The degradation of the antitumor agent gemcitabine hydrochloride in an acidic aqueous solution at pH 3.2 and identification of degradation products

Tumor Microenvironment Modulates Invadopodia Activity of Non-Selected and Acid-Selected Pancreatic Cancer Cells and Its Sensitivity to Gemcitabine and C18-Gemcitabine

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with high mortality due to early metastatic dissemination and high chemoresistance. All these factors are favored by its extracellular matrix (ECM)-rich microenvironment, which is also highly hypoxic and acidic. Gemcitabine (GEM) is still the first-line therapy in PDAC. However, it is quickly deaminated to its inactive metabolite. Several GEM prodrugs have emerged to improve its cytotoxicity. Here, we analyzed how the acidic/hypoxic tumor microenvironment (TME) affects the response of PDAC cell death and invadopodia-mediated ECM proteolysis to both GEM and its C18 prodrug.

METHODS

For this, two PDAC cell lines, PANC-1 and Mia PaCa-2 were adapted to pHe 6.6 or not for 1 month, grown as 3D organotypic cultures and exposed to either GEM or C18 in the presence and absence of acidosis and the hypoxia inducer, deferoxamine.

RESULTS

We found that C18 has higher cytotoxic and anti-invadopodia activity than GEM in all culture conditions and especially in acid and hypoxic environments.

CONCLUSIONS

We propose C18 as a more effective approach to conventional GEM in developing new therapeutic strategies overcoming PDAC chemoresistance.

Ionophore-Based Polymeric Sensors for Potentiometric Assay of the Anticancer Drug Gemcitabine in Pharmaceutical Formulation: A Comparative Study

Gemcitabine is a chemotherapeutic agent used to treat various malignancies, including breast and bladder cancer. In the current study, three innovative selective gemcitabine hydrochloride sensors are developed using 4-tert-butylcalix-[8]-arene (sensor 1), β-cyclodextrin (sensor 2), and γ-cyclodextrin (sensor 3) as ionophores. The three sensors were prepared by incorporating the ionophores with o-nitrophenyl octyl ether as plasticizer and potassium tetrakis(4-chlorophenyl) borate as ionic additive into a polyvinyl chloride polymer matrix. These sensors are considered environmentally friendly systems in the analytical research. The linear responses of gemcitabine hydrochloride were in the concentration range of 6.0 × 10-6 to 1.0 × 10-2 mol L-1 and 9.0 × 10-6 to 1.0 × 10-2 mol L-1 and 8.0 × 10-6 to 1.0 × 10-2 mol L-1 for sensors 1, 2, and 3, respectively. Over the pH range of 6-9, fast-Nernst slopes of 52 ± 0.6, 56 ± 0.3, and 55 ± 0.8 mV/decade were found in the same order with correlation regressions of 0.998, 0.999, and 0.998, respectively. The lower limits of detection for the prepared sensors were 2.5 × 10-6, 2.2 × 10-6, and 2.7 × 10-6 mol L-1. The sensors showed high selectivity and sensitivity for gemcitabine. Validation of the sensors was carried out in accordance with the requirements established by the IUPAC, while being inexpensive and easy to use in drug formulation. A statistical analysis of the methods in comparison with the official method showed that there was no significant difference in accuracy or precision between them. It was shown that the new sensors could selectively and accurately find gemcitabine hydrochloride in bulk powder, pharmaceutical formulations, and quality control tests. The ionophore-based sensor shows several advantages over conventional PVC membrane sensor sensors regrading the lower limit of detection, and higher selectivity towards the target ion.

Physicochemical and in vitro cytotoxicity studies of inclusion complex between gemcitabine and cucurbit[7]uril host

Gemcitabine, a cytostatic drug from the pyrimidine antimetabolite group, exhibits limited storage stability and numerous side effects during therapy. One of the strategies to improve the effectiveness of therapy with such drugs is the use of supramolecular nano-containers, including dendrimers and macrocyclic compounds. The ability of gemcitabine to attach a proton in an aqueous environment necessitates the search for a carrier that is well-tolerated by an organism and capable of supramolecular binding of a ligand (drug) in a cationic form. In the current study a promising strategy was tested for using cucurbituril Q7 to bind gemcitabine cations for its efficient intracellular delivery on three selected cancer cell lines (MOLT4, THP-1 and U937). Based on physicochemical studies (equilibrium dialysis, UV and ¹H NMR titrations, DOSY ¹H NMR measurements, DSC calorimetry) and cytotoxicity tests on cells with a free and blocked hENT1 transporter, the conclusion was drawn about the binding and penetration of the cucurbituril-drug complex into cancer cells.

