Identification and characterization of urapidil stress degradation products by LC-Q-TOF-MS and NMR: Toxicity prediction of degradation products.

Urapidil, an antihypertensive drug is subjected to various stress conditions (acidic, basic, neutral, oxidative and photolytic) as per ICH guidelines. A stability indicating HPLC method was developed using InertSustain C8 (250 × 4.6 mm; 5 µm) column and 10 mM ammonium formate (pH 3.5) with gradient elution at a flow rate of 1 mL/min to separate all the DPs. The drug was susceptible to acidic and basic hydrolysis, oxidative and photolytic stress conditions in the solution phase and stable in neutral solution phase and photolytic solid state conditions. A total of five DPs were detected under different stress conditions including DP4 which was previously reported in the literature. An extensive fragmentation pattern of drug and DPs were established using LC-Q-TOF-MS which aided the characterization of DPs. The ambiguity in the position of N-oxide formation in DP5 was confirmed by NMR studies. In silico toxicity of the drug and its DPs were also evaluated. The plausible mechanism of DPs formation was explained.

In vivo metabolite identification of acotiamide in rats using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry.

Acotiamide hydrochloride (ACT) is a drug used for the treatment of functional dyspepsia. Understanding which metabolites are likely to be formed in vivo is essential for interpreting pharmacology, pharmacokinetic and toxicology data. The metabolism of ACT has been investigated using a specific and sensitive liquid chromatography positive ion electrospray ionization high-resolution tandem mass spectrometry method. In vivo samples including rat plasma, urine and feces were collected separately after dosing healthy Sprague-Dawley rats at a dose of 20 mg kg -1 ACT at different time points up to 24 h. The metabolites were enriched by optimized sample preparation involving protein precipitation using acetonitrile followed by solid-phase extraction. The mass defect filter technique was used for better detection of both predicted and unexpected drug metabolites with the majority of interference ions removed. The structural elucidation of the metabolites was performed by comparing their [M + H]+ ions and their product ions with those of the parent drug. As a result, a total of seven hitherto unknown metabolites were characterized from the biosamples. The only phase I metabolite detected was N-despropyl acotiamide, whereas six phase II glucuronide conjugate metabolites were identified.

LC-ESI-MS/MS evaluation of forced degradation behaviour of silodosin: In vitro anti cancer activity evaluation of silodosin and major degradation products.

Silodosin (SLD) a novel α1-adrenoceptor antagonist was subjected to forced degradation involving hydrolysis (acidic, alkaline and neutral), oxidative, photolysis and thermal stress, as per ICH specified conditions. The drug underwent significant degradation under hydrolytic (acidic, alkaline and neutral) and oxidative stress conditions whereas, it was found to be stable under other stress conditions. A rapid, precise, accurate and robust chromatographic method for the separation of the drug and its degradation products (DPs) was developed on a Fortis C18 analytical column (150×4.6mm, 5µm) using 0.1% formic acid and acetonitrile as a mobile phase in gradient elution mode at a flow rate of 1.0mL/min. A total of 5 (DP 1 to DP 5) hitherto unknown DPs were identified by LC-ESI-TOF-MS/MS experiments and accurate mass measurements. The most probable mechanisms for the formation of DPs have been proposed based on a comparison of the fragmentation of the [M+H]+ ions of silodosin and its DPs. The major DPs (DP 1 and DP 2) were isolated and evaluated for anticancer activity using PC3 (human prostate cancer) cell lines by MTT assay. The results revealed that silodosin, DP 1 and DP 2 have potential anticancer activity with IC50 values (µM) 72.74 (±4.51), 25.21 (±2.36), and, 114.07 (±11.90) respectively.

Quantitation of acotiamide in rat plasma by UHPLC-Q-TOF-MS: method development, validation and application to pharmacokinetics.

A novel, sensitive and selective ultra-high-performance liquid chromatography-electrospray ionization mass spectrometry method was developed and validated for the quantification of acotiamide (ACT), a first-in-class drug used in functional dyspepsia, in rat plasma. A simple protein precipitation method with acetonitrile as precipitating solvent was used to extract ACT from rat plasma. ACT and an internal standard (mirabegron, IS) were separated on an Agilent poroshell EC C18 column (50 × 3.0 mm, 2.7 µm) using methanol-10 mM ammonium acetate binary gradient mobile phase at a flow rate of 0.4 mL/min over 4 min run time. Detection was performed using target ions of [M + H](+) at m/z 451.2010 for ACT and m/z 397.1693 for IS in selective ion mode. The method was validated in the calibration range of 1.31-1000 ng/mL. All the validation parameters were well within the limits. The method demonstrated good performances in terms of intra- and inter-day precision (3.27-12.60% CV) and accuracy (87.96-104.94%). Thus the present ultra-high-pressure liquid chromatograhy-high-resolution mass spectrometry method for determination of ACT in rat plasma, is highly sensitive and rapid with a short run-time of 4 min, can be suitable for high sample throughput and for large batches of biological samples in pharmacokinetic studies. This method can be extended to measure plasma concentrations of ACT in humans to understand drug metabolism, drug interaction and adverse effects.

