PHARMACOKINETICS AND SCINTIGRAPHY OF INDIUM-111-DTPA-MOC-31 IN SMALL-CELL LUNG-CARCINOMA

Radiolabeled MOC-31 retains its immunoreactivity and shows good in viv o immunolocalization to human SCLC xenografted in nude rats. Methods: We evaluated the immunotargeting properties and safety of In-111-label ed monoclonal antibody (MAb) MOC-31 (125 MBq, 5 mg) in six patients wi th histologically proven small-cell lung cancer (SCLC). Scintigraphy a nd pharmacokinetics were performed up to 3 days after injection. Resul ts: No adverse reactions were found after injection of MAb MOC-31. Pha rmacokinetics obtained from plasma radioactivity showed plasma disappe arance described most properly by a monoexponential model with a mean half-life value of 17.0 +/- 1.4 hr. HPLC analysis documented the monom eric MOC-31 without evidence of immune complexes or radioactive lower molecular weight fractions. Mean 24-hr urinary excretion of radioactiv ity was 4.3% of the injected dose. Scintigraphy detected primary tumor or metastases in five of six patients. Localization of radioactivity in normal tissue was restricted, but additional experiments need to be performed to elucidate possible cross-reactivity of MOC-31 with norma l tissue in vivo. Conclusion: Preliminary results justify further stud ies to reveal the possible usefullness of radiolabeled MOC-31 in the t herapeutic and diagnostic management of SCLC.