6-125I-iodo-2-methyl-1,4-naphthoquinol bis (diammonium phosphate) as a potential radio-halogenated anti-cancer agent: in vitro investigations and possible clinical implications.

6-125-I-iodo-2-methyl-1,4-naphthoquinol bis (diammonium phosphate) (6-125I-iodo-MNDP) has been synthesised and studied as the prototype of a class of potential radio-halogenated anti-cancer agents. The incorporated 125I provides Auger electron radiations which behave like high LET radiations in the treatment of tumours, though the accompanying X- and gamma-radiations make an undesirable contribution to the total body dose. The in vitro experiments reported show that 6-125I-iodo-MNDP is selectively concentrated in the cells of some human malignant tumours by factor of about 15 to 20 or more in relation to the cells of normal origin studied. On the basis of dosimetric considerations and comparison with clinical treatment with tritiated methylnaphthoquinol diphosphate, practical dosage of 6-125I-iodo-MNDP is suggested and clinical indications and safety of use are discussed. The types of tumour of particular interest are inoperable cases of carcinoma of the colon, carcinoma of the pancreas, malignant melanoma and osteosarcoma. Further investigations are in progress.