Increasing throughput of parallel on-line extraction liquid chromatography/electrospray ionization tandem mass spectrometry system for GLP quantitative bioanalysis in drug development

The effects of lapatinib on cardiac repolarization: results from a placebo controlled, single sequence, crossover study in patients with advanced solid tumors

PURPOSE

To evaluate the effect of lapatinib on the QTc interval and ECG parameters in patients with advanced solid tumors.

METHODS

This was a multicenter, placebo-controlled study in subjects with advanced solid tumors. Subjects were administered two doses of matching placebo on day 1, 12 h apart and one dose in the morning on day 2. Two doses of lapatinib 2000 mg were administered orally on day 3, 12 h apart and one dose in the morning on day 4. Twelve-lead digital ECGs were extracted from continuous Holter recordings at pre-specified time points over the 24-h period on days 2 and 4. Venous blood samples for lapatinib concentrations were obtained immediately following the ECGs.

RESULTS

A maximum mean baseline-adjusted, placebo time-matched increase in QTcF, (ddQTcF) in the evaluable, (EV) population (n = 37) of 8.8 ms (90% CI 4.1, 13.4) occurred approximately 10 h after the third lapatinib dose. These results were consistent with those in the pharmacodynamic, PD population, (n = 52) (ddQTcF = 7.9 ms; 90% CI 4.1, 11.7). No subject experienced QTcF increases from baseline of > 60 ms on lapatinib or placebo. The geometric mean lapatinib C_max of 3902 ng/mL was observed at 3.6 h post-dose.

CONCLUSIONS

These data show a relevant, treatment-related increase in QTcF after treatment with three doses of lapatinib 2000 mg. This study confirms the need for caution in patients with solid tumors treated with lapatinib, and who are concomitantly receiving drugs that are strong CYP3A inhibitors and/or prolong the QTc.

High-throughput paper spray mass spectrometry via induced voltage

RATIONALE

Paper spray (PS) has been developed as a method of choice for point-of-care analysis in many real cases, where its applications can be further expanded with delicate high-throughput design. To achieve this goal, we developed a new PS regime, with the assembly of an induced high voltage into the ion source. Compared with regular DC high voltage, the newly developed setup is capable of high-throughput, simple configuration and rapid switching between individual papers without complicated electric/mechanic design.

METHODS

A device of high-throughput induced PS (IPS) was designed by using a two-dimensional (2D) rotating platform equipped with a circular glass plate. The paper substrate was placed on the circular glass plate and separated from the electrode. The method avoids physical contact between the electrode and the sample. Charged droplets were generated at the paper tip once an induced high voltage was applied to a wet paper.

RESULTS

A relatively rapid analytical speed of 2.6 s per sample was achieved via IPS-MS. Rapid quantification of amitriptyline (AMT) in complicated matrices was obtained within 1 min using an isotope internal standard method. Limits of detection for AMt in urine, FBS and blood were calculated to be 1.04, 0.84 and 1.33 ng/mL, respectively. In addition, high-throughput IPS-MS can be used for chemical reaction monitoring.

CONCLUSIONS

We have demonstrated the versatility of high-throughput IPS-MS in ambient ionization, which successfully simplified the experimental installation and facilitated the experimental operation. Therefore, we believe that high-throughput IPS-MS analysis will be widely used for discovering drugs and screening reactions, and the present design has the potential for applications in paper chip-MS analysis.

The effects of lapatinib on CYP3A metabolism of midazolam in patients with advanced cancer

PURPOSE

The potential inhibition of CYP3A4 by lapatinib was studied using midazolam as a probe substrate in patients with cancer.

METHODS

This was a partially randomized, 4-period, 4-sequence, 4-treatment, cross-over study in 24 patients with advanced cancer. Single 1-mg IV and 3-mg oral doses of midazolam were given 2 days apart, in a partially random order, on study days 1, 3, 9, and 11. Lapatinib 1500-mg was administered orally once daily on study days 4 through 11. Midazolam plasma concentrations were measured up to 24-h post dosing, and lapatinib plasma concentrations measured prior to each midazolam dose.

RESULTS

Lapatinib increased the geometric mean (95% CIs) midazolam AUC_(o-∞) by 45% (31-60%) after the oral dose and by 14% (0-29%) after the IV dose, and prolonged the midazolam elimination half-life by 48% (22-81%) after the oral dose and by 20% (2-40%) after the IV dose. Lapatinib decreased midazolam total clearance by 13% (1-23%), while total bioavailability was increased 23% (4-46%) without changes in apparent volume of distribution or hepatic bioavailability.

CONCLUSION

These data show that lapatinib caused weak inhibition of gastrointestinal CYP3A4 in vivo. This suggests that oral CYP3A4 drug substrates with a narrow therapeutic index may need dose reduction if lapatinib is to be co-prescribed.

Discovery of hepatitis B virus capsid assembly inhibitors leading to a heteroaryldihydropyrimidine based clinical candidate (GLS4)

Inhibition of hepatitis B virus (HBV) capsid assembly is a novel strategy for the development of chronic hepatitis B (CHB) therapeutics. Herein we described our lead optimization studies including the synthesis, molecular docking studies and structure-activity relationship (SAR) studies of a series of novel heteroaryldihydropyrimidine (HAP) inhibitors of HBV capsid assembly inhibitors, and the discovery of a potent inhibitor of HBV capsid assembly of GLS4 (ethyl 4-[2-bromo-4-fluorophenyl]-6-[morpholino-methyl]-2-[2-thiazolyl]-1,4-dihydro-pyrimidine-5-carboxylate) which is now in clinical phase 2. GLS4 demonstrated potent inhibitory activities in HBV HepG2.2.15 cell assay with an EC₅₀ value of 1nM, and it also exhibited high potency against various drug-resistant HBV viral strains with EC₅₀ values in the range of 10-20nM, more potent than the typical HBV polymerase inhibitors such as lamivudine, telbivudine, and entecavir. Pharmacokinetic profiles of GLS4 were favorable and safety evaluation including acute toxicity and repeated toxicity study indicated that GLS4 was safe enough to support clinical experiments in human.

