Testing protocols endpoint selection

Also, the test procedure (protocol) is fundamental because it allows comparing results from different laboratories and from different experimental sets. Moreover, selected test protocol could affect the interpretation of the results, the information content and its application in the safety evaluation process, as stated by Frazer if the biological system is exposed to a test chemical for 24 h and the endpoint assay is immediately conducted, the data produced would be most relevant to the acute toxicity of the test material. If, on the other hand, the system is exposed to material for 24 h and the system is cultured in the absence of the test material for additional 48 h before the endpoint assay is conducted, the data would be more relevant to recovery from toxicity rather than acute toxicity [7]. 

The protocols in this unit are divided into (1) observational assessments, and (2) manipulative tests. Each protocol is further subdivided into specific tests or endpoints (Table 5.4). These various end points may be combined into a battery of tests for neurobehavioral screening. Most or all of these protocols or end points should be used in the context of a broad neurobehavioral test battery, whereas judicious selection of specific end points may be appropriate for more focused neurological testing. Originally developed by Gad [4], Moser [7], and Moscardo [8], the functional observational battery provides excellent detailed descriptions of the method using rats, the most common species used. 

The selection of suitable single species and protocols is not a trivial task and may be dependent on various factors. Some of these include simplicity, low cost, or modest material and equipment demand. However, a higher sensitivity than other species to toxicants may be decisive in this choice in order to serve as warning systems. Table 1 shows the sensitivity in terms of effective concentration (EC50), which is the toxicity endpoint for the organisms (bacteria, crustaceans, algae, and fish) selected for the toxicity bioassays. These toxicity bioassays are usually classified according to the test species involved. 

In the third randomized trial of an MMPI (British Biotech Study 145) (12), patients with locally advanced or metastatic gastric cancer were randomized in a double-blind fashion to a low dose (10 mg bid) of marimastat or matching placebo. Marimastat 10 mg po bid, which had inferior survival compared to the higher dose of marimastat, was presumably selected as the active control arm for this trial based on its superior tolerability compared to high-dose marimastat. Patients randomized to marimastat had a trend to better overall survival (167 d vs 135 d p = 0.07) at the protocol stipulated endpoint of the study, and this statistical trend strengthened with an additional 6 mo of follow up (p = 0.048). Nevertheless, patients randomized to marimastat 10 mg po bid had statistically superior progression-free survival compared to patients randomized to placebo (p = 0.027). Marimastat 25 mg po bid, which was the most efficacious dose in British Biotech Study 128, was not tested in Study 145. 

In the case of fish, although major testing methods have been proposed in relation to sex hormones, there would be plenty of scope for the selection of biologically relevant endpoints. And the research for effects of the other hormones would be the next step. Medaka methods have been comprehensively examined and found to be one of the most excellent protocols. In the case of crustaceans, since it is unclear whether the effects detected are endocrine disrupting or not on daphnids or other aquatic arthropods species, the clarification of fundamental hormonal systems would be imperative. 

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