Simple and rapid determination of irinotecan and its metabolite SN-38 in plasma by high-performance liquid-chromatography: application to clinical pharmacokinetic studies

Prediction of irinotecan toxicity in metastatic colorectal cancer patients based on machine learning models with pharmacokinetic parameters

Irinotecan (CPT-11) is a drug used against a wide variety of tumors, which can cause severe toxicity, possibly leading to the delay or suspension of the cycle, with the consequent impact on the prognosis of survival. The main goal of this work is to predict the toxicities derived from CPT-11 using artificial intelligence methods. The data for this study is conformed of 53 cycles of FOLFIRINOX, corresponding to patients with metastatic colorectal cancer. Supported by several demographic data, blood markers and pharmacokinetic parameters resulting from a non-compartmental pharmacokinetic study of CPT-11 and its metabolites (SN-38 and SN-38-G), we use machine learning techniques to predict high degrees of different toxicities (leukopenia, neutropenia and diarrhea) in new patients. We predict high degree of leukopenia with an accuracy of 76%, neutropenia with 75% and diarrhea with 91%. Among other variables, this study shows that the areas under the curve of CPT-11, SN-38 and SN-38-G play a relevant role in the prediction of the studied toxicities. The presented models allow to predict the degree of toxicity for each cycle of treatment according to the particularities of each patient.

Phase I clinical and pharmacokinetic/pharmacogenetic study of a triplet regimen of S-1/irinotecan/oxaliplatin in patients with metastatic colorectal or gastric cancer

PURPOSE

We conducted a phase I study of S-1 combined with irinotecan and oxaliplatin (TIROX) to determine the maximum-tolerated dose (MTD) and recommended dose (RD) and to assess its safety, pharmacokinetics, pharmacogenetics, and preliminary efficacy in patients with metastatic colorectal cancer (MCRC) or metastatic gastric cancer (MGC).

METHODS

Patients received escalating doses of S-1 (30-40 mg/m² b.i.d.) orally on days 1-14, an escalating dose of intravenous irinotecan (120-150 mg/m²) on day 1, and a fixed dose of intravenous oxaliplatin (85 mg/m²) on day 1 every 3 weeks.

RESULTS

Twenty-three patients (10 MCRC, 13 MGC; 13 chemonaive, 10 previously treated for metastatic disease) were treated across six dose levels. Because only one patient experienced a dose-limiting toxicity of grade 3 anorexia at the highest dose level (S-1 40 mg/m² b.i.d., irinotecan 150 mg/m², and oxaliplatin 85 mg/m²) (n = 8), the MTD was not obtained, and this level was established as the RD. With a median of 10 cycles per patient, the most common grade 3 or 4 adverse events included neutropenia (43 %), diarrhea (13 %), and nausea (13 %). In 22 efficacy-evaluable patients, the objective tumor response rate was 59.1 % (75 % for both MCRC and MGC in the first-line setting) and the disease control rate was 100 %. The exploratory pharmacokinetic/pharmacogenetic study showed that CYP2A6 variants (*4, *7, *9) are associated with a lower metabolic ratio of S-1 (exposure ratio of 5-fluorouracil to tegafur).

CONCLUSIONS

The new triplet TIROX regimen has shown promising antitumor activity and a favorable toxicity profile in patients with MCRC and MGC.

UPLC and LC-MS studies on degradation behavior of irinotecan hydrochloride and development of a validated stability-indicating ultra-performance liquid chromatographic method for determination of irinotecan hydrochloride and its impurities in pharmaceutical dosage forms

The objective of the current investigation was to study the degradation behavior of irinotecan hydrochloride under different International Conference on Harmonization (ICH) recommended stress conditions using ultra-performance liquid chromatography and liquid chromatography-mass spectrometry and to establish a validated stability-indicating reverse-phase ultra-performance liquid chromatographic method for the quantitative determination of irinotecan hydrochloride and its seven impurities and degradation products in pharmaceutical dosage forms. Irinotecan hydrochloride was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Irinotecan hydrochloride was found to degrade significantly in oxidative and base hydrolysis and photolytic degradation conditions. The degradation products were well resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. Chromatographic separation was achieved on a Waters Acquity BEH C8 (100 × 2.1 mm) 1.7-µm column with a mobile phase containing a gradient mixture of solvent A (0.02M KH(2)PO(4) buffer, pH 3.4) and solvent B (a mixture of acetonitrile and methanol in the ratio of 62:38 v/v). The mobile phase was delivered at a flow rate of 0.3 mL/min with ultraviolet detection at 220 nm. The run time was 8 min, within which irinotecan and its seven impurities and degradation products were satisfactorily separated. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. This method was also suitable for the assay determination of irinotecan hydrochloride in pharmaceutical dosage forms.

