Considerations and perspectives on the practice of incurred sample reanalysis assessment for chiral drugs.

Given the inherent complexities of bioanalysis, the role of incurred sample reanalysis (ISR) is increasingly appreciated in regulatory bioanalysis. Incurred sample reanalysis has evolved as an integral part of an assay to ensure method reproducibility. The current regulatory ISR guidelines do not provide clarity regarding ISR assessment for chiral drugs comprising enantiomers. Because chiral assays evaluate two enantiomers, there are additional complexities associated with the ISR data generation and interpretation. Based on the current literature, the practices for conducting ISR in chiral methods were reviewed and assessed. While ISR was conducted in chiral methods for both enantiomers using the acceptance criteria prescribed for non-chiral methods, there may be a need to streamline the nuances of ISR data interpretation and define the ISR requirements for chiral methods. The article provides perspectives on the ISR of enantiomeric drugs, including strategy development, by providing various hypothetical scenarios and possible considerations for defining ISR evaluation for chiral assays.

Evaluation of the Generic Drug User Fee Act (GDUFA) Program for Fiscal Years 2013-2022.

The effectiveness of the regulatory initiatives, strategies, and incentives put forth in the first two authorizations of the Generic Drug User Fees Act (GDUFA) were evaluated using factors including the number of Abbreviated New Drug Application (ANDA) withdrawals and first-cycle approvals. GDUFA was originally authorized in 2012 for FY 2013-2017 (GDUFA I) and reauthorized for FY 2018-2022 (GDUFA II). ANDA approvals were analyzed from the Drugs @ FDA database covering 2013-2022. From the applications, the approval time, dosage form and route of administration (ROA), product indication, market status of the product, first generic status, company and company size filing the ANDA were noted. Despite the COVID pandemic, there was more than a 40% increase in ANDA approvals during GDUFA II relative to GDUFA I. Oral and parenteral drugs were the two leading categories of approved generics during both iterations of GDUFA. There was more than a 120% increase in withdrawn applications during GDUFA II, which reflects the partial refund that is now offered to incentivize companies to withdraw inadequate applications prior to review. This also appears to have contributed to an increase in the number of first-cycle approvals, which increased by 100% between GDUFA I and II. Due to the COVID-19 public health emergency, there was a decrease in activity within the generic drug program and market. Therefore, it is important to consider this impact when observing actual trends from this study.

Probing the Mechanisms Underlying the Transport of the Vinca Alkaloids by P-glycoprotein.

The efficacy of many cancer drugs is hindered by P-glycoprotein (Pgp), a cellular pump that removes drugs from cells. To improve chemotherapy, drugs capable of evading Pgp must be developed. Despite similarities in structure, vinca alkaloids (VAs) show disparate Pgp-mediated efflux ratios. ATPase activity and binding affinity studies show at least two binding sites for the VAs: high- and low-affinity sites that stimulate and inhibit the ATPase activity rate, respectively. The affinity for ATP from the ATPase kinetics curve for vinblastine (VBL) at the high-affinity site was 2- and 9-fold higher than vinorelbine (VRL) and vincristine (VCR), respectively. Conversely, VBL had the highest Km (ATP) for the low-affinity site. The dissociation constants (KDs) determined by protein fluorescence quenching were in the order VBL < VRL< VCR. The order of the KDs was reversed at higher substrate concentrations. Acrylamide quenching of protein fluorescence indicate that the VAs, either at 10 µM or 150 µM, predominantly maintain Pgp in an open-outward conformation. When 3.2 mM AMPPNP was present, 10 µM of either VBL, VRL, or VCR cause Pgp to shift to an open-outward conformation, while 150 µM of the VAs shifted the conformation of Pgp to an intermediate orientation, between opened inward and open-outward. However, the conformational shift induced by saturating AMPPNP and VCR condition was less than either VBL or VRL in the presence of AMPPNP. At 150 µM, atomic force microscopy (AFM) revealed that the VAs shift Pgp population to a predominantly open-inward conformation. Additionally, STDD NMR studies revealed comparable groups in VBL, VRL, and VCR are in contact with the protein during binding. Our results, when coupled with VAs-microtubule structure-activity relationship studies, could lay the foundation for developing next-generation VAs that are effective as anti-tumor agents. A model that illustrates the intricate process of Pgp-mediated transport of the VAs is presented.