LC-MS-MS Determination of Cytostatic Drugs on Surfaces and in Urine to Assess Occupational Exposure.

The ever-increased usage of cytostatic drugs leads to high risk of exposure among healthcare workers. Moreover, workers are exposed to multiple compounds throughout their lives, leading to cumulative and chronic exposure. Therefore, multianalyte methods are the most suitable for exposure assessment, which minimizes the risks from handling cytostatic drugs and ensures adequate contamination containment. This study describes the development and full validation of two liquid chromatography-tandem mass spectrometry methods for the detection of gemcitabine, dacarbazine, methotrexate, irinotecan, cyclophosphamide, doxorubicinol, doxorubicin, epirubicin, etoposide, vinorelbine, docetaxel and paclitaxel in working surfaces and urine samples. The urine method is the first to measure vinorelbine and doxorubicinol. For surfaces, limits of detection (LOD) and limits of quantification (LOQ) were 5-100 pg/cm2, and linearity was achieved up to 500 pg/cm2. Inaccuracy was between -11.0 and 8.4%. Intra-day, inter-day and total imprecision were <20%, except for etoposide and irinotecan (<22.1%). In urine, LOD and LOQ were 5-250 pg/mL, with a linear range up to 1,000-5,000 pg/mL. Inaccuracy was between -3.8 and 14.9%. Imprecision was <12.4%. Matrix effect was from -58.3 to 1,268.9% and from -66.7 to 1,636% in surface and urine samples, respectively, and extraction efficiency from 10.8 to 75% and 47.1 to 130.4%, respectively. All the analytes showed autosampler (6°C/72 h), freezer (-22°C/2 months) and freeze/thaw (three cycles) stability. The feasibility of the methods was demonstrated by analyzing real working surfaces and patients' urine samples. Contamination with gemcitabine, irinotecan, cyclophosphamide, epirubicin and paclitaxel (5-4,641.9 pg/cm2) was found on biological safety cabinets and outpatients' bathrooms. Analysis of urine from patients under chemotherapy identified the infused drugs at concentrations higher than the upper LOQ. These validated methods will allow a comprehensive evaluation of both environmental and biological contamination in hospital settings and healthcare workers.

Blood contamination of the pharmaceutical staff by irinotecan and its two major metabolites inside and outside a compounding unit.

BACKGROUND: Caregivers in healthcare settings are exposed to a risk of antineoplastic drug contamination which can lead to adverse health effects. Biological monitoring is necessary to estimate the actual level of exposure of these workers. This study was conducted with the aim of assessing blood contamination levels by irinotecan and its metabolites of pharmaceutical staff operating inside and outside a compounding unit. METHODS: The study took place within the pharmaceutical unit of a French comprehensive cancer centre. Blood samples were collected from the pharmacy workers operating inside and outside the compounding unit, and analysed by UHPLC-MS/MS. Plasma and red blood cell irinotecan and its metabolites (SN-38; APC) were determined with a validated analytical method detection test. RESULTS: A total of 17/78 (21.8%) plasma and red blood cell-based assays were found to be contaminated among staff. Overall, the total number of positive assays was significantly higher for staff members working outside the compounding unit than for workers working inside it (P = 0.022), with respectively 5/42 (11.9%) and 12/36 (33.3%) positive assays. For plasma dosages, the "outside" group had a significantly higher number of positive assays (P = 0.014). For red blood cell-based assays, no significant difference was found (P = 0.309). CONCLUSIONS: This study reveals that pharmaceutical staff serving in health care settings are exposed to a risk of antineoplastic drug contamination, not only inside the compounding room but also in adjacent rooms. The results would help to raise awareness and potentially establish protective measures for caregivers working in areas close to the compounding room as well.

Occupational exposure to antineoplastic drugs: what about hospital sanitation personnel?