SN-38 loaded polymeric micelles to enhance cancer therapy

7-Ethyl-10-hydroxycamptothecin (SN-38) loaded poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic F-108) and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) nanoparticles were successfully prepared by a modified film hydration method and characterized by scanning electric microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and dynamic light scattering (DLS). Satisfactory drug loading of 20.73 ± 0.66% and a high encapsulation efficiency of 83.83 ± 1.32% were achieved. The SN-38 nanoparticles (SN-38 NPs) can completely disperse into a phosphate buffered saline (PBS) medium to produce a clear aqueous suspension that remains stable for up to three days. Total drug releases were 67.91% and 91.09% after 24 h in a PBS or fetal bovine serum (FBS) medium. Half maximal inhibitory concentration (IC(50)) tests of SN-38 and SN-38 NPs on A549 lung cells produced results of 200.0 ± 14.9 ng ml(-1) and 80.0 ± 4.6 ng ml(-1), respectively. Similarly, IC(50) tests of SN-38 and SN-38 NPs on MCF-7 breast cells yielded results of 16.0 ± 0.7 ng ml(-1) and 8.0 ± 0.5 ng ml(-1), respectively. These in vitro IC(50) studies show significant (p < 0.01) enhancement of the SN-38 NP drug efficiency in killing cancer cells in comparison to the free drug SN-38 control. All the materials used for this nanoformulation are approved by the US FDA, with the virtue of extremely low toxicity to normal cells.

Quantification of irinotecan, SN38, and SN38G in human and porcine plasma by ultra high-performance liquid chromatography-tandem mass spectrometry and its application to hepatic chemoembolization

An analytical method was developed and validated for the quantitative determination of irinotecan, its active metabolite SN38, and glucuronidated SN38 (SN38-G) in both porcine and human plasma. Calibration curves were linear within the concentration range of 0.5-100 ng/mL for SN38 and SN38-G, and 5-1000 ng/mL for irinotecan. Sample pretreatment involved solid-phase extraction of 0.1 mL aliquots of plasma. Irinotecan, SN38, SN38-G, and the internal standards, irinotecan-d10, tolbutamide, and camptothecin, respectively, were separated on a Waters ACQUITY UPLC BEH RP18 column (2. 1mm × 50 mm, 1.7 μm), using a mobile phase composed of methanol and 0.1% formic acid. Accuracy of quality control samples in human plasma ranged from 98.5 to 110.3%, 99.5 to 101.7% and 96.2 to 98.9% for irinotecan, SN38, and SN38-G, respectively. Precision of the three analytes in the same order ranged from 0.8 to 2.8%, 2.4 to 5.7%, and 2.4 to 2.8%. All three analytes proved stable in plasma through four freeze/thaw cycles, as well as through 6h in whole blood at room temperature. The method was likewise validated in porcine plasma with comparable accuracies and precisions also within the generally acceptable range. The validated method was applied to both preclinical and clinical trials involving hepatic chemoembolization of irinotecan drug-eluting beads to study the pharmacokinetics of the three analytes.

A safety and toxicity assessment of the administration of multiple intracerebral injections of irinotecan or doxorubicin drug-eluting beads

OBJECTIVE Previous research in a rat glioma model has shown that the local intratumoral application of polymerbased drug-eluting beads (DEBs) loaded with doxorubicin or irinotecan suppress tumour growth and prolong survival. For translation into a clinical setting, the present experiment investigates in the healthy cat brain the local and systemic toxicity of a multiple injection shot technique. METHODS Three injection shots were placed, each at a 1 cm distance in the frontal lobe. The DEBs were suspended in an aqueous alginate excipient solution, which becomes subject to a sol-gel transition when injected into the Ca(2+)- rich brain tissue environment. Systemic and local side effects were monitored over a period of two weeks. Injection sites were histologically investigated. RESULTS Gelling of the alginate results in the permanent immobilisation of the microspheres at the implantation site. A distinct local cytotoxic effect of doxorubicin was found with intracerebral and intraventricular haemorrhages, and signs of brain tissue necrosis. In cats injected with irinotecan DEBs, such local adverse side effects did not occur. No signs of systemic toxicity were found with both chemotherapeutics. DISCUSSION We conclude that the multiple injection shot technique with irinotecan DEBs meets feasibility criteria and safety requirements for a clinical application.

