A new UPLC-MS/MS method for the determination of irinotecan and 7-ethyl-10-hydroxycamptothecin (SN-38) in mice: Application to plasma and brain pharmacokinetics

Synergistic Nanomedicine Delivering Topoisomerase I Toxin (SN-38) and Inhibitors of Polynucleotide Kinase 3'-Phosphatase (PNKP) for Enhanced Treatment of Colorectal Cancer

Inhibitors of a DNA repair enzyme known as polynucleotide kinase 3'-phosphatase (PNKP) are expected to show synergistic cytotoxicity in combination with topoisomerase I (TOP1) inhibitors in cancer. In this study, the synergistic cytotoxicity of a novel inhibitor of PNKP, i.e., A83B4C63, with a potent TOP1 inhibitor, i.e., SN-38, against colorectal cancer cells was investigated. Polymeric micelles (PMs) for preferred tumor delivery of A83B4C63, developed through physical encapsulation of this compound in methoxy poly(ethylene oxide)-poly(α-benzyl carboxylate-ε-caprolactone) (mPEO-b-PBCL) micelles, were combined with SN-38 in free or PM form. The PM form of SN-38 was prepared through chemical conjugation of SN-38 to the functional end group of mPEO-b-PBCL and further assembly of mPEO-b-PBCL-SN-38 in water. Moreover, mixed micelles composed of mPEO-b-PBCL and mPEO-b-PBCL-SN-38 were used to co-load A83B4C63 and SN-38 in the same nanoformulation. The loading content (% w/w) of the SN-38 and A83B4C63 to mPEO-b-PBCL in the co-loaded formulation was 7.91 ± 0.66 and 16.13 ± 0.11% (w/w), respectively, compared to 15.67 ± 0.34 (% w/w) and 23.06 ± 0.63 (% w/w) for mPEO-b-PBCL micelles loading individual drugs. Notably, the average diameter of PMs co-encapsulating both SN-38 and A83B4C63 was larger than that of PMs encapsulating either of these compounds alone but still lower than 60 nm. The release of A83B4C63 from PMs co-encapsulating both drugs was 76.36 ± 1.41% within 24 h, which was significantly higher than that of A83B4C63-encapsulated micelles (42.70 ± 0.72%). In contrast, the release of SN-38 from PMs co-encapsulating both drugs was 44.15 ± 2.61% at 24 h, which was significantly lower than that of SN-38-conjugated PMs (74.16 ± 3.65%). Cytotoxicity evaluations by the MTS assay as analyzed by the Combenefit software suggested a clear synergy between PM/A83B4C63 (at a concentration range of 10-40 μM) and free SN-38 (at a concentration range of 0.001-1 μM). The synergistic cytotoxic concentration range for SN-38 was narrowed down to 0.1-1 or 0.01-1 μM when combined with PM/A83B4C63 at 10 or 20-40 μM, respectively. In general, PMs co-encapsulating A83B4C63 and SN-38 at drug concentrations within the synergistic range (10 μM for A83B4C63 and 0.05-1 μM for SN-38) showed slightly less enhancement of SN-38 anticancer activity than a combination of individual micelles, i.e., A83B4C63 PMs + SN-38 PMs at the same molar concentrations. This was attributed to the slower release of SN-38 from the SN-38 and A83B4C63 co-encapsulated PMs compared to PMs only encapsulating SN-38. Cotreatment of cells with TOP1 inhibitors and A83B4C63 formulation enhanced the expression level of γ-HA2X, cleaved PARP, caspase-3, and caspase-7 in most cases. This trend was more consistent and notable for PMs co-encapsulating both A83B4C63 and SN-38. The overall result from the study shows a synergy between PMs of SN-38 and A83B4C63 as a mixture of two PMs for individual drugs or PMs co-encapsulating both drugs.