A Phase II Biomarker-Embedded Study of Lapatinib plus Capecitabine as First-line Therapy in Patients with Advanced or Metastatic Gastric Cancer

An exploratory phase II biomarker-embedded trial (LPT109747; NCT00526669) designed to determine the association of lapatinib-induced fluoropyrimidine gene changes with efficacy of lapatinib plus capecitabine as first-line treatment for advanced gastric cancer or gastroesophageal junction adenocarcinoma independent of tumor HER2 status. Tumor biopsies obtained before and after 7-day lapatinib (1,250 mg) to analyze changes in gene expression, followed by a 14-day course of capecitabine (1,000 mg/m(2) twice daily, 14/21 days) plus lapatinib 1,250 mg daily. Blood samples were acquired for pharmacokinetic analysis. Primary clinical objectives were response rate (RR) and 5-month progression-free survival (PFS). Secondary objectives were overall survival (OS), PFS, time to response, duration of response, toxicity, and identification of associations between lapatinib pharmacokinetics and biomarker endpoints. Primary biomarker objectives were modulation of 5-FU-pathway genes by lapatinib, effects of germline SNPs on treatment outcome, and trough steady-state plasma lapatinib concentrations. Sixty-eight patients were enrolled; (75% gastric cancer, 25% gastroesophageal junction). Twelve patients (17.9%) had confirmed partial response, 31 (46.3%) had stable disease, and 16 (23.9%) had progressive disease. Median PFS and OS were 3.3 and 6.3 months, respectively. Frequent adverse events included diarrhea (45%), decreased appetite (39%), nausea (36%), and fatigue (36%). Lapatinib induced no changes in gene expression from baseline and no significant associations were found for SNPs analyzed. Elevated baseline HER3 mRNA expression was associated with a higher RR (33% vs. 0%; P = 0.008). Lapatinib plus capecitabine was well tolerated, demonstrating modest antitumor activity in patients with advanced gastric cancer. The association of elevated HER3 and RR warrants further investigation as an important player for HER-targeted regimens in combination with capecitabine. Mol Cancer Ther; 15(9); 2251-8. ©2016 AACR.

Lapatinib Plasma and Tumor Concentrations and Effects on HER Receptor Phosphorylation in Tumor

PURPOSE

The paradigm shift in cancer treatment from cytotoxic drugs to tumor targeted therapies poses new challenges, including optimization of dose and schedule based on a biologically effective dose, rather than the historical maximum tolerated dose. Optimal dosing is currently determined using concentrations of tyrosine kinase inhibitors in plasma as a surrogate for tumor concentrations. To examine this plasma-tumor relationship, we explored the association between lapatinib levels in tumor and plasma in mice and humans, and those effects on phosphorylation of human epidermal growth factor receptors (HER) in human tumors.

EXPERIMENTAL DESIGN

Mice bearing BT474 HER2+ human breast cancer xenografts were dosed once or twice daily (BID) with lapatinib. Drug concentrations were measured in blood, tumor, liver, and kidney. In a randomized phase I clinical trial, 28 treatment-naïve female patients with early stage HER2+ breast cancer received lapatinib 1000 or 1500 mg once daily (QD) or 500 mg BID before evaluating steady-state lapatinib levels in plasma and tumor.

RESULTS

In mice, lapatinib levels were 4-fold higher in tumor than blood with a 4-fold longer half-life. Tumor concentrations exceeded the in vitro IC90 (~ 900 nM or 500 ng/mL) for inhibition of HER2 phosphorylation throughout the 12-hour dosing interval. In patients, tumor levels were 6- and 10-fold higher with QD and BID dosing, respectively, compared to plasma trough levels. The relationship between tumor and plasma concentration was complex, indicating multiple determinants. HER receptor phosphorylation varied depending upon lapatinib tumor concentrations, suggestive of changes in the repertoire of HER homo- and heterodimers.

CONCLUSION

Plasma lapatinib concentrations underestimated tumor drug levels, suggesting that optimal dosing should be focused on the site of action to avoid to inappropriate dose escalation. Larger clinical trials are required to determine optimal dose and schedule to achieve tumor concentrations that maximally inhibit HER receptors.

TRIAL REGISTRATION

CLINICAL TRIAL REGISTRATION

NCT00359190.

Effect of lapatinib on oral digoxin absorption in patients

The potential for an interaction between lapatinib and absorption of the P-glycoprotein (ABCB1) substrate digoxin at a therapeutic dose in breast cancer patients was characterized. Seventeen women with HER2-positive metastatic breast cancer received a single oral 0.5-mg dose of digoxin on days 1 and 9 and oral lapatinib 1500 mg once daily on days 2 through 9. Digoxin pharmacokinetic parameters were determined on day 1 (digoxin administration alone) and on day 9 (coadministration of lapatinib and digoxin), and parameters were compared to determine the effects of lapatinib on digoxin absorption. Concomitant medications that could affect ABCB1 were accounted for. Lapatinib 1500 mg/day increased digoxin absorption approximately 80%, implicating lapatinib inhibition of intestinal ABCB1-mediated efflux. In summary, coadministration of lapatinib with narrow therapeutic index drugs that are substrates of ABCB1 should be undertaken with caution and dose adjustment should be considered.

Bioequivalence study with lapatinib powder for oral suspension and the original tablet formulation in cancer patients

Lapatinib is approved for use in various therapeutic combinations for treating metastatic breast cancers that over-express HER2. To deliver the approved doses, up to six large tablets need to be ingested with the current 250-mg tablets. For ease of ingestion, a powder for oral suspension was developed. This study was an open-label, randomized, adaptive design, two-period crossover bioequivalence study of the powder for suspension relative to the commercial tablet at steady state following once daily dosing for 7 days in patients with advanced cancer. To minimize the number of cancer patients required for a pivotal bioequivalence study (144 in this case), a four-stage adaptive group sequential design with interim analyses after every 36 subjects was implemented to allow for early termination. Bioequivalence for the oral suspension relative to the commercial tablet was demonstrated in both the first (and only) interim analysis and the final analysis, as the 90% confidence intervals for the treatment comparison ratios for both AUC0-24 and Cmax were contained within the acceptance criteria (0.80, 1.25). Additionally, there was no statistical difference in tlag or tmax , suggesting no difference in the absorption rate between treatments. There were no unexpected safety findings during this study.

A phase I pharmacokinetics study of lapatinib and tamoxifen in metastatic breast cancer (EORTC 10053 Lapatam study)

OBJECTIVE

This phase I study assessed the pharmacokinetic (PK), tolerability, safety and preliminary clinical activity of tamoxifen (T) and lapatinib (L) in patients with metastatic breast cancer (MBC).

METHODS

Patients (pts) with hormone receptor positive MBC, irrespective of HER-2 status, were randomly assigned to T → T + L group, tamoxifen in cycle 1 for 28 days then adding lapatinib on day 1 of cycle 2; or L → T + L group, lapatinib in cycle 1 for 14 days, then adding tamoxifen on day 1 of cycle 2 to evaluate the potential drug-drug PK interaction at steady-state. The dose of tamoxifen was 20 mg/day and lapatinib 1500 mg/day.

