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Papers by Joseph Sinkule

Journal of Chromatography B: Biomedical Sciences and Applications, 1983

A novel, dual-column high-performance liquid chromatographic method for determination of the anti... more A novel, dual-column high-performance liquid chromatographic method for determination of the anti-cancer drug cytosine arabinoside (Ara-C) and its major metabolite uracil arabinoside (Ara-U) has been developed. The analytical procedure is sensitive (25 ng/ml) and specific for Ara-C, Ara-U and the endogenous nucleosides that may influence response to Ara-C therapy, cytidine and deoxycytidine. Conventional and high dose calibration curves were linear and the method precise with the assay coefficient of variation for Ara-C and Ara-U not greater than 9.1% over the range of 0.1-10 micrograms/ml. Accuracy was determined to be within +/- 3 to 9% over this concentration range. Using this method, patient plasma samples from both conventional dose (100-200 mg/m2 per day) and high dose (3500-6500 mg/m2 per day) Ara-C can be simultaneously analyzed for Ara-C, Ara-U and nucleosides so that comparative pharmacokinetic and pharmacodynamic studies can be conducted.

PubMed, Mar 1, 1984

The clinical pharmacokinetics of teniposide (VM-26, NSC 122819) has been studied in 21 children (... more The clinical pharmacokinetics of teniposide (VM-26, NSC 122819) has been studied in 21 children (median age, 4.7 years) with acute lymphocytic leukemia. Teniposide was administered at a dosage of 165 mg/sq m as a 30- to 60-min i.v. infusion. Patients were studied either on the first or second dosage of the drug. Plasma samples were assayed for teniposide and metabolites by high-performance liquid chromatography with electro-chemical detection. Both compartmental and noncompartmental pharmacokinetic analyses were performed. Systemic clearance and apparent volume of distribution of steady state averaged 13.82 +/- 6.0 ml/min/sq m (S.D.) and 7.9 +/- 4.0 liter/sq m, respectively. Univariate and multivariate stepwise regression analyses were used to construct mathematical models to describe the relationships between certain patient-specific demographic and laboratory values and the pharmacokinetic parameters, systemic clearance, elimination rate constant, and area under the concentration-time curve. A significant relationship between serum alkaline phosphatase and systemic clearance, elimination rate constant, and area under the concentration-time curve was found, suggesting that liver function influences the disposition of this anticancer drug in humans.

Clinical Pharmacology & Therapeutics, Apr 1, 1989

Steady-state plasma levels of doxorubicin and doxorubicinol were analyzed in 32 patients with adv... more Steady-state plasma levels of doxorubicin and doxorubicinol were analyzed in 32 patients with advanced cancer, each of whom was given doxorubicin by long-term continuous infusion at progressively increasing infusion rates. Patients received doxorubicin for 2 to 50 weeks at rates of 0.2 to 6.1 mg/m2/day. Dose-limiting stomatitis and leukopenia were observed. The mean maximum steady-state doxorubicin concentration was 6.04 ng/ml at a mean maximum infusion rate of 3.92 mg/m2/day. Clearance mechanisms did not appear to be saturated at the durations or infusion rates used in this study. The maximum steady-state doxorubicin level and the ln (initial WBC) were significant correlates of the ln (nadir WBC) (p = 0.002 and 0.02, respectively). A model was constructed according to these two parameters that significantly describes ln (nadir WBC) (p = 0.001). Neither age, infusion rate, nor doxorubicinol level correlated with nadir WBC. Stomatitis did not correlate with any of these parameters. The demonstration of this pharmacodynamic relationship highlights the potential importance of pharmacologic data collection in ongoing attempts to predict the clinical effects of anticancer drugs.

