Approaches to Assessment, Testing Decisions, and Analytical Determination of Genotoxic Impurities in Drug Substances

A sensitive UPLC-MS/MS method for the simultaneous assay and trace level genotoxic impurities quantification of SARS-CoV-2 inhibitor-Molnupiravir in its pure and formulation dosage forms using fractional factorial design

Two potential genotoxic impurities were identified (PGTIs)-viz. 4-amino-1-((2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)pyrimidin-2(1H)-one (PGTI-1), and 1-(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)pyrimidin-2,4(1H,3H)-one (PGTI-II) in the Molnupiravir (MOPR) synthetic routes. COVID-19 disease was treated with MOPR when mild to moderate symptoms occurred. Two (Q)-SAR methods were used to assess the genotoxicity, and projected results were positive and categorized into Class-3 for both PGTIs. A simple, accurate and highly sensitive ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method was optimized for the simultaneous quantification of the assay, and these impurities in MOPR drug substance and formulation dosage form. The multiple reaction monitoring (MRM) technique was utilized for the quantification. Prior to the validation study, the UPLC-MS method conditions were optimised using fractional factorial design (FrFD). The optimized Critical Method Parameters (CMPs) include the percentage of Acetonitrile in MP B, Concentration of Formic acid in MP A, Cone Voltage, Capillary Voltage, Collision gas flow and Desolvation temperature were determined from the numerical optimization to be 12.50 %, 0.13 %, 13.6 V, 2.6 kV, 850 L/hr and 375 °C, respectively. The optimized chromatographic separation achieved on Waters Acquity HSS T3 C18 column (100 mm × 2.1 mm, 1.8 µm) in a gradient elution mode with 0.13% formic acid in water and acetonitrile as mobile phases, column temperature kept at 35 °C and flow rate at 0.5 mL/min. The method was successfully validated as per ICH guidelines, and demonstrated excellent linearity over the concentration range of 0.5-10 ppm for both PGTIs. The Pearson correlation coefficient of each impurity and MOPR was found to be higher than 0.999, and the recoveries were in between the range of 94.62 to 104.05% for both PGTIs and 99.10 to 100.25% for MOPR. It is also feasible to utilise this rapid method to quantify MOPR accurately in biological samples.

Determination of Potential Genotoxic Impurities (Orthophenylene Diamine Dihydrochloride), 4'-Bromomethyl-2-Cyanobiphenyl, 4'(Dibromomethyl)[1,1'-Biphenyl]-2-Carbonitrile in Telmisartan by ESI-MS/MS

A sensitive, simple, rapid and robust LC-MS/MS method was developed for the determination of potential genotoxic impurities OPDA HCl (orthophenylene diamine dihydrochloride), bromo OTBN (4'-bromomethyl-2-cyanobiphenyl), dibromo (4'(dibromomethyl)[1,1'-biphenyl]-2-carbonitrile) in Telmisartan by using ESI-MS/MS Technic; the study was performed with gradient elution (time/% mobile phase B: 0/10, 3/10, 30/80, 35/80, 36/10, 40/10). The mobile phase consisted of a mixture of formic acid, methanol and acetonitrile. The buffer was degassed before running at a flow rate of 1.0 mL/min. The column temperature was at 40°C. The 20 μL volume of sample was injected per run and peaks were detected using DAD detector. The LC-ESI/MS/MS studies were carried out on Ultivo Triple Quadrupole LC/MS/MS (Agilent, USA) G6470A mass spectrometer, ion source voltage 3500 V, de clustering potential 40 V, entrance potential 10 V, with the nebulizer gas as nitrogen at 45 psi. The LC part consisted of Agilent 1260 series HPLC system with binary gradient pump with a degasser and an auto sampler. Inert sustain AQ-C18, 250 × 4.6 mm, 5-μm particle size was used for chromatographic separation. Developed method is validated as per ICH guidelines and found to be linear, accurate, specific, selective, precise and robust. Test solution was found to be stable up to 48 h. This method can be successfully applied for the determination of genotoxic impurities in Telmisarta for routine analysis and stability assessment.

