Tumor localization and biodistribution of 99mTc-muramylpolypeptide (MPP) in the rat

Muramylpolypeptide, extracted from Nocardia opaca bacteria and originally designed for immunotherapy of malignant tumors, proved to localize in malignant tumors, when labeled with 99mTc. In the tumor-bearing rat 99mTc-muramylpolypeptide (MPP) showed a fast turnover and optimum tumor to soft tissue ratios were obtained as early as between 30-60 min after application. The uptake mechanism in malignant tumors remains uncertain.