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1.  Androgenic Biomarker Profiling in Human Matrices and Cell Culture Samples Using High Through put, Electrospray Tandem Mass Spectrometry 
The Prostate  2014;74(7):722-731.
A high throughput, high pressure liquid chromatographic (HPLC) method with triple quadrupole mass spectral detection (LC/MS/MS) was validated for the measurement of 5 endogenous androgens in human plasma and serum and applied to various in vivo and in vitro study samples to pursue a better understanding of the interrelationship of the androgen axis, intracrine metabolism, and castration-recurrent prostate cancer (CaP).
A Shimadzu HPLC system interfaced with a Sciex QTRAP 5500 mass spectrometer with electrospray ionization was used with inline column-switching. Samples were liquid/liquid extracted and chromatographed on a Luna C18(2) column at 60°C with a biphasic gradient using a 15-min run time.
The method was validated for five androgens in human plasma and serum, and applied to four sets of samples. Plasma (n = 188) and bone marrow aspirate (n = 129) samples from patients with CaP, who received abiraterone acetate plus prednisone for up to 945 days (135 weeks), had undetectable androgens after 8 weeks of treatment. Plasma dehydroepiandrosterone (DHEA) concentrations were higher in African Americans than Caucasian Americans with newly diagnosed CaP. Analysis of prostate tumor tissue homogenates demonstrated reproducible testosterone (T) and dihydrotestosterone (DHT) concentrations with a minimal sample size of ~1.0–2.0 mg of tissue. Finally, cell pellet and media samples from the LNCaP C4-2 cell line showed conversion of T to DHT.
The proposed LC/MS/MS method was validated for quantitation of five endogenous androgens in human plasma and serum, and effectively profiles androgens in clinical specimens and cell culture samples.
PMCID: PMC4335642  PMID: 24847527
androgen axis; prostate cancer; testosterone; dihydrotestosterone; steroid 5α-reductase; LC/MS/MS
2.  Carboplatin Pharmacokinetics in a Patient Receiving Hemodialysis 
Pharmacotherapy  2013;34(2):e9-13.
With refinements and advances in hemodialysis techniques, survival for patients with end-stage renal disease has improved significantly. To our knowledge, however, no prospective trials have been performed in patients receiving hemodialysis who are also diagnosed with cancer and are candidates for chemotherapy. We describe a 73-year-old man who was diagnosed with high-grade neuroendocrine carcinoma, metastatic to the bone and lymph nodes, and was undergoing hemodialysis. Although cisplatin is more commonly used in the treatment of metastatic neuroendocrine cancers, it may not be the best option in patients who suffer from renal insufficiency. Carboplatin is a second-generation, nonnephrotoxic platinum analog that can be hemodialyzed, although no formal guidelines are available regarding the dosing for patients receiving hemodialysis. This case describes a patient who was treated with five cycles of combination carboplatin 115 mg/m2 on day 1 and etoposide 50 mg/m2 on day 1 and day 3 of a 28-day cycle. Dialysis was performed for 3.5 hours starting 90 minutes after completion of carboplatin on day 1. Pharmacokinetic assessments were performed at 1, 2, 4, and 12 hours after chemotherapy infusion on day 1 of cycle 1. Total carboplatin concentrations in plasma and platinum ultrafiltrate were measured. The plasma concentration of free platinum at the end of the infusion was 31,000 ng/ml, and the area under the plasma concentration–time curve was 2.9 minute·mg/ml. No significant carboplatin-related toxicities were reported. This case report indicates that carboplatin can be safely administered in patients receiving hemodialysis.
PMCID: PMC4321781  PMID: 24037992
carboplatin; oncology; dialysis; chemotherapy; pharmacokinetics; neuroendocrine
3.  Synergistic interactions between sorafenib and everolimus in pancreatic cancer xenografts in mice 
Cancer chemotherapy and pharmacology  2013;71(5):1231-1240.