Journal of Chromatography B: Biomedical Sciences and Applications, 1985

PubMed, Dec 1, 1983

We compared the effects of the epipodophyllotoxins 4'-demethylepipodophyllotoxin-9-(4,6-O-2-ethyl... more We compared the effects of the epipodophyllotoxins 4'-demethylepipodophyllotoxin-9-(4,6-O-2-ethylidene-beta-D-glucopyranoside) (VP-16-213) and 4'-demethylepipodophyllotoxin-9-(4,6-O-2-thenylidene-beta-D-glucopyranoside) (VM-26) and several of their derivatives on cell cycle progression and viability of human leukemic lymphoblasts (CCRF-CEM). The cis-(picro)-lactone derivatives, like both VP-16-213 and VM-26, produced G2-phase arrest and cytotoxicity, but only at concentrations 100 times greater than required with the parent compounds. The epiaglycone derivative showed potent cytotoxicity: at 100 to 250 nM, it reduced cloning efficiency by 50%, an effect requiring 25 to 40 nM VM-26 and 340 to 425 nM VP-16-213. In contrast to VM-26 and VP-16-213, the epiaglycone arrested cells in M, consistent with evidence that it, like podophyllotoxin, is an inhibitor of microtubule assembly. At concentrations resulting in 50% cell kill and an increase of cells in M, however, the epiaglycone produced little change in the proportion of cells in G1 or early S phase, while podophyllotoxin produced a shift of cells to mid- and late S. The hydroxy acid derivatives, although found in detectable quantities in patients' urine and serum, were inactive in vitro. Structural differences among the compounds account for their different biochemical and cell kinetic effects and, hence, different cytotoxic activities. Because the epiaglycone is a potent compound and combines activities of both the podophyllotoxins and 4'-demethyl derivatives, further studies of its cytotoxicity are indicated.

$Research paper thumbnail of Pharmacokinetics of etoposide (VP16) in children and adolescents with refractory solid tumors$

PubMed, Jul 1, 1984

The clinical pharmacokinetics of etoposide were studied in eight pediatric patients with refracto... more The clinical pharmacokinetics of etoposide were studied in eight pediatric patients with refractory solid tumors. The alpha-phase half-life, beta-phase half-life, volume of distribution, and elimination rate constant averaged 0.82 hr, 6.5 hr, 4.0 liters/sq m, and 0.25 hr-1, respectively. Noncompartmental parameters such as systemic clearance, mean residence time, and volume of distribution at steady-state averaged 20.9 ml/min/sq m, 7.8 hr, and 7.2 liters/sq m, respectively. A significant relationship between serum glutamic pyruvic transaminase and systemic clearance was observed, with patients having elevated serum glutamic pyruvic transaminase showing slower systemic clearance of etoposide. Systemic clearance, mean residence time, and beta-phase half-life of etoposide were significantly lower in those patients who had received cisplatin prior to their Phase II etoposide trial. The average pharmacokinetic values derived from these eight pediatric patients with solid tumors did not differ significantly from those previously reported in children with leukemia administered similar dosages and in adults given radioactively labeled etoposide.

PubMed, Apr 1, 1987

Etoposide (VP-16) is a semisynthetic epipodophyllotoxin that exhibits cell cycle phase specific c... more Etoposide (VP-16) is a semisynthetic epipodophyllotoxin that exhibits cell cycle phase specific cytotoxicity and enhanced effectiveness with increasing duration of drug exposure. We have therefore conducted a Phase I trial to determine the side effects, tolerable doses, and pharmacokinetic parameters of VP-16 given by continuous i.v. infusion to patients with advanced cancer. Eighteen patients were treated with varying dosages of VP-16 infused continuously for 72 consecutive hours every 28 days. Using this schedule, the maximally tolerated dosage of VP-16 was 150 mg/m2/day for patients with good performance status and 125 mg/m2/day for more debilitated cancer patients. Hematological toxicity was dose limiting with median granulocyte and platelet nadirs of 700/mm3 and 116,000/mm3, respectively, at a dose of 150 mg/m2/day. Other toxicities included only mild nausea, vomiting, and alopecia. Plasma and urine VP-16 concentrations were determined using a high-performance liquid chromatography assay. At a VP-16 dosage of 150 mg/m2/day, steady-state VP-16 concentrations were in the range of 2.1 to 7.0 micrograms/ml in all patients. Further pharmacokinetic analysis revealed that the plasma clearance of VP-16 was consistently near 25 ml/min/m2 (independent of dosage) and that renal clearance accounted for only 15% of VP-16 total plasma clearance. Patient age was found to be the most important factor correlating with plasma clearance of VP-16. Linear regression analysis also revealed that both the plasma VP-16 concentration at steady state and the concentration of VP-16 in plasma at 24 h from the start of the infusion correlated with hematological toxicity; no other patient characteristics correlated with hematological toxicity. The recommended VP-16 dose for Phase II trials of 72-h continuous infusion VP-16 is 150 mg/m2/day in patients with good performance status.

