Spirogermanium--a novel antitumour agent expressing a lack of cross-resistance in vitro with a range of 'standard' antitumour drugs.

We have used a series of drug resistant continuous tumour cell lines of murine, hamster or human origin, to screen in vitro for new drugs effective at overcoming resistance expressed to clinically useful antitumour drugs. We have established that spirogermanium appears to express a unique lack of cross resistance to a wide range of 'standard' antitumour drugs including 5-fluorouracil, cisplatin, methotrexate, vincristine and adriamycin, as judged by its equivalent effectiveness in reducing survival, measured by clonogenic assays, of the parental and drug-resistant sublines following 24 hour in vitro treatments. Spirogermanium was also able to overcome the multidrug resistance exhibited by the colchicine-resistant mutant CHRC5 cells and a subline of vincristine-resistant MCF-7 human breast carcinoma cells, following 1 or 24 hour drug treatments. These preclinical studies suggest that this novel compound may prove a potentially useful agent for inclusion in 'non-cross-resistant drug combinations'.