Tier II (Follow-Up Mechanistic) Assays

Many regulations and governing bodies require a standard (harmonized) battery of  genetic toxicology assays to assess a chemical compound’s potential to induce a genotoxic response. This genotoxicity can occur in a number of different ways including mutagenicity, clastogenicity or aneugenicity.

Studies have shown that 29% of marketed drugs contained positive findings in one of the four categories of standard battery assays (bacterial mutation, in vitro mammalian cell gene mutation, in vitro and in vivo cytogenetics). For these reasons, a range of approaches are available to assess the relevance of a positive genotoxicity result. While there are techniques such as QSAR and FISH/CREST to assess whether a positive result is real, if indeed these techniques result in a real positive, “Tier II” assays can be conducted to further define the biological relevance of the result.

Although guidelines do vary somewhat by governing body (US, EU, Japan, etc.) and by product type (Pharmaceuticals, Food Additives, Veterinary Medicine, Medical Devices, Industrial and Agricultural Chemicals, Consumer Products and Flavors and Fragrances), BioReliance provides a portfolio and consultation on the myriad of assays available to meet these regulations and product types. All assays conform to OECD guidelines (when applicable) and are GLP-compliant.

In Vivo Tier II Assays*:

In Vivo Single Cell Gel Electrophoresis “Comet” Assay

• Mice and Rat
• Tissues include: peripheral blood, bone marrow, brain, colon, deudenum, jejunum, kidney, liver, lung, nasal cavity, skin, spleen, stomach, testis, uterus

May also be combined with an In Vivo Micronucleus Assay

In Vitro/In Vivo Unscheduled DNA Synthesis (UDS) Assay

• Rat and Mouse Liver

Pig-a In Vivo Gene Mutation Assay

• Rat peripheral blood with Flow Cytometric Scoring

Big Blue® Transgenic Rodent Mutation (TGR) Assay

• Mice and Rat
• Tissues include:  liver, bone marrow, testes, caudal sperm, stomach, intestine, bladder, skin, heart, skeletal muscle, nasal turbinates, mammary tissue, lung, kidney, spleen, tongue, palate, gingiva, trachea, larynx and esophagus.

* Integrated Genetic Toxicology Endpoints and Repeat Dose Studies

In vivo endpoints may be integrated into general toxicology studies with repeat dosing. Endpoints can be evaluated by Flow Cytometry (when available) or manual scoring (microscopy).

Endpoints include:  In Vivo Micronucleus, In Vivo Comet, Chromosome Aberrations, Pig-a, Big Blue®