Irinotecan and its active metabolite, SN-38: review of bioanalytical methods and recent update from clinical pharmacology perspectives

The introduction of irinotecan has revolutionized the applicability of camptothecins as predominant topoisomerase I inhibitor for anti-cancer therapy. The potent anti-tumor activity of irinotecan is due to rapid formation of an in vivo active metabolite, SN-38. Therefore, irinotecan is considered as a pro-drug to generate SN-38. Over the past decade, side-by-side with the clinical advancement of the use of irinotecan in the oncology field, a plethora of bioanalytical methods have been published to quantify irinotecan, SN-38 and other metabolites. Because of the availability of HPLC, LC-MS and LC-MS/MS methods, the pharmacokinetic profiling of irinotecan and its metabolites has been accomplished in multiple species, including cancer patients. The developed assays continue to find use in the optimization of newly designed delivery systems with regard to pharmacokinetics to promote safe and effective use of either irinotecan or SN-38. This review intends to: firstly, provide an exhaustive compilation of the published assays for irinotecan, SN-38 and other metabolite(s) of irinotecan, as applicable; secondly, to enumerate the validation parameters and applicable conclusions; and thirdly, provide some recent perspectives in the clinical pharmacology arena pertaining to efflux transporters, pediatric profiling, role of kidney function in defining toxicity, drug-drug interaction potential of irinotecan, etc.

Simple liquid chromatography method for the quantification of irinotecan and SN38 in sheep plasma: application to in vivo pharmacokinetics after pulmonary artery chemoembolization using drug eluting beads

A rapid and simple liquid chromatography-fluorescence detection (LC-FD) method was developed and validated for the simultaneous quantification of irinotecan (CPT11) and SN38 in sheep plasma. Camptothecin (CPT) was used as the internal standard. A single step protein precipitation with acetonitrile was used for sample preparation. The separation was achieved using a 5 microm C18 column (250 mm x 4.5 mm, 5 microm) with a mobile phase composed of 36 mM sodium dihydrogen phosphate dehydrate and 4 mM sodium 1 heptane sulfonate-acetonitrile (72:28), the pH of the mobile phase was adjusted to 3. The flow rate was 1.45 mL/min and the fluorescence detection was operated at 355/515 nm (excitation/emission wavelengths). The run time was 13 min. The method was validated with respect to selectivity, extraction recovery, linearity, intra- and inter-day precision and accuracy, limit of quantification and stability. The method has a limit of quantification of 5 ng/mL for both CPT11 and SN38. The assay was linear over concentrations ranging from 5 to 5000 ng/mL and to 240 ng/mL for CPT11 and SN38, respectively. This method was used successfully to perform plasma pharmacokinetic studies of CPT11 after pulmonary artery embolization (PACE) in a sheep model. It was also validated for CPT11 and SN38 analysis in sheep lymph and human plasma.

Functional study of the 830C>G polymorphism of the human carboxylesterase 2 gene

PURPOSE

Carboxylesterase 2 (CES2) is involved in the activation of the anticancer drug irinotecan to its active metabolite SN-38. We previously identified a single nucleotide polymorphism (SNP), with an allele frequency around 10%, as possibly involved in enzyme expression (Clin Pharmacol Ther 76:528-535, 2004), which could explain the large individual variation in SN-38 disposition.

METHODS

The 830C>G SNP, located in the 5' untranslated region of the gene, was analysed in various DNA samples extracted from: (1) the National Cancer Institute NCI-60 panel of human tumour cell lines; (2) a collection of 104 samples of normal tissue from colorectal cancer patients; (3) blood samples from a population of 95 normal subjects; (4) a collection of 285 human livers. CES2 genotypes were tentatively related to irinotecan cytotoxicity and CES2 expression in the NCI-60 panel; to response to treatment and event-free survival in colorectal cancer patients; and to CES2 expression and catalytic activity in subsets of the human liver collection.

RESULTS

No significant relationship was found in the NCI-60 panel between CES2 830C>G genotype and irinotecan cytotoxicity or CES2 expression. No significant relationship was found between CES2 830C>G genotype and the toxicity and therapeutic efficacy (tumour response, event-free survival) of irinotecan in colorectal cancer patients. There was no significant relationship between CES2 830C>G genotype and CES2 expression and catalytic activity determined in a subset of genotype-selected liver samples.

CONCLUSION

The 830C>G SNP of CES2 is unlikely to have significant functional consequences on CES2 expression, activity or function.