Journal of Clinical Oncology, Jul 1, 1987

Teniposide (VM-26) is an effective anticancer drug usually administered as a short infusion in do... more Teniposide (VM-26) is an effective anticancer drug usually administered as a short infusion in doses of 150 to 165 mg/m2. The objectives of the trial reported here were to evaluate clinical responses and assess pharmacokinetic parameters as a determinant of outcome when VM-26 was administered as a 72-hour continuous infusion (CI) with doses escalated from 300 to 750 mg/m2 per course. Twenty-eight patients with recurrent leukemia, lymphoma, or neuroblastoma received 53 courses of CI VM-26 and 16 had measurable responses. There were two partial remissions and one stable disease among seven neuroblastoma patients and 13 of 21 leukemia/lymphoma patients had oncolytic responses (greater than or equal to 75% decrease in circulating blasts). Toxicity included moderate to severe mucositis and myelosuppression. Pharmacokinetic parameters determined during 35 courses administered to 23 patients were highly variable. Clearance (CI) ranged between 3.7 and 43.8 ml/min/m2, resulting in VM-26 plasma concentrations from 2.8 to 30.6 mg/L across all dose levels. The interpatient pharmacokinetic variability reflected in CI and VM-26 steady state concentrations (Css), obscured any dose-response relationship. However, when pharmacokinetic parameters for responding and nonresponding patients were compared, statistically significant relationships were observed. For responders, the mean Css was 15.2 mg/L and mean CI was 12.1 mL/min/m2; for nonresponders, mean Css was 6.2 mg/L (P less than .01) and mean CI was 21.3 mL/min/m2 (P less than .05). Thus, patients with higher CI and lower Css were less likely to respond. Clinical responses occurred in ten of ten patients with Css greater than 12 mg/L, and only five of 13 patients with Css less than 12 mg/L (P less than .01). In this study, interpatient pharmacokinetic variability yielded a four- to sixfold difference in intensity of systemic exposure (Css) within the same dose level, which was an important determinant of clinical response. These data indicate that achieving a VM-26 target concentration for individual patients could ensure an increased intensity of systemic exposure in patients with a high CI and improve the likelihood of effective therapy.

Journal of Chromatography B: Biomedical Sciences and Applications, 1987

A sensitive and specific high-performance liquid chromatographic (HPLC) assay was developed for t... more A sensitive and specific high-performance liquid chromatographic (HPLC) assay was developed for the quantitation of mitoxantrone in plasma using electrochemical detection. Bisantrene was chosen as the internal standard. A reversed-phase, 10-microns muBondapak C18 analytical column (30 cm X 3.9 mm) with an isocratic mobile phase of 28% acetonitrile in 80 mM sodium formate buffer (pH 3.0) was used. The eluent was monitored by both electrochemical detection at an applied potential of +0.75 V vs. Ag/AgCl and visible absorbance at 660 nm. Only electrochemical detection was able to quantitate the internal standard and provided ten times higher sensitivity than visible absorbance for mitoxantrone with a detection limit as low as 0.1 ng/ml. Calibration curves in the range 0.1-1000 ng/ml showed good linearity (r = 0.998) and precision (coefficient of variation less than 10%). This HPLC method utilized a reproducible and inexpensive liquid-liquid extraction procedure. Using methylene chloride, the extraction efficacy of mitoxantrone from plasma was 85.3% with a coefficient of variation less than 2.1%. This new assay was then applied to measure mitoxantrone concentrations in plasma obtained from two leukemic patients receiving 12 mg/m2 mitoxantrone as a 1-h infusion.