RESULTS

Twenty-five pts were enrolled of which 23 started treatment, five (22%) of them were HER-2 positive. Median age was 59 years and 96% had PS ≤1. Eleven (91.7%) pts in the T → T + L group and 10 (76.9%) in L → T + L group received at least 2 cycles of treatment. The most frequently reported drug-related adverse events (>25% of patients) were diarrhoea (62%), anaemia (56%), rash (52%), fatigue (52%), dermatology other (34%) and leukopenia (28%). Grade 3-4 drug-related toxicities were infrequent (<10%). No cardiotoxicity was observed. T plasma concentrations did not appeared to be affected by the presence of lapatinib. L steady-state plasma concentrations were 20% lower after 28 days of co-administration with T. Eight (36.4%) patients experienced stable disease and median progression free survival was 2.7 months.

CONCLUSIONS

The combination of L and T was safe and clinically active. T affected L plasma concentrations, which remained within the therapeutic index.

Phase I dose-escalation study of 5-day intermittent oral lapatinib therapy in patients with human epidermal growth factor receptor 2-overexpressing breast cancer

PURPOSE

The highly effective treatment of human epidermal growth factor receptor (HER) 2-amplified breast cancer has proven challenging because of a signal buffering capacity inherent in the functionally relevant HER2-HER3 target. HER2-HER3 signaling can be inactivated by doses of lapatinib that fully inactivate the HER2 kinase. In mouse models, such doses are not tolerable in continuous administration, but they are tolerable and highly effective in intermittent dosing. We pursued the clinical translation of this treatment hypothesis.

PATIENTS AND METHODS

We conducted a phase I dose-escalation study in women with advanced HER2-overexpressing breast cancer. Lapatinib was administered on days 1 through 5 of repeating 14-day cycles. Dose escalation was conducted using a 3+3 design with plasma lapatinib level monitoring.

RESULTS

Forty patients were evaluable for toxicity, and 34 patients were evaluable for dose-limiting toxicity (DLT). Lapatinib dose was escalated to 7,000 mg per day in twice-daily dosing with no DLTs; however, plasma lapatinib concentrations plateaued in this dose range. Additional cohorts evaluated strategies to increase lapatinib exposure, including the food effect, CYP3A4 inhibition, and dose fractionation. Of these, only ketoconazole was able to increase lapatinib exposure, despite highly variable lapatinib bioavailability. Intolerable exposure levels were not encountered. Eight patients (20%) experienced grade 3 diarrhea. Six patients achieved a response, and dramatic responses were seen in three patients with lapatinib concentrations approaching 10,000 ng/mL.

CONCLUSION

Lapatinib exposure can be safely and significantly increased through intermittent dosing but reaches a ceiling that currently impedes clinical translation of the treatment hypothesis. Preliminary efficacy data suggest that exposures approaching those seen in mouse models can result in highly significant tumor responses.

Phase I study evaluating the combination of lapatinib (a Her2/Neu and EGFR inhibitor) and everolimus (an mTOR inhibitor) in patients with advanced cancers: South West Oncology Group (SWOG) Study S0528

PURPOSE

Everolimus, an oral inhibitor of mammalian target of rapamycin, can augment the efficacy of HER inhibitors in preclinical studies. This study was conducted to determine the safety and pharmacokinetics (PK) of the combination of lapatinib, a Her1 and 2 inhibitor, and everolimus and to describe its anti-tumor activity in the Phase I setting.

METHODS

In Part I, dose escalation to define the maximum tolerated dose (MTD) was performed. In Part II, PK of both drugs were analyzed to assess drug-drug interaction.

RESULTS

Twenty-three evaluable patients with advanced cancers were treated on six different dose levels in Part I of the study. The dose-limiting toxicities were diarrhea, rash, mucositis, and fatigue. The MTD of the combination was 1,250 mg of lapatinib and 5 mg of everolimus once daily. In Part II of the study, 54 patients were treated with the combination at the MTD. The mean everolimus time to maximum concentration was increased by 44 %, and mean clearance was decreased by 25 % when co-administered with lapatinib, though these differences were not statistically significant. There was no significant influence on the PK of lapatinib by everolimus. Two patients achieved a partial response [thymic cancer (45+ months) and breast cancer (unconfirmed PR; 7 months)]; 11 patients attained stable disease of at least 4 months.

CONCLUSIONS

Lapatinib and everolimus are well tolerated at doses of 1,250 and 5 mg po daily, respectively. Stable disease ≥4 months/PR was achieved in 13 of 78 patients (17 %).

A stable isotope-labeled internal standard is essential for correcting for the interindividual variability in the recovery of lapatinib from cancer patient plasma in quantitative LC-MS/MS analysis

The development and validation of a LC-MS/MS method is often performed using pooled human plasma, which may fail to account for variations in interindividual matrices. Since calibrator standards and quality control samples are routinely prepared in pooled human plasma, variations in the extraction recovery and/or matrix effect between pooled plasma and individual patient plasma can cause erroneous measurements. Using both pooled human plasma as well as individual healthy donor and cancer patient plasma samples, we evaluated the analytical performance of two classes of internal standards (i.e., non-isotope-labeled and isotope-labeled) in the quantitative LC-MS/MS analysis of lapatinib. After exhaustive extraction with organic solvent, the recovery of lapatinib, a highly plasma protein-bound drug, varied up to 2.4-fold (range, 29-70%) in 6 different donors of plasma and varied up to 3.5-fold (range, 16-56%) in the pretreatment plasma samples from 6 cancer patients. No apparent matrix effects were observed for lapatinib in both pooled and individual donor or patient plasma samples. The calibration curve range was 5-5000ng/ml of lapatinib in plasma. Both the non-isotope-labeled (zileuton) and isotope-labeled (lapatinib-d3) internal standard methods showed acceptable specificity, accuracy (within 100±10%), and precision (<11%) in the determination of lapatinib in pooled human plasma. Nevertheless, only the isotope-labeled internal standard could correct for the interindividual variability in the recovery of lapatinib from patient plasma samples. As inter- and intra-patient matrix variability is commonly presented in the clinical setting, this study provides an example underscoring the importance of using a stable isotope-labeled internal standard in quantitative LC-MS/MS analysis for therapeutic drug monitoring or pharmacokinetic evaluation.

Effects of Esomeprazole on the Pharmacokinetics of Lapatinib in Breast Cancer Patients

The aqueous solubility of lapatinib declines significantly at pH >4, suggesting that its bioavailability might be lowered by acid-reducing drugs. A study was therefore conducted to assess the effects of esomeprazole on lapatinib pharmacokinetics (PK). Women with metastatic human epidermal growth factor receptor 2 positive (HER2(+) ) breast cancer were enrolled. Patients received 1,250 mg lapatinib once daily (QD) in the morning on Days 1-7 (Period 1) and Days 8-14 (Period 2) with 40 mg esomeprazole QD at bedtime 3 hours after dinner on Days 8-14. Lapatinib PK sampling occurred during the 24-hour steady-state dosing intervals on Day 7 (lapatinib alone) and Day 14 (lapatinib with esomeprazole). Esomeprazole treatment resulted in decreased lapatinib bioavailability (mean 26%, range 6-49%) that was inversely associated with patient age as a significant covariate.