Molecular targeting of cellular signaling pathways is a promising approach in cancer therapy, but often fails to achieve sustained benefit because of the activation of collateral cancer cell survival and proliferation pathways. We tested the hypothesis that a combination of targeted agents that inhibit compensatory pathways would be more effective than single agents in controlling pancreatic cancer cell growth. We investigated whether everolimus, an mTOR inhibitor, and sorafenib, a multi-kinase inhibitor, would together inhibit growth of low-passage, patient-derived pancreatic cancer xenografts in mice more efficaciously than either agent alone.
Tumor volume progression was measured following treatment with both drugs as single agents, in combination, and at multiple doses. Pharmacokinetics in tumors and other tissues was also assessed. Pharmacodynamic interactions were evaluated quantitatively.
A 5-week regimen of daily oral doses of 10 mg/kg sorafenib and 0.5 mg/kg everolimus, alone and in combination, did not achieve significant tumor growth inhibition. Higher doses (20 mg/kg of sorafenib and 1 mg/kg of everolimus) inhibited tumor growth significantly when given alone and caused complete inhibition of growth when given in combination. Tumor volume progression was described by a linear growth model, and drug effects were described by Hill-type inhibition. Using population modeling approaches, dual-interaction parameter estimates indicated a highly synergistic pharmacodynamic interaction between the two drugs.
The results indicate that combinations of mTOR and multi-kinase inhibitors may offer greater efficacy in pancreatic cancer than either drug alone. Drug effects upon tumor stromal elements may contribute to the enhanced anti-tumor efficacy.
PMCID: PMC3752659  PMID: 23455452
Everolimus; Sorafenib; Xenografts; Non-competitive interaction model; PBPK-PD; Pancreatic cancer
4.  Physiologically based pharmacokinetic models for everolimus and sorafenib in mice 
Cancer chemotherapy and pharmacology  2013;71(5):1219-1229.
Everolimus is a mammalian target of rapamycin (mTOR) inhibitor approved as an immunosuppressant and for second-line therapy of hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC). Sorafenib is a multikinase inhibitor used as first-line therapy in HCC and RCC. This study assessed the pharmacokinetics (PK) of everolimus and sorafenib alone and in combination in plasma and tissues, developed physiologically based pharmacokinetic (PBPK) models in mice, and assessed the possibility of PK drug interactions.
Single and multiple oral doses of everolimus and sorafenib were administered alone and in combination in immunocompetent male mice and to severe combined immune-deficient (SCID) mice bearing low-passage, patient-derived pancreatic adenocarcinoma in seven different studies. Plasma and tissue samples including tumor were collected over a 24-h period and analyzed by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Distribution of everolimus and sorafenib to the brain, muscle, adipose, lungs, kidneys, pancreas, spleen, liver, GI, and tumor was modeled as perfusion rate-limited, and all data from the diverse studies were fitted simultaneously using a population approach.
PBPK models were developed for everolimus and sorafenib. PBPK analysis showed that the two drugs in combination had the same PK as each drug given alone. A twofold increase in sorafenib dose increased tumor exposure tenfold, thus suggesting involvement of transporters in tumor deposition of sorafenib.
The developed PBPK models suggested the absence of PK interaction between the two drugs in mice. These studies provide the basis for pharmacodynamic evaluation of these drugs in patient-derived primary pancreatic adenocarcinomas explants.
PMCID: PMC3755750  PMID: 23455451
Everolimus; Sorafenib; Pancreatic cancer; PBPK; Patient-derived pancreatic adenocarcinoma
5.  Development of a Preclinical PK/PD Model to Assess Antitumor Response of a Sequential Aflibercept and Doxorubicin-Dosing Strategy in Acute Myeloid Leukemia 
The AAPS Journal  2013;15(3):662-673.
