Amsacrine analog-loaded solid lipid nanoparticle to resolve insolubility for injection delivery: characterization and pharmacokinetics.

Amsacrine analog is a novel chemotherapeutic agent that provides potentially broad antitumor activity when compared to traditional amsacrine. However, the major limitation of amsacrine analog is that it is highly lipophilic, making it nonconductive to intravenous administration. The aim of this study was to utilize solid lipid nanoparticles (SLN) to resolve the delivery problem and to investigate the biodistribution of amsacrine analog-loaded SLN. Physicochemical characterizations of SLN, including particle size, zeta potential, entrapment efficiency, and stability, were evaluated. In vitro release behavior was also measured by the dialysis method. In vivo pharmacokinetics and biodistribution behavior of amsacrine analog were investigated and incorporated with a non invasion in vivo imaging system to confirm the localization of SLN. The results showed that amsacrine analog-loaded SLN was 36.7 nm in particle size, 0.37 in polydispersity index, and 34.5±0.047 mV in zeta potential. More than 99% of amsacrine analog was successfully entrapped in the SLN. There were no significant differences in the physicochemical properties after storage at room temperature (25°C) for 1 month. Amsacrine analog-loaded SLN maintained good stability. An in vitro release study showed that amsacrine analog-loaded SLN sustained a release pattern and followed the zero equation. An in vivo pharmacokinetics study showed that amsacrine analog was rapidly distributed from the central compartment to the tissue compartments after intravenous delivery of amsacrine analog-loaded SLN. The biodistribution behavior demonstrated that amsacrine analog mainly accumulated in the lungs. Noninvasion in vivo imaging system images also confirmed that the drug distribution was predominantly localized in the lungs when IR-780-loaded SLN was used.

Formulation and pharmacokinetic evaluation of an asulacrine nanocrystalline suspension for intravenous delivery.

Asulacrine (ASL) is an inhibitor of topoisomerase II, which has shown potential against breast and lung cancer. It is a poorly water soluble drug. To allow intravenous (i.v.) administration, ASL was formulated as a nanocrystalline suspension by high pressure homogenization. The nanosuspension was lyophilized to obtain the dry ASL nanoparticles (average size, 133+/-20nm), which enhanced both the physical and chemical stability of the ASL nanoparticles. ASL dissolution and saturation solubility were enhanced by the nanosuspension. Differential scanning calorimetry and X-ray diffraction analysis showed that the crystallinity of the ASL was preserved during the high pressure homogenization process. The pharmacokinetics and tissue distribution of ASL administered either as a nanosuspension or as a solution were compared after i.v. administration to mice. In plasma, ASL nanosuspension exhibited a significantly (P<0.01) reduced C(max) (12.2+/-1.3microg ml(-1)vs 18.3+/-1.0microg ml(-1)) and AUC(0-infinity) (18.7+/-0.5microg ml(-1)h vs 46.4+/-2.6microg ml(-1)h), and a significantly (P<0.01) greater volume of distribution (15.5+/-0.6lkg(-1)vs 2.5+/-0.1lkg(-1)), clearance (1.6+/-0.04lh(-1)kg(-1)vs 0.6+/-0.04lh(-1)kg(-1)) and elimination half-life (6.1+/-0.1h vs 2.7+/-0.2h) compared to the ASL solution. In contrast, the ASL nanosuspension resulted in a significantly greater AUC(0-infinity) in liver, lung and kidney (all P<0.01), but not in heart.

Development and validation of bioanalytical method for the determination of asulacrine in plasma by liquid chromatography.

Asulacrine (9-[(2-methoxy-4-methylsulphonylamino)phenylamino]-N,5-dimethyl-4-acridinecarboxamide), an analogue of the antileukaemia drug amsacrine, has high antitumour activity in mice and has also shown clinical activity. A simple method is described for the quantitation of asulacrine in plasma by liquid chromatography. Chromatographic separation was achieved on a reversed phase C 18 column (250 mm x 4.6mm, particle size 5 microm, Gemini) using isocratic elution (acetonitrile and 0.01 M sodium acetate buffer pH 4.0, 45/55, v/v) at a flow rate of 1 ml/min. Asulacrine and internal standard (the ethylsulphonanilide analogue) were measured using UV detection at 254 nm. The total chromatographic run-time was 8 min with asulacrine and internal standard eluting at approximately 4.7 and approximately 6.5 min, respectively. Limit of quantification was 0.1microg/ml. The linearity range of the method was 0.1-10 microg/ml (r2=0.9995). Mean recoveries from plasma were 100-105%. Intra-batch and inter-batch precision was 7.1 and 7.8%, respectively, and intra-batch and inter-batch accuracy (relative error) was 4.9 and 8.4%, respectively (n=8 in all cases). The bench top, freeze thaw, short-term storage and stock solution stability evaluation indicated no evidence of degradation of asulacrine. The validated method is simple, selective and rapid and can be used for pharmacokinetic studies in mice.

Highly sensitive analysis of the anti-tumor agent 1-[4-(furo[2,3-b]-quinolin-4-ylamino)phenyl]ethanone in rat plasma by high-performance liquid chromatography using electrochemical detection.