OBJECTIVE: Occupational exposure to antineoplastic drugs (ANPs) occurs mainly through dermal contact. Our study was set up to assess the potential exposure of hospital sanitation (HS) personnel, for whom almost no data are available, through contamination of surfaces they regularly touch. METHODS: In the oncology departments of two hospitals around Montreal, surface wipe samples of 120-2000 cm2 were taken at 10 sites cleaned by the HS personnel and five other sites frequently touched by nursing and pharmacy personnel. A few hand wipe samples were collected to explore skin contamination. Wipes were analyzed by ultra-performance liquid chromatography tandem-mass spectrometry for 10 ANPs. RESULTS: Overall, 60.9% of 212 surface samples presented at least one ANP above the limits of detection (LOD). Cyclophosphamide and gemcitabine were most often detected (52% and 31% of samples respectively), followed by 5-fluorouracil and irinotecan (15% each). Highest concentrations of five ANPs were found in outpatient clinics on toilet floors (5-fluorouracil, 49 ng/cm2; irinotecan, 3.6 ng/cm2), a perfusion pump (cyclophosphamide, 19.6 ng/cm2) and on a cytotoxic waste bin cover (gemcitabine, 4.97 ng/cm2). Floors in patient rooms had highest levels of cytarabine (0.12 ng/cm2) and methotrexate (6.38 ng/cm2). Hand wipes were positive for two of 12 samples taken on HS personnel, seven of 18 samples on nurses, and two of 14 samples on pharmacy personnel. CONCLUSIONS: A notable proportion of surfaces showed measurable levels of ANPs, with highest concentrations found on surfaces cleaned by HS personnel, who would benefit from appropriate preventive training. As potential sources of worker exposure, several hospital surfaces need to be regularly monitored to evaluate environmental contamination and efficacy of cleaning.

Evaluation of a safe infusion device on reducing occupational exposure of nurses to antineoplastic drugs: a comparative prospective study. Contamoins-1.

PURPOSE: Despite the decreasing of environmental contamination throughout the anticancer drug circuit, the administration of chemotherapies remains at risk of occupational exposure for nurses. Many medical devices aim at securing administration, but none have been scientifically evaluated to verify the actual improvement. METHODS: A monocentric comparative before/after study was carried out in an oncology day hospital to evaluate the efficacy of Safe Infusion Devices in reducing drug exposure compared to usual infusion practices. The rate of nurses' gloves contamination was estimated. To avoid false negatives and to ensure sampling reproducibility, each sample of gloves was contaminated with a drop of topotecan. Association between contamination and other variables was investigated using a multivariate logistic regression analysis. RESULTS: The usual practice led to a rate of 58.3% of contaminated samples while Safe Infusion Devices to a rate of 15%: Safe Infusion Devices reduced the risk of gloves contamination by 85% in multivariate analysis (Odds ratio = 0.15; 95% confidence interval = 0.05-0.46; p < 0.001). Topotecan was identified in 100% of the samples. Only one case of cross-contamination has occurred. CONCLUSION: Despite the current practice of using neutral solvent-purged infusers, the occupational exposure remains high for nurses and Safe Infusion Devices significantly reduced this risk of exposure. However, glove contamination is only a surrogate endpoint. The results confirmed that the disconnection of empty bags resulted in occupational exposure. Except a contamination due to the leakage of a bag, no cross-contamination was detected. Safe Infusion Devices were highly effective but did not completely eliminate exposure.

Quality control of cytostatic drug preparations-comparison of workflow and performance of Raman/UV and high-performance liquid chromatography coupled with diode array detection (HPLC-DAD).

The drugs used for treatment during chemotherapy are manufactured individually for each patient in specialised pharmacies. Thorough quality control to confirm the identity of the delivered active pharmaceutical ingredient and the final concentration of the prepared application solution is not standardized yet except for optical or gravimetric testing. However, solution stability problems, counterfeit drugs, and erroneous or deliberate underdosage may occur and negatively influence the quality of the product and could cause severe health risks for the patient. To take a step towards analytical quality control, an on-site analytical instrument using Raman and UV absorption spectroscopy was employed and the results were compared to high-performance liquid chromatography coupled to diode array detection. Within the scope of the technology evaluation, the uncertainty of measurement was determined for the analysis of the five frequently used cytostatic drugs 5-fluorouracil, cyclophosphamide, gemcitabine, irinotecan and paclitaxel. The Raman/UV technique (2.0-3.2% uncertainty of measurement; level of confidence: 95%) achieves a combined uncertainty of measurement comparable to HPLC-DAD (1.7-3.2% uncertainty of measurement; level of confidence: 95%) for the substances 5-fluorouracil, cyclophosphamide and gemcitabine. However, the uncertainty of measurement for the substances irinotecan and paclitaxel is three times higher when the Raman/UV technique is used. This is due to the fact that the Raman/UV technique analyses the undiluted sample; therefore, the sample has a higher viscosity and tendency to foam. Out of 136 patient-specific preparations analysed within this study, 96% had a deviation of less than 10% from the target content.