Timing of the anti-angiogenic agent with respect to the chemotherapeutic agent may be crucial in determining the success of combination therapy in cancer. We investigated the effects of sequential therapy with the potent VEGF inhibitor, aflibercept, and doxorubicin (DOX) in preclinical acute myeloid leukemia (AML) models. Mice were engrafted with human HL-60 and HEL-luciferase leukemia cells via S.C. and/or I.V. injection and treated with two to three doses of aflibercept (5–25 mg/kg) up to 3–7 days prior to doxorubicin (30 mg/kg) administration. Leukemia growth was determined by local tumor measurements (days 0–16) and systemic bioluminescent imaging (days 0–28) in animals receiving DOX (3 mg/kg) with or without aflibercept. A PK/PD model was developed to characterize how prior administration of aflibercept altered intratumoral DOX uptake. DOX concentration–time profiles were described using a four-compartment PK model with linear elimination. We determined that intratumoral DOX concentrations were 6-fold higher in the aflibercept plus DOX treatment group versus DOX alone in association with increased drug uptake rates (from 0.125 to 0.471 ml/h/kg) into tumor without affecting drug efflux. PD modeling demonstrated that the observed growth retardation was mainly due to the combination of DOX plus TRAP group; 0.00794 vs. 0.0043 h−1. This PK/PD modeling approach in leukemia enabled us to predict the effects of dosing frequency and sequence for the combination of anti-VEGF and cytotoxic agents on AML growth in both xenograft and marrow, and may be useful in the design of future rational combinatorial dosing regimens in hematological malignancies.
PMCID: PMC3691438  PMID: 23550025
acute myeloid leukemia; aflibercept; doxorubicin; pharmacokinetics/pharmacodynamics; VEGF TRAP
6.  A phase 2 study of KX2-391, an oral inhibitor of Src kinase and tubulin polymerization, in men with bone-metastatic castration-resistant prostate cancer 
KX2-391 is an oral non–ATP-competitive inhibitor of Src kinase and tubulin polymerization. In phase 1 trials, prostate-specific antigen (PSA) declines were seen in patients with advanced prostate cancer. We conducted a single-arm phase 2 study evaluating KX2-391 in men with chemotherapy-naïve bone-metastatic castration-resistant prostate cancer (CRPC).
We treated 31 patients with oral KX2-391 (40mg twice-daily) until disease progression or unacceptable toxicity. The primary endpoint was 24-week progression-free survival (PFS); a 50% success rate was predefined as clinically significant. Secondary endpoints included PSA progression-free survival (PPFS) and PSA response rates. Exploratory outcomes included pharmacokinetic studies, circulating tumor cell (CTC) enumeration, and analysis of markers of bone resorption (urinary N-telopeptide [uNTx]; C-telopeptide [CTx]) and formation (bone alkaline phosphatase [BAP]; osteocalcin).
The trial closed early after accrual of 31 patients, due to a prespecified futility rule. PFS at 24 weeks was 8%, and median PFS was 18.6 weeks. The PSA response rate (≥30% decline) was 10%, and median PPFS was 5.0 weeks. Additionally, 18% of men with unfavorable (≥5) CTCs at baseline converted to favorable (<5) CTCs with treatment. The proportion of men with declines in bone turnover markers was 32% for uNTx, 21% for CTx, 10% for BAP, and 25% for osteocalcin. In pharmacokinetic studies, median Cmax was 61 (range 16–129) ng/mL, and median AUC was 156 (35–348) ng*hr/mL. Common toxicities included hepatic derangements, myelosuppression, fatigue, nausea and constipation.
KX2-391 dosed at 40mg twice-daily lacks antitumor activity in men with CRPC, but has modest effects on bone turnover markers. Because a Cmax of ≥142 ng/mL is required for tubulin polymerization inhibition (defined from preclinical studies), higher once-daily dosing will be used in future trials.
PMCID: PMC3609871  PMID: 23314737
KX2-391; prostate cancer; Src inhibitor; tubulin polymerization
7.  Interactions of Everolimus and Sorafenib in Whole Blood Lymphocyte Proliferation 
Pharmaceutical research  2012;30(3):707-713.