Development and validation of an UPLC-MS/MS method for the determination of irinotecan (CPT-11), SN-38 and SN-38 glucuronide in human plasma and peritoneal tumor tissue from patients with peritoneal carcinomatosis

Irinotecan (CPT-11), an antineoplastic drug, is used for the treatment of colorectal and pancreatic cancer due to its topoisomerase I inhibitory activity. CPT-11 is a prodrug which is converted to its active metabolite SN-38 by carboxylesterases. SN-38 is further metabolized to its inactive metabolite SN-38 glucuronide. When evaluating the pharmacokinetic properties of CPT-11 and its metabolites, it is important to accurately assess the concentrations in both plasma as well as tumor tissues. Therefore, the aim of the current study was to develop and validate a robust and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry method to quantify the concentration of CPT-11 and its metabolites (SN-38 and SN-38 glucuronide) in human plasma and peritoneal tumor tissue. The sample preparation of plasma and tumor tissue consisted of protein precipitation and enzymatic digestion/liquid-liquid extraction, respectively. Chromatographic separation was achieved with an Acquity UPLC BEH C18 column combined with a VanGuard pre-column. The mobile phases consisted of water +0.1 % formic acid (mobile phase A) and acetonitrile +0.1 % formic acid (mobile phase B). Mass analysis was performed using a Xevo TQS tandem mass spectrometer in the positive electrospray ionization mode. Method validation was successfully performed by assessing linearity, precision and accuracy, lower limit of quantification, carry over, selectivity, matrix effect and stability according to the following guidelines: "Committee for Medicinal Products for Human use, Guideline on Bioanalytical Method Validation". A cross-validation of the developed method was performed in a pilot pharmacokinetic study, demonstrating the usefulness of the current method to quantify CPT-11 and its metabolites in the different matrices.

Evaluation on the Metabolic Activity of Two Carboxylesterase Isozymes in Mouse Liver Microsomes by a LC-MS/MS Method

An applicable method for the precise measurement of major carboxylesterase (CESs) activity in liver still limited. Clopidogrel and irinotecan are specific substrates for CES1 and CES2, respectively. Clopidogrel is metabolized to the inactive metabolite clopidogrel carboxylate (CCAM) by CES1. Irinotecan is metabolized to the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) by CES2. In the present study, the LC-MS/MS method for the determination of CCAM and SN-38 were separately developed to characterize the metabolic activities of CES1 and CES2 in mouse liver microsomal. CCAM was separated on a Ecosil ODS column with an isocratic mobile phase consisted of 5 mmol/L ammonium formate and 0.1% formic acid in water and acetonitrile (15:85, V:V) at a flow rate of 0.4mL/min. SN-38 was separated on a Waters symmetry C18 column with an gradient mobile phase consisted of 5 mmol/L ammonium formate and 0.1% formic acid in water and acetonitrile at a flow rate of 0.3 mL/min. Calibration curves were linear within the concentration range of 100-20,000 ng/mL for CCAM and 1-200 ng/mL for SN-38. The results of method showed excellent accuracy and precision. The recovery rate, matrix effect and stability inspection results were within the acceptance criteria. The optimized incubation conditions were as follows: protein concentration of microsomes were all 0.1 mg/mL, incubation time was 60 min for clopidogrel and 30 min for irinotecan, respectively. This method was sensitive and applicable for the determination of the activity of CESs in the mouse liver microsomes.

Identification of the bioactive components of Banxia Xiexin Decoction that protect against CPT-11-induced intestinal toxicity via UPLC-based spectrum-effect relationship analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Irinotecan (CPT-11) is a valuable chemotherapeutic compound, but its use is associated with severe diarrhea in some patients. The CPT-11 prodrug is converted into the active 7-ethyl-10-hydroxycamptothecin (SN-38) metabolite, which can then be retained for extended periods in the intestine, leading to the onset of diarrhea and related symptoms. Banxia Xiexin Decoction (BXD) is commonly employed for the treatment of gastroenteritis in traditional Chinese medicine (TCM), and in clinical settings, it is used to prevent diarrhea in patients undergoing CPT-11 treatment. To date, however, there have been no studies specifically examining which components of BXD can alleviate the gastrointestinal symptoms associated with CPT-11 administration.

AIM

This study aimed to identify the main herbal components of BXD associated with protection against CPT-11-induced intestinal toxicity in a murine model system.

MATERIALS AND METHODS

SN-38 levels were measured by UPLC-ESI-MS/MS in samples collected from mice subjected to CPT-11-induced diarrhea that had been administered BXD or different components thereof. Pearson correlation and Grey relational analyses were then used to explore spectrum-effect relationships between reductions in intestinal SN-38 levels and specific chemical fingerprints in samples from mice administered particular combinations of BXD component herbs.

