Zorubicin Research Articles

Arachidonic Acid Metabolism by Human Cardiovascular CYP2J2 Is Modulated by Doxorubicin.

Doxorubicin (DOX) is a chemotherapeutic that is used in the treatment of a wide variety of cancers. However, it causes cardiotoxicity partly because of the formation of reactive oxygen species. CYP2J2 is a human cytochrome P450 that is strongly expressed in cardiomyocytes. It converts arachidonic acid (AA) into four different regioisomers of epoxyeicosatrienoic acids (EETs). Using kinetic analyses, we show that AA metabolism by CYP2J2 is modulated by DOX. We show that cytochrome P450 reductase, the redox partner of CYP2J2, metabolizes DOX to 7-deoxydoxorubicin aglycone (7-de-aDOX). This metabolite then binds to CYP2J2 and inhibits and alters the preferred site of metabolism of AA, leading to a change in the ratio of the EET regioisomers. Furthermore, molecular dynamics simulations indicate that 7-de-aDOX and AA can concurrently bind to the CYP2J2 active site to produce these changes in the site of AA metabolism. To determine if these observations are unique to DOX/7-de-aDOX, we use noncardiotoxic DOX analogues, zorubicin (ZRN) and 5-iminodaunorubicin (5-IDN). ZRN and 5-IDN inhibit CYP2J2-mediated AA metabolism but do not change the ratio of EET regioisomers. Altogether, we demonstrate that DOX and 7-de-aDOX inhibit CYP2J2-mediated AA metabolism and 7-de-aDOX binds close to the active site to alter the ratio of cardioprotective EETs. These mechanistic studies of CYP2J2 can aid in the design of new alternative DOX derivatives.

Stability and compatibility studies of zorubicin in intravenous fluids and PVC infusion bags

The stability of zorubicin (ZOR) in admixtures for continuous intravenous infusion was studied. ZOR was reconstituted and diluted to 600 μg ml −1 for simulated infusion and to 250 and 1000 μg ml −1 for storage in poly(vinyl chloride) (PVC) bags containing 5% dextrose injection or 0.9% sodium chloride injection (0.9% NaCl). Bags were then stored at refrigerated temperature (4°C) and in the dark for 24 h. ZOR concentrations in each admixture were tested by stability-indicating high-performance liquid chromatographic (HPLC) assay with ultraviolet detection. No substantial loss of ZOR was observed during simulated infusions ( n = 4) using PVC infusion bags and administration sets over a 1 h infusion. The drug stored at 4°C in the dark in PVC bags showed that it is highly unstable at 250 μg ml −1 in 0.9% NaCl injection and in 5% dextrose injection. On the other hand, under the same storage conditions, at 1000 μg ml −1, ZOR is more stable in 0.9% NaCl injection (6 h) than in 5% dextrose (4 h). The reported superior stability of the 1000 μg ml −1 in 0.9% NaCl can be explained, at least in part, by the difference in pH. Changes in pH, particularly a decrease, seem to affect adversely the stability of ZOR. In fact, ZOR is rapidly converted into daunorubicin, the dominant degradation product, which is more cardiotoxic than the parent drug. Therefore, several precautions must be observed when the commercial product (Rubidazone) is prepared and reconstituted in i.v. fluids and containers.