A sensitive high-performance liquid chromatography method with electrochemical detection was developed for the purpose of determining the concentration of the new anti-tumor agent 1-[4-(furo[2,3-b]-quinolin-4-ylamino)phenyl]ethanone (FQPE) in rats. The plasma samples were spiked with the internal standard diclofenac and extracted using dichloromethane. A C(18) 250 mm x 4mm column was used for the separation of analyte with a mobile phase consisting of 50% acetonitrile and 50% pH 3.0 of sodium 1-pentansulfonate solution at a flow rate of 1.0 mL/min. FQPE was detected by electrochemical detector at 1.0 V and 20 nA. Intra-day and inter-day precision and accuracy were acceptable down to the limit of quantization of 1 ng/mL. The lower limit of detection (LOD) was 0.5 ng/mL. The pharmacokinetic parameters of FQPE in rats after intravenous administration of 2.1 and 4.2 mg/kg were determined. The apparent volume of distribution, half-life of elimination, and clearance showed no significant difference between the two dosages. The area under the plasma concentration time curve increased proportionally with dose. The half-life of FQPE was prolonged about 2.4-fold, compared with amsacrine.

Plasma and cellular pharmacokinetics of m-AMSA related to in vitro toxicity towards normal and leukemic clonogenic bone marrow cells (CFU-GM, CFU-L).

Plasma and cellular pharmacokinetics of m-AMSA were investigated in 5 patients with acute leukemia, using HPLC. The pharmacokinetic data served as a guideline for in vitro toxicity tests on clonogenic bone marrow cells. m-AMSA was administered as a 3-hour intravenous infusion of 100 mg/m2. Median plasma and nucleated blood cell peak concentrations were 1.25 and 6.36 micrograms/ml followed by biphasic elimination with a median T1/2 alpha alpha of 1.6 h and 0.3 h and a median T1/2 beta of 5.0 h and 5.0 h respectively. Median plasma and cellular area under the curve (AUC) for a 24-h period amounted 6.2 micrograms.h/ml and 49.8 micrograms.h/ml respectively. In vitro cellular uptake was maximal at least within 30 minutes. No differential toxicity for CFU-GM and CFU-L was observed in relation to exposure time. Median IC50 for CFU-GM and CFU-L was 2.2, 1.8 and 1.6 micrograms/ml after incubation periods of resp. 0.08, 4 and 24 h. The corresponding m-AMSA concentration x time products to achieve 50% inhibition (IAUC50) were 0.18, 7.2 and 38.4 micrograms.h/ml, respectively. 48-h prestimulation of the clonogenic bone marrow cells with Human Placenta Conditioned Medium increased sensitivity (median 1.7 x) after 4 h incubation with mAMSA. Short exposure provides maximal, concentration-related, cellular uptake, resulting in effective inhibition of growth of clonogenic bone marrow cells.

Oxidative metabolism of amsacrine by the neutrophil enzyme myeloperoxidase.

Oxidative metabolism of the anti-cancer drug amsacrine 4'-(9-acridinylamino) methane-sulphan-m-anisidide has been suggested to account for its cytotoxicity. However, enzymes capable of oxidizing it in non-hepatic tissue have yet to be identified. A potential candidate, that may be relevant to the metabolism of amsacrine in blood and its action in myeloid leukaemias and myelosuppression, is the haem enzyme myeloperoxidase. We have found that the purified human enzyme oxidizes amsacrine to its quinone diimine, either directly or through the production of hypochlorous acid. In comparison, the 4-methyl-5-methylcarboxamide derivative of amsacrine, CI-921 9-[[2-methoxy-4[(methylsulphonyl)-amino]phenyl]amino)-N, 5-dimethyl-4-acridine carboxamide, reacted poorly with myeloperoxidase, although it was oxidized by hypochlorous acid. Detailed studies of the mechanism by which myeloperoxidase oxidizes amsacrine revealed that the semiquinone imine free radical is a likely intermediate in this reaction. Oxidation of amsacrine analogues indicated that factors other than their reduction potential determine how readily they are metabolized by myeloperoxidase. Both amsacrine and CI-921 inhibited production of hypochlorous acid by myeloperoxidase. CI-921 acted by trapping the enzyme as the inactive redox intermediate compound II. Amsacrine inhibited by a different mechanism that may involve conversion of myeloperoxidase to compound III, which is also unable to oxidize Cl-. The susceptibility of amsacrine to oxidation by myeloperoxidase indicates that this reaction may contribute to the cytotoxicity of amsacrine toward neutrophils, monocytes and their precursors.

Thiolytic cleavage and binding of the antitumour agent CI-921 in blood.