An European Organisation for Research and Treatment of Cancer phase I study of lapatinib and docetaxel as neoadjuvant treatment for human epidermal growth factor receptor 2 (HER2) positive locally-advanced/inflammatory or large operable breast cancer

BACKGROUND

Lapatinib is an effective anti-HER2 therapy in advanced breast cancer and docetaxel is one of the most active agents in breast cancer. Combining these agents in pre-treated patients with metastatic disease had previously proved challenging, so the primary objective of this study aimed to determine the maximum tolerated dose (MTD) in treatment-naive patients, by identifying acute dose-limiting toxicities (DLT) during cycle 1 in the first part of a phases 1-2 neoadjuvant European Organisation for Research and Treatment of Cancer (EORTC) trial.

PATIENTS AND METHODS

Patients with large operable or locally-advanced HER2 positive breast cancer were treated with continuous lapatinib, and docetaxel every 21days for 4 cycles. Dose levels (DLs) were: 1000/75, 1250/75, 1000/85, 1250/85, 1000/100 and 1250/100 (mg/day)/(mg/m(2)).

RESULTS

Twenty-one patients were included. Two DLTs occurred at dose level 5 (1000/100); one grade 4 neutropenia ≥ 7days and one febrile neutropenia. A further 3 patients were therefore treated at the same dose with prophylactic granulocyte-colony stimulating factor (G-CSF), and 3 patients at dose level 6. No further DLTs were observed.

CONCLUSIONS

Our recommended dose for phase II is lapatinib 1000mg/day and docetaxel 100mg/m(2) with G-CSF in HER2 positive non-metastatic breast cancer. The dose of lapatinib should have been 1250mg/day but we were mindful of the high rate of treatment discontinuation in GeparQuinto with lapatinib 1250mg/day combined with docetaxel. No grade 3-4 diarrhoea was observed. Pharmacodynamics analysis suggests that concomitant medications altering P-glycoprotein activity (in addition to lapatinib) can modify toxicity, including non-haematological toxicities. This needs verification in larger trials, where it may contribute to understanding the sources of variability in clinical toxicity and treatment discontinuation.

Development of an ultra fast online-solid phase extraction (SPE) liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS) based approach for the determination of drugs in pharmacokinetic studies

High-throughput analyses of a large number of samples for pharmacokinetic (PK) studies are essential in drug development. Analysis of drug candidates from blood using LC-ESI-MS generally requires separation of the plasma fraction followed by various offline sample preparation procedures. This step is a bottleneck that impedes throughput. In order to overcome this difficulty and accelerate analysis in PK and other studies, we developed an approach allowing the direct analysis of low volumes of whole blood (10 μL) after dilution and centrifugation. Samples were injected in an online-SPE-LC-ESI-MS/MS setup allowing a total run time of only 126 s for a full gradient separation. Analytes were extracted from the matrix within 30 s by turbulent flow chromatography. Subsequently, a full gradient separation was carried out within 1.5 minutes on a 50 × 2.1 mm (1.7 μm) RP-18 column and the analytes were sensitively detected by ESI-MS/MS in SRM mode. The performance of this new ultra fast online SPE-LC-ESI-MS/MS approach was demonstrated by the analysis of diclofenac (DCF), a widely used anti-inflammatory drug. DCF eluted at stable retention times (±0.33%) with narrow peak width (FWHM 3.3 ± 0.15 s). The method displays excellent analytical performance, with a limit of detection of 6 fmol on column, a linear range of over four orders of magnitude and a negligible carry over of 0.12 ± 0.03% for DCF. The PK profile of DCF administered by topical and intraperitoneal routes in rats and by oral route in one human volunteer is investigated using this method. Finally, general applicability of the approach for drugs is demonstrated by analysis of rofecoxib and several inhibitors of the soluble epoxide hydrolase. This new method requires only readily available, off the shelf standard LC instrumentation, and is compliant with the requirements of green analytical chemistry.

Resiliency and vulnerability in the HER2-HER3 tumorigenic driver

About 25% of breast cancers harbor the amplified oncogene human epidermal growth factor receptor 2 (HER2) and are dependent on HER2 kinase function, identifying HER2 as a vulnerable target for therapy. However, HER2-HER3 signaling is buffered so that it is protected against a nearly two-log inhibition of HER2 catalytic activity; this buffering is driven by the negative regulation of HER3 by Akt. We have now further characterized HER2-HER3 signaling activity and have shown that the compensatory buffering prevents apoptotic tumor cell death from occurring as a result of the combined loss of mitogen-activated protein kinase (MAPK) and Akt signaling. To overcome the cancer cells' compensatory mechanisms, we coadministered a phosphoinositide 3-kinase-mammalian target of rapamycin inhibitor and a HER2 tyrosine kinase inhibitor (TKI). This treatment strategy proved equivocal because it induced both TKI-sensitizing and TKI-desensitizing effects and robust cross-compensation of MAPK and Akt signaling pathways. Noting that HER2-HER3 activity was completely inhibited by higher, fully inactivating doses of TKI, we then attempted to overcome the cells' compensatory buffering with this higher dose. This treatment crippled all downstream signaling and induced tumor apoptosis. Although such high doses of TKI are toxic in vivo when given continuously, we found that intermittent doses of TKI administered to mice produced sequential cycles of tumor apoptosis and ultimately complete tumor regression in mouse models, with little toxicity. This strategy for inactivation of HER2-HER3 tumorigenic activity is proposed for clinical testing.

Phase I trial of pelvic radiation, weekly cisplatin, and 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) for locally advanced cervical cancer

PURPOSE

This study assessed the safety/tolerability, pharmacokinetics, and clinical activity of three times weekly i.v. 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) in combination with once-weekly i.v. cisplatin and daily pelvic radiation in patients with gynecologic malignancies. 3-AP is a novel small-molecule inhibitor of ribonucleotide reductase (RNR) and is being tested as a potential radiosensitizer and chemosensitizer.

EXPERIMENTAL DESIGN

Patients with stage IB2 to IVB cervical cancer (n = 10) or recurrent uterine sarcoma (n = 1) were assigned to dose-finding cohorts of 2-hour 3-AP infusions during 5 weeks of cisplatin chemoradiation. Pharmacokinetic and methemoglobin samples and tumor biopsy for RNR activity were obtained on day 1 and day 10. Clinical response was assessed.