Development and validation of a stability indicating isocratic HPLC method for gemcitabine with application to drug release from poly lactic-co-glycolic acid nanoparticles and enzymatic degradation studies

Objectives

Previously reported HPLC methods for gemcitabine determination are time-consuming with complicated mobile phases and gradient elution. Thus, a sensitive and stability-indicating isocratic HPLC method, which provides simple, fast and precise measurements, was developed. This method was applied to study the digestive enzymatic degradation of gemcitabine, for the first time, and the protection afforded following incorporation into poly lactic-co-glycolic acid (PLGA) nanoparticles.

Methods

An analytical HPLC method was developed with an optimized combination of operating conditions. Forced degradation and application of the method to in-vitro drug release studies were conducted. Finally, gemcitabine-loaded nanoparticles were exposed to the digestive enzymes pepsin, trypsin and α-chymotrypsin, and the resulting degradation evaluated.

Key findings

The analytical method was linear between 1 and 100 μg/ml, with excellent accuracy of 99.91–101.77% and precision of 1.71 or lower, with a 0.014 μg/ml limit of detection (LOD) and a 0.043 μg/ml limit of quantification (LOQ). Following exposure of gemcitabine to stressors, the drug was relatively stable in strong acid (1 N HCl), base (1 N NaOH) and as an aqueous solution exposed to light over 7 days, with less than 10% degradation. However, gemcitabine was more susceptible to degradation at 70°C and oxidative conditions (3% v/v H2O2) with greater than 10% degradation noted after 7 days. In-vitro drug release studies demonstrated a sustained drug release profile from PLGA nanoparticles, which also improved the resistance of gemcitabine to enzymatic degradation.

Conclusion

These results demonstrate the utility and effectiveness of this simple isocratic HPLC method in evaluating the overall performance of a gemcitabine-loaded formulation.

A multicenter, open-label, Phase 1 study evaluating the safety and tolerability of pegaspargase in combination with gemcitabine in advanced metastatic solid tumors and lymphoma

PURPOSE

To evaluate the maximum tolerated dose, safety profile, pharmacokinetics, and pharmacodynamics of pegaspargase (PEG-ASP) in combination with gemcitabine in patients with advanced metastatic solid tumors and lymphoma.

METHODS

We conducted a multicenter, open label, nonrandomized, Phase 1 dose escalation study designed to evaluate up to 10 cohorts of patients with advanced or metastatic solid tumors and lymphoma. Seventeen patients were treated with of PEG-ASP in combination with gemcitabine.

RESULTS

The study was terminated early because the doses for PEG-ASP suggested for de-escalation were predicted not to provide desired sustained asparaginase concentrations based on the analysis of treated patients.

Stability-indicating HPLC determination of gemcitabine in pharmaceutical formulations

A simple, sensitive, inexpensive, and rapid stability indicating high performance liquid chromatographic method has been developed for determination of gemcitabine in injectable dosage forms using theophylline as internal standard. Chromatographic separation was achieved on a Phenomenex Luna C-18 column (250 mm × 4.6 mm; 5μ) with a mobile phase consisting of 90% water and 10% acetonitrile (pH 7.00 ± 0.05). The signals of gemcitabine and theophylline were recorded at 275 nm. Calibration curves were linear in the concentration range of 0.5–50 μg/mL. The correlation coefficient was 0.999 or higher. The limit of detection and limit of quantitation were 0.1498 and 0.4541 μg/mL, respectively. The inter- and intraday precision were less than 2%. Accuracy of the method ranged from 100.2% to 100.4%. Stability studies indicate that the drug was stable to sunlight and UV light. The drug gives 6 different hydrolytic products under alkaline stress and 3 in acidic condition. Aqueous and oxidative stress conditions also degrade the drug. Degradation was higher in the alkaline condition compared to other stress conditions. The robustness of the methods was evaluated using design of experiments. Validation reveals that the proposed method is specific, accurate, precise, reliable, robust, reproducible, and suitable for the quantitative analysis.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