Simultaneous determination of irinotecan (CPT-11) and SN-38 in tissue culture media and cancer cells by high performance liquid chromatography: Application to cellular metabolism and accumulation studies

A simple and sensitive HPLC method was developed to simultaneously determine CPT-11 and its major metabolite SN-38 in culture media and cell lysates. Camptothecin (CPT) was used as internal standard (I.S.). Compounds were eluted with acetonitrile-50 mM disodium hydrogen phosphate buffer containing 10 mM sodium 1-heptane-sulfonate, with the pH adjusted to 3.0 using 85% (w/v) orthophosphoric acid (27/73, v/v) by a Hyperclon ODS (C18) column (200 mm x 4.6 mm i.d.), with detection at excitation and emission wavelengths of 380 and 540 nm, respectively. The average extraction efficiencies were 96.9-108.3% for CPT-11 in culture media and 94.3-107.2% for CPT-11 in cell lysates; and 87.7-106.8% for SN-38 in culture media and 90.1-105.6% for SN-38 in cell lysates. Within- and between-day precision and accuracy varied from 0.1 to 10.3%. The limit of quantitation (precision and accuracy <20%) was 5.0 and 2.0 ng/ml for CPT-11 and 1.0 and 0.5 ng/ml for SN-38 in culture media and cell lysates, respectively. This method was successfully applied to quantitate the cellular accumulation and metabolism of CPT-11 and SN-38 in H4-II-E, a rat hepatoma cell line.

Irinotecan drug eluting beads for use in chemoembolization: in vitro and in vivo evaluation of drug release properties

Drug eluting beads that release irinotecan in a controlled manner may be useful for application in the chemoembolization of colorectal cancer metastases to the liver. In this study, irinotecan drug eluting beads were prepared with loadings up to 50 mg drug/mL hydrated beads. Drug loading was via an ion-exchange mechanism with sulfonate binding sites in the bead. Release in vitro was shown to be sustained and dependent upon the presence of ions in the elution medium, drug loading and bead size. Drug elution in PBS was controlled by solute diffusion within the beads and gave rise to values for the diffusion coefficient, D, of between 2.4x10(-9) and 1.4x10(-7) cm(2)s(-1). The beads were shown to decrease in size (by a maximum 25-30%), and concomitantly their modulus of compression increased (from approximately 27 kPa to a maximum of about 49 kPa), with increasing drug loading. This did not however, influence their ability to be suspended homogeneously in contrast agent or delivered through a microcatheter. Following porcine hepatic artery embolization, maximum plasma levels were 70-75% lower for both irinotecan and SN-38 compared to intraarterial bolus administration, with peak levels observed at 2 and 5 min after completion of the embolization procedure. The in vivo data were shown to correlate well with the in vitro release measured using a T-apparatus model of embolization.

HPLC method for determination of SN-38 content and SN-38 entrapment efficiency in a novel liposome-based formulation, LE-SN38

A simple HPLC method was developed for quantification of SN-38, 7-ethyl-10-hydroxycamptothecin, in a novel liposome-based formulation (LE-SN38). The chromatographic separation was achieved on an Agilent Zorbax SB-C18 (4.6 mmx250 mm, 5 microm) analytical column using a mobile phase consisting of a mixture of NaH2PO4 (pH 3.1, 25 mM) and acetonitrile (50:50, v/v). SN-38 was detected at UV wavelength of 265 nm and quantitatively determined using an external calibration method. The limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.05 and 0.25 microg/mL, respectively. The individual spike recovery of SN-38 ranged from 100 to 101%. The percent of relative standard deviation (%R.S.D.) of intra-day and inter-day analyses were less than 1.6%. The method validation results confirmed that the method is specific, linear, accurate, precise, robust and sensitive for its intended use. The current method was successfully applied to the determination of SN-38 content and drug entrapment efficiency in liposome-based formulation, LE-SN38 during early stage formulation development.

Novel nanoliposomal CPT-11 infused by convection-enhanced delivery in intracranial tumors: pharmacology and efficacy

We hypothesized that combining convection-enhanced delivery (CED) with a novel, highly stable nanoparticle/liposome containing CPT-11 (nanoliposomal CPT-11) would provide a dual drug delivery strategy for brain tumor treatment. Following CED in rat brains, tissue retention of nanoliposomal CPT-11 was greatly prolonged, with >20% injected dose remaining at 12 days for all doses. Tissue residence was dose dependent, with doses of 60 microg (3 mg/mL), 0.8 mg (40 mg/mL), and 1.6 mg (80 mg/mL) resulting in tissue half-life (t(1/2)) of 6.7, 10.7, and 19.7 days, respectively. In contrast, CED of free CPT-11 resulted in rapid drug clearance (tissue t(1/2) = 0.3 day). At equivalent CED doses, nanoliposomal CPT-11 increased area under the time-concentration curve by 25-fold and tissue t(1/2) by 22-fold over free CPT-11; CED in intracranial U87 glioma xenografts showed even longer tumor retention (tissue t(1/2) = 43 days). Plasma levels were undetectable following CED of nanoliposomal CPT-11. Importantly, prolonged exposure to nanoliposomal CPT-11 resulted in no measurable central nervous system (CNS) toxicity at any dose tested (0.06-1.6 mg/rat), whereas CED of free CPT-11 induced severe CNS toxicity at 0.4 mg/rat. In the intracranial U87 glioma xenograft model, a single CED infusion of nanoliposomal CPT-11 at 1.6 mg resulted in significantly improved median survival (>100 days) compared with CED of control liposomes (19.5 days; P = 4.9 x 10(-5)) or free drug (28.5 days; P = 0.011). We conclude that CED of nanoliposomal CPT-11 greatly prolonged tissue residence while also substantially reducing toxicity, resulting in a highly effective treatment strategy in preclinical brain tumor models.