An analytical "quality by design" approach in RP-HPLC method development and validation for reliable and rapid estimation of irinotecan in an injectable formulation.

The objective of the present study was to develop a robust, simple, economical and sensitive HPLC-UV method using the "quality-by-design" approach for the estimation of irinotecan (IRI) in marketed formulations. RP-HPLC method was developed by applying Box-Behnken design with Hyper-Clone (Phenomenex®) C18 column (250 × 4.6 mm id, particle size 5 µm, ODS 130 Å) as a stationary phase. Acetonitrile and 20 mmol L-1 potassium phosphate buffer (pH 2.5) containing 0.1 % triethylamine in a ratio of 45:55 % (V/V) was used as a mobile phase. The sample was injected in a volume of 20 µL into the HPLC system. UV detector at 254 nm was used to estimate and quantify IRI. Isocratic elution was opted while the flow rate was maintained at 0.75 mL min-1. The retention time of IRI was found to be 4.09 min. The responses were found to be linear for concentration range of 0.5 to 18.0 µg mL-1 and the coefficient of determination value was found to be 0.9993. Percent relative standard deviation for intra- and inter-day precisions was found in the range of 0.1 to 0.4 %. LOD and LOQ values were found to be 4.87 and 14.75 ng mL-1, resp. Robustness studies confirmed that the developed method is robust with RSD of a maximum 0.1 %. The method is simple, precise, sensitive, robust and economical making it applicable to the estimation of IRI in an injectable formulation.

A Rapid and Sensitive HPLC Method for Simultaneous Determination of Irinotecan Hydrochloride and Curcumin in Co-delivered Polymeric Nanoparticles.

In recent years, a great deal of attention has been paid to the combined use of multiple antitumor drugs for better cancer treatment. The aims of the study are to construct a nanoparticle drug delivery system for the co-delivery of irinotecan hydrochloride and curcumin and to develop an analytical method for simultaneously quantifying these molecules, which is essential for further studies of the co-delivered nano system. The irinotecan hydrochloride and curcumin co-delivered nanoparticle (ICN) were prepared by combinatorially entrapping them into polyethylene glycol-poly lactic acid-co-glycolic acid (PEG-PLGA) polymeric nanoparticles. A simple, sensitive and rapid high-performance liquid chromatography method was developed and validated to simultaneously quantify the compounds in the co-delivered nanoparticle system. Acetonitrile and ultrapure water containing sodium dodecyl sulfate (0.08 mol/L), disodium phosphate (Na2HPO4, 0.002 mol/L) and acetic acid (4%, v/v) were used as the mobile phase and their ratio was set at 50:50. The flow rate was set to 1.0 mL/min, and the temperature in the column oven was maintained at 40°C. The analysis was carried out at 256 and 424 nm to assess irinotecan hydrochloride and curcumin, respectively. Detectors with only one channel can also visualize both analytes in one chromatogram at 379 nm and still demonstrate acceptable sensitivity. The retention times for irinotecan hydrochloride and curium were 3.317 and 5.560 min, respectively. The method developed was confirmed to be sensitive, accurate (recovery, 100 ± 2%), precise (relative standard deviation, RSD ≤ 1%), robust and linear (R2 ≥ 0.9996) in the range from 2.05 to 1050 µg/mL. The presented method has been used to quantify irinotecan hydrochloride and curcumin in the co-delivered ICN nano system to assess the drug delivery quality of the nanoparticles and can also be used for routine analysis because of its simplicity and accuracy.

Bioanalytical method for the simultaneous quantification of irinotecan and its active metabolite SN-38 in mouse plasma and tissue homogenates using HPLC-fluorescence.

A simple and rapid bioanalytical method was developed for the simultaneous quantification of irinotecan and SN-38 in mouse plasma and tissue homogenates using High-Performance Liquid Chromatography with Fluorescence detection (HPLC-FL). Camptothecin was used as internal standard and protein precipitation with acetonitrile-methanol (1:1, v/v) followed by acidification with 0.5 M hydrochloric acid was used for sample pre-treatment. The analytes and the internal standard were detected using an excitation and emission wavelength of 368 and 515 nm, respectively. The linearity, selectivity, accuracy and precision, carry-over, limit of detection and lower limit of quantification of the method are described. The method was linear from 7.5 to 1500 ng/mL for irinotecan and from 5 to 1000 ng/mL for SN-38. For all matrices, the accuracy bias and precision variation were within ±15% and ≤15%, respectively. This method was successfully applied to study the pharmacokinetics of irinotecan and SN-38 using in vivo mouse models.