RESULTS

We found that different herbal combinations were associated with significant differences in intestinal SN-38 reductions in treated mice. Our spectrum-effect analysis revealed that BXD components including chrysin 6-C-arabinoside-8-C-glucoside, coptisine, hydroxyl oroxylin A 7-O-glucuronide (hydroxyl wogonoside), baicalin, an isomer of 5,6,7-trihydroxyl-flavanone-7-O-glucuronide, berberine, palmatine, and chrysin-7-O-glucuronide were all directly linked with reductions in intestinal SN-38 levels. We therefore speculate that these compounds are the primary bioactive components of BXD, suggesting that they offer protection against CPT-11-induced diarrhea.

CONCLUSION

By utilizing UPLC to analyze SN-38 levels in mice treated with a variety of herbal combinations, we were able to effectively explore BXD spectrum-effect relationships and to thereby establish the components of this medicinal preparation that were bioactive and capable of preventing CPT-11-induced diarrhea in mice. This and similar spectrum-effect studies represent a robust means of exploring the mechanistic basis for the pharmacological activity of TCM preparations.

Pharmacovigilance of herb-drug interactions: A pharmacokinetic study on the combination administration of herbal Kang'ai injection and chemotherapy irinotecan hydrochloride injection by LC-MS/MS

Chinese herbal drugs are often combined with chemotherapy drugs for the treatment of cancers. However, the combination administrations often do not have scientifically sound bases established on full preclinical and clinical investigations. A commonly used anti-colon-cancer herb-drug pair, irinotecan (CPT-11) hydrochloride injection and Kang'ai (KA) injection was taken as an example to investigate the possible pharmacokinetic interactions between Chinese herbal drugs and chemotherapy injections to determine the potential adverse drug reactions (ADRs). Rats were randomly divided into three groups and received 20 mg/kg CPT-11 injection 15 min after administration of 4 mL/kg saline for the CPT-11 single administration group and 4 mL/kg KA injection for the separated co-administration group, respectively. In the pre-mixed co-administration group, rats received a mixture of 20 mg/kg CPT-11 injection and 4 mL/kg KA injection. Blood samples were collected at 10 pre-determined time points between 0 and 24 h. The tissue samples were collected at 5 and 8 min after the injections, respectively. A reliable LC-MS/MS method was established for the simultaneous determination of CPT-11 and its metabolites, SN-38, SN-38 G and APC in the rat plasma and tissue samples, after full confirmation of two injections chemical and stability compatibilities. Compared to the C₀ (5129 ± 757 ng/mL) and AUC_0-t (7858 ± 1307 ng h/mL) of CPT-11 in the CPT-11 single administration group, the C₀ (4574 ± 371 ng/mL) and AUC_0-t (8779 ± 601 ng h/mL) after the separated co-administration remained unchanged, but the pre-mixed co-administration resulted with a significant increased C₀ (29,454 ± 12,080 ng/mL) and AUC_0-t (15,539 ± 5165 ng h/mL) (p < 0.05). Since the exposures of CPT-11 in most tissues in the pre-mixed co-administration group were dramatically lower than the separated co-administration group, the increased CPT-11 plasma concentration may be produced by the delayed tissue distribution because of the encapsulation by the components contained in KA injection, such as polysaccharides. Similar differences were also found in its metabolite, SN-38 G. There are obvious herb-drug interactions between CPT-11 injection and KA injection after the pre-mixed co-administration. The resulting excessive CPT-11 in the plasma may lead to many serious ADRs. Therefore, the full evaluation of herb-drug interactions is necessary and inappropriate combinations should be avoided.

Structural Optimization and Enhanced Prodrug-Mediated Delivery Overcomes Camptothecin Resistance in High-Risk Solid Tumors

