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Key components of toxicology studies for large molecules
While the fundamental goals of studies for large and small molecules are similar, there are notable differences in their requirements. Both types require pharmacology, pharmacokinetics, and toxicology studies, but the specifics can vary significantly. Large molecule studies often incorporate additional analyses, such as anti-drug antibody (ADA) sampling.
These analyses provide crucial data on how the drug interacts with the body, focusing on the immune system and potentially toxic effects. For biologics, it is essential to design these studies carefully to capture relevant data that help predict human responses.
These studies also involve different species selection criteria, which should include the following elements:
- Criteria for selecting appropriate species: The choice of species is based on pharmacological relevance rather than metabolic similarity, as is common with small molecules.
- Challenges in finding suitable species: Large molecules often interact with specific human receptors, necessitating species with receptors that are highly homologous to human. This can be challenging, as not all laboratory animals have receptors similar to humans.
- Use of non-human primates and alternative models: Non-human primates are frequently used due to their close genetic resemblance to humans. In cases where relevant targets are absent in common species, alternative strategies to assess safety, including transgenic mice, surrogate molecules, or human cell-based assays, may be acceptable when scientifically justified.
The challenges of immunogenicity
Immunogenicity is a significant concern for large molecules. This response can lead to the development of ADAs, which may neutralize the drug’s therapeutic effects or cause unexpected toxicities. Preclinical assessment of immunogenicity does not translate well to the clinic, but it can help predict the clinical response and provide insight for the consequences of immunogenicity. The real value in preclinical ADA data is to interpret the toxicology study itself. For example, if exposure measured by toxicokinetic sampling decreases during the study, it may be due to neutralization of the drug by ADA. Lowered exposure also affects any signs of toxicity, and if there are not animals available to help explain the findings, the results may be confounded.
ADA sampling involves collecting blood from study animals at various times to detect antibodies. This process helps interpret toxicology findings and assesses the potential impact of immunogenicity on drug safety and efficacy. The frequency of ADA blood sampling during preclinical studies can vary based on the study design, the therapeutic candidate, and regulatory requirements. Typically, blood sampling for ADA analysis might be included several times depending on the duration of the study to provide a comprehensive profile of the immune response to the therapeutic protein.
Immunogenicity can also complicate the interpretation of toxicology data, as immune responses may obscure or mimic toxic effects. Understanding and accounting for immunogenicity is essential to assess a drug’s safety profile accurately. Strategies to mitigate immunogenicity include optimizing dosing regimens to reduce immune responses and incorporating immunosuppressive treatments in study designs to manage severe immune reactions.
Safety pharmacology considerations
Including assessments of the central nervous system, cardiovascular, and respiratory functions is critical, as these evaluations provide a comprehensive understanding of the drug’s safety profile.
ICH Guidance S6 allows integrating safety pharmacology endpoints into toxicology studies so that separate standalone studies are not necessarily needed for large molecules. The cardiovascular and respiratory endpoints can be obtained using jacketed external telemetry (JET) in non-rodents. The CNS assessments can be performed within the rodent study, requiring that animals’ identities (dose group) are blinded temporarily so that CNS observations can be done objectively. This approach is consistent with the goal of minimizing the number of animals used in drug development and saves time and resources, leading to a more efficient path to IND submission.
Formulation “analysis”
Formulation analysis for large molecules can be performed spectrophotometrically using a UV Vis instrument. The concentration of the test article is measured based on absorbance of light—a convenient way to measure concentration, but it does not indicate purity, stability, or activity of the test article. Additional characterization using HPLC for purity (which indicates stability) and in vitro binding studies for activity are required for large molecule development.
Early formulation analysis is fundamental to ensure the drug remains stable and functional throughout the study. This early testing helps to identify any potential issues with the formulation before they become significant problems. By doing so, researchers can avoid complications that could delay the IND submission process, thereby ensuring a smoother and more efficient path to approval.
Early planning and regulatory considerations
Early engagement with regulatory bodies can identify potential issues and streamline the submission process, preventing delays and helping drug manufacturers more effectively meet requirements. Working closely with regulatory authorities from the outset can clarify expectations and facilitate smoother communication. This proactive approach helps address unique challenges early and align study designs with regulatory expectations. Providing detailed, well-documented study plans and being responsive to feedback can significantly enhance the likelihood of a successful IND submission.
The bottom line
Successful toxicology studies for large molecule drugs hinge on careful planning, appropriate species selection, thorough immunogenicity assessment, and robust formulation analysis. Avoid common pitfalls by involving experienced lab testing partners familiar with the IND process and large molecule toxicology studies. These partners can provide valuable insights into the regulatory environment and help navigate complex requirements. Engage regulatory authorities early, adopt best practices in study design, and ensure all analyses comply with current guidelines.
By focusing on these key considerations, drug developers and sponsors can navigate the complexities of large molecule toxicology studies, ultimately accelerating their IND submissions and bringing innovative therapies to patients more quickly.
Tina Rogers
Tina Rogers, Ph.D., DABT, MBA an expert in preclinical drug development services, joined WuXi AppTec Laboratory Testing Division in 2022. Her leadership positions include senior technical director at WuXi AppTec, vice president of preclinical sciences at Altasciences (formerly SNBL USA), executive vice president, and director of research at M.P.I. Research (now Charles River), and vice president of drug development at Southern Research Institute. She has served as an advisor and driven growth and profitability in all of her leadership roles. Dr. Rogers holds a doctoral degree in molecular and cellular biology and pathobiology from the Medical University of South Carolina and an M.B.A. from Auburn University. She has a broad technical background, including cell biology, immunology, toxicology, cell and gene therapy, sepsis, inflammation, BL-3 and select agents, flow cytometry and predictive/in vitro toxicology. Dr. Rogers also serves as a board member for several biotech, academic and not-for-profit institutions and is a Diplomate of the American Board of Toxicology (DABT).
Filed Under: Biologics, Regulatory affairs
