Enantioselective separation of zopiclone on immobilized polysaccharide chiral stationary phase by HPLC: Method development and validation

A specific chiral HPLC method for lifitegrast and determination of enantiomeric impurity in drug substance, ophthalmic product and stressed samples

Lifitegrast is a lymphocyte function-associated antigen-1 (LFA-1) antagonist used to treat the indications and symptoms associated with dry eye disease (DED), one of the most common ocular surface diseases. Lifitegrast has a chiral center, and the S-enantiomer (S-Lif) is responsible for the therapeutic effects, while the R-enantiomer (R-Lif) lacks efficacy in the treatment of DED. Lifitegrast ophthalmic solution containing 5% lifitegrast was approved by the United States Food and Drug Administration (FDA) in July 2016 for the treatment of DED in patients 17 years of age and older. The objective of this study was to develop a chiral HPLC method for the determination of the enantiomeric impurity of lifitegrast in the drug substance and in the ophthalmic product. In addition, we aimed to investigate the effect of stress and stability conditions on the enantiomeric purity of lifitegrast in both drug substance and ophthalmic solution. During the method development studies, four known lifitegrast impurities (Lif. Imp. A-D) and stressed lifitegrast samples were injected to ensure the specificity of the developed method. The enantiomers of lifitegrast are well separated with a resolution of higher than 4.0. They are also well separated from the peaks of the diluent, impurities, and the placebo used to prepare the ophthalmic solution without interference in 20 min. Chiral separation was achieved using a Chiralpak AD-H column (250 × 4.6 mm, 5.0 μm) at 40 °C with a mobile phase consisting of a mixture of n-hexane, 2-propanol, and formic acid (500:500:2, v/v/v) at a flow rate of 1.0 mL/min and a detection wavelength of 260 nm. Methanol was used as the diluent, and the drug substance solution was found to be stable for 48 h at 15 °C. The optimized chiral HPLC method for lifitegrast was validated according to ICH Q2, and the calibration curves showed excellent linearity for R-Lif (0.0369 - 1.816 µg/mL). This is the first stability-indicating, specific / selective, sensitive, linear, precise, accurate, and robust chiral HPLC method for the determination of R-Lif in S-Lif. The amount of enantiomeric impurity R-Lif in S-Lif increased under all stress and photostability test conditions without exceeding the acceptable impurity limit, with the most significant increase observed at elevated temperatures (105 °C) for both the drug substance in powder form and the ophthalmic drug solution.

Enantioselective polar-organic mode high-performance liquid chromatographic separation of lifitegrast on immobilized polysaccharide stationary phase and its application to pH-dependent chiral interconversion studies

(S)-Lifitegrast (LFT) is the novel integrin antagonist, approved by the Food and drug administration, to treat signs and symptoms of dry eye disease. Synthesis of racemic LFT, preparative and analytical enantiomer separation, and chiral interconversion studies are lacking in the literature. Hence, in our study, synthesis of LFT racemate, chiral preparative purification procedure of enantiomer, and comprehensive analytical advancements are focused on rapid enantioselective separation and pH-dependent chiral interconversion studies. The synthesis of LFT racemate employed 2-amino-3-(3-(methylsulfonyl)phenyl)propanoic acid hydrochloride and 2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl chloride as starting materials. (R)-LFT was isolated from the racemate by preparative chiral HPLC and characterized using Q-TOF, FT-IR, NMR spectroscopy, and chiral HPLC. The purity of (R)-LFT was determined to have an enantiomeric excess of 99.12%. A precise, accurate, rapid HPLC-DAD enantioselective analytical method has been developed on Chiralpak IC [tris(3,5-dichloro phenyl carbamate) immobilized on cellulose] using water and methanol as mobile phase. The chiral interconversion study reveals 0.22% and 0.21% of interconversion of (S)-LFT into (R)-LFT at 80°C in pH 7.4 and 9.5 buffers, respectively, on the 24th day. An alternative route to enantioselective synthesis of LFT enantiomers by chromatographic separation is proposed. The validated enantioselective HPLC method will help to test the regular quality control samples.

