Multi-responsive polymer micelles as ellipticine delivery carriers for cancer therapy.

In the present study, we describe the synthesis and physicochemical properties of a novel pH- and thermoresponsive micellar drug delivery system for an anticancer ellipticinium derivative based on the triblock copolymer poly(ethylene oxide)-block-[tert-butylacrylamide-co-6-(N-methacryloylamino)hexanoic acid hydrazide]-block-poly(ethylene oxide). The system was designed to meet the basic criteria required for drug carrier systems, namely, solubility in water (overcoming the insolubility of ellipticine), satisfactory drug loading, particle size suitable for an efficient enhanced permeability and retention effect and adequate stability in blood plasma (pH 7.4) followed by rapid drug release in tumors or tumor cell endosomes (pH<6.5). The copolymer in the form of a unimer can be eliminated by kidneys because the weight-average molecular weight of 21 kDa is sufficiently below the renal threshold. The half-life of drug release in a pH 5.0 buffer solution (pH of a late endosome) was ~45 h, but a negligible amount of the free ellipticine derivative was detected at pH 7.4 (pH of blood). Consequently, this supramolecular polymer conjugate is a good candidate for the delivery of ellipticine-based drugs and will therefore be subjected to more detailed studies.

Determination of ellipticine in biological samples by high-performance liquid chromatography.

Ellipticine, a plant alkaloid effective against murine leukemias and solid tumors, is presently undergoing toxicological assessment prior to clinical trial. A rapid, sensitive, reversed-phase high-performance liquid chromatographic method employing an internal standard was developed for the detection of ellipticine and its principal metabolite 9-hydroxyellipticine after extraction from biological samples. The method was successfully applied to the quantitation of ellipticine in mouse blood and tissues after intravenous administration of ellipticine and to mouse blood levels of drug after oral administration. Similar success was achieved in determinations of ellipticine and 9-hydroxyellipticine in samples of spiked human blood and plasma. Mouse blood ellipticine levels monitored over 3 h after the intravenous administration of drug demonstrated a biphasic decline with a terminal half-life of 52 min.

A possible mechanism of ellipticine-induced hemolysis.

Ellipticine (E) [5,11-dimethyl-6H-pyrido-(4,3-b)-carbazole, NSC-71795] is an antineoplastic agent which is active against L1210 lymphocytic leukemia in mice. Preclinical toxicologic studies demonstrated hemolysis in dogs and monkeys following intravenous administration of 1.5 mg/kg. This finding prompted this investigation of the mechanism of hemolysis and a study of the various factors that might ameliorate this effect. Initial experiments demonstrated that human red blood cells were completely hemolyzed at an E concentration of 10(-3) M, while a concentration of 10(-4) M stabilized red blood cells against 150 mOsM NaCl. The extent of hemolysis correlated well with the surface activities, lipophilic properties and cellular uptake of E and some of its derivatives (7,10-dimethylellipticine, isoellipticine, 9-methoxyellipticine and 11-demethylellipticine). The greatest hemolysis occurred with 7,10-dimethylellipticine and the least with 11-demethylellipticine. The cellular uptake of E and its derivatives was linear over a wide concentration range and was not temperature-dependent. Hemolysis could be blocked by citrate, sodium ethylenediamine tetraacetate, oxytetracycline and [(+/-)-1,2-bis(3,5-dioxopiperazin-1-y1)propane]. The inhibition of E uptake by citrate appears to be a noncompetitive process and has a K1 of 1.9 X 10(-3) M. These data suggest that Ca++ might be involved in the hemolytic process and in the cellular uptake of E. The intravenous administration of ellipticine to rhesus monkey caused severe hemolysis which could be prevented by simultaneous injection of citrate.