Camptothecins are potent topoisomerase I inhibitors used to treat high-risk pediatric solid tumors, but they often show poor efficacy due to intrinsic or acquired chemoresistance. Here, we developed a multivalent, polymer-based prodrug of a structurally optimized camptothecin (SN22) designed to overcome key chemoresistance mechanisms. The ability of SN22 vs. SN38 (the active form of irinotecan/CPT-11) to overcome efflux pump-driven drug resistance was tested. Tumor uptake and biodistribution of SN22 as a polymer-based prodrug (PEG-[SN22]₄) compared with SN38 was determined. The therapeutic efficacy of PEG-[SN22]₄ to CPT-11 was compared in: (i) spontaneous neuroblastomas (NB) in transgenic TH-MYCN mice; (ii) orthotopic xenografts of a drug-resistant NB line SK-N-BE(2)C (mutated TP53); (iii) flank xenografts of a drug-resistant NB-PDX; and (iv) xenografts of Ewing sarcoma and rhabdomyosarcoma. Unlike SN38, SN22 inhibited NB cell growth regardless of ABCG2 expression levels. SN22 prodrug delivery resulted in sustained intratumoral drug concentrations, dramatically higher than those of SN38 at all time points. CPT-11/SN38 treatment had only marginal effects on tumors in transgenic mice, but PEG-[SN22]₄ treatment caused complete tumor regression lasting over 6 months (tumor free at necropsy). PEG-[SN22]₄ also markedly extended survival of mice with drug-resistant, orthotopic NB and it caused long-term (6+ months) remissions in 80% to 100% of NB and sarcoma xenografts. SN22 administered as a multivalent polymeric prodrug resulted in increased and protracted tumor drug exposure compared with CPT-11, leading to long-term "cures" in NB models of intrinsic or acquired drug resistance, and models of high-risk sarcomas, warranting its further development for clinical trials. SIGNIFICANCE: SN22 is an effective and curative multivalent macromolecular agent in multiple solid tumor mouse models, overcoming common mechanisms of drug resistance with the potential to elicit fewer toxicities than most cancer therapeutics.

Development of a method to quantify total and free irinotecan and 7-ethyl-10-hydroxycamptothecin (SN-38) for pharmacokinetic and bio-distribution studies after administration of irinotecan liposomal formulation

In 2015, liposomal formulation of irinotecan (ONIVYDE) has been approved by FDA and widely applied in the treatment of pancreatic cancer. ONIVYDE is a novel liposome formulation, entrapping CPT-11 in the aqueous core of vesicles using a modified gradient loading method. Due to toxicity concerns, it is essential to explore a rapid and reliable method to effectively isolate and quantify the non-liposomal, namely, free CPT-11and total CPT-11 in plasma. This study focuses on separation of non-liposomal CPT-11, evaluation of the pharmacokinetics of free CPT-11 and total CPT-11 and bio-distribution after intravenous administration of CPT-11 liposome. Free CPT-11 in plasma was separated by solid-phase extraction (SPE). The amount of total CPT-11 and main metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) in plasma was quantified by ultra-performance liquid chromatography-MS/MS. The calibration curves fitted well and lower limit of quantitation for SN-38, free CPT-11, total CPT-11 and CPT-11 in tissue and were 5 ng/ml, 10 ng/ml, 4.44 ng/ml and 25 ng/ml respectively. The recoveries, precision and accuracy of the method appear satisfactory. Using this method, the pharmacokinetics and bio-distribution of CPT-11 liposome formulation after an intravenous dose of 2.5 mg/kg were then investigated.

Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) in practice: analysis of drugs and pharmaceutical formulations

Background

UHPLC-MS/MS is connected in various research facilities for the qualitative and quantitative investigation of a pharmaceutical substance, pharmaceutical items, and biological specimen.

Main body

The commence review article is an endeavor to offer pervasive awareness around assorted aspects and details about the UHPLC-MS/MS and related techniques with the aim on practice to an estimation of medicinal active agents in the last 10 years. The article also focused on isolation, separation, and characterization of present impurity in drug and biological samples.

Conclusion

Review article compiles a general overview of medicinally important drugs and their analysis with UHPLC-MS/MS. It gives fundamental thought regarding applications of UHPLC-MS/MS for the study on safety limit. The summary of developed UHPLC-MS/MS methods gives a contribution to the future trend and limitations in this area of research.

Enhanced Intratumoral Delivery of SN38 as a Tocopherol Oxyacetate Prodrug Using Nanoparticles in a Neuroblastoma Xenograft Model

