Photodegradation of irinotecan (CPT-11) in aqueous solutions: identification of fluorescent products and influence of solution composition

Long term and simulated in-use stabilities of irinotecan chemotherapy polyolefin infusion bags in dose banding conditions

PurposeThe dose-banding of irinotecan provides the opportunity to anticipate the preparation of this anticancer drug on condition of carrying out stability studies. The aim of this study was to develop and validate a HPLC method for measuring the concentration of irinotecan and to evaluate its long-term stability at standardized rounded doses in polyolefin (POF) infusion bags at 4°C and protected from daylight. Microbiological and Physical stability tests were periodically performed including visual inspection, turbidity, lightness and chromaticity measurements. In addition, in a simulated in-use study, irinotecan quantification was also performed on the solution emitted from the POF infusion bags on a short period (24 h), at room temperature (25°C) and in daylight.MethodsThe HPLC with photodiode array (PDA) detector method was developed and validated (linearity, precision, accuracy, limits of detection and quantification, robustness and degradation test). Diluted irinotecan infusion solutions were aseptically prepared by further dilution of irinotecan stock solution with 0.9% sodium chloride in POF bags at banded doses 200 mg, 300 mg and 370 mg, the three most frequently produced doses in the pharmacy department. The POF bags were stored under refrigeration (4°C) in the dark (long term stability conditions) or at room temperature (25°C) in daylight for a short period 24 h (simulated in-use conditions). Microbiological tests were carried out and the physical and chemical stabilities were evaluated respectively through visual inspection, turbidity, lightness, chromaticity measurements and through chromatographic assays, pH and osmolality monitoring.ResultsThe long - term stability of irinotecan at selected standardized rounded doses (200 mg-300 mg-370 mg) in NaCl 0.9% polyolefin bags was confirmed for at least 84 days at 4 °C and in the dark. Microbiological tests performed on the samples were negative. As well, during the simulated in-use study, no signs of chemical instability were observed.ConclusionsA simple, accurate and stability-indicating HPLC method was developed to determine irinotecan concentrations in dose-banding conditions. As well, this present work including HPLC peak width, lightness and chromaticity measurements of a cytotoxic drug during the time of storage may be a guidance in stability studies. This study supports a centralized production of irinotecan in accordance with the studied conditions.

Fundamental properties and principal areas of focus in antibody-drug conjugates formulation development

Antibody-drug conjugates (ADCs) have emerged as a rapidly expanding class of therapeutics driven by their superior specificity and clinical efficacy. 14 out of 16 commercially approved ADCs are formulated as lyophilized forms because ADC is generally considered to be less stable than unmodified antibody. The formulation development for ADCs, particularly liquid formulation, presents unique challenges due to their intricate structural complexity, physicochemical properties, and degradation pathways. This review provides the first comprehensive analysis of formulation strategies employed in commercial ADCs. Furthermore, this review discusses the key areas of focus for ADCs throughout the formulation development workflow, spanning from the initial formulation development to the final stage of drug product manufacturing. In addition, we identify and analyze the distinctive technical challenges in ADC formulation development compared to unconjugated antibody, while proposing potential solutions to these challenges. Finally, we offer strategic perspectives on future directions in ADC formulation development to advance this promising therapeutic modality.

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 ± 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.

Physicochemical stability of irinotecan injection concentrate and diluted infusion solutions in PVC bags

Purpose. To determine the physicochemical stability of irinotecan injection concentrate and irinotecan infusion solutions after dilution in two commonly used infusion fluids (0.9% sodium chloride, 5% dextrose) in PVC bags, stored under refrigeration (2-8°C) or at room temperature either light protected or exposed to light.

Methods. Stability of irinotecan injection concentrate was determined in the original amber glass vials. Diluted irinotecan infusion solutions were aseptically prepared by further dilution of irinotecan stock solution with either 0.9% sodium chloride or 5% dextrose in PVC bags, in amounts yielding irinotecan concentrations of 0.4, 1.0, or 2.8 mg/ml. Test solutions were stored under refrigeration (2-8°C) or at room temperature either light protected or exposed to light (mixed daylight and normal laboratory fluorescent light) in parallel. Irinotecan concentrations were determined periodically throughout a 4-week storage period via a stability-indicating HPLC assay with ultraviolet detection. In addition, measurements of pH values were performed regularly and test solutions were visually examined for colour change and precipitation.