St. John's Wort modulates the toxicities and pharmacokinetics of CPT-11 (irinotecan) in rats

CPT-11 is a DNA topoisomerase I inhibitor for the therapy of colorectal cancer, whereas St. John's Wort (Hypericum perforatum, SJW) is a widely used herbal anti-depressant. This study aimed to investigate the effects of co-administered SJW on the toxicities and pharmacokinetics of CPT-11 and the underlying mechanisms. The body weight loss, gastrointestinal and hematological toxicities induced by CPT-11, and the pharmacokinetic parameters of CPT-11 were evaluated in rats pretreated with SJW or vehicle. Rats treated with CPT-11 alone experienced rapid decrease in body weight, whereas co-administration of SJW with CPT-11 resulted in lesser body weight loss. The gastrointestinal and hematological toxicities following CPT-11 injection were both alleviated in the presence of SJW. The rat pharmacokinetics of both CPT-11 and its metabolite SN-38 were significantly altered in presence of SJW. In conclusion, co-administered SJW significantly ameliorated the toxicities induced by CPT-11. The protective effect of SJW may be partially due to pharmacokinetic interaction between CPT-11 and SJW.

Liquid chromatographic–tandem mass spectrometric assay for the simultaneous quantification of Camptosar® and its metabolite SN-38 in mouse plasma and tissues

A simple, rapid and sensitive LC-MS/MS bioanalytical method has been developed to simultaneously quantify Camptosar (CPT-11) and its active metabolite, SN-38, in mouse plasma and tissues. A single step protein precipitation with acetonitrile in 96-well plates was used for sample preparation. Camptothecin (CPT) was used as the internal standard. Fast separation of SN-38, CPT-11 and CPT was carried out isocratically on a C18, 2 mm x 50 mm, 5 microm HPLC column with a mobile phase containing acetonitrile and 20 mM ammonium acetate (pH 3.5) and a 2.5 min chromatographic run time. The API 4000 MS/MS system was operated in positive ionization multiple reaction monitoring mode, and the transitions for SN-38, CPT-11 and CPT were 393.4 --> 349.3, 587.6 --> 167.2 and 349.3 --> 305.3, respectively. The SN-38 and CPT-11 concentrations in samples were calculated from a standard curve of peak area ratios of the analyte to that of the internal standard using a 1/chi2 weighted linear regression. The quantitation limit of 0.5 ng/mL was achieved by using a low sample volume (100 microL) of plasma or tissue homogenates. The assay was linear over the concentration range of 0.5-500 ng/mL with acceptable precision and accuracy. The method was used for the quantification of CPT-11 and SN-38 in plasma and tissues to support a preclinical pharmacokinetics and tissue distribution study of CPT-11 in mice.

A simple and sensitive LC/MS/MS assay for 7-ethyl-10-hydroxycamptothecin (SN-38) in mouse plasma and tissues: application to pharmacokinetic study of liposome entrapped SN-38 (LE-SN38)

An LC/MS/MS method to quantify SN-38 in mouse plasma and tissue homogenates containing liposome entrapped SN-38 (LE-SN38) was developed. Camptothecin (CPT) was used as the internal standard (IS). Sample preparation consisted of simple protein precipitation by acetonitrile containing 0.5% acetic acid. SN-38 and IS were separated by a C18 HPLC column and detected using a mass spectrometer operating in the multiple reaction monitoring (MRM) mode. The peak area of the m/z 393.3-->349.1 transition of SN-38 and that of the m/z 349.1-->305.2 transition of the IS were measured and a standard curve was generated from their ratios. The method had a LLOQ of 0.5 ng/mL in mouse plasma, which corresponds to 2.5 pg for the 5 microL injection volume. The linear range was 0.5-1000 ng/mL of SN-38 in plasma sample spiked with LE-SN38. The LLOQ in tissue homogenates (5%, w/v) quantitation was 1 ng/mL (20 ng/g tissue) of SN-38 in kidney, liver, lung, and spleen homogenates, and 2 ng/mL (40 ng/g tissue) in heart homogenate containing LE-SN38. The assay was linear up to 400 ng/mL of SN-38 in tissue homogenates, and may be extended to 120 microg/mL by proper dilution of samples over the upper limit of quantitation. Acceptable precision and accuracy were obtained for concentrations over the entire standard curve range, both between-run and within-run for plasma and tissue homogenates. The method was successfully used to quantify SN-38 in plasma and tissues samples for pharmacokinetic and tissue distribution studies of LE-SN38 in mice.

