BIODISTRIBUTION AND DOSIMETRY OF TECHNETIUM-99M-HYDRAZINO NICOTINAMIDE IGG, COMPARISON WITH INDIUM-111-DTPA-IGG

The biological behavior of human polyclonal immunoglobulin G (IgG), ra diolabeled with Tc-99m via. a nicotinyl hydrazine derivative (Tc-99m-H YNIC-IgG), was evaluated in normal human subjects. Methods: Initial bi odistribution and dosimetry studies were performed in six normal male volunteers. Additionally, (TC)-T-99m-IgG and In-111-DTPA-IgG were co-i njected into six subjects and scintillation camera images were acquire d at 6 and 18 hr later and serial blood and urine samples were collect ed. Biodistribution of both radiopharmaceuticals were measured by regi on of interest analysis. In the dual-injection group, images were cros sover-corrected. Results: All subjects tolerated injection of the radi olabeled IgG preparations without apparent ill effects, Biodistributio n of the two antibody preparations were remarkably similar with an inc rease in liver and abdominal activity for the In-111 preparation. Line ar correlation of the tissue-to-blood ratios of Tc-99m and In-111-labe led IgG was observed at both times (r(2) > 0.98). The slopes of the re gression line were 0.97 and 0.76 at 6 and 18 hr, respectively. The bet a phase of the blood clearance of Tc-99m-HYNIC-IgG Was significantly d elayed (p < 0.01) compared with In-111-IgG (t(1/2): 51.9 +/- 6.5 versu s 35.3 +/- 3.4 hr). In contrast, the volumes of distribution and urina ry excretions of the radiopharmaceuticals were not significantly diffe rent. Conclusion: These studies establish that the biodistribution of Tc-99m-HYNIC-IgG in normal human subjects is nearly identical to In-11 1-DTPA-lgG.