Everolimus is an immunosuppressant that blocks growth factor-mediated proliferation of hematopoietic cells by targeting the mammalian target of rapamycin (mTOR). Sorafenib is a multikinase inhibitor that inhibits cell proliferation by arresting cells in the G0–G1 phase of the cell cycle. These agents are under investigation as combination therapy for various cancers. Because the two drugs individually inhibit lymphocyte proliferation, this study examined the effects of everolimus and sorafenib on lymphocyte proliferation in order to anticipate possible immunosuppression.
Inhibition of lymphocyte proliferation was evaluated ex vivo over a range of concentrations of these drugs, alone and in combination. Data analysis, using a population approach to characterize interactions, employed the Ariens noncompetitive interaction model, which was modified to accommodate interactions of the two drugs.
Everolimus alone caused partial inhibition of lymphocyte proliferation, with a mean IC50 of 4.5 nM for females and 10.5 nM in males. Sorafenib alone caused complete inhibition, with a mean IC50 of 11.4 µM and no difference between genders.
The population estimate for the interaction term was greater than 1, suggesting that the two drugs exert slight antagonism in terms of inhibition of lymphocyte proliferation.
PMCID: PMC3726064  PMID: 23151723
everolimus; lymphocyte proliferation; modeling interactions; population analysis; sorafenib
8.  Synergism between clofarabine and decitabine through p53R2: A pharmacodynamic drug-drug interaction modeling 
Leukemia research  2012;36(11):1410-1416.
Clofarabine (CLO), a purine nucleoside analog with promising efficacy in acute myeloid leukemia (AML), inhibits the ribonucleotide reductase, p53R2. We have shown that p53R2 mRNA is up-regulated by decitabine (DEC), another drug with promising activity in AML. We developed a pharmacodynamic model to characterize the interaction between CLO and DEC on an AML cell line and down-regulated p53R2 protein to understand its role. These results confirm a role for p53R2 in both CLO and DEC mechanism of action, demonstrate synergism between these two drugs in this AML model and support the use of this combination in a future clinical trial.
PMCID: PMC3457067  PMID: 22884950
Clofarabine; Decitabine; AML; synergy; pharmacodynamic modeling
9.  Interactions of Everolimus and Sorafenib in Pancreatic Cancer Cells 
The AAPS Journal  2012;15(1):78-84.
Everolimus targets the mammalian target of rapamycin, a kinase that promotes cell growth and proliferation in pancreatic cancer. Sorafenib inhibits the Raf-mitogen-activated protein kinase, vascular endothelial growth factor, and platelet-derived growth factor pathways, thus inhibiting cell growth and angiogenesis. Combinations of these two agents are under evaluation for therapy of several cancers. This study examined the effects of everolimus and sorafenib on proliferation of the pancreatic cancer cell lines MiaPaCa-2 and Panc-1. Cell growth inhibition was evaluated in vitro for a range of concentrations of the drugs alone and in combination. Maximum inhibition capacity (Imax) and potency (IC50) were determined. The data were analyzed to characterize drug interactions using two mathematical analysis techniques. The Ariens noncompetitive interaction model and Earp model were modified to accommodate alterations in the inhibition parameters of one drug in the presence of another. Sorafenib alone inhibited growth of both cell lines completely (Imax = 1), with an IC50 of 5–8 μM. Maximal inhibition by everolimus alone was only 40% (Imax = 0.4) in both cell lines, with an IC50 of 5 nM. Slight antagonistic interaction occurred between the drugs; both analytic methods estimated the interaction term Ψ as greater than 1 for both cell lines. The in vitro data for two pancreatic cancer cell lines suggest that a combination of these two drugs would be no more efficacious than the individual drugs alone, consistent with the drug interaction analysis that indicated slight antagonism for growth inhibition.