Sensitive HPLC-fluorescence method for irinotecan and four major metabolites in human plasma and saliva: application to pharmacokinetic studies

BACKGROUND

We developed gradient HPLC methods for quantification of the antimitotic drug irinotecan (CPT-11) and its four metabolites, SN-38, SN-38 G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin (APC), and 7-ethyl-10-[4amino-1-piperidino]-carbonyloxycamptothecin (NPC), as the sum of the lactone and carboxylate forms, in human plasma and saliva. Camptothecin was used as internal standard.

METHODS

The sample pretreatment involved protein precipitation with methanol-acetonitrile (50:50 by volume) followed by acidification with hydrochloric acid to convert the lactone ring-opened form into its lactone form, quantitatively. HPLC separation was performed on a Xterra RP18 column. The excitation wavelength was 370 nm, and the emission wavelength was set at 470 nm for the first 24 min and then at 534 nm for the next 4 min. The stabilities of irinotecan and its four metabolites in plasma, saliva, and acidic extracts were also investigated under various conditions.

RESULTS

Assays were linear in the tested range of 0.5-1000 micro g/L. For the five analytes, limits of quantification were 0.5 micro g/L in both matrices. The interassay imprecision (as relative standard deviation) was 3.2-14% in plasma and 2.6-5.6% in saliva. Assay recoveries ranged from 92.8% to 111.2% for plasma and 100.1% to 104.1% for saliva. Mean extraction recovery from plasma or saliva was 90%.

CONCLUSION

The developed assay can be used to determine pharmacokinetic parameters for CPT-11, SN-38, SN-38 G, APC, and NPC in plasma and saliva from patients with metastatic colorectal cancer.

Liquid chromatography determination of 10-hydroxycamptothecin in human serum by a column-switching system containing a pre-column with restricted access media and its application to a clinical pharmacokinetic study

A simple, rapid, sensitive column-switching HPLC method is described for the analysis of the 10-hydroxycamptothecin (HCPT) in human serum. A pre-column containing restricted access media (RAM) is used for the sample clean-up and trace enrichment and is combined with a C18 column for the final separation. The analytical time is 8 min. The HCPT is monitored with fluorescence detector, excitation and emission wavelengths being 385 and 539 nm, respectively. There is a linear response range of 1-1000 ng/ml with correlation coefficient of 0.998 while the limit of quantification is 0.1 ng/ml. The intra-day and inter-day variations are less than 5%. This analytic procedure has been applied to a pharmacokinetic study of HCPT in clinical patients and the pharmacokinetic parameters of one-compartment model are calculated.

Determination by liquid chromatography with fluorescence detection of total 7-ethyl-10-hydroxy-camptothecin (SN-38) in beagle dog plasma after intravenous administration of liposome-based SN-38 (LE-SN38)

An HPLC- fluorescence method to quantitate total 7-ethyl-10-hydroxy-camptothecin (SN-38) in beagle dog plasma spiked with liposome based formulation of SN-38 (LE-SN38) and using camptothecin (CPT) as the internal standard (I.S.) was developed and validated to support pharmacokinetics/toxicokinetics studies. Sample preparation was done by protein precipitation using acetonitrile with 0.5% acetic acid. The supernatant was evaporated, and reconstituted in acetonitrile-20 mM ammonium acetate, pH 3.5 (20:80, v/v). When injected onto a Zorbax SB-C(18) HPLC column SN-38 as well as I.S. were detected by fluorescence using an excitation at 368 nm and emission at 515 nm. The SN-38 concentrations in samples were calculated from a standard curve of peak area ratios of SN-38 to the I.S. using weighted linear regression. The sensitivity limit for SN-38 was 1.00 ng/ml in beagle dog plasma with a precision (expressed as relative standard deviation) of 12.4% and an accuracy (expressed as analytical recovery) of 104%. The assay was linear within the standard curve range of 1-750 ng/ml. Acceptable precision and accuracy were also obtained for concentrations over the balance of the standard curve range from between-run and within-run calculations.

High-performance liquid chromatographic analysis of the anticancer drug irinotecan (CPT-11) and its active metabolite SN-38 in human plasma

A rapid, sensitive, and specific high-performance liquid chromatography (HPLC) method for the simultaneous determination of irinotecan (CPT-11) and its active metabolite SN-38 in human plasma is described. The analytes are quantified as the totals of their carboxylate and lactone form. The sample pretreatment consisted of a simple protein precipitation with acetonitrile-methanol (1:1, v/v), after which CPT-11 and SN-38 were quantitatively converted to their carboxylate form by adding 0.01 mol/L sodium tetraborate (pH, 9). Chromatography was carried out on a Zorbax SB-C18 column with fluorescence detection. The method has been validated, and stability tests under various clinically relevant conditions have been performed. The lower limit of quantification (LLOQ) was 5.0 ng/mL for CPT-11 and 0.5 ng/mL for SN-38. Standard concentration ranges were linear between 5 and 1,500 ng/mL for CPT-11 and between 0.5 and 100 ng/mL for SN-38. This assay is simple, rapid, and very useful for therapeutic monitoring of CPT-11 and SN-38.