RESULTS

The maximum tolerated 3-AP dose was 25 mg/m(2) given three times weekly during cisplatin and pelvic radiation. Two patients experienced manageable 3-AP-related grade 3 or 4 electrolyte abnormalities. 3-AP pharmacokinetics showed a 2-hour half-life, with median peak plasma concentrations of 277 ng/mL (25 mg/m(2)) and 467 ng/mL (50 mg/m(2)). Median methemoglobin levels peaked at 1% (25 mg/m(2)) and 6% (50 mg/m(2)) at 4 hours after initiating 3-AP infusions. No change in RNR activity was found on day 1 versus day 10 in six early complete responders, whereas elevated RNR activity was seen on day 10 as compared with day 1 in four late complete responders (P = 0.02). Ten (100%) patients with stage IB2 to IVB cervical cancer achieved complete clinical response and remained without disease relapse with a median 18 months of follow-up (6-32 months).

CONCLUSIONS

3-AP was well tolerated at a three times weekly i.v. 25 mg/m(2) dose during cisplatin and pelvic radiation. Clin Cancer Res; 16(4); 1298-306.

EGFR signaling through an Akt-SREBP-1-dependent, rapamycin-resistant pathway sensitizes glioblastomas to antilipogenic therapy

Glioblastoma, the most common malignant brain tumor, is among the most lethal and difficult cancers to treat. Although epidermal growth factor receptor (EGFR) mutations are frequent in glioblastoma, their clinical relevance is poorly understood. Studies of tumors from patients treated with the EGFR inhibitor lapatinib revealed that EGFR induces the cleavage and nuclear translocation of the master transcriptional regulator of fatty acid synthesis, sterol regulatory element-binding protein 1 (SREBP-1). This response was mediated by Akt; however, clinical data from rapamycin-treated patients showed that SREBP-1 activation was independent of the mammalian target of rapamycin complex 1, possibly explaining rapamycin's poor efficacy in the treatment of such tumors. Glioblastomas without constitutively active EGFR signaling were resistant to inhibition of fatty acid synthesis, whereas introduction of a constitutively active mutant form of EGFR, EGFRvIII, sensitized tumor xenografts in mice to cell death, which was augmented by the hydroxymethylglutaryl coenzyme A reductase inhibitor atorvastatin. These results identify a previously undescribed EGFR-mediated prosurvival metabolic pathway and suggest new therapeutic approaches to treating EGFR-activated glioblastomas.

A phase I and pharmacokinetic study of oral lapatinib administered once or twice daily in patients with solid malignancies

PURPOSE

This study determined the range of tolerable doses, clinical safety, pharmacokinetics, and preliminary evidence of clinical activity following once or twice daily administration of lapatinib in patients with solid malignancies.

EXPERIMENTAL DESIGN

Cancer patients (n = 81) received oral doses of lapatinib ranging from 175 to 1,800 mg once daily or 500 to 900 mg twice daily. Clinical assessments of safety and antitumor activity were recorded and blood was sampled for pharmacokinetic assessments. The effect of a low-fat meal on lapatinib pharmacokinetics was assessed in a subset of patients.

RESULTS

Lapatinib was well tolerated, such that dose escalation was limited at 1,800 mg once daily only by pill burden. Twice-daily dosing was implemented to further explore tolerability, and was limited by diarrhea to 500 mg twice daily. The most commonly reported adverse events with once-daily dosing were diarrhea (48%), nausea (40%), rash (40%), and fatigue (38%) and with twice-daily dosing were diarrhea (85%), rash (54%), and nausea (34%). Lapatinib serum concentrations accumulated upon repeated dosing, increasing nearly in proportion with dose, and were significantly increased when dosed with food or administered twice daily. One patient with head and neck cancer achieved a confirmed complete response and 22 patients had stable disease of >or=8 weeks including three patients with stable disease of >10 months (renal, lung, and salivary gland cancers).

CONCLUSION

Lapatinib was well tolerated following once and twice daily administration. Systemic exposure to lapatinib was dependent on the dose, duration and frequency of dosing, and prandial state. Clinical activity was observed.

Effects of ketoconazole and carbamazepine on lapatinib pharmacokinetics in healthy subjects

AIMS

To characterize the impact of potent CYP3A4 inhibition and induction on lapatinib pharmacokinetics.

METHODS

Two studies were conducted in healthy subjects. One study examined the effect of ketoconazole 200 mg b.i.d. for 7 days on a single 100-mg dose of lapatinib in 22 healthy subjects. The other study examined the effect of carbamazepine titrated up to 200 mg b.i.d. over 20 days on a single 250-mg dose of lapatinib in 24 healthy subjects.

RESULTS

Ketoconazole altered lapatinib AUC, C(max) and half-life, with geometric mean [95% confidence interval (CI)] increases of 3.57-fold (3.07, 4.15), 2.14-fold (1.74, 2.64) and 1.66-fold (1.50, 1.84), respectively, but had no effect on absorption rate. Carbamazepine altered lapatinib AUC, C(max) and absorption rate, with geometric mean (95% CI) decreases of 72% (68, 77), 59% (49, 66) and 28% (4, 46), respectively, but had no effect on half-life.

CONCLUSIONS

Systemic exposure to lapatinib was significantly altered by potent inhibition and induction of CYP3A4. Dose adjustments may be required when lapatinib is administered with orally administered drugs that potently alter the activity of this enzyme.

A phase I study of a 2-day lapatinib chemosensitization pulse preceding nanoparticle albumin-bound Paclitaxel for advanced solid malignancies

PURPOSE

Systemic chemotherapy fails to access much of the tumor burden in patients with advanced cancer, significantly limiting its efficacy. In preclinical studies, brief high doses of tyrosine kinase inhibitors (TKI) targeting the human epidermal growth factor receptor (HER) family can prime tumor vasculature for optimal chemotherapeutic delivery and efficacy. This study investigates the clinical relevance of this approach.

EXPERIMENTAL DESIGN

A phase I clinical study of escalating doses of the HER TKI lapatinib given as a 2-day pulse before a weekly infusion of nab-paclitaxel (100 mg/m(2)) was conducted in patients with advanced solid tumors.

RESULTS

Twenty-five patients were treated. Treatment was associated with grade 1 to 2 toxicities including diarrhea, nausea, rash, neutropenia, neuropathy, fatigue, alopecia, and anemia. The two dose-limiting toxicities were grade 3 vomiting and grade 4 neutropenia, and the maximum tolerated dose of lapatinib was defined as 5250 mg/day in divided doses. Lapatinib concentrations increased with increasing dose. Dynamic Contrast Enhanced Magnetic Resonance Imaging studies in a subset of patients confirmed a decrease in tumor vascular permeability immediately following a lapatinib pulse. Sixty-five percent of evaluable patients experienced a partial or stable response on this therapy, 72% of whom were previously taxane-refractory.