The antitumour agent 9-[[2-methoxy-4-[methylsulphonylamino]-phenyl]amino]-N,5-dimethyl- 4-acridinecarboxamide (CI-921; NSC 343499) is currently undergoing clinical evaluation. The plasma disposition of this compound together with its ability to bind to plasma proteins has been investigated in the mouse. Five minutes after intravenous administration of [acridinyl-G-3H]-CI-921 (57.7 mol/kg) to male BDF1 mice, plasma samples were taken and precipitated with acetonitrile. 17% of the total plasma radioactivity was found to be bound to plasma proteins, increasing to 31% by 30 min. To ascertain the mechanism of binding, [acridinyl-G-3H]-CI-921 was incubated at 37 degrees C in mouse blood or plasma and the radioactivity analysed after precipitation with acetonitrile. CI-921 and the cleavage product 4-amino-3-methoxy-methanesulphonanilide (MSA) were detected in the acetonitrile supernatants by HPLC using electrochemical and ultraviolet detection. After incubation for 1 h with blood, extensive association of radioactivity (80% of total) with plasma proteins, together with a rapid decrease in CI-921 concentration and a concomitant increase in MSA concentration, was observed. In blood samples from mice given CI-921, low concentrations (1 to 2 mumol/l) of MSA were detected up to 1 h after injection. The results suggest that in vivo at least part of the covalent binding in blood arises from the nucleophilic attack by protein thiols at the C-9 position of the acridine ring resulting in covalent protein adducts and release of MSA.

Determination of amsacrine in human nucleated hematopoietic cells.

A new method has been developed for the determination of amsacrine (AMSA) in human nucleated hematopoietic cells. In order to prevent efflux during the cell separation procedure, white blood cells (WBCs) were separated from red blood cells by dextran sedimentation, leaving the WBCs in their natural environment. After cell counting, pelletting the cell suspension and correcting for the admixture of supernatant, AMSA was extracted from the WBCs and determined by high-performance liquid chromatography. Linearity of extraction was observed up to 40.10(6) cells. The inter-assay variation was 4.7%. Plasma and cellular concentrations were measured in five patients at the end of a 3-h infusion of 100 mg/m2 AMSA. A pharmacokinetic study of plasma and cellular AMSA concentrations up to 19 h after infusion was carried out. AMSA concentrations in WBCs correlated well with the plasma levels (n = 20, r = 0.967) with an accumulation factor compared to the plasma concentration of 2.6-9.8 in the patients studied. The method described is useful for studying cellular pharmacokinetics of AMSA in man.

The effect of food on the bioavailability and kinetics of the anticancer drug amsacrine and a new analogue, N-5-dimethyl-9-[(2-methoxy-4-methylsulphonylamino)phenylamino]-4 acridinecarboxamide in rabbits.

Both amsacrine and its analogue, N-5-dimethyl-9-[(2-methoxy-4- methylsulphonylamino)phenylamino]-4-acridinecarboxamide (CI-921) are absorbed from the gastrointestinal tract in rabbits. The mean bioavailability for amsacrine was 50% +/- 17 (s.d.) in non-fasting animals, and was significantly increased in fasting animals (mean, 90% +/- 10). The bioavailability for CI-921 (mean, 26% +/- 11) in the non-fasting animal was significantly less than that found for amsacrine, but this difference disappeared in the fasting animal when the bioavailability of CI-921 was significantly increased to 69% +/- 23. Oral administration of both agents resulted in significantly prolonged elimination half-lives and mean residence times compared to the i.v. infusion, but no significant difference was observed in these parameters between the fasting and non-fasting state. This study suggests that oral dosing may be a possible alternative route for the administration of these anticancer agents.

The effect of buthionine sulphoximine, cimetidine and phenobarbitone on the disposition of amsacrine in the rabbit.

Evidence suggests that the main elimination pathway for amsacrine is hepatic oxidation to the quinone diimine derivative followed by conjugation with glutathione (GSH) and excretion in the bile. If this is so, amsacrine elimination should be susceptible to induction by phenobarbitone (PB) and inhibition by cimetidine (CT) and perhaps by buthionine sulphoximine (BSO), a specific depleter of tissue GSH. This study was carried out in groups of six rabbits. Each rabbit acted as its own control and received pretreatment with saline or PB, CT, or BSO, followed by an amsacrine infusion. Blood (8 X 3 mL) was collected up to 12 h and total plasma amsacrine concentrations determined by HPLC. PB pretreatment resulted in a significant increase in amsacrine's Cl (mean 46%, range 25%-70%) and also in the Vd (mean 58%, range 25%-117%), but had no effect on t1/2 alpha, t1/2 beta or MRTni. In addition, there was no change in the plasma protein binding of amsacrine after PB pretreatment. CT pretreatment had the opposite effect, resulting in a significant decrease in amsacrine's Cl (mean 33%, range 21%-38%) and a decrease in Vd, although this latter decrease was not significant at the 5% level. As with PB, the time parameters were not significantly changed. BSO pretreatment resulted in a significantly reduced Cl (mean 22%, range 15%-30%), no effect on Vd or on t1/2 alpha, but significantly prolonged t1/2 beta and MRTni. BSO pretreatment was also associated with a significant reduction in red blood cell GSH concentration. These results are consistent with the involvement of the hepatic mixed function oxidase system and GSH status in the elimination of amsacrine in the rabbit.