Characterization of forced degradation products of pazopanib hydrochloride by UHPLC-Q-TOF/MS and in silico toxicity prediction.

Pazopanib (PZ), an anti-cancer drug, was subjected to forced degradation under hydrolytic (acid, base and neutral), oxidative, photolytic and thermal stress conditions as per International Conference on Harmonization guidelines. A selective stability indicating validated method was developed using a Waters Acquity UPLC HSS T3 (100 × 2.1 mm, 1.7 µm) column in gradient mode with ammonium acetate buffer (10 mM, pH 5.0) and acetonitrile. PZ was found to degrade only in photolytic conditions to produce six transformation products (TPs). All the TPs were identified and characterized by liquid chromatography/atmospheric pressure chemical ionization-quadrupole-time of flight mass spectrometry experiments in combination with accurate mass measurements. Plausible mechanisms have been proposed for the formation of TPs. In silico toxicity was predicted using TOPKAT and DEREK softwares for all the TPs. The TP, N4-(2,3-dimethyl-2H-indazol-6-yl)-N4-methylpyrimidine-2,4-diamine, was found to be genotoxic, whereas all other TPs with sulfonamide moiety were hepatotoxic. The data reported here are expected to be of significance as this study foresees the formation of one potential genotoxic and five hepatotoxic degradation/transformation products.

Forced degradation of fingolimod: effect of co-solvent and characterization of degradation products by UHPLC-Q-TOF-MS/MS and 1H NMR.

Fingolimod (FGL), an immunomodulator drug for treating multiple sclerosis, was subjected to hydrolysis (acidic, alkaline and neutral), oxidation, photolysis and thermal stress, as per International Conference on Harmonization specified conditions. The drug showed extensive degradation under base hydrolysis, however, it was stable under all other conditions. A total of three degradation products (DPs) were observed. The chromatographic separation of the drug and its degradation products was achieved on a Fortis C18 (100×2.1mm, 1.7µm) column with a mobile phase composed of 0.1% formic acid (Solvent A) and acetonitrile (Solvent B) in gradient mode. All the DPs were identified and characterized by liquid chromatography-quadrupole time of flight-mass spectrometry (LC-Q-TOF-MS) in combination with accurate mass measurements. The major DP was isolated and characterized by Nuclear Magnetic resonance spectroscopy. This is a typical case of degradation where acetonitrile used as co-solvent in stress studies, reacts with FGL in base hydrolytic conditions to produce acetylated DPs. Hence, it can be suggested that acetonitrile is not preferable as a co-solvent for stress degradation of FGL. The developed UHPLC method was validated as per ICH guidelines.

Characterization of forced degradation products of ketorolac tromethamine using LC/ESI/Q/TOF/MS/MS and in silico toxicity prediction.

Ketorolac, a nonsteroidal anti-inflammatory drug, was subjected to forced degradation studies as per International Conference on Harmonization guidelines. A simple, rapid, precise, and accurate high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (LC/ESI/Q/TOF/MS/MS) method has been developed for the identification and structural characterization of stressed degradation products of ketorolac. The drug was found to degrade in hydrolytic (acidic, basic, and neutral), photolytic (acidic, basic, and neutral solution), and thermal conditions, whereas the solid form of the drug was found to be stable under photolytic conditions. The method has shown adequate separation of ketorolac tromethamine and its degradation products on a Grace Smart C-18 (250 mm × 4.6 mm i.d., 5 µm) column using 20 mM ammonium formate (pH = 3.2): acetonitrile as a mobile phase in gradient elution mode at a flow rate of 1.0 ml/min. A total of nine degradation products were identified and characterized by LC/ESI/MS/MS. The most probable mechanisms for the formation of degradation products have been proposed on the basis of a comparison of the fragmentation of the [M + H](+) ions of ketorolac and its degradation products. In silico toxicity of the drug and degradation products was investigated by using topkat and derek softwares. The method was validated in terms of specificity, linearity, accuracy, precision, and robustness as per International Conference on Harmonization guidelines.

Identification of forced degradation products of tamsulosin using liquid chromatography/electrospray ionization tandem mass spectrometry.

A rapid and gradient high-performance liquid chromatography combined with quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS) method has been developed for the identification and structural characterization of stressed degradation products of tamsulosin. Tamsulosin, a selective α1-adrenoceptor antagonist, was subjected to forced degradation studies under hydrolytic (acid, base and neutral), oxidative, photolytic and thermal stress conditions as per ICH guidelines Q1A (R2). The drug degraded significantly under hydrolytic (base and neutral), thermal, oxidative and photolytic conditions, while it was stable to acid hydrolytic stress conditions. A total of twelve degradation products were formed and the chromatographic separation of the drug and its degradation products were achieved on a GRACE C-18 column (250mm×4.6mm, 5µm). All the degradants have been identified and characterized by LC/ESI-MS/MS and accurate mass measurements. To elucidate the structures of degradation products, fragmentation of the [M+H](+) ions of tamsulosin and its degradation products was studied by using LC-MS/MS experiments combined with accurate mass measurements. The product ions of all the protonated degradation products were compared with the product ions of protonated tamsulosin to assign most probable structures for the observed degradation products.