Prevention of adriamycin toxicity

Formation of transition metal-doxorubicin complexes inside liposomes

Doxorubicin complexation with the transition metal manganese (Mn(2+)) has been characterized, differentiating between the formation of a doxorubicin-metal complex and doxorubicin fibrous-bundle aggregates typically generated following ion gradient-based loading procedures that rely on liposome encapsulated citrate or sulfate salts. The physical and chemical characteristics of the encapsulated drug were assessed using cryo-electron microscopy, circular dichroism (CD) and absorbance spectrophotometric analysis. In addition, in vitro and in vivo drug loading and release characteristics of the liposomal formulations were investigated. Finally, the internal pH after drug loading was measured with the aim of linking formation of the Mn(2+) complex to the presence or absence of a transmembrane pH gradient. Doxorubicin was encapsulated into either 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol (Chol) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/Chol liposomes, where the entrapped salts were citrate, MnSO(4) or MnCl(2). In response to a pH gradient or a Mn(2+) ion gradient, doxorubicin accumulated inside to achieve a drug-to-lipid ratio of approximately 0.2:1 (wt/wt). Absorbance and CD spectra of doxorubicin in the presence of Mn(2+) suggested that there are two distinct structures captured within the liposomes. In the absence of added ionophore A23187, drug loading is initiated on the basis of an established pH gradient; however, efficient drug uptake is not dependent on maintenance of the pH gradient. Drug release from DMPC/Chol is comparable regardless of whether doxorubicin is entrapped as a citrate-based aggregate or a Mn(2+) complex. However, in vivo drug release from DSPC/Chol liposomes indicate less than 5% or greater than 50% drug loss over a 24-h time course when the drug was encapsulated as an aggregate or a Mn(2+) complex, respectively. These studies define a method for entrapping drugs possessing coordination sites capable of complexing transition metals and suggest that drug release is dependent on lipid composition, internal pH, as well as the nature of the crystalline precipitate, which forms following encapsulation.

Structure-dependent antitumor activities of novel anthracyclines YM1, YM3, YM4 and YM6: drug transport properties and effects on biomacromolecule synthesis in drug sensitive and resistant leukemia cells

The antitumor activities of four novel doxorubicin (DOX) analogues, YM1, YM3, YM4 and YM6 in relation to their structure and drug transport properties, have been investigated in U937 monocytic and CCRF-CEM lymphoid drug sensitive leukemia cell lines, as well as in CEM/VLB100, a drug resistant subline displaying high levels of P-glycoprotein. Treatment of all cell lines with YM1, 3, 4 and 6 produced a dose-dependent decrease in DNA, RNA and protein synthesis as measured by [3H]-thymidine, [3H]-uridine and [3H]-leucine uptake respectively. YM1 was more effective than YM3, YM4 or YM6 against the drug sensitive cells. The antitumor effects of all these DOX-analogues on macromolecule synthesis in U937 and CCRF-CEM cells were lower than that of DOX and epirubicin (EDR). A rapid accumulation of the novel anthracyclines was found in all cell lines compared with DOX or EDR. However, the maximal accumulation of the DOX-analogues was lower than that of EDR. There is a greater efflux from CCRF-CEM sensitive cells and less from CEM/VLB100 resistant cells of the DOX-derivatives when compared with EDR and DOX. Drug-induced cytotoxicity significantly correlated (P < 0.05) with drug retention levels in CCRF-CEM and U937 drug sensitive cells as indicated by an inverse correlation curve between anthracycline retention and drug-induced IC50 value. It was demonstrated that an increased level of drug retained within the sensitive cells would therefore produce a more cytotoxic effect of the drug. However, no such correlation was observed in CEM/VLB100 resistant cells. YM3 was shown to have an increased antitumor activity against CEM/VLB100 resistant cells compared with DOX with a lower resistance factor. These results showed that the antitumor effects of four novel DOX-analogues, like DOX or EDR, were associated with inhibition of DNA replication, transcription and translation. The finding that resistant leukemic cells are more susceptible to the cytotoxic effect of YM3 than DOX warrants further investigation to identify the intrinsic mechanism of resistance.

DMSO protects against adriamycin-induced tissue necrosis

Inadvertent extravasation of Adriamycin (Adria) can result in severe tissue necrosis. The mechanism of this tissue damage is believed to be the release of free radicals into the tissue. Topical applications of dimethylsulfoxide (DMSO) used after Adria extravasation have been shown to decrease ulcer size. This may be due to DMSO's ability to scavenge free radicals. However, effective topical therapy requires prompt recognition of extravasation, which is often difficult. We hypothesized that the delivery of Adria in low concentrations DMSO would reduce Adria-induced ulcer size and ulcer incidence caused by Adria extravasation. To test this hypothesis, 180, male Sprague-Dawley rats were randomly allocated into three treatment groups of 60 each. All three groups received intradermal injections of Adria (1 mg) diluted in 0.5 cc of saline (Group 1), 10% DMSO (Group 2), or 20% DMSO (Group 3). Rats were observed for 4 weeks. Ulcer incidence (%) and size of ulcers (mm2) were assessed over time. Area of skin ulceration was calculated as the product of the two greatest diameters. Statistical evaluation of the differences in incidence and ulcer size between Group 1 and Groups 2 or 3 were evaluated using analysis of variance. Delivery of Adriamycin in 10 or 20% DMSO resulted in a statistically significant (P less than 0.001) decrease in the incidence of ulceration caused by intentional Adria extravasation.

Experimental chemotherapy-induced skin necrosis in swine. Mechanistic studies of anthracycline antibiotic toxicity and protection with a radical dimer compound

The reactivity of antitumor anthracycline and mitomycin C antibiotics with the oxomorpholinyl radical dimers, bi(3,5,5-trimethyl-2-oxomorpholin-3-yl) (TM3) and bi(3,5-dimethyl-5-hydroxymethyl-2-oxomorpholin-3-yl) (DHM3), was studied in vitro. The oxomorpholinyl radical reduced daunorubicin to a quinone methide intermediate that reacted with solvent to form 7-deoxydaunorubicinone. The solvolysis reaction followed first order kinetics, and the reactivity rate constants (k2) measured for seven anthracycline analogues ranged from 2 X 10(-2) s-1 to 8.0 X 10(-4) s-1. The chemical reactivity of each anthracycline quinone methide correlated with the total skin toxicity caused by the respective parent anthracycline following injection into swine skin. Microscopic examination of experimental lesions in swine skin resemble those observed in humans after inadvertant chemotherapy extravasation. Hydrocortisone sodium succinate was not effective for the treatment of doxorubicin-induced skin necrosis, whereas DHM3 was effective for the treatment of skin necrosis caused by all seven anthracyclines and by the quinone containing antibiotic, mitomycin C.

Anthracycline antitumour agents. A review of physicochemical, analytical and stability properties

A review of physicochemical and analytical properties of anthracycline antitumour agents is presented. The following subjects are discussed: protolytic equilibria, partition and partition coefficients, self-association, adsorptive properties, metal complexation, spectroscopy and chromatography. Furthermore, the stability of anthracyclines in solutions, in pharmaceutical preparations and in biological media is discussed.