$Research paper thumbnail of Phase I clinical and pharmacokinetic study of bisantrene in refractory pediatric solid tumors$

Investigational New Drugs, Jun 1, 1986

Fourteen patients with pediatric malignant solid tumors, median age 15 years, received 22 courses... more Fourteen patients with pediatric malignant solid tumors, median age 15 years, received 22 courses of bisantrene in a Phase I study. Dosage escalations ranged from 10 to 120 mg/m2 daily for 5 consecutive days. Toxicity included myelosuppression and phlebitis. A sensitive (detection limit of 2 ng/ml) and specific HPLC method was developed to quantitate bisantrene in patient's plasma and urine. Peak plasma concentrations at the end of 60 minute infusions ranged from 568 ng/ml at 10 mg/m2 to 6800 ng/ml at the 100 mg/m2 dosage. The elimination half life (T 1/2 beta) averaged about 10 hours but increased to 20 hours in a patient with liver disease. Only 2.4 - 10% of the bisantrene dose was eliminated in the urine suggesting that the liver may be the major route of elimination for this antineoplastic anthracene derivative.

Journal of Clinical Oncology, Jul 1, 1988

Thiotepa is an established alkylating agent whose pharmacokinetics in standard doses are well def... more Thiotepa is an established alkylating agent whose pharmacokinetics in standard doses are well defined. In order to ascertain whether dose-dependent variations in pharmacokinetics occur, we have undertaken an analysis of plasma thiotepa levels in 16 patients entered on a phase I-II study of bialkylator chemotherapy. High-dose thiotepa (1.8 to 7.0 mg/kg) and cyclophosphamide (2.5 g/m2) were administered intravenously (IV) on days -6, -4, and -2 followed by autologous marrow reinfusion on day 0. Plasma and urinary thiotepa was assayed by gas chromatography. Biexponential plasma decay curves were seen in ten patients, with a t 1/2 alpha of 10.0 +/- 6.4 minutes, a t 1/2 beta of 174 +/- 61 minutes and a total body clearance of 379 +/- 153 mL/h/kg (mean +/- SD). Six patients displayed monoexponential plasma decay curves with a terminal t 1/2 of 137 +/- 83 minutes and a total body clearance of 440 +/- 195 mL/h/kg. Although there was a trend toward reduced plasma clearance in the three patients treated at the highest dose level, the available data suggest that metabolic clearance mechanisms for thiotepa were not saturated with the doses used in this study. By stepwise regression analysis, linear functions using only 15-minute and four-hour postinfusion plasma levels were derived that correlated closely with area under the plasma concentration X time curves (AUC) (P less than .002). We conclude that high-dose thiotepa results in similar pharmacokinetic values to conventional doses with no apparent dose-dependent variation. The value of specific time points to predict AUC and clearance will require prospective evaluation.