CONCLUSION

A 2-day pulse of high-dose lapatinib given before weekly nab-paclitaxel is a feasible and tolerable clinical regimen, suitable for testing this novel vascular-priming chemosensitization hypothesis developed in preclinical models.

Effects of food on the relative bioavailability of lapatinib in cancer patients

PURPOSE

This study was conducted to characterize the effect of food on the relative bioavailability of lapatinib.

PATIENTS AND METHODS

A single 1,500-mg, oral dose of lapatinib was administered to 27 patients with advanced solid tumors on each of three occasions that were 1 week apart, in random order: after an overnight fast, with a low-fat breakfast, and with a high-fat breakfast.

RESULTS

The low-fat breakfast produced mean increases in lapatinib area under the concentration-time curve (AUC) of 167% (2.67-fold) and maximum concentration (C(max)) of 142% (2.42-fold). The high-fat breakfast produced mean increases in lapatinib AUC of 325% (4.25-fold) and C(max) of 203% (3.03-fold) compared with the fasted state. Increased bioavailability in the fed state did not significantly decrease relative variability. Therefore, absolute variability in systemic exposure was increased.

CONCLUSION

These large increases in lapatinib bioavailability and absolute variability support the recommendation for dosing in the fasted state to achieve consistent therapeutic exposure. Prescribers and patients should consider the potential consequences of toxicity or diminished efficacy that might result from dosing without regard to variations in diet.

Evaluation of lapatinib and topotecan combination therapy: tissue culture, murine xenograft, and phase I clinical trial data

PURPOSE

Topotecan resistance can result from drug efflux by P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) as well as survival signals initiated by epidermal growth factor receptor family members. The present studies were done to determine the effect of combining topotecan and the dual epidermal growth factor receptor/HER2 inhibitor lapatinib in tissue culture, a murine xenograft model, and a phase I clinical trial.

EXPERIMENTAL DESIGN

The effects of lapatinib on topotecan accumulation and cytotoxicity in vitro were examined in paired cell lines lacking or expressing Pgp or BCRP. Antiproliferative effects of the combination were assessed in mice bearing HER2+ BT474 breast cancer xenografts. Based on tolerability in this preclinical model, 37 patients with advanced-stage cancers received escalating doses of lapatinib and topotecan in a phase I trial.

RESULTS

Lapatinib increased topotecan accumulation in BCRP- or Pgp-expressing cells in vitro, and the combination showed enhanced efficacy in HER2+ BT474 xenografts. In the phase I study, nausea, vomiting, diarrhea, and fatigue were dose limiting. The maximum tolerated doses were 1,250 mg/d lapatinib by mouth for 21 or 28 days with 3.2 mg/m2 topotecan i.v. on days 1, 8, and 15 of 28-day cycles. Pharmacokinetic analyses showed that combined drug administration resulted in decreased topotecan clearance consistent with transporter-mediated interactions. Seventeen (46%) patients had disease stabilization.

CONCLUSIONS

The lapatinib/topotecan combination is well tolerated and warrants further study.

A phase I study of lapatinib in combination with carboplatin in women with platinum sensitive recurrent ovarian carcinoma

OBJECTIVES

To determine the maximum tolerated dose (MTD), spectrum of toxicities, clinical activity, and pharmacokinetics of carboplatin given in combination with lapatinib in women with a first recurrence of platinum sensitive epithelial ovarian carcinoma.

METHODS

Patients with measurable, platinum sensitive recurrent epithelial ovarian carcinoma were eligible. Cohorts of 3-6 patients were to receive up to 6 cycles of intravenous carboplatin AUC of 6 every 21 days in combination with escalating dosages of oral lapatinib (starting at a dose of 750 mg daily). Toxicity was assessed using NCI CTC for Adverse Events. Clinical response was monitored using RECIST criteria. Pharmacokinetic (PK) analysis was performed for the second cohort of patients.

RESULTS

Twelve patients were enrolled. No dose limiting toxicity was noted. Two of 6 patients in the first cohort had unanticipated excessive delays in treatment due to non-dose limiting G3 neutropenia. Therefore, the study was modified to reduce the carboplatin dose in the second cohort. The median number of courses administered to the 11 evaluable patients in these two cohorts was 2.8 (range 1-6). Drug-related grade 3 or 4 toxicities included non-dose limiting G4 thrombocytopenia (n=1), and non-dose limiting G3 neutropenia (n=3). Of the 11 patients who received >or=1 course of therapy, 3 (27%) had a partial response, and 3 (27%) had stable disease. The pharmacokinetics of carboplatin were not significantly altered by concomitant administration of lapatinib.

CONCLUSIONS

This regimen of lapatinib and carboplatin was associated with unacceptable non-dose limiting toxicities, excessive treatment delays and limited clinical responses.

Phase I Dose Escalation and Pharmacokinetic Study of Lapatinib in Combination With Trastuzumab in Patients With Advanced ErbB2-Positive Breast Cancer

Purpose

The combination of lapatinib and trastuzumab has been observed to have a synergistic, antiproliferative effect against ErbB2-positive breast cancer cells in vitro. This phase I study assessed the safety, clinical feasibility, optimally tolerated regimen (OTR), pharmacokinetics (PK), and preliminary clinical activity of this combination in patients with ErbB2-positive advanced breast cancer.

Patients and Methods

Cohorts of three patients with ErbB2-positive advanced breast cancer were treated with escalating doses of lapatinib (750 to 1,500 mg) administered once daily (continuous) in combination with trastuzumab (4 mg/kg loading dose then 2 mg/kg weekly) to determine the OTR. Once the OTR was determined, additional patients were enrolled to provide the PK profile of both agents alone and in combination.

Results

A total of 54 patients were treated: 27 in the dose-escalation group and 27 in the PK group. Overall, adverse events were mild to moderate in severity, with no drug-related grade 4 events. The most frequent drug-related grade 3 events included diarrhea (17%), fatigue (11%), and rash (6%). The OTR was 1,000 mg lapatinib with standard weekly trastuzumab. One patient had a complete response and seven patients had partial responses. The PK parameters (maximum concentration in plasma and area under the curve) of lapatinib and trastuzumab in combination were not significantly different than when either was administered alone.

Conclusion

The OTR of the lapatinib/trastuzumab combination was lapatinib 1,000 mg per day with standard weekly trastuzumab. At these doses, the regimen was well tolerated and clinically active in this heavily pretreated ErbB2-positive breast cancer population.

Phase I and Pharmacokinetic Study of Lapatinib and Docetaxel in Patients With Advanced Cancer

Purpose

This phase I study assessed the safety, optimally tolerated regimen (OTR), pharmacokinetics, pharmacodynamics, and preliminary clinical activity of lapatinib and docetaxel in patients with advanced solid tumors.

