NM600 (hereafter simplified to ⁹⁰Y-NM600). Radiolabeling of NM600 with ^86/90Y was performed by mixing 185–370 MBq (5 −10 mCi) of ^86/90Y and 54–81nmol/GBq (10–15 nmol/mCi) of NM600 in 0.1 M NaOAc (pH = 5.5) buffer. After incubation at 90°C for 30 min under constant shaking (500 rpm), ^86/90Y-NM600 was purified by solid phase extraction using an HLB cartridge (Waters^™ Corp., Milford, MA). For in vivo use, ^86/90Y-NM600 was formulated in vehicle consisting of normal saline containing 0.4% v/v Tween^™ 20 and sodium ascorbate (0.5% w/v). Yields and radiochemical purity were consistently >95%, and a similar apparent molar activity of 18 GBq/μmol was obtained for both ⁸⁶Y-NM600 and ⁹⁰Y-NM600. Additionally, radiotracer stability in vivo has been demonstrated from mouse serum samples up to 48 h, with no significant radio peaks corresponding to metabolites observed (37 (link)).