Identification and validation of potential genotoxic impurities, 1,3-dichloro-2-propanol, and 2,3-dichloro-1-propanol, at subtle levels in a bile acid sequestrant, colesevelam hydrochloride, using hyphenated GC-MS technique

Potential genotoxic impurities (PGI) and N-nitrosamine impurities in active pharmaceutical ingredients (APIs) and their determination at low levels are substantial challenges for cholesterol-lowering agents in recent years. Herein we developed a robust, reliable, rapid, accurate and validated technique of gas chromatography equipped with a mass spectrometer (GC-MS) for quantifying subtle levels of 1,3-dichloro-2-propanol (PGI-I) and 2,3-dichloro-1-propanol (PGI-II) in colesevelam hydrochloride drug substance (bile acid sequestrant). The separation of colesevelam hydrochloride, PGI-I and PGI-II was executed with chromatographic technique using a capillary column, DB-624 measuring with 30 m × 0.32 mm × 1.8 μm specification of 6% cyanopropylphenyl-94% dimethylpolysiloxane copolymer and helium carrier gas. This developed technique gave a good intensity peak without any interference and extra masses at the retention times of 11.17 min for PGI-I and 11.59 min for PGI-II, which was adequate, with mass spectra (m/z) of 79 and 62, respectively. The method's sensitivity and linearity are demonstrated by its detection and quantification limits at subtle levels with correlation coefficients of 0.9965 for PGI-I and 0.9910 for PGI-II. The determination is mainly focused on improving sensitivity with the limits of detection and quantitation far below the specifications, which can support tighter limits. This results in a cost-effective and easily adoptable methodology having precise and accurate results in colesevelam hydrochloride API at subtle levels.

A selective and sensitive near-infrared fluorescent probe for in vivo real time tracking of exogenous and metabolized hydrazine, a genotoxic impurity

The hydrazine level in the liver and kidneys of mice after administration of isoniazid was monitored by using probe Hcy-DB.

Stepwise dissolution and composition determination of samples of multiple crystals using a dissolution medium containing aqueous alcohol and fluorocarbon phases

A biphasic medium gave controlled partial dissolution of crystals in multi-particle samples allowing the distribution of impurities to be determined.

Managing emerging mutagenicity risks: Late stage mutagenic impurity control within the atovaquone second generation synthesis

The mutagenic-impurity control strategy for a second generation manufacturing route to the non-mutagenic antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. Preliminary assessment highlighted multiple materials of concern which were largely discharged either through returning a negative bacterial mutagenicity assay or through confidence that the impurity would be purged during the downstream processing from when it was first introduced. Additional genotoxicity testing highlighted two materials of concern where initial assessment suggested that testing for these impurities at trace levels within the drug substance would be required. Following a thorough review of process purging detail, spiking and purging experimentation, and an understanding of the process parameters to which they were exposed an ICH M7 Option 4 approach could be justified for their control. The development of two 1H NMR spectroscopy methods for measurement of these impurities is also described as well as a proposed summary table for describing the underlying rationale for ICH M7 control rationales to regulators. This manuscript demonstrates that process purging of potential mutagenic impurities can be realised even when they are introduced in the later stages of a process and highlights the importance of scientific understanding rather than relying on a stage-counting approach.

Determination of composition distributions of multi-particle crystalline samples by sequential dissolution with concomitant particle sizing and solution analysis

Sequential dissolution of multi-particle samples with before-and-after sizing gave composition data that can be assigned to defined sample particle regions.

A highly efficient heterogeneous copper-catalyzed Chan–Lam coupling reaction of sulfonyl azides with arylboronic acids leading to N-arylsulfonamides

A highly efficient and practical method for the synthesis of N-arylsulfonamides has been developed by a heterogeneous copper-catalyzed Chan–Lam coupling between sulfonyl azides and boronic acids.

Mild Pd-catalyzed N-arylation of methanesulfonamide and related nucleophiles: avoiding potentially genotoxic reagents and byproducts

A convenient, general, and high yielding Pd-catalyzed cross-coupling of methanesulfonamide with aryl bromides and chlorides is reported. The use of this method eliminates concern over genotoxic impurities that can arise when an aniline is reacted with methanesulfonyl chloride. The application of this method to the synthesis of dofetilide is also reported.

Overall impact of the regulatory requirements for genotoxic impurities on the drug development process

In the last decade a considerable effort has been made both by the regulators and the pharmaceutical industry to assess genotoxic impurities (GTI) in pharmaceutical products. Though the control of impurities in drug substances and products is a well established and consolidated procedure, its extension to GTI has given rise to a number of problems, both in terms of setting the limits and detecting these impurities in pharmaceutical products. Several papers have dealt with this issue, discussing available regulations, providing strategies to evaluate the genotoxic potential of chemical substances, and trying to address the analytical challenge of detecting GTI at trace levels. In this review we would like to discuss the available regulations, the toxicological background for establishing limits, as well as the analytical approaches used for GTI assessment. The final aim is that of providing a complete overview of the topic with updated available information, to address the overall GTI issue during the development of new drug substances.