PHARMACOKINETICS AND RADIATION-DOSIMETRY OF TC-99(M)-LABELED MONOCLONAL-ANTIBODY B43.13 IN OVARIAN-CANCER PATIENTS

OVAREX(TM) MAb B43.13 is a new radiopharmaceutical based on a monoclon al antibody (MAb-B43.13) known to recognize CA 125, a tumour antigen a ssociated with epithelial ovarian cancer. This MAb is capable of facil e radiolabelling with Tc-99(m) and has been shown previously to locali ze in the tumours of ovarian cancer patients. The present study was in itiated to measure the pharmacokinetics of this MAb in the serum of 10 patients with primary or metastatic ovarian cancer. A two-compartment model was found to be best at representing the biodistribution of the Tc-99(m)-labelled MAb, yielding a 2.6 h distribution phase half-Life and a 31.3 h elimination phase half-life. The serum and renal clearanc es for Tc-99(m)- MAb-B43.13 were 221 and 53 mi h(-1) respectively. The se parameters were compared with a similar model developed from the se rum values of the MAb itself (determined using an ELISA detection meth od). Based on the serum pharmacokinetics of (99)Tc(m-)MAb-B43.13 and w hole-body planar gamma camera images, an estimate of the radiation dos e from Tc-99(m) was calculated using standard MIRD schema. The organs demonstrating significant Tc-99(m) uptake included the Liver, kidneys, heart and spleen. The whole body dose was similar to other Tc-99(m)-l abelled MAbs.