PMCID: PMC3535103  PMID: 23054975
everolimus; MiaPaCa-2; modeling interactions; Panc-1; sorafenib
10.  Pharmacokinetics of Oritavancin in Plasma and Skin Blister Fluid following Administration of a 200-Milligram Dose for 3 Days or a Single 800-Milligram Dose 
Oritavancin is a novel glycopeptide currently being developed for the treatment of complicated skin and skin structure infections (cSSSI), including those caused by multidrug resistant gram-positive pathogens. The disposition of oritavancin in skin structures was investigated using a cantharide-induced blister fluid model. Seventeen healthy male subjects received oritavancin, but only 16 subjects were evaluated after one subject discontinued study drug. Each subject (eight per dose group) received 200 mg of oritavancin once a day for 3 days (group A) or 800 mg as one single dose (group B). Group A plasma samples and exudates from blister fluid were collected on days 3, 4, 7, 9, and 12 and on days 3, 4, 7, and 9, respectively. Group B samples and exudates were collected on days 1, 2, 5, 7, and 10 and on days 1, 2, 5, and 7, respectively. Drug concentrations were determined using a liquid chromatography-tandem mass spectrometry assay and, subsequently, pharmacokinetic analysis was performed. Differences between treatment groups in ratios for area under the concentration-time curve for blister fluid and plasma (AUCblister fluid/AUCplasma ratios) were evaluated using a t test (α = 0.05). Mean maximum concentration of drug in plasma or blister fluid was approximately 8-fold and 11-fold higher in plasma than in blister fluid following the 200- or 800-mg doses of oritavancin, respectively. Mean AUCblister fluid/AUCplasma ratios at 24 h were 0.190 (standard deviation [SD], 0.052) and 0.182 (SD, 0.062) for groups A and B, respectively (P = 0.791). To place these results in a clinical context, mean drug concentrations in blister fluid exceed the oritavancin MIC at which 90% of strains are inhibited of Staphylococcus aureus (2 μg/ml) by approximately 2- to 5.5-fold at 12 h and 1.5- to 3-fold at 24 h following administration of both dosing regimens. These results support the potential use of oritavancin for the treatment of cSSSI.
PMCID: PMC538852  PMID: 15616289
11.  Pharmacokinetics of paclitaxel-containing liposomes in rats 
AAPS PharmSci  2003;5(4):90-100.
In animal models, liposomal formulations of paclitaxel possess lower toxicity and equal antitumor efficacy compared with the clinical formulation, Taxol. The goal of this study was to determine the formulation dependence of paclitaxel pharmacokinetics in rats, in order to test the hypothesis that altered biodistribution of paclitaxel modifies the exposure of critical normal tissues. Paclitaxel was administered intravenously in either multilamellar (MLV) liposomes composed of phosphatidylglycerol/phosphatidylcholine (L-pac) or in the Cremophor EL/ethanol vehicle used for the Taxol formulation (Cre-pac). The dose was 40 mg/kg, and the infusion time was 8 to 9 minutes. Animals were killed at various times, and pharmacokinetic parameters were determined from the blood and tissue distribution of paclitaxel. The area under the concentration vs time curve (AUC) for blood was similar for the 2 formulations (L-pac: 38.1±3.32 μg-h/mL; Cre-pac: 34.5±0.994 μg-h/mL), however, the AUC for various tissues was formulation-dependent. For bone marrow, skin, kidney, brain, adipose, and muscle tissue, the AUC was statistically higher for Cre-pac. For spleen, a tissue of the reticuloendothelial system that is important in the clearance of liposomes, the AUC was statistically higher for L-pac. Apparent tissue partition coefficients (Kp) also were calculated. For bone marrow, a tissue in which paclitaxel exerts significant toxicity, Kp was 5-fold greater for paclitaxel in Cre-pac. The data are consistent with paclitaxel release from circulating liposomes, but with efflux delayed sufficiently to retain drug to a greater extent in the central (blood) compartment and reduce penetration into peripheral tissues. These effects may contribute to the reduced toxicity of liposomal formulations of paclitaxel.
PMCID: PMC2750994  PMID: 15198520
drug delivery; paclitaxel; liposomes; physiological modeling; cancer chemotherapy

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