A sensitive and rapid liquid chromatography tandem mass spectrometry method for quantitative determination of 7-ethyl-10-hydroxycamptothecin (SN-38) in human plasma containing liposome-based SN-38 (LE-SN38)

7-Ethyl-10-hydroxycamptothecin (SN-38) is an active metabolite of Irinotecan (CPT-11), an anticancer pro-drug. To support clinical pharmacokinetic studies for liposome based formulation of SN-38 (LE-SN38) in cancer patients, a rapid, simple and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the quantification of total SN-38 in human plasma. Sample preparation was carried out by one-step protein precipitation using cold acetonitrile with 0.5% acetic acid (v/v). Camptothecin was used as an internal standard (IS). Chromatographic separation of SN-38 and IS was achieved using a Synergi Hydro-RP column (C(18), 50 x 2 mm, 4 micro m), with a gradient elution of acetonitrile and 0.1% acetic acid. After ionization in electrospray source (positive ions), the acquisition was performed in the multiple reactions monitoring mode. Quantitation was accomplished using the precursor-->product ion combinations of m/z 393.1-->349.2 for SN-38 and 349.1-->305.1 for IS. The quantification limit of 0.05 ng/mL was achieved by using much lower volume (0.2 mL) of plasma and in the presence of LE-SN38. The method was validated over the concentration range of 0.05-400 ng/mL. Accuracy was within +/-12% of nominal at all concentration levels. Inter-day and intra-day precisions expressed as percentage coefficient of variation (%CVs) for quality control (QC) samples were less than 14 and 5%, respectively.

Simultaneous determination of the carboxylate and lactone forms of 10-hydroxycamptothecin in human serum by restricted-access media high-performance liquid chromatography

A simple restricted-access media (RAM) HPLC method for simultaneous determination of the lactone and carboxylate forms of 10-hydroxycamptothecin (HCPT) in human serum was established. Using a RAM Hisep analytical column, serum samples were directly injected into the HPLC system. The eluted peaks of two forms of HCPT were monitored with a fluorescence detector. The separation was completed in 17 min. The linear range was 20-1000 ng/ml, intra-day and inter-day variations being less than 5%. The kinetic equation was introduced according to the analytical results. The equation shows that the course of the HCPT lactone form converting to carboxylate form in human serum at 4 degrees C is a first-order kinetic course. The concentration of each form at the moment of sampling was calculated by extrapolation.

An analytical method for irinotecan (CPT-11) and its metabolites using a high-performance liquid chromatography: parallel detection with fluorescence and mass spectrometry

Irinotecan or 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) is an anticancer pro-drug used in the treatment of many types of cancer. We describe here the validation of an analytical method for CPT-11 and its metabolites, including an active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), its glucuronidated form, SN-38G, and several cytochrome P450 3A-mediated products such as 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC) using a high-performance liquid chromatography connected to parallel fluorescence and mass spectrometry detection systems. This method is characterized as follows: (1) simple extraction of the analytes from biomaterials with perchloric acid/methanol; (2) sensitive quantitation of major metabolites (SN-38G, SN-38 and APC) with a fluorescence detector (FLD), where the limits of quantitation by FLD were 2.5 ng/mL for SN-38G and APC, 5 ng/mL for CPT-11 and 1 ng/mL for SN-38, respectively; (3) parallel selective monitoring of the metabolites including minor metabolites with a mass selected detector (MSD). There was no observed interference by other drugs expected to be co-administered. This method showed its usefulness by identifying a novel metabolite produced in human hepatic microsomes. The results indicate that this combination of FLD and MSD enables a highly selective analysis of CPT-11 and its metabolites, and is useful for studies both in vivo and in vitro.

Separation methods for camptothecin and related compounds

This paper reviews working procedures for the analytical determination of camptothecin and analogues. We give an overview of aspects such as the chemistry, structure-activity relationships, stability and mechanism of action of these antitumor compounds. The main body of the review describes separation techniques. Sample treatment and factors influencing high-performance liquid chromatography development are delineated. Published high-performance liquid chromatographic methods are summarized to demonstrate the variability and versatility of separation techniques and a critical evaluation of separation efficiency, detection sensitivity and specificity of these methods is reported.