Patients and Methods

Doses of lapatinib (oral once daily, continuous) and docetaxel (intravenous, every 3 weeks) were escalated in cohorts of at least three patients based on dose-limiting toxicities in the first treatment cycle until the OTR was reached. The protocol was amended to include pegfilgrastim because of dose-limiting toxicity (neutropenia), and a second dose-escalation phase was conducted to determine the OTR for the combination of docetaxel, lapatinib, and pegfilgrastim. After the determination of the OTR, the pharmacokinetics of lapatinib and docetaxel were determined to estimate the potential for an interaction between docetaxel and lapatinib at the OTR dose level.

Results

Fifty-two patients with advanced solid tumors were enrolled. The OTR dose level for lapatinib and docetaxel with pegfilgrastim was 1,250 mg (once daily) and 75 mg/m2 (once every 3 weeks), respectively. Overall, adverse events (AEs) were mild to moderate in severity. The drug-related AEs reported by most patients (≥ 25%) were diarrhea (56%), rash (52%), fatigue (27%), and nausea (25%). Of 43 patients assessable for clinical response, two patients had confirmed partial responses. The pharmacokinetics of lapatinib (area under the curve, maximum serum concentration) and docetaxel (area under the curve, clearance) in combination were not significantly different than when the drugs are administered separately.

Conclusion

The combination of docetaxel and lapatinib with pegfilgrastim was well tolerated. No pharmacokinetic interaction was observed. Clinical activity was seen in this phase I drug combination trial.

A phase I and pharmacokinetic study of lapatinib in combination with infusional 5-fluorouracil, leucovorin and irinotecan

BACKGROUND

This study determined the optimally tolerated regimen (OTR) of oral lapatinib administered in combination with infusional 5-fluorouracil (5-FU), leucovorin and irinotecan (FOLFIRI) and assessed the safety, tolerability and pharmacokinetics of the combination.

PATIENTS AND METHODS

Twenty-five patients were enrolled; 12 patients were treated at three dose levels to determine OTR; then 13 patients were treated at OTR to evaluate the pharmacokinetics of the combination.

RESULTS

The 2-weekly OTR comprised lapatinib 1250 mg/day with irinotecan 108 mg/m(2) (day 1) and leucovorin 200 mg/m(2), 5-FU bolus 240 mg/m(2) and 5-FU infusion 360 mg/m(2) (days 1 and 2); doses of 5-FU and irinotecan represent a 40% reduction in dose compared to conventional FOLFIRI. Dose-limiting toxicities were grade 3 diarrhoea and grade 4 neutropenia. Co-administration of lapatinib increased the area under the plasma concentration-time curve of SN-38, the active metabolite of irinotecan, by an average of 41%; no other pharmacokinetic interactions were observed. Of 19 patients evaluable for disease response assessment, four patients had partial response and nine patients had stable disease.

CONCLUSION

The combination of lapatinib and FOLFIRI is safe and demonstrates clinical activity; the documented PK interaction can effectively be compensated by lowering the doses of 5-FU and irinotecan. This regime may be further tested in a phase II trial.

Determination of sitagliptin in human urine and hemodialysate using turbulent flow online extraction and tandem mass spectrometry

High turbulence liquid chromatography (HTLC, or turbulent flow online extraction) and tandem mass spectrometry (MS/MS) methods for the determination of sitagliptin in human urine and hemodialysate were developed and validated to support clinical studies. A narrow bore large particle size reversed-phase column (Cyclone, 50 mm x 1.0 mm, 60 microm) and a BDS Hypersil C18 column (30 mm x 2.1 mm, 3 microm) were used as extraction and analytical columns, respectively. For the urine assay, the LLOQ was 0.1 microg/ml, the linear calibration range was 0.1 to 50 microg/ml, the interday precision (R.S.D.%, n=5) was 2.3-6.5%, and the accuracy was 96.9-106% of the nominal value. For the urine quality control samples (QCs), the intraday precision (R.S.D.%, n=5) and accuracy were 1.8-2.6% and 96.2-106% of the nominal value, respectively. The interday precision (R.S.D.%) for 56 sets of urine QCs over a 6-month period varied from 3.8% to 5.5% and the accuracy from 102% to 105% of the nominal value. For the hemodialysate assay, the LLOQ was 0.01 ng/ml, the linear dynamic range was 0.01-5.0 ng/ml, the interday precision was 1.6-4.1%, and the accuracy was 89.8-104% of the nominal value. For hemodialysate QCs, the intraday precision and accuracy varied from 2.3% to 8.9% and from 99.8% to 111% of the nominal value, respectively. These results demonstrated that both methods are selective, accurate, precise, reproducible, and suitable for quantifying sitagliptin in hemodialysate and human urine samples.

Development of a μ-turbulent flow chromatography focus mode method for drug quantitation in discovery bioanalysis

An online turbulent flow chromatography method coupled to tandem mass spectrometry (TFC-MS/MS) has been developed within our bioanalytical group, suited to the analysis of mid to late stage discovery compounds. A dual column configuration utilising isocratic focusing of the analyte upon the analytical column maintained an excellent peak shape for a large proportion of compounds encountered and enabled consistent quantitation to sub-nanogram concentrations (<15 pg on column). Furthermore, the low sample injection volume coupled with rapid column washing using basic and acidic mobile phases, has proved advantageous in removing sample carryover and also the overall exposure to biological material; favourable for good system robustness. All the data discussed were generated with a method cycle time of 5 min providing accurate quantitation (acceptance criteria based upon FDA method validation guidelines) with multiple analytes and biological matrices.

Phase I Pharmacokinetic Study of the Safety and Tolerability of Lapatinib (GW572016) in Combination with Oxaliplatin/Fluorouracil/Leucovorin (FOLFOX4) in Patients with Solid Tumors

PURPOSE

This phase I study was designed to determine the optimally tolerated regimen (OTR), safety, and clinical activity of lapatinib in combination with FOLFOX4 [oxaliplatin/leucovorin/5-fluorouracil (5-FU)] in patients with solid tumors. Furthermore, the pharmacokinetics of lapatinib, oxaliplatin, and 5-FU when given alone and in combination were evaluated.

EXPERIMENTAL DESIGN

This study was conducted in two parts. Part 1 was designed to determine the OTR and part 2 was the pharmacokinetic part of the study. Lapatinib was administered once daily for the entire duration of the study. Leucovorin and oxaliplatin were given concurrently over 2 h as an i.v. infusion, after which 5-FU was given as a bolus followed by continuous infusion over 22 h on day 1. 5-FU and leucovorin administration were repeated in an identical manner on day 2. Cycles were repeated every 2 weeks. Once the OTR was determined, it was to become the dose level for patients included in the pharmacokinetic part of the study.