Results. Irinotecan injection concentrate and infusion solutions are shown to be physicochemically stable (at a level of >90% irinotecan) for 4 weeks when stored under refrigeration or light protected at room temperature, independent of the vehicle (0.9% sodium chloride, 5% dextrose) or the concentration (0.4, 1.0, or 2.8 mg/ml). Irinotecan infusion solutions exposed to daylight exhibited concentration-dependent instability, solutions were stable for only 7 to 14 days.

Conclusions. Irinotecan injection concentrate and diluted infusion solutions are shown to have adequate physicochemical stability for convenient pharmacy-based centralized preparation.

DOSY NMR and MALDI-TOF evidence of covalent binding the DNA duplex by trimethylammonium salts of topotecan upon near UV irradiation

Using DOSY NMR and MALDI-TOF MS techniques, we present evidence that quaternary trimethylammonium salts of topotecan, [TPT-NMe3 ](+) X(-) (X = CF3SO3, HCOO), bind covalently the natural DNA oligomer upon near UV irradiation in water under physiological conditions. It is shown that formate salt is very reactive at pH 7 and requires short irradiation time. This weak irradiation at 365 nm paves the way for a new application of TPT derivatives in clinical use, which can dramatically increase the therapeutic effects of a medicine.

Stability of irinotecan-loaded drug eluting beads (DC BeadTM) used for transarterial chemoembolization

Purpose. The aim of this study was to determine the loading efficiency, physicochemical stability, and release of irinotecan-loaded DC BeadsTM (bead size 100—300 μm, 300—500 μm) before and after mixing with nonionic contrast medium (Accupaque® 300, Imeron® 300, Ultravist ® 300) during a prolonged period of time (28 days) when stored at room temperature or refrigerated.

Methods. DC Beads TM were loaded with 50 mg irinotecan (Campto®) per milliliter beads in a 2 h loading period. Drug loading efficiency and stability were determined by measuring the irinotecan concentration in the excess solution. A free-flowing in vitro elution method for a period of 2 h and phosphate buffered solution (PBS, pH 7.2) as elution medium were used to analyze the integrity of the irinotecan-loaded. Stability of irinotecan-loaded beads after mixing with an equal volume of three different nonionic contrast agents was determined by measuring irinotecan concentrations in the excess solutions. Vials with loaded beads were stored protected from light at room temperature. Mixtures with contrast media were stored protected from light under refrigeration (2—8°C). Samples were taken periodically over a 4 week period (day 0, 1, 3, 7 and 28). A reversed phase HPLC assay with ultraviolet detection was utilized to analyze the concentration and purity of irinotecan.

Results. The loading procedure of DC BeadsTM with irinotecan drug solution resulted in a loading percentage of 96% (bead size 100—300 μm) independent of the storage time. No differences in loading levels and no irinotecan degradation products were observed over the period of 28 days, while the test vials were stored light protected at room temperature. Integrity of loaded irinotecan was also given over that same period of time according to the purity and concentration of irinotecan measured after intentional elution with PBS. Mixing of irinotecan-loaded beads (bead size 100—300 μm, 300—500 μm) with nonionic contrast media decreased the irinotecan loading efficiency by ∼5—10% during a maximum period of 24 h. However, no further elution or degradation was observed during a 4-week period when stored protected from light under refrigeration.

Conclusions. Irinotecan-loaded DC BeadsTM are shown to have adequate physicochemical stability over a period of at least 28 days when stored light protected at room temperature. Due to concerns of microbiological overgrowth refrigeration should always be considered. The preparation of admixtures of irinotecan-loaded beads with contrast medium in centralized cytotoxic preparation units is not recommended, because of rapid elution of 5—10% of irinotecan from the loaded beads. Furthermore, physicians see no advantages of admixtures due to the wide variation of mixing ratios of drug-loaded beads with contrast medium. In addition varying volumes of 0.9% sodium chloride solution are to be admixed during the chemoembolization procedure

A conjugate of camptothecin and a somatostatin analog against prostate cancer cell invasion via a possible signaling pathway involving PI3K/Akt, αVβ3/αVβ5 and MMP-2/-9

