Abstract

Aim To evaluate the biodistribution, internal radiation dosimetry and toxicity of the humanized MAb h-R3 labelled with Tc-99m in humans. Methods Twenty-five patients with suspected epithelial-derived tumours were included in this study and divided into two groups: group I consisted of 10 patients who received 3 mg/1110 MBq (3 mg/30 mCi); and group II consisted of 15 patients who received 6 mg/2220 MBq (6 mg/60 mCi). Single photon emission computed tomography (SPECT) and planar images, and multiple blood and urine samples were collected up to 24 h after injection. Haematological parameters and adverse effects were classified according to the WHO criteria. Biodistribution, human anti-mouse antibody (HAMA) response and absorbed doses were estimated and reported. Results Liver, spleen, kidneys and heart were identified as source organs. Their higher uptakes were 53.3 +/- 6.4%ID, 2.0 +/- 1.4%ID, 9.8 +/- 4.3%ID and 2.8 +/- 0.9%ID, respectively. The urinary bladder and large intestine also had a significant uptake. The mean urinary excretion was around 22%ID. The liver received the highest absorbed doses followed by the kidneys and the urinary bladder wall. There were no haematological or biochemical abnormalities with clinical significance related to the product. No patient developed HAMA response. Preliminary analysis of clinical results showed a sensitivity of 76.5% and a specificity of 100%. Conclusions The results of this study suggest that Tc-99m-h-R3 could be used in patients in a safe and effective way, for the diagnosis of epithelial-derived tumours at the two evaluated dose levels.