A pharmacologically relevant species is an animal species in which a test substance is pharmacologically active due to the expression of its receptor or, in the case of monoclonal antibodies, its epitope. The selection of such a species determines whether nonclinical findings can be meaningfully interpreted for humans. Studies in a non-relevant animal species can be misleading under ICH S6(R1) and are therefore not considered a substitute for an appropriate species.<\/p>\n
For biopharmaceuticals, superficial similarity between humans and animals is not sufficient. What matters are target sequence homology, relative binding affinity, receptor or ligand occupancy, kinetic properties, and functional activity. The FDA Addendum to ICH S6(R1) requires that these aspects be assessed in species-specific cell-based systems, in vivo pharmacology studies, or in vivo toxicology studies.<\/p>\n
A known biological effect or a pharmacodynamic marker can demonstrate that the active substance is functionally active in the animal species. For target structures with very low expression in healthy standard animals, affinity and activity in cell models may be sufficient for species selection. The selection also takes into account the planned dosing regimen, since differences in binding and effect may carry different weight at the intended exposure level.<\/p>\n
ICH S6(R1) generally calls for two relevant species in safety programs but allows for a single relevant species in justified situations. This may apply when only one suitable animal species can be identified or when the biological activity is well understood. For long-term studies, a deviating justification may likewise be possible based on comparable short-term profiles.<\/p>\n
If no relevant species is available, transgenic animals expressing the human receptor or homologous proteins may be considered. A humanized receptor is particularly informative when its interaction with the product is expected to produce physiological consequences comparable to those in humans. Homologous proteins can provide useful information but may differ from the clinical product in manufacturing process, impurities, pharmacokinetics, or mechanism of action.<\/p>\n
The pharmacologically relevant species is a decision made in nonclinical safety assessment. It addresses whether the active substance reaches and functionally affects the relevant receptor or epitope in an animal model, so that toxicity findings can be meaningfully translated. Its selection is not equivalent to demonstrating therapeutic efficacy.<\/p>\n
A xenograft model, for example, can investigate the growth of human tumor cells and the antitumor effect. This does not automatically make it a suitable species for the general toxicology of an antibody. The existing entry on xenograft models therefore relates to efficacy models in oncology, not to the selection question explained here.<\/p>\n
Relevance must be justified for the specific test substance, not merely for its drug class. Even small differences in the target sequence can alter affinity, receptor occupancy, or downstream signaling pathways. Likewise, a species may bind the epitope without showing a comparable functional response. The data package should therefore explicitly assess binding and biological effect together.<\/p>\n
A suitable species may vary depending on the study question. For a general toxicity study, the translatability of potential target organs is decisive, whereas a pharmacodynamic disease model may emphasize different properties. These differences should be clearly explained in the nonclinical strategy, rather than automatically inferring toxicological relevance from a successful efficacy model.<\/p>\n
Species selection is documented early in the program but should be reassessed as new data become available. Changes to the active substance format, new metabolite data, or findings on tissue distribution may confirm, limit, or require additional justification of the original assumption of sufficient relevance.<\/p>\n
For antibodies, the unintended tissue-binding profile should be compared in addition to receptor expression. A species with a matching epitope but a markedly different pattern outside the target tissue can only provide limited support for assessing certain off-target risks.<\/p>\n
The species rationale directly affects the robustness of the starting dose justification, the selection of target organs to be monitored, and the limits of human extrapolation. If an active substance is only partially active in the animal used, the absence of findings may carry limited significance. This residual risk must be clearly distinguished from a genuine safety margin in the Investigator’s Brochure and the clinical protocol.<\/p>\n
Full-service CROs such as Mediconomics support the documentation of receptor homology, functional assays, and species rationale, as well as the alignment of the resulting nonclinical studies. Project teams can then bring together appropriate monitoring measures, data summaries, and regulatory justifications for clinical development.<\/p>\n
Is receptor expression alone sufficient for relevance?<\/strong><\/p>\n It is an important criterion, but binding affinity, occupancy, and functional activity must also be appropriate for the active substance and its intended use.<\/p>\n Why are non-relevant species problematic?<\/strong><\/p>\n If the test substance does not reach or affect its target in that species, toxicity findings may be absent or misinterpreted.<\/p>\n What happens if no suitable animal species is available?<\/strong><\/p>\n ICH S6(R1) cites transgenic animals expressing the human receptor and homologous proteins as possible approaches; their limitations must be assessed separately.<\/p>\n A pharmacologically relevant species is an animal species in which a test substance is pharmacologically active due to the expression of its receptor or, in the case of monoclonal antibodies, its epitope. The selection of such a species determines whether nonclinical findings can be meaningfully interpreted for humans. Studies in a non-relevant animal species can […]<\/p>\n","protected":false},"author":10,"featured_media":0,"parent":0,"template":"","meta":{"_acf_changed":false,"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"glossary-cat":[27],"class_list":["post-8172","glossary","type-glossary","status-publish","hentry","glossary-cat-nichtklinik-pharmakologie"],"acf":[],"related_terms":"","external_url":"","internal_reference_id":"","_links":{"self":[{"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/glossary\/8172","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/types\/glossary"}],"author":[{"embeddable":true,"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/users\/10"}],"version-history":[{"count":0,"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/glossary\/8172\/revisions"}],"wp:attachment":[{"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/media?parent=8172"}],"wp:term":[{"taxonomy":"glossary-cat","embeddable":true,"href":"https:\/\/mediconomics.com\/en\/wp-json\/wp\/v2\/glossary-cat?post=8172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Regulatory References<\/h2>\n
\n