Camptothecin (CPT) was conjugated to the N-terminal of a somatostatin analog (SSA) directly via a carbamate group and a basic N-terminal linking motif, D-Lys-D-Tyr-Lys-D-Tyr-D-Lys. This new CPT-SSA conjugate termed JF-10-81 was evaluated as a receptor-specific delivery system for its anti-invasive and anti-angiogenic activities. It was found that, in addition to blocking migration and invasion of highly invasive prostate cancer PC-3 cells, this conjugate also inhibited in vitro capillary-like tube formation of endothelial cells and in vivo angiogenesis in C57B1/6N female mice. JF-10-81 was found to block PC-3 cell attachment to various extracellular matrix components, mainly to vitronectin, the ligand of cell surface receptors integrin alphaVbeta3 and alphaVbeta5. Additionally, JF-10-81 reduced expression of integrins alphaVbeta3 and alphaVbeta5 on PC-3 cell surfaces, without effects on beta1 or any alphabeta1 heterodimers. This conjugate also inactivated phosphorylation of protein kinase B (PKB/Akt), down-regulated the expression of latent matrix metalloproteinase (MMP) -2 and MMP-9, but had little effect on MMP-3/-10. Meanwhile, membrane type-1 matrix metalloproteinase (MT1-MMP) and the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) were not detectable in PC-3 cells. alphaVbeta3/alphaVbeta5 and MMP-2/-9 are known to be highly expressed in many tumor cells and play an important role in tumor progression. Our results support that this conjugate could possibly inhibit prostate cancer PC-3 cell invasion through a signaling pathway involving PI3K/Akt, alphaVbeta3/alphaVbeta5 and MMP-2/-9, and this SSA could be used as an efficient vector to deliver CPT or other cytotoxic agents to target sites for cancer therapy.

Liposomal irinotecan: formulation development and therapeutic assessment in murine xenograft models of colorectal cancer

PURPOSE

The purpose is to demonstrate whether an appropriately designed liposomal formulation of irinotecan is effective in treating mice with liver-localized colorectal carcinomas.

EXPERIMENTAL DESIGN

Irinotecan was encapsulated in 1,2-distearoyl-sn-glycero-3-phosphocholine/cholesterol (55:45 molar ratio) liposomes using an ionophore (A23187)-generated transmembrane proton gradient. This formulation was evaluated in vivo by measuring plasma elimination of liposomal lipid and drug after i.v. administration. Therapeutic activity was determined in SCID/Rag-2M mice bearing s.c. LS180 tumors or orthotopic LS174T colorectal metastases.

RESULTS

Drug elimination from the plasma was significantly reduced when irinotecan was administered in the liposomal formulation. At 1 hour after i.v. administration, circulating levels of the liposomal drug were 100-fold greater than that of irinotecan given at the same dose. High-performance liquid chromatographic analysis of plasma samples indicated that liposomal irinotecan was protected from inactivating hydrolysis to the carboxylate form. This formulation exhibited substantially improved therapeutic effects. For the LS180 solid tumor model, it was shown that after a single injection of liposomal irinotecan at 50 mg/kg, the time to progress to a 400-mg tumor was 34 days (as compared with 22 days for animals treated with free drug at an equivalent dose). In the model of colorectal liver metastases (LS174T), a median survival time of 79 days was observed after treatment with liposomal irinotecan (50 mg/kg, given every 4 days for a total of three doses). Saline and free drug treated mice survived for 34 and 53 days, respectively.

CONCLUSIONS

These results illustrate that liposomal encapsulation can substantially enhance the therapeutic activity of irinotecan and emphasize the potential for using liposomal irinotecan to treat liver metastases.

Oxygen activation by photoexcited protoberberinium alkaloids fromMahonia aquifolium

Protoberberinium salts, i.e. berberine (I), palmatine (II) and jatrorrhizine (III) prepared from Mahonia aquifolium (Pursh) Nutt. belong to isoquinoline alkaloids possessing interesting biological activity (e.g. antibacterial, antimalarial, antitumor). The characteristic UV/Vis absorption band maxima of I-III iodide salts were found in regions 350 and 425 nm in dimethylsulfoxide (DMSO) and ethanol solvents, and were only negligibly influenced by substitution changes on the C-2 and C-3 positions. The fluorescence intensity of protoberberinium salts monitored in ethanol solutions was significantly lowered by iodide counter-ions, and decreased in the order berberine > palmatine > jatrorrhizine. EPR spectroscopy supplied evidence of the formation of super-oxide anion radicals and singlet oxygen upon irradiation of berberine in oxygenated DMSO solvent. The photochemical generation of O(2) (.-) and (1)O(2) in DMSO solutions of palmatine and jatrorrhizine was substantially lower, and probably reflected the replacement of a photolabile methylenedioxy group at C-2 and C-3 positions in the berberine molecule by two methoxy groups in palmatine, and methoxyl (C-2) and hydroxyl (C-3) substitution in jatrorrhizine. Additionally, the powder EPR spectra of protoberberinium iodides I-III measured at 290 K revealed the presence of single-line EPR signals (g(eff) = 2.0044), which were attributed to hydroperoxidic structures produced by the autoxidation process. The photochemical reactions of protoberbenium salts producing reactive oxygen species after UVA excitation should be integrated in biological activity investigations, as well as in their applications in skin disorder treatment.