Antitumor drugs possessing topoisomerase I inhibition: applicable separation methods

Separation methods for antitumor drugs capable of topoisomerase I inhibition were reviewed in this study. Camptothecin (CPT) its related analogues seemed to be promising anticancer drugs that exhibit topoisomerase I inhibition. This group of compounds contain a closed alpha-hydroxy-delta-lactone ring (lactone form) that can undergo reversible hydrolysis to form the open-ring form (carboxylate form). In vitro pharmacological study showed that the antitumor activity of the lactone form was higher than that of the carboxylate form. Thus a quantitative method to separate these two forms is important to evaluate the pharmacokinetics and pharmacodynamics of these compounds. Nevertheless, current separation methods are complicated by the pH-dependent instability of the lactone moiety. High-performance liquid chromatography (HPLC) coupled with fluorometric detection has been widely used for the quantitation of the drug as the intact lactone form or as the total lactone carboxylate forms in biological matrices. In this report we reviewed current applicable chromatographic techniques for further bioanalytical studies of CPT derivatives including sample preparations, HPLC columns, mobile phases and additives.

Quantitation of camptothecin and related compounds

Camptothecin and congeners represent a clinically very useful class of anticancer agents. Proper identification and quantitation of the original compounds and their metabolites in biological fluids is fundamental to assess drug metabolism and distribution in animals and in man. In this paper we will review the recent literature available on the methods used for separation and quantitative determination of the camptothecin family of drugs. Complications arise from the fact that they are chemically labile, and the pharmacologically active lactone structure can undergo ring opening at physiological conditions. In addition, a number of metabolic changes usually occur, producing a variety of active or inactive metabolites. Hence, the conditions of extraction, pre-treatment and quantitative analysis are to be carefully calibrated in order to provide meaningful results.

Analytical approaches for traditional chinese medicines exhibiting antineoplastic activity

Traditional Chinese medicines have attracted great interest in recent researchers as alternative antineoplastic therapies. This review focuses on analytical approaches to various aspects of the antineoplastic ingredients of traditional Chinese medicines. Emphasis will be put on the processes of biological sample extraction, separation, clean-up steps and the detection. The problems of the extraction solvent selection and different types of column chromatography are also discussed. The instruments considered are gas chromatography, capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) connected with various detectors (ultraviolet, fluorescence, electrochemistry, mass, etc.). In addition, determinations of antineoplastic herbal ingredients, including camptothecin, taxol (paclitaxel), vinblastine. vincristine, podophyllotoxin, colchicine, and their related compounds, such as irinotecan, SN-38, topotecan, 9-aminocamptothecin, docetaxel (taxotere) and etoposide, are briefly summarized. These drugs are structurally based on the herbal ingredients, and some of them are in trials for clinical use. Evaluation of potential antineoplastic herbal ingredients, such as harringtonine, berberine, emodin, genistein, berbamine, daphnoretin, and irisquinone, are currently investigated in laboratories. Other folk medicines are excluded from this paper because their antineoplastic ingredients are unknown.

High-performance liquid chromatographic technique for the simultaneous determination of lactone and hydroxy acid forms of camptothecin and SN-38 in tissue culture media and cancer cells

Analysis of camptothecins in biologic media is hampered by chemical hydrolysis of the parent lactone (form I) to an inactive hydroxy acid (form II). A solid-phase extraction (SPE) method utilizing C2-bonded silica particles (100 mg, 1 ml) is presented for simultaneous determination of forms I and II of camptothecin (CPT) and SN-38 (active metabolite of clinically used CPT-11) in culture media and cell lysates. A new HPLC separation is described that efficiently resolves all four compounds employing gradient elution with 10 mM ammonium acetate, increasing methanol (20-80% over 15 min), and a 15-cm by 3-mm Symmetry Shield (RP8) column. Components were detected by fluorescence at an excitation wavelength of 380 nm and emission wavelength of 423 nm. Lactones were shown to be unstable at alkaline pH and hydroxy acids unstable at alkaline pH while the following conditions preserved the chemical equilibrium in specimens: samples kept on ice, final pH of eluates 7.4, autosampler temperature 4 degrees C, and analysis cycle <4 h. Quantitative recovery of lactones was achieved from RPMI culture medium over a wide concentration range (93.5-111.6% for 1-400 ng/ml) although greater variability was noted with the hydroxy acids (59.6-110.3%, 1-400 ng/ml). Limit of quantitation (precision and accuracy <20%) was 0.2 ng/ml for CPT lactone, 0.5 ng/ml for SN-38 lactone, and 2 ng/ml for the two hydroxy acids. The method was applied to quantitate the accumulation of SN-38 and CPT (form I and II) in HT29 and HCT116 human colon cancer cells.