Blood-brain barrier disruption and delivery of irinotecan in a rat model using a clinical transcranial MRI-guided focused ultrasound system.

We investigated controlled blood-brain barrier (BBB) disruption using a low-frequency clinical transcranial MRI-guided focused ultrasound (TcMRgFUS) device and evaluated enhanced delivery of irinotecan chemotherapy to the brain and a rat glioma model. Animals received three weekly sessions of FUS, FUS and 10 mg/kg irinotecan, or irinotecan alone. In each session, four volumetric sonications targeted 36 locations in one hemisphere. With feedback control based on recordings of acoustic emissions, 98% of the sonication targets (1045/1071) reached a pre-defined level of acoustic emission, while the probability of wideband emission (a signature for inertial cavitation) was than 1%. BBB disruption, evaluated by mapping the R1 relaxation rate after administration of an MRI contrast agent, was significantly higher in the sonicated hemisphere (P < 0.01). Histological evaluation found minimal tissue effects. Irinotecan concentrations in the brain were significantly higher (P < 0.001) with BBB disruption, but SN-38 was only detected in <50% of the samples and only with an excessive irinotecan dose. Irinotecan with BBB disruption did not impede tumor growth or increase survival. Overall these results demonstrate safe and controlled BBB disruption with a low-frequency clinical TcMRgFUS device. While irinotecan delivery to the brain was not neurotoxic, it did not improve outcomes in the F98 glioma model.

Does equipment change impact blood contamination with irinotecan and its two major metabolites in a centralized cytotoxic pharmacy unit?

BACKGROUND: Antineoplastic drugs exposure is a major problem for caregivers' health. The aim of this study is to assess blood contamination with irinotecan and its two metabolites in a centralized pharmacy unit for cytotoxic drug preparations workers before and after protective equipment changes. METHODS: The study took place in a university hospital centralized pharmacy unit for cytotoxic drug and was performed in two parts, before (Round 1: R1) and after equipment changes (Round 2: R2). Collection of pharmacy staff blood samples was performed in UHPLC-MS/MS. Plasma and red blood cell irinotecan and its metabolites (SN38; APC) were determined with a validated analytical method detection test. RESULTS: A total of 15/36 (41.6%) assays were positive in R1 and 16/72 (22.2%) in R2 with a significant decrease between periods (P = 0.035). For plasma dosages, no difference between the two periods was found (P = 0.71); respectively 4/18 (22.2%) assays were positive in R1 and 6/36 (16.6%) in R2. For red blood cells dosages, a significant decrease between periods was found (P = 0.01); respectively 11/18 (61%) were positive in R1 and 10/36 (27.8%) in R2. CONCLUSIONS: These dosages make it possible to have the very first evaluation for plasma and red blood cell contamination with irinotecan and its metabolites in the context of equipment changes, both at individual and collective levels. This work would help to protect health workers from the potential risks represented by these molecules, especially by revealing a contamination of workers in order to objectify the results of exposure.

Cetuximab enhances the efficiency of irinotecan through simultaneously inhibiting the MAPK signaling and ABCG2 in colorectal cancer cells.

BACKGROUND: The present study sought to investigate the combined effects of cetuximab and irinotecan on colorectal cancer cells as well as the mechanisms underlying their anti-cancer effects. MATERIAL AND METHODS: High performance liquid chromatography, Hoechst staining assay, and western blotting analysis were used to detect intracellular drug concentrations, cell apoptosis, and protein expression in the presence of cetuximab, irinotecan, and the combination of both. RESULTS: Cetuximab was found to increase intracellular concentrations of irinotecan as well as cytotoxicity by inhibiting the epidermal growth factor receptor and, by extension, the downstream RAS-RAF-MEK-ERK signaling pathway. Cetuximab therefore induced apoptosis and improved the effect of irinotecan in colorectal cancer cells. It was also shown that cetuximab inhibited the drug efflux activity of ABCG2. In combination with irinotecan, cetuximab can both significantly induce cell apoptosis by inhibiting the RAS-RAF-MEK-ERK signaling pathway and improve the effects of irinotecan by decreasing drug efflux through the inhibition of ABCG2. CONCLUSION: These features contribute to its anti-cancer potential.