Journal of Clinical Oncology, Mar 1, 1987

Twenty-two patients with relapsed or refractory acute leukemia received 31 treatment courses of m... more Twenty-two patients with relapsed or refractory acute leukemia received 31 treatment courses of mitoxantrone (10 to 12 mg/m2/d) as a one-hour infusion for five days. Seven of the 13 patients who had greater than or equal to 95% reduction in the leukemia cell mass, calculated using the bone marrow examination on day 6, achieved a complete remission (CR). These remissions lasted up to 14 months without additional therapy. There were no CRs among the 18 patients who had less than 95% cytoreduction by day 6. The sequential addition of 5-azacytidine (200 mg/m2/d) for three days in those patients with residual disease on day 6 provided little additional benefit. Nonhematological toxicity from mitoxantrone was mild, although fever and infection were common. A new high-performance liquid chromatography (HPLC) assay was used to describe the clinical pharmacokinetics of mitoxantrone. Neither clinical response nor toxicity was strongly correlated with the peak plasma mitoxantrone concentration on the first day (mean +/- SD, 510 +/- 206 ng/mL), nor the area under the concentration-time curve (484 +/- 229 ng X h/mL), nor the systemic clearance (405 +/- 124 mL/min/m2). Mitoxantrone causes rapid cytoreduction in acute nonlymphocytic leukemia (ANLL), but the optimal dose and schedule remain to be determined.

Journal of Pharmaceutical Sciences, Feb 1, 1984

Cancer Chemotherapy and Pharmacology, Apr 1, 1982

The clinical pharmacokinetics of VM26 and VP16-213 were assessed in 15 children (median age 10 ye... more The clinical pharmacokinetics of VM26 and VP16-213 were assessed in 15 children (median age 10 years) with acute leukemia, using a new high-performance liquid chromatography-electrochemical assay. Pharmacokinetic parameters were calculated by both model-dependent and compartment model-independent methods. These studies demonstrated substantial differences in the central volumes of distribution (VDc), steady-state volumes of distribution (VDss) and systemic clearances (Cls) of VM26 and VP16-213; with the VDo VD~s, and Cls all being smaller for VM26. Systemic clearances determined by model-independent methods were 5.2 + 1.0 ml/min/me(mean +_ SD) for VM26 and 17.8 + 11.2 ml/min/m 2 for VP16-213. The major metabolites detected in serum and urine were the hydroxy acids. Low levels of the picro-lactone isomers were detected in some patients while the aglycones were not detected in the serum or urine of any patients.

Journal of Chromatography B: Biomedical Sciences and Applications, Nov 1, 1982

A selective and sensitive high-performance liquid chromatographic method was developed for the se... more A selective and sensitive high-performance liquid chromatographic method was developed for the separation and quantitation of daunorubicin and its metabolites in serum, plasma, and other biological fluids. Daunorubicin and metabolites in human plasma were injected directly into the high-performance liquid chromatography system via a loop-column to pre-extract the drugs from the plasma, and quantitated against a multilevel calibration curve with adriamycin as the internal standard. The column effluent was monitored with an electrochemical detector at an applied oxidative potential of 0.65 V and by fluorescence. Daunorubicin and four metabolites were separated and characterized by this method. In a blinded evaluation of accuracy and precision, the mean coefficients of variation were 3.8, 3.6 and 9.8% at concentrations of 150, 75 and 15 ng/ml, respectively, and blank samples gave negligible readings. The amperometric sensitivity was greater than achieved by fluorescence detection, and offers an alternative method for quantitation of these compounds. The new method has a limit of detection of less than 2 ng on column, allowing quantitation of less than 10 ng/ml in plasma samples without organic extraction prior to chromatographic analysis.