Purpose: Currently, <50% of high-risk pediatric solid tumors like neuroblastoma can be cured, and many survivors experience serious or life-threatening toxicities, so more effective, less toxic therapy is needed. One approach is to target drugs to tumors using nanoparticles, which take advantage of the enhanced permeability of tumor vasculature.Experimental Design: SN38, the active metabolite of irinotecan (CPT-11), is a potent therapeutic agent that is readily encapsulated in polymeric nanoparticles. Tocopherol oxyacetate (TOA) is a hydrophobic mitocan that was linked to SN38 to significantly increase hydrophobicity and enhance nanoparticle retention. We treated neuroblastomas with SN38-TOA nanoparticles and compared the efficacy with the parent prodrug CPT-11 using a mouse xenograft model.Results: Nanoparticle treatment induced prolonged event-free survival (EFS) in most mice, compared with CPT-11. This was shown for both SH-SY5Y and IMR-32 neuroblastoma xenografts. Enhanced efficacy was likely due to increased and sustained drug levels of SN38 in the tumor compared with conventional CPT-11 delivery. Interestingly, when recurrent CPT-11-treated tumors were re-treated with SN38-TOA nanoparticles, the tumors transformed from undifferentiated neuroblastomas to maturing ganglioneuroblastomas. Furthermore, these tumors were infiltrated with Schwann cells of mouse origin, which may have contributed to the differentiated histology.Conclusions: Nanoparticle delivery of SN38-TOA produced increased drug delivery and prolonged EFS compared to conventional delivery of CPT-11. Also, lower total dose and drug entrapment in nanoparticles during circulation should decrease toxicity. We propose that nanoparticle-based delivery of a rationally designed prodrug is an attractive approach to enhance chemotherapeutic efficacy in pediatric and adult tumors. Clin Cancer Res; 24(11); 2585-93. ©2018 AACR.

A pH-responsive prodrug delivery system of 10-HCPT for controlled release and tumor targeting

We synthesized a pH-responsive conjugate of 10-hydroxycamptothecin-thiosemicarbazide-linear polyethylene glycol 2000 (PEG2000). The conjugate was confirmed by matrix-assisted laser desorption time of flight mass spectrometry, ¹H NMR, and ¹³C NMR. The water solubility of the prodrug was increased by over 3,000 times; much longer body circulation time, higher tumor-targeting ability, and reduced toxicity were observed, compared with commercial 10-HCPT injection. The linker contains a pH-sensitive hydrazone bond, which breaks under low pH conditions in the tumor microenvironment. The conjugates showed good stability in phosphate-buffered saline (pH 7.4) and rat plasma. This amphiphilic conjugate could self-assemble into nanosized micelles of 80–100 nm. Cytotoxicity assay results indicate significantly higher efficacy of the conjugate (IC₅₀ [half maximal inhibitory concentration] =0.117 µM on SW180 cells) than 10-HCPT solution (IC₅₀ =0.241 µM on SW480 cells). Cellular uptake analysis suggested its rapid internalization and nuclear transport. Pharmacokinetic analysis of the conjugates demonstrated that the conjugate circulated for a longer time in the blood circulation system (T_2/1 =10.516±1.158 h) than did 10-HCPT solution (T_2/1 =1.859±1.385 h), and that it also enhanced the targeting and mean residence time (MRT_0–inf =39.873±4.549 h) in the tumor site, compared with 10-HCPT (MRT_0–inf =9.247±1.026 h). Finally, the conjugate demonstrated an increased tumor growth inhibition effect (TIR =82.66%±7.175%) in vivo and lower side effects than 10-HCPT (TIR =63.85%±5.233%). This prodrug holds great promise in improving therapeutic efficacy and overcoming multidrug resistance.

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

Development and validation of an UPLC-MS/MS method for the quantification of irinotecan, SN-38 and SN-38 glucuronide in plasma, urine, feces, liver and kidney: Application to a pharmacokinetic study of irinotecan in rats

