Considerations in the extrapolation of drug toxicity between humans and dogs

Comparative epigenomics to clinical trials in human breast cancer and canine mammary tumor

Epigenetics and epigenomics are captivating fields of molecular biology, dedicated to the exploration of heritable alterations in gene expression and cellular phenotypes, which transpire devoid of any discernible modifications to the fundamental DNA sequence. This intricate regulatory apparatus encompasses multiple mechanisms, prominently featuring DNA methylation, histone modifications, and the involvement of non-coding RNA molecules in pivotal roles. To achieve a comprehensive grasp of these diverse mechanisms, it is imperative to conduct research employing animal models as proxies for human studies. Since experimental animal models like mice and rats struggle to replicate the diverse environmental conditions experienced by humans, this review focuses on comparing common epigenetic alterations in naturally occurring tumors in canine models, which share the human environment, with those in humans. Through this, we emphasize the importance of an epigenetic regulation in the comparative medical approach to a deeper understanding of cancers and further development of cancer treatments. Additionally, we elucidate epigenetic modifications pertinent to specific developmental stages, the ageing process, and the progression of various diseases.

A cross-species assessment of in silico prediction methods of steady-state volume of distribution using Simcyp simulators

Predicting steady-state volume of distribution (Vss) is a key component of pharmacokinetic predictions and often guided using preclinical data. However, when bottom-up prediction from physiologically-based pharmacokinetic (PBPK) models and observed Vss misalign in preclinical species, or predicted Vss from different models varies significantly, no consensus exists for selecting models or preclinical species to improve the prediction. Through systematic analysis of Vss prediction across rat, dog, monkey, and human, using common methods, a practical strategy for predicting human Vss, with or without integration of preclinical PK information is warranted. In this analysis, we curated a dataset of 57 diverse compounds with measured physicochemical and protein binding data, together with observed Vss in these species. Using a bottom-up approach, prediction performance was consistent across species for each method. Although no method consistently outperformed others for all compound types and across species, M2 (Rodgers-Rowland method) performed marginally better for acids. Comparable compound-specific global tissue Kp scalars were needed to match observed Vss for both, human and preclinical species. Consequently, application of geometric mean values of preclinical Kp scalar to human Vss prediction improved accuracy. We propose a decision tree for human Vss prediction using PBPK methods with or without integrating preclinical PK information.

Experimental animal models for brain abscess: a systematic review

BACKGROUND

Brain abscess (BA) is a rare, but severe infection and experimental BA animal models may prove crucial for advances in treatment. This review describes the development of experimental BA models and the clinical advances obtained from these, in a historical perspective.

MATERIAL AND METHODS

Experimental BA studies from inception until June 15, 2022, were included by searching the PubMed and Embase databases. Inclusion required the use of an experimental BA animal model. Non-bacterial BA models, in vitro studies, veterinarian case-reports, and articles written in non-English language were excluded. Bias was not systematically assessed, and the review was not registered at the PROSPERO.

RESULTS

79 studies were included. The majority of animal BA models have been based on small rodents using Staphylococcus aureus. The models have delineated the natural development of BA and provided detailed descriptions of the histopathological characteristics consisting of a necrotic centre surrounded by layers of inflammatory cells and fibroblasts encapsulated by a dense collagenous layer. Radiological studies of animal BA have been shown to correlate with the corresponding stages of human BA in both computed tomography and magnetic resonance imaging and may guide diagnosis as well as the timing of neurosurgical intervention. Moreover, pharmacokinetic studies of the intracavitary penetration of various antimicrobials have helped inform medical treatment of BA. Other studies have examined the diverse effects of corticosteroids including decreased cerebral oedema, intracranial pressure, and intracavitary drug concentration, whereas concerns on decreased or weakened capsule formation could not be confirmed. Finally, studies on the immunological response to BA have highlighted potential future immunomodulatory targets.

CONCLUSIONS

Animal models have been vital for improvements in the management of BA. Experimental BA models resembling human disease including polymicrobial infection by oral cavity flora in large animals are needed.

Cyanotoxins associated with macrophytes in Berlin (Germany) water bodies - Occurrence and risk assessment

Fatal dog poisoning after uptake of neurotoxic cyanobacteria associated with aquatic macrophytes in Tegeler See (Berlin, Germany) raised concerns about critical exposure of humans, especially children, to cyanotoxins produced by macrophyte associated cyanobacteria during recreational activity. From 2017 to 2021 a total of 398 samples of macrophytes washed ashore at bathing sites located at 19 Berlin lakes were analysed for anatoxins, microcystins, and cylindrospermopsins, as were 463 water samples taken in direct proximity to macrophyte accumulations. Cyanotoxins were detected in 66 % of macrophyte samples and 50 % of water samples, with anatoxins being the most frequently detected toxin group in macrophyte samples (58 %) and cylindrospermopsins in water samples (41 %). Microcoleus sp. associated with the water moss Fontinalis antipyretica was identified as anatoxin producing cyanobacterium in isolated strains as well as in field samples from Tegeler See. Anatoxin contents in macrophyte samples rarely exceeded 1 μg/g macrophyte fresh weight and peaked at 9. 2 μg/g f.w. Based on established toxicological points of departure, a critical anatoxin content of macrophyte samples of 3 μg/g f.w. is proposed. Five samples, all taken in Tegeler See and all associated with the water moss Fontinalis antipyretica, exceeded this value. Contents and concentrations of microcystins and cylindrospermopsins did not reach critical levels. The potential exposure risks to anatoxins for children and dogs are assessed and recommendations are given.

Comparison of Canine and Human Physiological Factors: Understanding Interspecies Differences that Impact Drug Pharmacokinetics

This review is a summary of factors affecting the drug pharmacokinetics (PK) of dogs versus humans. Identifying these interspecies differences can facilitate canine-human PK extrapolations while providing mechanistic insights into species-specific drug in vivo behavior. Such a cross-cutting perspective can be particularly useful when developing therapeutics targeting diseases shared between the two species such as cancer, diabetes, cognitive dysfunction, and inflammatory bowel disease. Furthermore, recognizing these differences also supports a reverse PK extrapolations from humans to dogs. To appreciate the canine-human differences that can affect drug absorption, distribution, metabolism, and elimination, this review provides a comparison of the physiology, drug transporter/enzyme location, abundance, activity, and specificity between dogs and humans. Supplemental material provides an in-depth discussion of certain topics, offering additional critical points to consider. Based upon an assessment of available state-of-the-art information, data gaps were identified. The hope is that this manuscript will encourage the research needed to support an understanding of similarities and differences in human versus canine drug PK.