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Background: Although doxorubicin remains one of the most effective agents for the treatment of solid tumors, there is an intensive effort to synthesize doxorubicin analogues (compounds with similar chemical structures) that may have improved antitumor properties. We have synthesized a novel doxorubicin disaccharide analogue (MEN 10755) and have characterized some of its relevant biochemical, biologic, and pharmacologic properties. Methods: The antitumor activity of this compound (MEN 10755) was studied in a panel of human tumor xenografts, including xenografts of A2780 ovarian tumor cells, MX-1 breast carcinoma cells, and POVD small-cell lung cancer cells. MEN 10755 was compared with doxorubicin according to the optimal dose and schedule for each drug. The drug's cytotoxic effects, induction of DNA damage, and intracellular accumulation were studied in A2780 cells. DNA cleavage mediated by the enzyme topoisomerase II was investigated in vitro by incubating fragments of simian virus 40 DNA with the purified enzyme at various drug concentrations and analyzing the DNA cleavage-intensity patterns. Drug-induced apoptosis (programmed cell death) in tumors was determined with the use of MX-1 and POVD tumor-bearing athymic Swiss nude mice. Results: MEN 10755 was more effective than doxorubicin as a topoisomerase II poison and stimulated DNA fragmentation at lower intracellular concentrations. In addition, MEN 10755 exhibited striking antitumor activity in the treatment of human tumor xenografts, including those of the doxorubicin-resistant breast carcinoma cell line MX-1. Conclusions: The high antitumor activity of MEN 10755 in human tumor xenografts, including doxorubicin-resistant xenografts, and its unique pharmacologic and biologic properties make this disaccharide analogue a promising candidate for clinical evaluation. [J Natl Cancer Inst 1997;89:1217-23]

Background: The doxorubicin analogues cyanomorpholino doxorubicin (MRA-CN) and morpholino doxorubicin (MRA) were synthesized in an attempt to avoid the cardiotoxicity and drug resistance of doxorubicin therapy. MRA-CN forms interstrand DNA cross-links without requiring microsomal metabolic activation in the presence of reduced nicotinamideadenine dinucleotide phosphate (NADPH) to form a product that alkylates DNA, but MRA requires metabolic activation. Alkylation produces DNA cross-links, which are associated with potentiation of the cytotoxicity of some drugs. Purpose: Our purpose was to study the DNA binding of MRA-CN and MRA with and without metabolic activation in order to better understand the mechanisms for cross-linking DNA. Methods: We used [[H.sup.3]]MRA and [[H.sup.3]]MRA-CN, with the [H.sup.3] labeled at C-2 and C-6 of the morpholino ring. MRA (10 nM) was incubated with human liver microsomes with or without NADPH to measure DNA binding. In addition, a filter elution assay was used to determine the nature and extent of drug binding to DNA in the human ovarian carcinoma cell line ES-2. We studied the appearance of interstrand crosslinks versus total DNA adducts in pBR322 plasmid DNA incubated with 100 nM MRA-CN in cell-free medium and then subjected to denaturation and agarose gel electrophoresis. Results: Regardless of the extracellular concentration of the drug (1-100 nM), 85% of intracellular MRA-CN was covalently bound to DNA, and the total amount of drug bound to DNA was proportional to extracellular drug concentration. No covalent binding of MRA to DNA was found in cells exposed to 10 nM MRA alone for 2 hours. In contrast, 10% of the intracellular drug was bound to DNA if the cells were exposed to MRA preincubated with human liver microsomes and NADPH. The percentage of plasmids containing at least one interstrand cross-link rose from 35% at 15 minutes to 92% at 2 hours. We estimate that eight molecules of MRA-CN were adducted per molecule of pBR322 DNA (or one drug adduct per 545 base pairs), with a minimum of 12.% of the adducts forming interstrand cross-links. Conclusions: These results suggest that the carbons at positions 2 and 6 of the morpholino ring of both MRA-CN and the activated metabolite of MRA are retained in the drug-DNA adduct. They also indicate that the formation of interstrand DNA cross-links by MRA-CN is preceded by formation of drug adducts to a single strand of DNA. [J Natl Cancer Inst 1587-1592, 1992]

Cal Bio wins big grant California Biotechnology Inc. is celebrating a $470,000 Small Business Innovation Research Program grant from the National Institutes of Health. The grant will be used to [...]