A Stable and Cleavable O-Linked Spacer for Drug Delivery Systems.

Anti-cancer chemotherapy with good efficacy and fewer side effects is highly desirable. A drug delivery system comprising a cancer-targeting module and a cytotoxic agent connected with a cleavable linker is promising for reducing side effects. The development of a cleavable linker satisfying the requirements of both stability and cleavability, however, is difficult, especially when a carbonate moiety is used for conjugating the linker to a hydroxy group in a drug of interest. We herein report a new stable linker comprising carbamate and ester spacers, which can be introduced on a hydroxy group of a drug. This linker is more stable in aqueous neutral buffer than a corresponding carbonate-type linker, and releases a payload anti-cancer drug, SN-38, through a two-step sequence upon cathepsin B treatment. This linker may have potential use in other drug delivery systems to lower side effects by selectively transporting cytotoxic drugs to tumor cells.

Stable Isotope Dilution LC-HRMS Assay To Determine Free SN-38, Total SN-38, and SN-38G in a Tumor Xenograft Model after Intravenous Administration of Antibody-Drug Conjugate (Sacituzumab Govitecan).

Antibody-drug conjugates (ADCs) have gained significant interest over the past few years due to their targeted delivery, higher efficacy, decreased toxicity and improved therapeutic index over conventional anticancer therapies. Sacituzumab govitecan (SG) is an ADC composed of a Trop-2-targeted antibody conjugated to the cytotoxic payload SN-38. SG is currently being evaluated in clinical trials of several solid cancers. In this nonclinical study, we have developed a highly sensitive and selective approach to measure free and total SN-38 and its glucuronidation metabolite (SN-38G) using stable isotope dilution (SID) ultrahigh-performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). An efficient and fast hydrolysis procedure (2 h at 100 °C) was established to release SN-38, conjugated to the antibody by carbonate linkage. The assay involves the extraction of free SN-38, SN-38G by protein precipitation, and subsequent acid hydrolysis of the protein layer to release antibody-bound SN-38. The developed UHPLC-HRMS method resulted in good linearity (r2 ≥ 0.997), accuracy (RE ≤ ± 9.1%), precision (CVs ≤ 7.7%), and extraction recoveries (85.6-109.3%). The validated method was applied in the plasma and tumor of mice bearing human brain (U251) and breast (MDA-MB-468) tumor xenografts treated with a single dose (0.5 mg) of SG for 6 h. Results revealed the presence of trace level of SN-38G and free SN-38 in plasma, which suggests an improved therapeutic index of SG. The established method makes a significant contribution to the assessment of SG in different cancers.

Development and validation of a UHPLC-MS/MS method for the identification of irinotecan photodegradation products in water samples.

Irinotecan (CPT-11) is a water-soluble anticancer drug widely used to treat several types of cancer. Even if the metabolites of CPT-11 are well-known and investigated, only limited information is available in the literature about the formation of photo-degradation products that can naturally originate from sunlight irradiation when the drug is released in aqueous systems. CTP-11 solutions at 10.0 mg L-1 were irradiated by simulated sunlight. The intensity of the drug decreased by 90% after 7.5 days of irradiation and no significant reduction of absorbance values was observed after 13 days. A sensitive UHPLC-MS/MS method was developed employing a hybrid triple quadrupole/linear ion trap mass spectrometer, that is able to work in data-dependent acquisition mode and to obtain information about the compounds formed during the photoirradiation. Moreover, a selected reaction monitoring method was built using the MS/MS fragmentation pattern of the compounds previously investigated. The method was validated considering LOD, LOQ, linearity, precision, selectivity, recovery and matrix effect. LOD and LOQ values were 0.02 and 0.05 ng mL-1, respectively, whereas MDL and MQL values in real water samples (river water, groundwater, well water, and wastewater) were lower than 0.05 and 0.2 ng mL-1, respectively. Eight photodegradation products were identified, among which five for the first time. Based on the MS and MS/MS fragmentation, the chemical structures of the degradation products were proposed. Hydrolysis experiments were carried out on the same solutions preserved in the dark, but no formation of other species was highlighted. The method was applied to several real samples: CPT-11 was detected and quantified only in a hospital effluent sample at the concentration of 0.41 ±â€¯0.2 ng mL-1 together with the occurrence of PDP3. The outcomes of this study may be useful for updating the pollutant screening in water samples.