Pharmacotherapy, Mar 4, 1984

Etoposide (VP 16) is a semi-synthetic derivative of 4'- demethylepipodophyllotoxin , a na... more Etoposide (VP 16) is a semi-synthetic derivative of 4'- demethylepipodophyllotoxin , a naturally occurring compound synthesized by the North American May apple (Podophyllum peltatum ) and the Indian species Podophyllum emodi Wallich . Although podophyllotoxins are classical spindle poisons causing inhibition of mitosis by blocking mitrotubular assembly, etoposide inhibits cell cycle progression at a premitotic phase (late S and G2), probably via inhibition of DNA synthesis. There appears to be a selective antileukemic dose response relationship when compared to normal hematopoietic elements. Etoposide is effective when administered orally at about twice the recommended parenteral dosage. Schedule dependency in both animal models and clinical trials has been observed; multiple dosing over three to five consecutive days is superior to weekly single dose administration. Etoposide's dose-limiting toxicity is myelosuppression (leukopenia), which is quite predictable; alopecia and Gl toxicity (nausea, vomiting, stomatitis) occur in about 20-30% of patients given recommended dosages. Etoposide appears to be one of the most active drugs for small cell lung cancer, testicular carcinoma (the Food and Drug Administration approved indication), ANLL and malignant lymphoma. Etoposide also has demonstrated activity in refractory pediatric neoplasms, hepatocellular, esophageal, gastric and prostatic carcinoma, ovarian cancer, chronic and acute leukemias and non-small cell lung cancer, although additional single and combination drug studies are needed to substantiate these data. Its contribution in front-line combination chemotherapeutic regimens for these cancers will be better defined in the forthcoming years. Etoposide appears to have minimal activity in breast cancer and, based on current data, it is inactive against malignant melanoma, colorectal adenocarcinoma and cancer of the head and neck, although the dosage and schedules used in many of the Phase II studies may have been suboptimal.

$Research paper thumbnail of Continuous infusion high-dose cytosine arabinoside in refractory childhood leukemia$

Journal of Clinical Oncology, 1984

Ten pediatric patients with refractory leukemia received continuous infusion high-dose cytosine a... more Ten pediatric patients with refractory leukemia received continuous infusion high-dose cytosine arabinoside (ara-C) according to one of two escalating dosage schedules: (1) a 500-mg/m2 rapid infusion loading dose followed by 3.5 g/m2 per day continuous infusion daily for four consecutive days, or (2) a 600-mg/m2 rapid infusion loading dose followed by 5.0 g/m2 per day continuous infusion daily for four consecutive days. Major toxicity at the lower dosage level was grade IV hematopoietic aplasia of three weeks' duration. At the higher dosage level, there was a prohibitive toxicity in multiple organ systems including transient noncardiogenic pulmonary edema, fungal infections, peritonitis, severe diarrhea, transaminase elevations, and one treatment-related death due to acute renal failure. In contrast to other methods of administration of high-dose ara-C, no CNS toxicity occurred. Oncolytic responses were seen in all patients and two achieved brief, partial remissions. Steady-stat...

Cancer Chemotherapy and Pharmacology, 1990

Continuous-infusion etoposide was given to 15 patients with newly diagnosed small-cell lung cance... more Continuous-infusion etoposide was given to 15 patients with newly diagnosed small-cell lung cancer (extensive disease) and 10 patients with various refractory malignancies. The untreated patients with lung cancer received 200 mg/m2 etoposide over 24 h in combination with 100 mg/m2 cisplatin, and the pretreated patients received 400 mg/m2 etoposide over 36 h as monotherapy. Pharmacokinetic studies of etoposide were carried out in all patients. High-performance liquid chromatography (HPLC) was used to measure etoposide. All patients had normal hepatic and renal function tests and were followed weekly for hematologic toxicity after therapy. In all, 14 untreated and 9 pretreated patients were evaluable. Biostatistical analysis was done to correlate pharmacokinetic results to hematologic effects. Pearson correlation coefficients were calculated for continuous variables (i.e., blood counts), and Spearman correlation coefficients were calculated for ranked variables (i.e., toxicity grades). The values for the area under the plasma concentration vs time curve (AUC) and systemic clearance varied widely among patients. However, the AUC and clearance were significantly correlated (P less than 0.05) with the WBC and platelet nadirs and the decrease in hemoglobin. The grade of leukopenia and total grade of hematologic toxicity were also correlated with AUC and clearance. Because the interpatient variability in etoposide pharmacokinetics correlates with the variable degree of hematologic toxicity, pharmacokinetic drug monitoring is suggested.

Journal of Clinical Oncology, 1988

Journal of Clinical Oncology, 1987