A Rapid and Sensitive LC Method for Determination of Diastereomeric Purity of Tenofovir Alafenamide

Splitting and separation mechanism of tenofovir alafenamide fumarate chiral isomers based on indirect chiral ligand exchange chromatography

The isolation and analysis of chiral isomers are critical parts of the drug development process to ensure effective and safe drug administration to patients. Indirect chiral ligand exchange chromatography (ICLEC) was developed to separate and determine tenofovir alafenamide fumarate (TAF) and its diastereoisomer GS-7339, with a hypothesized separation mechanism. The effect of using a chiral column versus a standard C18 column on the separation of the TAF chiral isomer mixture was investigated. Various factors in ICLEC, including ligand type, ligand ratio, mobile phase composition, and column temperature, were optimized. The separation of TAF and GS-7339 was successfully achieved by selecting L-phenylalanine as the chiral selective agent and Cu(II) as the central metal ion, using a C18 column as the analytic column and a mobile phase of 20 mM ammonium dihydrogen phosphate buffer (pH = 4.0)-acetonitrile (79 : 21, v/v). The corresponding linearity range for TAF and GS-7339 indicated a good correlation with R2 > 0.9960. The average recoveries of TAF and GS-7339 ranged from 98.2% to 106.9%. None of the eight manufacturers detected GS-7339, and the percentage of TAF-labeled amounts in the drugs ranged from 95.0% to 98.5%. TAF tablets from eight manufacturers were of satisfactory quality. The separation mechanism of TAF and GS-7339 by ICLEC is due to the different spatial configurations of the two ternary complexes formed by the two chiral isomers, leading to differences in their thermodynamic stability and retention behavior. The established ICLEC method is economical, simple, and flexible, providing an effective strategy for studying chiral drug separation and analysis.

Analytical Lifecycle Management (ALM) and Analytical Quality by Design (AQbD) for analytical procedure development of related substances in tenofovir alafenamide fumarate tablets

Analytical procedure development for quantifying 10 impurities in Tenofovir Alafenamide Fumarate (TAF) tablets was a challenge for analytical and formulation researchers. The aim of this paper was to develop a robust, regulatory-flexible, application-specific Ultra Performance Liquid Chromatography (UPLC) analytical procedure using the Analytical Lifecycle Management (ALM) and the Analytical Quality by Design (AQbD) for the estimation of the TAF tablets. In this work, the Analytical Target Profile (ATP) for the analytical procedure and the Critical Analytical Attributes (CAAs) were identified. Through the risk assessment studies, the high-risk analytical conditions were found, and they were screened and optimized by the Design of Experiment (DoE) to obtain the Design Space (DS) and identify the working point. The prediction intervals were used to examine the robustness of the analytical procedure. And the procedure performance qualification and the continued procedure performance verification were used to ensure routine application of analytical procedure. Finally, the 10 impurities were separated within 20 min by UPLC. The success of this study demonstrates the usefulness of using ALM and AQbD for analytical procedure development and provides a reference for the analytical procedure development for other drugs.

Assessment of the greenness of new stability indicating micellar UPLC and HPTLC methods for determination of tenofovir alafenamide in dosage forms

In this study, a green stability indicating chromatographic methods were developed and validated for the quantitative determination of tenofovir alafenamide in the presence of its degradation products in bulk powder as well as in dosage forms. The first method was micellar UPLC in which separation was achieved on kinetex ® 1.7 μm HILIC 100A, LC column using an ecofriendly micellar mobile phase consisting (0.05 M sodium dodecyl sulphate and 0.05 M sodium dihydrogen phosphate, (pH 5.5) and 10% 1-propanol (70:30) at a flow rate of 1 mL min-1 with a UV detection at 210 nm. The second method depended on HPTLC method performed on HPTLC plates pre-coated with silica gel 60 F254 using a mobile phase consisting of n-butanol-acetic acid (7:3, v/v) and detection at 260 nm. Tenofovir alafenamide was subjected to stress conditions including alkaline and acidic degradation. Beer' law was obeyed over the concentration range of 1-18 μg mL-1 and 0.1-4 μg/spot for micellar UPLC and HPTLC methods, respectively. Both methods are successfully applied to the analysis of the drug in its tablets and validated according to ICH guidelines. In addition, their greenness was assessed using three different tools indicating their least hazardous effect on the environment.