Combinatorial pharmacologic effects of gemcitabine and its metabolite dFdU

Recent evidence has shown that the gemcitabine metabolite, dFdU, is pharmacologically active. Though less potent, dFdU has a longer half-life and could potentiate or antagonize the activity of gemcitabine. Hence, studies were undertaken to evaluate the combined effects. Following chemical synthesis, an improved purification procedure for dFdU was developed (80 % yield; >99 % purity). Zebrafish phenotype-based embryo screens revealed no acute toxicity after gemcitabine or dFdU treatment. Only gemcitabine affected zebrafish development in a dose-dependent manner. Synergy or antagonism for the combination was not observed. Antitumor effects for dFdU were dose dependent. Antagonism was tumor cell-line dependent and did not depend on formation of the intracellular active metabolite of gemcitabine, suggesting that the drug-metabolite interaction occurs later. These studies highlight a platform for testing the pharmacologic activity for anticancer agent and metabolite combinations. Such analyses are expected to provide insight into the beneficial or harmful effect(s) of metabolites towards parent drug activity.

Improved plasma stability and sustained release profile of gemcitabine via polypeptide conjugation

To enhance the stability of the anticancer drug gemcitabine (2'-deoxy-2',2'-difluorocytidine), it was conjugated to poly-l-glutamic acid (PG-H) via a carbodiimide reaction. The synthesised poly-l-glutamic acid-gemcitabine (PG-G) was purified and characterised by using SDS-PAGE to estimate its molecular weight, HPLC to determine its purity and degree of drug loading, and NMR to elucidate the structure. In vitro aqueous hydrolytic studies showed that the gemcitabine release from the polymeric drug conjugate was pH dependent, and that the conjugation to PG-H improved its stability in human plasma. The release of the bound gemcitabine from PG-G in plasma was mediated by a hydrolytic process. It began with a lag phase, followed by linear release between 12 and 48h, and reached equilibrium at 72h with 51% of the gemcitabine released. In vitro cytotoxicity studies using MCF-7 and MDA-MB-231 human mammary cancer cells, as well as human dermal fibroblasts (HDF), showed that PG-G displayed a lower dose dependent cytotoxic effect with respect to the parent drug gemcitabine. On the other hand, in 4T1 mouse mammary tumour cells, PG-G and gemcitabine showed similar toxicities. Gemcitabine was more than likely released hydrolytically from PG-G and taken up by MCF-7, MDA-MB-231 and HDF, whereas both released gemcitabine and PG-G were taken up by 4T1 to mediate the observed cytotoxicities. The improved stability and extended sustained release profile may render PG-G a potential anticancer prodrug.

An Expedient Assay for Determination of Gemcitabine and Its Metabolite in Human Plasma Using Isocratic Ion-Pair Reversed-Phase High-Performance Liquid Chromatography

An expedient method is presented for determination in human plasma of gemcitabine and its metabolite 2',2'-difluorodeoxyuridine (dFdU) by ion-pair reversed-phase HPLC. Samples were simply prepared by protein precipitation. Separation was processed on a Thermo Hypersil column (250 x 4.6 mm, 5 microm Hypersil BDS C18) with UV detection at 272 nm. The mobile phase consisted of 17% methanol and 83% phosphate buffer (20 mM, pH 3.1) containing 10 mM sodium 1-heptanesulfonate with a flow rate of 0.8 mL/min. The lower limit of quantification (LLOQ) of gemcitabine was 0.08 microg/mL with linear response over the range 0.08-20.0 microg/mL, and LLOQ of dFdU was 0.1 microg/mL with linear response over the range 0.1-50.0 microg/mL. Assay accuracy for both compounds was within +/- 4%. The coefficient of variation (CV %) for intra- and interday precision for both compounds was <7%. The correlation coefficients (r2) were greater than 0.9996 for all standard curves. The simple method with adequate sensitivity has been successfully used in phase I and II gemcitabine pharmacokinetic and pharmacodynamic studies in an Asian population.