Nonrodent studies

Data from 6 months of administration in nonrodents should be available before the initiation of clinical trials longer than 3 months. Alternatively, if applicable, data from a 9-month nonrodent study should be available before the treatment duration exceeds that which is supported by the available toxicity studies. dTo support Phase I and II Trials in the EU AND Phase I, II and III Trials in the U.S. and Japan. 

The above table also reflects the marketing recommendations in the 3 regions except that a chronic nonrodent study is recommended for clinical use longer than 1 month. 

The above table also reflects the marketing recommendations in all three ICH regions except that a chronic nonrodent study is recommended for clinical use > 1 month Source Taken from the ICH M3 guideline. Nonclinical Safety Studies for the Conduct of Human Clinical Trials for Pharmaceuticals, November 1997 and updated November 2000, Available at http //www.fda.gov/cder/guidance. 

The duration for chronic toxicology studies depends on the projected duration of administration to humans (Table 1). The present consensus according to the FDA (5) is that 6-month rodent and nonrodent studies are sufficient for drug candidates intended for long-term human use, provided the candidate is studied in rats, or other appropriate species, to evaluate the potential for tumor production. 

Both rodent and nonrodent studies have been conducted on the parent CDs. Szejtli and Sebestyen reported the parent CDs to be nontoxic at very high oral doses. Mortality was not observed, even in animals treated with the highest possible oral doses. Therefore, the LD50 in rats is reported to be greater than 12.5, 18.8, and 8g/kg body weight for a-, p-, and y-CD, respectively. 

The in vitro human whole blood assay and the outbred mouse are considered binary (yes/no) hazard identification tools in lead optimization screening for compound selection. In our experience to date, chemically modified conjugate siRNAs do not provoke acute pro-inflammatory effects in subsequent rodent or nonrodent studies or in clinical trials if they test negative in these two assays. Lacking positive controls, it is not yet feasible to assess whether the immuno-stimulation screening during lead optimization is predictive or relevant for human outcomes. 

Preclinical drug development also involves animal testing [61]. Data from one rodent species and one nonrodent species are usually collected to determine the absorption, metabolism, and toxicity characteristics of the compound. Both short-term (2 weeks to 3 months) and long-term (up to several years) studies are done. The long-term studies are particularly useful for... 

Chronic Toxicity. Traditionally, chronic toxicity of new pharmaceuticals in the United States was assessed in studies of one-year duration in both the rodent and the nonrodent species of choice. The European view was that studies of six months are generally sufficient. The resulting guideline (S4A) was a compromise. Studies of six months duration were recommended for the rodent, as rodents would also be examined in two-year studies. For the nonrodent (dog, nonhuman primate, and pig) studies of nine months duration were recommended. 

Chronic and subchronic toxicity studies are conducted to define the dose level, when given repeatedly, that cause toxicity, and the dose level that does not lead to toxic findings. In Japan, such studies are referred to as repeated-dose toxicity studies. As with single-dose studies, at least two animal species should be used, one rodent and one nonrodent (rabbit not acceptable). In rodent studies, each group should consist of at least 10 males and 10 females in nonrodent species, 3 of each sex are deemed adequate. Where interim examinations are planned, however, the numbers of animals employed should be increased accordingly. The planned route of administration in human subjects is normally explored. The duration of the study will be dictated by the planned duration of clinical use (Table 2.14). 

Keep in mind that the objective of such studies is to gain information about lethality and gross tolerance. For nonrodents (especially monkeys), if none of the animals dies or demonstrates obvious signs of toxicity, little would be gained by euthanizing and necropsying such animals. They can be saved and used again,... 

FIGURE 5.14. Example of pyramiding dose study for acute toxicity testing in a nonrodent species. 

Ophthalmology. Ophthalmological examination of all animals in study (particularly nonrodents) should be performed both before study initiation and at the completion of the period at which the drug is administered. This should be performed by an experienced veterinary ophthalmologist. 

The number of species necessary in preclinical testing programs varies. However, there is no specific requirement for the routine use of two species (e.g., one rodent and one nonrodent) in toxicology studies of biological products. 

Such studies provide important information for a better interpretation of the toxicity observed in animals, and aid in the selection of not only the proposed initial human dose but of the dose-escalation scheme and the frequency of dosing in the clinical trial(s). Further, once such exposure data are available in humans, the data can be used to better correlate the human and animal findings. Toxicity studies should be performed in the same species used to assess exposure. Often, exposure and toxicity are measured in the same study, particularly when nonrodents are used. 

In addition to rodent studies, regulatory guidelines for pharmaceuticals require that repeated dose safety studies of up to nine months (in the United States, six months elsewhere) in duration be conducted in a nonrodent species. The most commonly used nonrodent species is the dog, followed by the monkey and pig. Another nonrodent model used to a limited extent in systemic safety evaluation is the ferret. The major objectives of this chapter are (1) to discuss differences in rodent and nonrodent experimental design, (2) to examine the feasibility of using the dog, monkey, pig, and ferret in safety assessment testing, and (3) to identify the advantages and limitations associated with each species. 

---