The objective of this research is to develop and validate a sensitive and reproducible UPLC-MS/MS method to quantify irinotecan, its active metabolite SN-38 and SN-38 glucuronide (phase II metabolite of SN-38) simultaneously in different bio-matrices (plasma, urine, feces), tissues (liver and kidney) and to use the method to investigate its pharmacokinetic behavior in rats. Irinotecan, SN-38 and SN-38 glucuronide has been resolved and separated by C18 column using acetonitrile and 0.1% formic acid in water used as the mobile phases. Triple quadruple mass spectrometer using multiple reaction monitoring (MRM) with positive scan mode were employed to perform mass analysis. The results showed that the linear response range of irinotecan and SN-38 in plasma, feces, liver and kidney is 4.88-10000 nM, 39-5000 nM, 48.8-6250 nM and 48.8-6250 nM, respectively (R(2)>0.99). In case of SN-38 glucuronide, the standard curves were linear in the concentration range of 6.25-2000 nM, 4.88-1250 nM, 9.8-1250 nM and 9.8-1250 nM in plasma, feces, liver and kidney homogenates, respectively. The lower limit of detection (LLOD) of irinotecan, SN-38 and SN-38 glucuronide was determined to be less than 25 nM in all bio-matrices as well as tissue homogenates. Recoveries of irinotecan, SN-38 and SN-38 glucuronide at three different concentrations (low, medium and high) were not less than 85% at three different concentrations in plasma and feces. The percentage matrix factors in different bio-matrices and tissues were within 20%. The UPLC-MS/MS method was validated with intra-day and inter-day precision of less than 15% in plasma, feces, liver and kidney. Owing to the high sensitivity of this method, only 20 μl of plasma, urine and homogenates of liver, kidney and feces is needed. The validated method has been successfully employed for pharmacokinetic evaluation of irinotecan in male wistar rats to quantify irinotecan, SN-38 and SN-38 glucuronide in plasma, feces, and urine samples.

Ultrasound-induced opening of the blood-brain barrier to enhance temozolomide and irinotecan delivery: an experimental study in rabbits

OBJECT The blood-brain barrier (BBB) limits the intracerebral penetration of drugs and brain tumor treatment efficacy. The effect of ultrasound-induced BBB opening on the intracerebral concentration of temozolomide (TMZ) and irinotecan (CPT-11) was assessed. METHODS This study was performed using 34 healthy New Zealand rabbits. Half had unilateral BBB opening, and half served as controls. Sonications were performed by pulsing a 1.05-MHz planar ultrasound transducer with a duty cycle of 2.5% and an in situ acoustic pressure level of 0.6 MPa after injection of a microbubble ultrasound contrast agent. Drugs were injected either 5 minutes before (ChemoPreUS) or 15 minutes after (ChemoPostUS) the ultrasound sonication. The plasma and intracerebral concentrations of both drugs were quantified using ultra-performance liquid chromatography. RESULTS The mean intracerebral tissue-to-plasma drug concentration ratio in the control hemispheres was 34% for TMZ and 2% for CPT-11. After BBB opening, these values increased by up to 21% for TMZ and up to 178% for CPT-11. Intracerebral concentrations of drugs were enhanced in regions where the BBB was opened compared with the contralateral hemisphere (p < 0.01 and p < 0.0001 for CPT-11, p = 0.02 and p = 0.03 for TMZ, in ChemoPreUS and ChemoPostUS, respectively) and compared with the control group (p < 0.001 and p < 0.0001 for CPT-11, p < 0.01 and p = 0.02 for TMZ, in ChemoPreUS and ChemoPostUS, respectively). The intracerebral distribution of drugs was heterogeneous, depending on the distance from the ultrasound source. CONCLUSIONS Ultrasound-induced opening of the BBB significantly enhances the intracerebral concentration of both TMZ and CPT-11 in rabbits.

Challenges in SN38 drug delivery: current success and future directions

INTRODUCTION

Clinical use of SN38 is limited by its poor aqueous solubility and hydrolysis of the lactone ring at pH > 6 to inactive carboxylate form. A variety of drug delivery systems have been developed to improve the solubility and stability of SN38, and reduce its toxicity. A few noteworthy formulations with some success in initial phases of clinical trials are reported.

AREAS COVERED

This work aims to provide a comprehensive review on the various techniques and strategies employed (physical, chemical and biological methods) to improve physicochemical properties and to deliver the drug efficiently to the cancer cells. Physical methods such as nanoparticle encapsulation, cyclodextrin complexation; chemical methods such as prodrugs, polymer-, albumin- and immunoconjugates; and enzyme activated prodrug therapy are discussed.

EXPERT OPINION

The challenges in SN38 drug delivery may be overcome by two ways: ensuring multiple layers of protection against degradation and slow but sustained release of therapeutically effective drug concentrations. It may also be achieved by preparing a polymer-drug conjugate and further encapsulating the conjugate in suitable carrier system; tumor-targeted SN38 delivery by using immunoconjugates, enzyme-activated prodrug therapy and antibody-directed nanoparticle delivery. However, selection of a suitable ligand for tumor targeting and use of safe and biocompatible nanoparticle systems play an important role in realizing this goal.

