Neonate assessments (NHP)
In contrast to embryofetal development (EFD) studies, morphological exams, external malformations and skeletal assessment as well as grip strength are performed with NHP neonates. Skeletal assessments performed in EFD studies on the fixed fetus are performed in Enhanced Pre- and Post-Natal Development (ePPND) studies after the bones are fully developed via X-ray. Occasionally, body composition analysis and evaluation of bone growth can be included.
Postnatal evaluation of basic immune system functions is usually accomplished by a neonate follow-up period of 6 months. The T-cell-Dependent Antibody Response (TDAR) functional immune assay has been used with different antigens depending on the test article. In some instances, immune system development has been studied for periods of 12-18 months. Other parameters more typical for a standard toxicology evaluation have also been added to the postnatal parameter spectrum such as ocular and cardiovascular investigations. In cases targeting the central nervous system, the postnatal observation periods have been extended until 9 months.
The learning test is based upon the double choice object discriminations tasks using the Wisconsin General Testing Apparatus or a modification. Only animals older than 6 months can be successfully trained and cooperate for this test. On average, around 6 weeks are needed until the animals perform acceptably. Hence, in practice these learning tests require long-tailed macaques aged 9 months or older, also to ensure that the animals are tested at the same age. At the end of the study, a full anatomical pathology report is available. Due to the lower body weight of the infants, blood sample volumes are limited, but toxicokinetics (TK) and (antidrug antibodies) ADA analysis can be performed.