Tier 3 Tests

To screen for bone marrow toxicity early in drug discovery, assays must be able to evaluate hundreds of compounds, be inexpensive, report results within two weeks (in order to impact chemistry cycle times) and be able to detect toxicity irrespective of cytotoxic or cytostatic mechanisms. Only cell line-based assays can meet all of these various criteria. 

Tier 1 assay qualification entailed (i) evaluating compounds known to induce lineage specific hematotoxicity (ii) comparing the results from the myeloid tier 1 assay to the mouse CFU-GM assay (iii) comparing the results from the erythroid tier 1 assay to reduction in peripheral blood reticulocytes. 

Erythroid HCD57 IMDM 30% FBS, Pen/Strep, L-glutamine, lOOpg/mL rmEpo, 20 pM P-ME 5000/well Non- adherent Oh 72 h 

Stromal M2-10B4 RPMI- 1640 10%FBS, Pen/Strep 2000/well Adherent 24 h 72 h 

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If infectivity is clearly demonstrated in Tier 1 testing, organisms would not be considered for further development. 

Duan, J.J., M.S. Paradise, J.G. Lundgren, J.T. Bookout, C. Jiang, and R.N. Wiedenmann. 2006. Assessing nontarget impacts of Bt corn resistant to corn rootworms Tier-1 testing with larvae of Poecilus chalcites (Coleoptera Carabidae). Environ. Entomol. 35 135-142. 

In the summary of the aforementioned report, the authors recommend, as did earlier reviewers of this subject, the development and evaluation of a tiered testing strategy for neurotoxicity. The further development of in vitro models for establishing mechanisms of neurotoxicity should be part of this strategy. Full consideration should also be given to advances in the omics and other technological fields. 

Interest has been expressed in the possibility of using biomarker assays as a part of risk assessment for regulatory purposes, and some workers have suggested tiered testing procedures that follow this approach (see, for example, Handy et al. 2003). It is to be hoped that regulatory schemes, such as that of REACH (see European Union 2003), will be sufficiently flexible to incorporate new assays and testing strategies as the science advances. 

The Tier-Testing Approach Setting the Course for Modern Immunotoxicology... 

As was the case with tier testing, developmental immunotoxicology has been driven by expert workshops to reach consensus on the most important issues three workshops were held in 2001 [79-81], and another in 2003 [82], These workshops contributed to the development of a proposed testing framework to detect developmental immunotoxicity, which is described in detail in chapter 21. 

The usual way in which transition (or flow ) between the different phases is handled in safety assessment is to use a tiered testing approach. Each tier generates more specific data (and costs more to do so) and draws on the information generated in earlier tiers to refine the design of new studies. Different tiers are keyed to the... 

Gad, S.C. (1989b). A tier testing strategy incorporating in vitro testing methods for pharmaceutical safety assessment. Flumane Innovations and Alternatives in Animal Experimentation 3 75-79. 

Whatever the specific need or application, the use of a tier testing scheme can significantly reduce, and in some cases eliminate, the use of animals. An example of a decision-making tree and its applications in ocular testing is provided in Figure 17.3. First, all available data about a test material (or related compounds), including chemical characteristics, historical data, other known toxicity, and the like, are collected. Analysis of these data could provide a strong indication of irritation potential, in which case the material would be labeled a presumed positive and... 

Gad, S.C. (1989). A Tier Testing Strategy Incorporating In Vitro Testing Methods for Pharmaceutical Safety Assessment. Humane Innovations Alternatives Anim. Exp. 3 75-79. 

Gad, S.C. (1992). Industrial application for in vitro toxicity testing methods A tier testing strategy for product safety assessment. In In Vitro Toxicity Testing (Frazier, J., Ed.). Marcel Dekker, New York, pp. 253-279. 

It is concluded that the TTC concept for systemic toxicity is suitable as a starting point for a tiered testing and risk assessment strategy within REACH. However, it is also underlined that the... 

Martin MT, Knudsen TB, Judson RS, Kavlock RJ, Dix DJ (2012) Economic benefits of using adaptive predictive models of reproductive toxicity in the context of a tiered testing paradigm. Syst Biol Reprod Med 58 3-9... 

The European Union has adopted a tiered testing approach for new chemicals. This approach requires stepwise increases in detailed testing and evaluation when known factors (such as tonnage) warrant such increased testing. For those compounds that are produced at less than 1 tonne per annum and for which there are no structural or other alerts, no formal additional testing is required. As tonnage increases,... 

If the above acceptance criteria are not met because three to six of the 20 determinations are outside 80 to 120% of the label claim, 14 units but none are outside 75 to 125% of label claim, and the means for each of the beginning and end determinations are not outside 85 to 115% of label claim, an additional 20 containers should be sampled for second-tier testing. 

Single species tests and tests using bioassay batteries are called lower-tier tests.19 But in order to carry out a more stringent examination of the complex interactions between potentially toxic chemical compounds and organisms inhabiting specific ecosystems, experiments are sometimes carried out in microcosms and mesocosms the literature describes these as higher-tier tests.19... 

In 1982 the FDA published Its guidelines — Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used In Food (3). The guidelines in this so-called "Redbook define a system of recommended tiered testing for additives In food. Not only does the "Redbook" provide testing guidance. 

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