Preclinical impact of bevacizumab on brain and tumor distribution of irinotecan and temozolomide

Glioblastoma (GBM) is the most common primary malignant brain tumour in adults. Prognosis of GBM patients is poor with median overall survival around 15 months. Temozolomide is the chemotherapeutic agent used in the standard of care of newly diagnosed GBM patients relying on radiotherapy with concurrent chemotherapy followed by chemotherapy alone. Irinotecan has shown some efficacy in recurrent malignant gliomas. Bevacizumab has been combined with irinotecan in the treatment of recurrent GBM and with temozolomide in newly diagnosed GBM. As the efficacy of GBM treatments relies on their brain distribution through the blood brain barrier, the aim of the present preclinical work was to study, in in vivo models, the impact of bevacizumab on brain and tumor distribution of temozolomide and irinotecan. Our results show that bevacizumab pre-treatment was associated with a reduced temozolomide brain distribution in tumor-free mice. In tumor bearing mice, bevacizumab increased temozolomide tumor distribution, although not statistically significant. In both tumor-free and tumor-bearing mice, bevacizumab does not modify brain distribution of irinotecan and its metabolite SN-38. Bevacizumab impacts brain distribution of some anti-tumor drugs and potentially their efficacy in GBM. Further studies are warranted to investigate other therapeutic combination.

HPLC analysis and extraction method of SN-38 in brain tumor model after injected by polymeric drug delivery system

SN-38 is a highly potent anticancer drug but its poor solubility in aqueous solvent and adverse side effects limit clinical applications. To overcome these limitations, SN-38-loaded-injectable drug delivery depots have been intratumorally administered in xenograft tumor model in nude mice. The extraction and high performance liquid chromatography (HPLC) were performed in order to determine the amount of SN-38 inside tumors. SN-38 was extracted from tumors using DMSO. HPLC analysis was validated and resulted in linearity over the concentration range from 0.03 to 150 µg/mL (r(2) ≥ 0.998). Lower limit of detection (LLOD) and lower limit of quantitation (LLOQ) were 0.308 µg/mL and 1.02 µg/mL, respectively. The extraction efficiency (% recovery) of SN-38 in porcine tissues was similar to that of tumors which provided more than 90% recovery in all concentrations. Moreover, the variability of precision and accuracy within and between-day were less than 15%. Therefore, this extraction and HPLC protocol was applied to determine the amount of SN-38 in tumors. Results show higher remaining amount of SN-38 in tumor from SN-38-loaded polymeric depots than that of SN-38 solution. These results reveal that SN-38-loaded polymeric depots can prevent the leakage of free-drug out of tumors and can sustain higher level of SN-38 inside tumor. Thus, the therapeutic efficacy can be elevated by SN-38-loaded polymeric depots.

Irinotecan and temozolomide brain distribution: a focus on ABCB1

Glioblastoma (GBM), the most common primary brain tumor in adults, is usually rapidly fatal with median survival duration of only 15 months and a 3-year survival rate of <7 %. Temozolomide (TMZ) is the only anticancer drug that has improved survival in GBM when administered with concomitant radiotherapy. Irinotecan (CPT-11) has also shown efficacy in recurrent gliomas monotherapy with moderate response. As the efficacy of GBM treatments relies on their brain distribution through the blood-brain barrier (BBB), the aim of the present work was to study, on an in vivo model, the brain distribution of TMZ, CPT-11 and its active metabolite, SN-38. We have focussed on the role of ABCB1, the main efflux transporter at the BBB level, through pharmacokinetics studies in CF1 mdr1a(+/+) and mdr1a(-/-) mice. Our results show that TMZ, CPT-11 and SN-38 are transported by ABCB1 at the BBB level with brain/plasma ratios of 1.1, 2.1 and 2.3, respectively.

Development of a new UPLC-MSMS method for the determination of temozolomide in mice: application to plasma pharmacokinetics and brain distribution study

A sensitive and accurate liquid chromatography method with mass spectrometry detection was developed and validated for the quantification of temozolomide in mouse plasma and brain. Theophyllin was used as the internal standard. A single-step protein precipitation was used for plasma and brain sample preparation. 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 50 ng/mL for temozolomide in plasma and 125 ng/g in brain. This method was used successfully to perform brain and plasma pharmacokinetic studies of temozolomide in mice after intraperitoneal administration.