Adriamycin analogs. Rationale, synthesis, and preliminary antitumor evaluation of highly active DNA-nonbinding N-(trifluoroacetyl)adriamycin 14-O-hemiester derivatives

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Abstract
N-(Trifluoroacetyl)adriamycin 14-valerate (AD 32), a novel DNA nonbinding analogue of adriamycin with superior experimental antitumor activity, has undergone extensive clinical trial, with documentation of antitumor activity and low toxicity in human subjects. However, poor water solubility necessitates that the drug be administered to patients by continuous intravenous infusion at high dilution in a surfactant-containing formulation, with steroid prophylaxis to protect against a chest pain syndrome associated with the vehicle. On the basis of pharmacologic considerations, the title compounds have been prepared as second-generation analogues of N-(trifluoroacetyl)adriamycin 14-valerate with improved aqueous solubility; use is made of the available carboxylic acid function to solubilize the products in dilute aqueous alkaline medium. Target compounds were made by treating N-(trifluoroacetyl)-14-halodaunorubicin (bromo or iodo) with monosodium salts of dibasic acids (malonic, succinic, glutaric, adipic, pimelic, azelaic, sebacic) in aqueous acetone. All of the products showed significant in vivo antitumor activity against the murine P388 leukemia (ip tumor, ip treatment once daily on days 1, 2, 3, and 4); most compounds were superior to the +181% increase in life span afforded by adriamycin (optimal dose 3.0 mg/kg per day), one of two drugs used as positive controls for the assays. Several of the test compounds showed highly curative activity in this system, similar to N-(trifluoroacetyl)adriamycin 14-valerate, the other positive control agent. The hemiadipate product exhibited the most desirable properties of high antitumor efficacy (86% cure rate of all P388 tumor-bearing animals through four levels of a 40-70 mg/kg dose-response range), aqueous solubility (60 mg/mL in pH 7.4 phosphate buffer), and solution stability (no decomposition at 4.degree. C, 0.5% hydrolysis at 27.degree. C, over 24 h at pH 7.4).