RESULTS

A total of 34 patients was treated in this study. No dose-limiting toxicities were observed and the OTR was established at 1,500 mg/d lapatinib in combination with the standard FOLFOX4 regimen. Nonhematologic toxicities consisted mainly of nausea, diarrhea, vomiting, fatigue, neuropathy, and mucositis. The most important hematologic toxicity was neutropenia. No drug-drug interactions between lapatinib and the FOLFOX4 regimen were observed.

CONCLUSION

Lapatinib can be safely administered in combination with the standard FOLFOX4 regimen. Further studies are warranted to explore the potential additive antitumor effect of lapatinib in combination with the FOLFOX4 regimen.

Recent advances in high-throughput quantitative bioanalysis by LC–MS/MS

Liquid chromatography linked to tandem mass spectrometry (LC-MS/MS) has played an important role in pharmacokinetics and metabolism studies at various drug development stages since its introduction to the pharmaceutical industry. This article reviews the most recent advances in sample preparation, separation, and the mass spectrometric aspects of high-throughput quantitative bioanalysis of drug and metabolites in biological matrices. Newly introduced techniques such as ultra-performance liquid chromatography with small particles (sub-2 microm) and monolithic chromatography offer improvements in speed, resolution and sensitivity compared to conventional chromatographic techniques. Hydrophilic interaction chromatography (HILIC) on silica columns with low aqueous/high organic mobile phase is emerging as a valuable supplement to the reversed-phase LC-MS/MS. Sample preparation formatted to 96-well plates has allowed for semi-automation of off-line sample preparation techniques, significantly impacting throughput. On-line solid-phase extraction (SPE) utilizing column-switching techniques is rapidly gaining acceptance in bioanalytical applications to reduce both time and labor required to produce bioanalytical results. Extraction sorbents for on-line SPE extend to an array of media including large particles for turbulent flow chromatography, restricted access materials (RAM), monolithic materials, and disposable cartridges utilizing traditional packings such as those used in Spark Holland systems. In the end, this paper also discusses recent studies of matrix effect in LC-MS/MS analysis and how to reduce/eliminate matrix effect in method development and validation.

Principles and applications of LC-MS in new drug discovery

The use of high-performance liquid chromatography combined with mass spectrometry (HPLC-MS) or tandem mass spectrometry (HPLC-MS-MS) has proven to be the analytical technique of choice for most assays used in various stages of new drug discovery. A summary of the key components of HPLC-MS systems, as well as an overview of major application areas that use this technique as part of the drug discovery process, will be described here. This review will also provide an introduction into the various types of mass spectrometers that can be selected for the multiple tasks that can be performed using LC-MS as the analytical tool. The strategies for optimizing the use of this technique and also the potential problems and how to avoid them will be highlighted.

Determination of lapatinib (GW572016) in human plasma by liquid chromatography electrospray tandem mass spectrometry (LC–ESI-MS/MS)

A sensitive method for the determination of lapatinib (GW572016) in human plasma was developed using high-performance liquid chromatographic separation with tandem mass spectrometric detection. Plasma samples (100 microL) were prepared using solid phase extraction (SPE) columns, and 6.0 microL of the reconstituted eluate was injected onto a Phenomenex CuroSil-PFP 3 mu analytical column (50 mm x 2.0mm) with an isocratic mobile phase. Analytes were detected with a PE SCIEX API-365 LC-MS/MS system at unit (Q1) and low (Q3) resolution in positive multiple reaction monitoring mode (m/z 581 (precursor ion) to m/z 364 (product ion) for lapatinib). The mean recovery for lapatinib was 75% with a lower limit of quantification of 15 ng/mL (S/N=11.3, CV< or =14%). This method was validated over a linear range of 100-10,000 ng/mL, and results from a 5-day validation study demonstrated good within-day and between-day precision and accuracy. This method has been used to measure plasma lapatinib concentrations in a Phase I study in children with cancer.

Determination of MK-0431 in human plasma using high turbulence liquid chromatography online extraction and tandem mass spectrometry

A robust and sensitive method using high turbulence liquid chromatography (HTLC) online extraction with tandem mass spectrometry (MS/MS) for the determination of MK-0431 in human plasma was developed and validated to support the clinical studies. This HTLC online extraction method eliminated the time-consuming offline sample extraction procedures and significantly increased productivity. A narrow bore large particle size reversed-phase column (Cyclone, 50 x 1.0 mm, 60 microm) and a BDS Hypersil C18 column (30 x 2.1 mm, 3 microm) were used as extraction and analytical columns, respectively. The linear dynamic range of the calibration curve was 0.5 to 1000 ng/mL. Intraday validation was conducted using five calibration curves prepared in five lots of human control plasma, and the intraday precision (RSD%) was from 2.4 to 9.0% and the accuracy was from 98.0 to 103% of the nominal value. The intraday precision (RSD%, n = 5) for plasma quality control (QC) samples varied from 2.0 to 5.3% and accuracy from 103 to 105% of the nominal value. The interday precision (RSD%) for 100 sets of plasma QC samples in 29 analytical runs varied from 6.3 to 9.0% and the accuracy from 98.8 to 104% of the nominal value. No significant difference was observed between the interday and intraday precision and accuracy of the QC samples.

Development of an on-line extraction turbulent flow chromatography tandem mass spectrometry method for cassette analysis of Caco-2 cell based bi-directional assay samples

Caco-2 cells are frequently used for screening compounds for their permeability characteristics and P-glycoprotein (P-gp) interaction potential. Bi-directional permeability studies performed on Caco-2 cells followed by analysis by HPLC-UV or LC-MS method constitutes the "method of choice" for the functional assessment of efflux characteristics of a test compound. A high throughput LC-MS/MS method has been developed using on-line extraction turbulent flow chromatography coupled to tandem mass spectrometric detection to analyze multiple compounds present in Hanks balanced salt solution in a single analytical run. All standard curves (P-gp substrates: quinidine, etoposide, rhodamine 123, dexamethasone, and verapamil and non-substrates: metoprolol, sulfasalazine, propranolol, nadolol, and furosemide) were prepared in a cassette mode (ten-in-one) while Caco-2 cell incubations were performed both in discreet mode and in cassette mode. The standard curve range for most compounds was 10-2500 nM with regression coefficients (R(2)) greater than 0.99 for all compounds. The applicability and reliability of the analysis method was evaluated by successful demonstration of efflux ratio greater than 1 for the P-gp substrates studied in the Caco-2 cell model. The use of cassette mode analysis through selected reaction monitoring mass spectrometry presents an attractive option to increase the throughput, sensitivity, selectivity, and efficiency of the model over discreet mode UV detection.