Pharmacokinetics, drug metabolism, and tissue distribution of CPX-351 in animals.

CPX-351, a liposomal encapsulation of cytarabine and daunorubicin at a synergistic 5:1 molar ratio, is indicated for adults with newly diagnosed, therapy-related acute myeloid leukemia or acute myeloid leukemia with myelodysplasia-related changes. In preclinical species, this article demonstrated (1) similar release of cytarabine and daunorubicin by CPX-351 in plasma; (2) similar patterns of metabolism of cytarabine and daunorubicin following administration of CPX-351 versus non-liposomal cytarabine/daunorubicin combination; (3) prolonged tissue exposure to CPX-351; (4) dramatically different tissue distribution of cytarabine and daunorubicin following administration of CPX-351 versus non-liposomal combination (tissue:plasma ratios generally <1 versus >1, respectively); and (5) dramatically lower unbound plasma and tissue concentrations of cytarabine and daunorubicin following administration of CPX-351 versus non-liposomal combination. Together, these results provide insight into the safety profile of CPX-351, as well as mechanisms that drive the improved efficacy observed for CPX-351 versus the conventional 7 + 3 cytarabine/daunorubicin regimen in clinical studies.

Assessment of primary, oxidative and excision repaired DNA damage in hospital personnel handling antineoplastic drugs.

The International Agency for Research on Cancer has classified several antineoplastic drugs in Group 1 (human carcinogens), among which chlorambucil, cyclophosphamide (CP) and tamoxifen, Group 2A (probable human carcinogens), among which cisplatin, etoposide, N-ethyl- and N-methyl-N-nitrosourea, and Group 2B (possible human carcinogens), among which bleomycins, merphalan and mitomycin C. The widespread use of these mutagenic/carcinogenic drugs in the treatment of cancer has led to anxiety about possible genotoxic hazards to medical personnel handling these drugs. The aim of the present study was to evaluate work environment contamination by antineoplastic drugs in a hospital in Central Italy and to assess the genotoxic risks associated with antineoplastic drug handling. The study group comprised 52 exposed subjects and 52 controls. Environmental contamination was assessed by taking wipe samples from different surfaces in preparation and administration rooms and nonwoven swabs were used as pads for the surrogate evaluation of dermal exposure, 5-fluorouracil and cytarabine were chosen as markers of exposure to antineoplastic drugs in the working environment. The actual exposure to antineoplastic drugs was evaluated by determining the urinary excretion of CP. The extent of primary, oxidative and excision repaired DNA damage was measured in peripheral blood leukocytes with the alkaline comet assay. To evaluate the role, if any, of genetic variants in the extent of genotoxic effects related to antineoplastic drug occupational exposure, the study subjects were genotyped for GSTM1, GSTT1, GSTP1 and TP53 polymorphisms. Primary DNA damage significantly increased in leukocytes of exposed nurses compared to controls. The use of personal protective equipment (i.e. gloves and/mask) was associated with a decrease in the extent of primary DNA damage.

Cerebrospinal fluid and plasma pharmacokinetics of high doses of 1-beta-D-arabinofuranosylcytosine in nonhuman primates.

The pharmacokinetics of 1-beta-D-arabinofuranosylcytosine (ara-C) in plasma, cerebrospinal fluid (CSF), and urine was studied in nonhuman primates. Conventional and high-dose schedules of ara-C were administered i.v. and intraventricularly through indwelling Ommaya reservoirs. ara-C and its metabolite 1-beta-D-arabinofuranosyluracil (ara-U) were measured by high-pressure liquid chromatography. Due to rapid peripheral deamination (230 nm ara-C/hr/ml plasma), the half-life of ara-C in plasma after a 140-mg/kg i.v. 1-hr infusion was short (3.7 min). Peak plasma concentrations of ara-C, ranging between less than 0.1 and 49 micrograms/ml, were dose dependent (ara-C, 15 to 140 mg/kg). Under these conditions, ara-C was undetectable in CSF. About 53% of the administered dose (140 mg/kg) was excreted in urine during the first 5 hr mostly as ara-U. Intraventricular administration of 50 and 250 mg of ara-C resulted in peak lumbar CSF levels of 435 and 2235 micrograms/ml, respectively, at about 155 and 80 min postinjection. Concomitant ara-U levels were one-tenth of those of ara-C and increased progressively, suggesting deamination of the drug in the central nervous system. The half-life of ara-C in CSF ranged between 50 and 60 min. Administration of 50 mg of ara-U intraventricularly resulted in peak lumbar ara-U levels of 595 micrograms/ml at about 180 min with a prolonged clearance. Concomitant plasma levels throughout the study were less than 0.1 micrograms/ml, suggesting slower equilibrium. No hematological or nervous system toxicity was observed during these studies. The clinical implications of these findings are discussed.

Pharmacology of 5'-esters of 1-beta-D-arabinofuranosylcytosine.

