Assessing the Relevance of Solution Phase Stress Testing of Solid Dosage Form Drug Products: A Cross-Industry Benchmarking Study

Identification and Characterization of Rotigotine Degradation Products by HPLC Coupled DAD and CAD Detectors and HRMS Through Q-Orbitrap and Electrospray Ionization

Rotigotine (RTG) is a dopamine agonist used in the treatment of Parkinson's disease. As it is susceptible to oxidation, stability studies must be carefully designed for the identification and characterization of all possible degradation products. Here, RTG degradation was evaluated according to the International Conference on Harmonization guidelines under various stress conditions, including acidic and basic hydrolysis, oxidative, metallic, photolytic, and thermal conditions. Additionally, more severe stress conditions were applied to induce RTG degradation. Significant degradation was only observed under oxidative and photolytic conditions. The samples were analyzed by high performance liquid chromatography coupled to photodiode array detectors, charged aerosol, and high-resolution mass spectrometry. Chromatographic analyses revealed the presence of eight substances related to RTG, four of which were already described and were qualified impurities (impurities B, C, K and E) and four new degradation products (DP-1 - DP-4), whose structures were characterized by high-resolution mass spectrometry through Q-Orbitrap and electrospray ionization. In the stress testing of the active pharmaceutical ingredient in solid form, significant RTG degradation was observed in the presence of the oxidative matrix. The results corroborate the literature that confirm the high susceptibility of RTG to oxidation and the importance of using different detectors to detect degradation products in forced degradation studies.

Pharmaceutical Forced Degradation (Stress Testing) Endpoints: A Scientific Rationale and Industry Perspective

Forced degradation (i.e., stress testing) of small molecule drug substances and products is a critical part of the drug development process, providing insight into the intrinsic stability of a drug that is foundational to the development and validation of stability-indicating analytical methods. There is a lack of clarity in the scientific literature and regulatory guidance as to what constitutes an "appropriate" endpoint to a set of stress experiments. That is, there is no clear agreement regarding how to determine if a sample has been sufficiently stressed. Notably, it is unclear what represents a suitable justification for declaring a drug substance (DS) or drug product (DP) "stable" to a specific forced degradation condition. To address these concerns and to ensure all pharmaceutically-relevant, potential degradation pathways have been suitably evaluated, we introduce a two-endpoint classification designation supported by experimental data. These two endpoints are 1) a % total degradation target outcome (e.g., for "reactive" drugs) or, 2) a specified amount of stress, even in the absence of any degradation (e.g., for "stable" drugs). These recommended endpoints are based on a review of the scientific literature, regulatory guidance, and a forced degradation data set from ten global pharmaceutical companies. The experimental data set, derived from the Campbell et al. (2022) benchmarking study,1 provides justification for the recommendations. Herein we provide a single source reference for small molecule DS and DP forced degradation stress conditions and endpoint best practices to support regulatory submissions (e.g., marketing applications). Application of these forced degradation conditions and endpoints, as part of a well-designed, comprehensive and a sufficiently rigorous study plan that includes both the DS and DP, provides comprehensive coverage of pharmaceutically-relevant degradation and avoids unreasonably extreme stress conditions and drastic endpoint recommendations sometimes found in the literature.

The degradation map process - a tool for obtaining a lean stability strategy in drug development

Stability is fundamental when exploring a drug candidate's potential as a drug product. During the pharmaceutical industry drug development process information regarding stability and degradation are captured in different departments, e.g. from discovery to operations, and will be included in the overall control strategy. With a profound understanding of a drug candidate's degradation chemistry, a science and risk based approach in progressing a lean stability strategy is possible. This case study present a clear and visible concept to facilitate a lean stability strategy by the use of degradation maps and describes a process for how these can be used during drug development. The understanding of possible and/or observed degradation pathways will guide the design of the drug product and stability studies in development. A degradation map displays degradation pathways with short comments on the reaction/mechanism involved. The degradation map process starts with a theoretical degradation map. The map is updated as the drug project progresses, preferably after forced degradation experiments, after compatibility studies and finally when the late stage formulation is set. The degradation map should be used to capture information of intrinsic chemical properties of the active pharmaceutical ingredient (API) and can thereby be used to mitigate stability issues. The map is foremost a cross-functionally available tool collecting and visualizing stability information throughout the development process, and as such a valuable tool to efficiently develop a lean stability strategy.