Recent advances in chiral selectors immobilization and chiral mobile phase additives in liquid chromatographic enantio-separations: A review

For decades now, the separation of chiral enantiomers of drugs has been gaining the interest and attention of researchers. In 1991, the first guidelines for development of chiral drugs were firstly released by the US-FDA. Since then, the development in chromatographic enantioseparation tools has been fast and variable, aiming at creating a suitable environment where the physically and chemically identical enantiomers can be separated. Among those tools, the immobilization of chiral selectors (CS) on different stationary phases and the chiral mobile phase additives (CMPA) which have been progressed and studied extensively. This review article highlights the major advances in immobilization of CS together with their different recognition mechanisms as well as CMPA as a cheaper and successful alternative for chiral stationary phases. Moreover, the role of molecular modeling tool as a pre-step in the choice of CS for evaluating possible interactions with different ligands has been pointed up. Illustrations of reported methods and updates for immobilized CS and CMPA have been included.

Enantioseparation of Five Racemic N-alkyl Drugs by Reverse Phase HPLC Using Sulfobutylether-β-cyclodextrin as Chiral Mobile Phase Additive

Analytical enantioseparations of five N-alkyl drugs, fluoxetine hydrochloride, labetalol, venlafaxine hydrochloride, trans-paroxol and atropine sulfate, were investigated by RP-HPLC with sulfobutylether-β-cyclodextrin as chiral mobile phase additive. Effects of various factors such as composition of mobile phase, concentration of cyclodextrins and column temperature on retention and enantioselectivity were studied. Apparent formation constant between methanol, acetonitrile and sulfobutylether-β-cyclodextrin were determined to be 2.90 × 10^-3 and 1.00 × 10^-4 L mmol^-1 under 25 °C using UV-spectrophotometry. Van't Hoff plots were used to investigate thermodynamic parameters for enantiomers-stationary phase interaction and formation of inclusion complex. Two retention models were employed individually for evaluation of inclusion complexation between five racemates and sulfobutylether-β-cyclodextrin. The second model with complex adsorption was more accord with the retention behavior of fluoxetine hydrochloride, labetalol and venlafaxine hydrochloride enantiomers, while the first model was more consistent with the retention behaviors of trans-paroxol and atropine sulfate. In the selected mobile phase, stoichiometric ratio for both of inclusion complex was found to be 1:1. This article is protected by copyright. All rights reserved.

Anhydride-linked β-cyclodextrin-bonded silica stationary phases with enhanced chiral separation ability in liquid chromatography

β-Cyclodextrin can be functionalized by derivation of reactive hydroxyl on the ring due to its special chiral environment and structural characteristics, which can be used to identify or separate a variety of chiral substance. In this manuscript, a series of excellent chiral stationary phases for high-performance liquid chromatography were developed for enantioseparation by using anhydride modified β-cyclodextrin bearing chiral (R/S)-α-phenethylamine or (S)-(+)-2-amino-1-propanol. They were characterized by elemental analysis, Fourier transform infrared spectra (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and BET. These chiral stationary phases presented good resolution and repeatability, about 17 kinds of enantiomers were effectively separated. And most of enantiomers were separated better than those reported in the literature in the same both normal and reversed phase modes. The RSD values of R_s for repeatability and column-to-column were below 0.44% and 2.83%, respectively. All results revealed that these new CSPs show great prospect for chiral separation in actual applications.

An overview of chiral separations of pharmaceutically active substances by HPLC (2018-2020)

This review provides a brief survey of chiral separation of pharmaceutically active substances published over the last 3 years (2018-2020). Chiral separation of drugs is an important area of research. The control of enantiomeric purity and determination of individual enantiomeric drug molecules is a necessity especially for clinical, analytical, and regulatory purposes. Among chromatographic resolution methods, high-performance liquid chromatography based on chiral stationary phases remains the most popular and effective method used for chiral separation of various drugs. In this review, attention is paid to several classes of chiral stationary phases that have been the most frequently used for drug enantioseparation during this period.

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