Pharmacological studies of 5'-esters of 1 beta-D-arabinofuranosylcytosine (ara-C) were performed in three species (mouse, pig, and man). In mice, after a single i.p. injection of a suspension of tritiated 1-beta-D-arabinofuranosylcytosine 5'-palmitate (PalmO-ara-C) at a therapeutic dose of 150 mg/kg, 30% of the administered radioactivity was recovered in the urine in 24 hr and 56% was recovered after 7 days. Excretion was less rapid after s.c. administration. ara-C and 1-beta-D-arabino furanosyluracil each accounted for about 50% of the excreted radioactivity, and no PalmO-ara-C was found. Plasma ara-C concentrations of greater than 0.1 microng/ml were detected 24 hr after i.p. administration of PalmO-ara-C (150 mg/kg). Single doses of PalmO-ara-C were effective against L1210 leukemic mice when administered 5 to 7 days before tumor inoculation. In a pig, after i.m. injection of tritiated PalmO-ara-C (60 mg/kg, two sites), only 7% of the administered radioactivity was recovered in the urine over a 1-week period. Similar low rates of excretion were also observed in patients treated i.m. with PalmO-ara-C or 1-beta-D-arabinofuranosylcytosine 5'-benzoate. N ara-C was detected in the plasma, which is consistent with the absence of clinical toxicity or myelosuppression in Phase 1 trials of PalmO-ara-C at doses up to 1500 mg/sq m every 3 weeks for as many as eight courses.

Production of N4-succinyl-1-beta-D-arabinofuranosylcytosine, a novel metabolite of N4-behenoyl-1-beta-D-arabinofuranosylcytosine, in mice and its biological significance.

A novel metabolite was found in the urine and bile of mice given i.v. injections of N4-behenoyl-1-beta-D-arabinofuranosylcytosine (behenoyl-ara-C). Acid and alkaline hydrolysis of this metabolite resulted in the production of 1-beta-D-arabinofuranosylcytosine and succinic acid, as determined by thin-layer chromatography and high-performance liquid chromatography. Mass spectrometry identified this metabolite as N4-succinyl-1-beta-D-arabinofuranosylcytosine (succinyl-ara-C). This conclusion was supported by thin-layer chromatography and by the ultraviolet spectrum, upon which the characteristics of this metabolite agreed with those of succinyl-ara-C. Only a very small amount, if any, of this metabolite was found in the urine and bile of mice given injections of N4-stearoyl- or N4-palmitoyl-1-beta-D-arabinofuranosylcytosine, suggesting that behenoyl-ara-C was metabolized differently from the other two analogs. Comparison of the metabolites of behenoyl-ara-C, radiolabeled at different positions of the behenoyl-residue, suggested that behenoyl-ara-C was degraded by omega-oxidation and then by beta-oxidation, resulting in the production of succinyl-ara-C. This metabolite was more potent than behenoyl-ara-C in suppressing the in vitro proliferation of murine L1210 cells. The high therapeutic potency of behenoyl-ara-C in L1210-bearing mice may be ascribable to the contribution of succinyl-ara-C to the efficacy of behenoyl-ara-C, either by suppressing the proliferation of L1210 cells or by protecting 1-beta-D-arabinofuranosylcytosine, the possible eventual metabolite, from inactivation by deaminase.

Pharmacokinetics of Ara-CMP-Stearate (YNK01): phase I study of the oral Ara-C derivative.

Ara-CMP-Stearate (1-beta-D-arabinofuranosylcytosine-5'-stearylphosphate, YNK 01, Fosteabine) is the orally applicable prodrug of cytosine-arabinoside (Ara-C). During a phase I study in patients with advanced low-grade non-Hodgkin lymphomas or acute myeloid leukemia, the pharmacokinetic parameters of Ara-CMP-Stearate (kindly provided by ASTA Medica, Frankfurt, Germany) were determined by HPLC analysis. Seventy-two hours after a first starting dose which served for the determination of baseline pharmacokinetic parameters, Ara-CMP-Stearate was administered over 14 days by daily oral application. Ara-CMP-Stearate was started at a dose of 100 mg/day and was escalated in subsequent patients to 200 mg/day and 300 mg/day. Plasma and urine concentrations of Ara-CMP-Stearate, Ara-C and Ara-U were measured during the initial treatment phase and within 72 h after the end of the 14-day treatment cycle. So far six patients have been treated with 100 mg/day, three with 200 mg/day and another six with 300 mg/day. One patient was treated consecutively with 100 mg, 300 mg and 600 mg. Fitting the results of the plasma concentration measurements of Ara-CMP-Stearate to a one-compartment model, the following pharmacokinetic parameters were obtained (average and variation coefficient VC). Ara-CMP-Stearate dose-independent parameters: lag time = 1.04 h (0.57); tmax = 5.72 h (0.30); t1/2 = 9.4 h (0.36). Dose-dependent parameters: at 100 mg: AUC = 1099 ng/h/ml (0.31); concentration(max) = 53.8 ng/ml (0.28); at 200 mg: AUC = 2753 ng/h/ml (0.32); concentration(max) = 154.8 ng/ml (0.46); at 300 mg: AUC = 2940 ng/h/ml (0.66); concentration(max) = 160.0 ng/ml (0.59). The long lag time and late tmax can be explained by resorption in the distal part of the small intestine. No Ara-CMP-Stearate was detected in urine samples (limit of detection = 500 pg/ml). Pharmacokinetic parameters of Ara-C following Ara-CMP-Stearate application showed the following characteristics: t1/2 = 24.3 h (0.39); AUC (100 mg) = 262 ng/h/ml (0.93); AUC (200 mg) = 502 ng/h/ml (0.87); AUC (300 mg) = 898 ng/h/ml (1.07). Since Ara-CMP-Stearate causes intravascular hemolysis after intravenous administration, it was not possible to determine its bioavailability by comparing the AUC after oral and i.v. application. Instead, the renal elimination of Ara-U, as the main metabolite of Ara-C was measured during the first 72-h period and after the last application.(ABSTRACT TRUNCATED AT 400 WORDS)

