INVESTIGATION OF A RADIOACTIVE DRUG (TRA 119) WITH SPECIAL REFERENCE TO AUTORADIOGRAPHIC AND RELATED STUDIES

The development of a [211At]-astatinated endoradiotherapeutic drug: Part II. Therapeutic results for transplanted adenocarcinoma of the rectum in mice and associated studies

PURPOSE

6-[211At]-astato-MNDP is of a class of a high linear energy transfer endoradiotherapeutic drug, which selectively targets to an onco-APase isoenzyme expressed by certain epithelial and germ cell tumors. The therapeutic efficacy and acute toxicity of its endogenous alpha-particle emissions have been studied in a murine tumor model.

METHODS AND MATERIALS

211At was produced by the 207Bi(alpha,2n)211 At cyclotron-based nuclear reaction. High specific activity 6-[211At]-astato-MNDP was rapidly synthesized by in vacuo thermal heterogeneous isotopic exchange. The therapeutic potential of 6-[211At]-astato-MNDP and 211At- was determined in mice bearing a transplanted CMT-93 rectal carcinoma which exhibited onco-APase activity.

RESULTS

Significant therapeutic effects due to targeted alpha-particle emissions have been confirmed for the activity dose range, 10-750 kBq 6-[211At]-astato-MNDP. A therapeutic window has been identified, whereby cure rates of approximately 45-65% were achieved following administration of 55-300 kBq 6-[211At]-astato-MNDP. Estimated tumor absorbed radiation doses were not inconsistent with clinical response. Irreversible hematoxicity or stigmata of acute radiation damage in other critical normal tissues were not encountered. Nonspecifically internalized 211At- exerted no therapeutic effect.

CONCLUSION

Therapeutic results for 6-[211At]-astato-MNDP have confirmed the profound in vivo cytotoxicity of its targeted alpha-radiations in the CMT-93 tumor. Acute normal tissue toxicity was acceptable. A rationale for optimal fractionation of targeted 6-[211At]-astato-MNDP endoradiotherapy is discussed, and its putative role in the possible individualized management of certain human tumors has been proposed.

The development of A [211At]-astatinated endoradiotherapeutic drug: Part I. Localization by alpha-particle autoradiography in a murine tumor model

Alpha-particle track autoradiography has been used to define the in vivo cellular and intracellular distribution of radioactivity from the potential high linear energy transfer endoradiotherapeutic drug, 6-[211At]-astato-2-methyl-1,4-naphthoquinol bis(diphosphate) in tumor and relevant critical normal tissues of mice bearing a transplanted murine rectal carcinoma. A strikingly selective uptake of this compound into tumor cells, particularly into specific tumor cell nuclei, has been demonstrated. Its localization in certain tumor cells appears to depend on the presence of an onco-product, in this case an alkaline phosphatase isoenzyme, which is synthesized in some tumor cells and to which the compound targets. In curable tumors, it selectively concentrates in cells which may be regarded as tumor stem cells. There is low uptake into normal cells, particularly those in bone marrow, colon, and lung, where its sequestration is mainly extranuclear.

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.

Investigations of tritiated menadiol sodium diphosphate (T-MNDP) as a radioactive drug

An attempt has been made to develop tritiated derivatives of Synkavit (menadiol sodium diphosphate, MNDP) of high specific activity as a radioactive drug.This paper summarizes the preliminary biological and physical studies, with emphasis on approximate radiation dosimetry and the necessary preliminary testing, and then gives an account of the clinical investigations and the trials carried out so far, which correspond essentially to Phases I and II trials for a chemotherapeutic agent.In all, 214 patients with different sites and types of advanced and recurrent, inoperable, histologically verified malignant tumours including reticuloses have been treated with doses of at least 1 Ci of the various preparations. Among the 203 evaluable treated cases, some form of response was observed in 23 out of 151 (15·2%) receiving the drug by intravenous injections and 13 out of 52 (25%) after intra-arterial injections. For the sites and types of malignant diseases which showed responses after either intravenous or intra-arterial administration among the 55 patients surviving at least 3 months after the first injection, some form of response was observed in 32 but only 5 of these showed either a "complete" or a "partial" response.It is concluded that further investigation is desirable. It is suggested that clinical trials with randomization should be carried out for inoperable cases of carcinoma of the colon and of the pancreas.