The importance of tumor glucuronidase in the activation of irinotecan in a mouse xenograft model

The anticancer drug irinotecan (CPT-11) is activated to the potent topoisomerase I inhibitor, SN-38 (7-ethyl-10-hydroxycamptothecin), by esterases. SN-38 is in turn conjugated to the inactive SN-38 glucuronide (SN-38G). The reverse reaction is mediated by beta-glucuronidases. Hence, production of SN-38 may occur through either pathway. In this study we conducted in vitro studies to examine these two reactions in neuroblastoma xenograft tumors (NB1691) and compared the rates of SN-38 production with those observed in the liver and plasma of the host SCID (severe-combined immunodeficient) mice. The rate of formation of SN-38 from CPT-11 by esterases slowed considerably during a 60-min incubation, consistent with the known deacylation-limited nature of this reaction. For xenograft tumor tissue, K(m) and V(max) values of 1.6 microM and 4.4 pmol/min/mg of protein, respectively, were observed. By comparison, these parameters were estimated to be 6.9 microM and 9.4 pmol/min/mg for mouse liver and 2.1 microM and 40.0 pmol/min/mg for mouse plasma, respectively. The formation of SN-38 from SN-38G was very pronounced in both liver and xenograft tumor tissue, in which it was nonsaturable (0.125-50 microM) and time-independent (0-60 min). The derived values of V(max)/K(m) were 0.65 microl/min/mg for the tumor and 2.12 microl/min/mg for the liver preparations. Microdialysate experiments revealed the concentrations of SN-38G and CPT-11 in tumor to be comparable. At equal substrate concentrations, production of SN-38 from SN-38G in tumor extracts was comparable with that from CPT-11. Therefore, reactivation of SN-38 in the tumor by beta-glucuronidases may represent an important route of tumor drug activation for CPT-11.

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.

Metabolism of CPT-11. Impact on activity

Irinotecan (CPT-11) is a semi-synthetic camptothecin with a broad spectrum of clinical activity. It is a prodrug that is cleaved by esterases to the potent topoisomerase I poison, SN-38. In humans, this activation is relatively inefficient, but this may result in a more protracted formation of SN-38 lactone. Some intratumoral activation may also occur, but the significance of this process is uncertain. CPT-11 is metabolized by cytochrome P450 3A to yield a number of comparatively inactive compounds. SN-38 is glucurono-conjugated in the liver, and this metabolite, although inactive, may participate in the enterohepatic cycling of SN-38 after hydrolysis in the intestinal lumen. Overall, the production of SN-38 from CPT-11 is the result of the complex interplay of several metabolic pathways and the source of considerable interpatient variability.

Sensitive determination of irinotecan (CPT-11) and its active metabolite SN-38 in human serum using liquid chromatography-electrospray mass spectrometry

A couple of sensitive and accurate liquid chromatography-electrospray mass spectrometry (LC- S-MS) methods for the determination of the total forms of irinotecan and its active metabolite SN-38 in human serum, using the same chromatographic and detection conditions, is presented. Both used camptothecin as internal standard (I.S.). The sample pretreatment for irinotecan involved a simple protein precipitation with acetonitrile, whereas a liquid-liquid extraction was necessary for SN-38. A Symmetry C18, 3.5 microm (150 x 1 mm I.D.) reversed-phase column was used for the chromatographic separation, together with a gradient elution of acetonitrile in 5 mM ammonium formate buffer (pH 3) as mobile phase. After ionisation in the pneumatically-assisted electrospray source and in-source collision induced dissociation, acquisition was performed in the selected ion monitoring mode. Recoveries were 69 and 47% on average, detection limits 2.5 and 0.25 ng/ml and quantitation limits 10 and 0.5 ng/ml for irinotecan and SN-38, respectively. Reproducibility was good and the method was linear from limits of quantitation up to 10,000 ng/ml for irinotecan, and up to 100 ng/ml for SN-38. This sensitive and highly specific method is suitable both for pharmacokinetic studies and routine therapeutic drug monitoring.