High-performance liquid chromatographic analysis of cytosine arabinoside and metabolites in biological samples.

A rapid, non-radioactive method to quantitate therapeutically realistic levels of 1-beta-D-arabinofuranosylcytosine (Ara-C) and its metabolites would be useful both in the clinic, for monitoring drug levels, and in the laboratory for correlating drug levels with cellular and molecular perturbations. Liquid chromatographic analysis of arabinose-nucleoside analogs in biological samples is complicated by the presence of interfering nucleosides and nucleotides. We report the development of two analytic procedures to measure Ara-C and metabolite levels in biological samples. One method uses a quaternary ammonium type anion-exchange resin to achieve isocratic separation in less than one hour. The second method utilizes a boronate-derivatized polyacrylamide column which binds cis-diols to selectively retain cytosine and uridine, while arabinose compounds are eluted with recovery approaching 100%. The eluted compounds are then easily quantitated on a reversed-phase C18 column. The sensitivity of both procedures was sufficient to obtain pharmacokinetic data on Ara-C and uracil-arabinose levels in serum and urine and on Ara-C triphosphate levels in tumor cells.

Metabolism of the new liposomal anticancer drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine in mice.

Metabolism and excretion of the new antitumor drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) was investigated in mice. Mice were injected i.v. with tritium-labeled liposomal NOAC (4 micromol/mouse). Analysis of HPLC-purified extracts of liver homogenates by liquid chromatography coupled with mass spectrometry revealed only the presence of unmetabolized drug. To study the excretion of the administered drug, mice were injected with tritium-labeled liposomal NOAC or as comparison with 1-beta-D-arabinofuranosylcytosine (ara-C; 4 micromol/mouse) and housed up to 48 h in metabolic cages. Urine and feces were collected at different time points and the kinetics of excreted radioactivity were determined. After 48 h, 39% of the injected [5-3H]NOAC radioactivity was excreted in urine and 16% in feces, whereas ara-C radioactivity was only found in urine with 48% of the injected dose. Feces extracts and urine were purified by HPLC and radioactive fractions were further analyzed by liquid chromatography coupled with mass spectrometry. The radioactivity of feces extracts of NOAC-treated mice was composed of unmetabolized NOAC, hydroxylated NOAC (NOAC + OH), its sulfated derivative (NOAC + OSO3H), and unidentified metabolites, whereas in urine, the hydrophilic molecules ara-C and ara-U were found. During the period of 48 h only 2% of the injected NOAC was eliminated in its unmetabolized form, whereas 25% was identified as main metabolite ara-C. Urine collected during 48 h in ara-C-treated mice contained 33% of the injected dose as unmetabolized drug and 13% as the main metabolite ara-U. Thus, NOAC is metabolized by two major pathways, one leading to the hydrophilic metabolites ara-C and ara-U and the other to hydroxylated and sulfated NOAC.

Comparative studies of cyclocytidine (NSC-145668) and cytosine arabinoside (NSC-63878) in mice.

The distribution of cyclocytidine and cytosine arabinoside has been studied in normal BDF mice and in mice bearing 6-day solid L1210 lymphocytic leukemia by whole-body radioautography, bioassay, and radiochemical techniques. Radioactivity was widely distributed throughout the tissues between 15 minutes and 12 hours after a single intravenous dose of either cyclocytidine-2-14C or cytosine arabinoside-2-14C. Whole-body radioautograms demonstrated that for most tissues, cytosine arabinoside-derived 14C was uniformly excreted by 48 hours; cyclocytidine-derived 14C, however, was localized in certain tissues as early as 15 minutes after drug administration and was retained in these sites for 48 hours. Depot loci of 14C included salivary and adrenal glands, fat, cardiac muscle, gastrointestinal tract, and L1210 tumor. The distribution and persistence of cyclocytidine-derived radioactivity is consistent with other reports of toxicity induced by the drug in these tissues. Radiochromatography and bioassay data from BDF mice dosed intraperitoneally with cyclocytidine demonstrated that 65%-95% of the 14C-radioactivity in a number of tissues was the parent compound itself. Thus, cyclocytidine contributed in large measur to the generation of the radioautograms. This study demonstrates that the retention of cyclocytidine in body tissues may serve to effect the sustained release of the deaminase-resistant chemotherapeutic drug from these depot sites and thus prolong cytotoxic levels of drug in tumor tissue.