Quantification of Drug Molecules in Live Single Cells Using the Single-Probe Mass Spectrometry Technique.

Analyzing cellular constituents on the single-cell level through mass spectrometry (MS) allows for a wide range of compounds to be studied simultaneously. However, there is a need for quantitative single-cell mass spectrometry (qSCMS) methods to fully characterize drug efficacy from individual cells within cell populations. In this study, qSCMS experiments were carried out using the Single-probe MS technique. The method was successfully used to perform rapid absolute quantifications of the anticancer drug irinotecan in individual mammalian cancer cells under ambient conditions in real time. Traditional liquid chromatography/mass spectrometry (LC/MS) quantifications of irinotecan in cell lysate samples were used to compare the results from Single-probe qSCMS. This technique showcases heterogeneity of drug efficacy on the single-cell level.

Preparation and Evaluation of Irinotecan Poly(Lactic-co-Glycolic Acid) Nanoparticles for Enhanced Anti-tumor Therapy.

Irinotecan (IRT), the pro-drug of SN-38, has exhibited potent cytotoxicity against various tumors. In order to enhance the anti-tumor effect of IRT, we prepared IRT-loaded PLGA nanoparticles (IRT-PLGA-NPs) by emulsion-solvent evaporation method. Firstly, IRT-PLGA-NPs were characterized through drug loading (DL), entrapment efficiency (EE), particle size, zeta potential, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). We next studied the in vitro release characteristics of IRT-PLGA-NPs. Finally, the pharmacokinetics and pharmacodynamics profiles of IRT-PLGA-NPs were investigated. The results revealed that IRT-PLGA-NPs were spherical with an average size of (169.97 ± 6.29) nm and its EE and DL were (52.22 ± 2.41)% and (4.75 ± 0.22)%, respectively. IRT-PLGA-NPs could continuously release drug for 14 days in vitro. In pharmacokinetics studies, for pro-drug IRT, the t1/2ß of IRT-PLGA-NPs was extended from 0.483 to 3.327 h compared with irinotecan solution (IRT-Sol), and for its active metabolite SN-38, the t1/2ß was extended from 1.889 to 4.811 h, which indicated that IRT-PLGA-NPs could prolong the retention times of both IRT and SN-38. The pharmacodynamics results revealed that the tumor doubling time, growth inhibition rate, and specific growth rate of IRT-PLGA-NPs were 2.13-, 1.30-, and 0.47-fold those of IRT-Sol, respectively, which demonstrated that IRT-PLGA-NPs could significantly inhibit the growth of tumor. In summary, IRT-PLGA-NPs, which exhibited excellent therapeutic effect against tumors, might be used as a potential carrier for tumor treatment in clinic.

Enzyme-Based Electrochemical Biosensor for Therapeutic Drug Monitoring of Anticancer Drug Irinotecan.

Therapeutic drug monitoring (TDM) is the clinical practice of measuring pharmaceutical drug concentrations in patients' biofluids at designated intervals, thus allowing a close and timely control of their dosage. To date, TDM in oncology can only be performed by trained personnel in centralized laboratories and core facilities employing conventional analytical techniques (e.g., MS). CPT-11 is an antineoplastic drug that inhibits topoisomerase type I, causing cell death, and is widely used in the treatment of colorectal cancer. CPT-11 was also found to directly inhibit acetylcholine esterase (AChE), an enzyme involved in neuromuscular junction. In this work, we describe an enzymatic biosensor, based on AChE and choline oxidase (ChOx), which can quantify CPT-11. ACh (acetylcholine) substrate is converted to choline, which is subsequently metabolized by ChOx to give betaine aldehyde and hydrogen peroxide. The latter one is then oxidized at a suitably polarized platinum electrode, providing a current transient proportional to the amount of ACh. Such an enzymatic process is hampered by CPT-11. The biosensor showed a ∼60% maximal inhibition toward AChE activity in the clinically relevant concentration range 10-10 000 ng/mL of CPT-11 in both simple (phosphate buffer) and complex (fetal bovine serum) matrixes, while its metabolites showed negligible effects. These findings could open new routes toward a real-time TDM in oncology, thus improving the therapeutic treatments and lowering the related costs.