Re-evaluating the need for chronic toxicity studies with therapeutic monoclonal antibodies, using a weight of evidence approach

To support registration of monoclonal antibodies (mAbs) for chronic indications, 6-month toxicity studies have historically been conducted. Experience with mAb development has shown a relatively benign and well-understood safety profile for this class, with most toxicity findings anticipated based on pharmacology. We evaluated whether a 6-month toxicity study is necessary to assess the long-term safety of mAbs. Data on First-in-Human (FIH)-enabling and chronic toxicity studies were shared for 142 mAbs submitted by 11 companies. Opportunities to further optimize study designs to reduce animal usage were identified. For 71% of mAbs, no toxicities or no new toxicities were noted in chronic studies compared to FIH-enabling study findings. New toxicities of potential concern for human safety or that changed trial design were identified in 13.5% of cases, with 7% being considered critical and 2% leading to program termination. An iterative, weight-of-evidence model which considers factors that influence the overall risk for a mAb to cause toxicity was developed. This model enables an evidence-based justification, suggesting when 3-month toxicity studies are likely sufficient to support late-stage clinical development and registration for some mAbs.

The use of recovery animals in nonclinical safety assessment studies with monoclonal antibodies: further 3Rs opportunities remain

Assessment of reversibility from nonclinical toxicity findings in animals with potential adverse clinical impact is required during pharmaceutical development, but there is flexibility around how and when this is performed and if recovery animals are necessary. For monoclonal antibodies (mAbs) and in accordance with ICH S6(R1) if inclusion of recovery animals is warranted, this need only occur in one study. Data on study designs for first-in-human (FIH)-enabling and later-development toxicity studies were shared from a recent collaboration between the NC3Rs, EPAA, Netherlands Medicines Evaluation Board (MEB) and 14 pharmaceutical companies. This enabled a review of practices on recovery animal use during mAb development and identification of opportunities to reduce research animal use. Recovery animals were included in 68% of FIH-enabling and 69% of later-development studies, often in multiple studies in the same program. Recovery groups were commonly in control plus one test article-dosed group or in all dose groups (45% of studies, each design). Based on the shared data review and conclusions, limiting inclusion of recovery to a single nonclinical toxicology study and species, study design optimisation and use of existing knowledge instead of additional recovery groups provide opportunities to further reduce animal use within mAb development programs.

Exploring the Definition of "Similar Toxicities": Case Studies Illustrating Industry and Regulatory Interpretation of ICH S6(R1) for Long-Term Toxicity Studies in One or Two Species

ICH S6 (R1) states that safety evaluation of biotherapeutics should normally include 2 relevant species when available (i.e., a rodent and non-rodent species in which the test material is pharmacologically active), at least for short-term toxicology studies (generally supporting Phase I trials). For subsequent long-term toxicology studies (e.g., chronic studies up to 6 months dosing duration), there are options to reduce to only one species when justified, including when the mechanism of action of the biologic is well-understood or the toxicity findings in the short-term studies are “similar” in both the rodent and non-rodent species. Across the industry, around 25 to 33% of biologics assess multiple species within short-term toxicity studies but it is often unclear how different companies and regulators are applying the ICH S6 (R1) principles of “similar toxicity profiles” to progress with either 1 or 2 species in the long-term studies, in particular whether the absence of toxicities is considered within this definition. Sponsors may potentially continue to use 2 species to avoid regulatory risk and potential delays in development timelines, representing missed opportunities for reducing animal use, particularly of non-human primates, during drug development.

This article summarizes presentations from a symposium at the 41^st Annual meeting of the American College of Toxicology (ACT) in November 2020, in which industry case studies and regulatory perspectives addressed considerations and decisions for using 1 or 2 species for long-term toxicity studies, highlighting any common themes or experience that could be applicable for use in future decision-making.

Safety Assessment of 1-Hydroxyethyl 4,5-Diamino Pyrazole Sulfate as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) reviewed the safety of 1-Hydroxyethyl 4,5-Diamino Pyrazole Sulfate, which functions as an oxidative hair dye ingredient. The Panel reviewed relevant data provided in this safety assessment, and concluded that 1-Hydroxyethyl 4,5-Diamino Pyrazole Sulfate is safe in the present practices of use and concentration in oxidative hair dye formulations.

Time Course for Onset and Recovery from Effects of a Novel Male Reproductive Toxicant: Implications for Apical Preclinical Study Designs

In the pharmaceutic ICH S5(R2) guidelines for reproductive toxicity testing, a premating dose duration of 14 days is considered sufficient for assessment of male fertility for compounds that are not testicular toxicants. A novel α7 subtype of nicotinic acetylcholine receptor (α7nAChR) agonist, originally intended for treatment of Alzheimer's disease, did not cause changes in sperm counts, motility, or testicular histopathology in rat toxicity studies of up to 6 months duration. However, profound decrements in male fertility (reduced pregnancy rates and litter sizes) occurred after 11 weeks of dosing in male rats. In two time-course investigations, dosed male rats were paired with undosed females after 5, 14, and 28 daily doses and again after 2 and 4 weeks off-dose. Effects on male fertility were undetectable after 5 days. After 14 days, there was no effect on pregnancy rate, but preimplantation losses were increased. Effects on both pregnancy rates and preimplantation losses were clearly detectable after 28 days, but were of lesser magnitude than after 11 weeks of dosing. Fertility recovered rapidly after dose cessation. These studies illustrate the sensitivity of a long premating dose period at revealing hazard and determining the magnitude of effect on male fertility for compounds that are intended for chronic administration and do not affect testicular histopathology.

Evaluation of genotoxicity testing of FDA approved large molecule therapeutics

Large molecule therapeutics (MW>1000daltons) are not expected to enter the cell and thus have reduced potential to interact directly with DNA or related physiological processes. Genotoxicity studies are therefore not relevant and typically not required for large molecule therapeutic candidates. Regulatory guidance supports this approach; however there are examples of marketed large molecule therapeutics where sponsors have conducted genotoxicity studies. A retrospective analysis was performed on genotoxicity studies of United States FDA approved large molecule therapeutics since 1998 identified through the Drugs@FDA website. This information was used to provide a data-driven rationale for genotoxicity evaluations of large molecule therapeutics. Fifty-three of the 99 therapeutics identified were tested for genotoxic potential. None of the therapeutics tested showed a positive outcome in any study except the peptide glucagon (GlucaGen®) showing equivocal in vitro results, as stated in the product labeling. Scientific rationale and data from this review indicate that testing of a majority of large molecule modalities do not add value to risk assessment and support current regulatory guidance. Similarly, the data do not support testing of peptides containing only natural amino acids. Peptides containing non-natural amino acids and small molecules in conjugated products may need to be tested.