Vehicle Systems and Excipients Used in Minipig Drug Development Studies.

Minipigs have been used for dermal drug development studies for decades, and they are currently more frequently considered as the second nonrodent species for pivotal nonclinical studies, in lieu of the dog or nonhuman primate, for compounds delivered via standard systemic routes of administration. Little is known about the tolerability of different excipients in minipigs; sharing knowledge of excipient tolerability and compositions previously used in nonclinical studies may avoid testing of inadequate formulations, thereby contributing to reduced animal usage. This article reviews vehicles employed in the Göttingen(®)minipig based on the combined experience from a number of pharmaceutical companies and contract research organizations. The review includes vehicles tolerated for single or multiple dosing by the Göttingen minipig, some of which are not appropriate for administration to other common nonrodent species (e.g., dogs). By presenting these data for dermal, oral, subcutaneous, and intravenous routes of administration, studies to qualify these vehicles in minipigs can be minimized or avoided. Additionally, investigators may more frequently consider using the minipig in place of higher species if the tolerability of a vehicle in the minipig is known.

Histopathological nerve and skeletal muscle changes in rats subjected to persistent insulin-induced hypoglycemia.

New insulin analogues with a longer duration of action and a flatter pharmacodynamic profile are developed to improve convenience and safety for diabetic patients. During the nonclinical development of such analogues, safety studies must be conducted in nondiabetic rats, which consequently are rendered chronically hypoglycemic. A rat comparator model using human insulin would be valuable, as it would enable differentiation between effects related to either persistent insulin-induced hypoglycemia (IIH) or a new analogue per se. Such a model could alleviate the need for an in-study-comparator and thereby reduce the number of animals used during development. Thus, the aims of the present study were i) to develop a preclinical animal model of persistent hypoglycemia in rats using human insulin infusion for four weeks and ii) to investigate histopathological changes in sciatic nerves and quadriceps femoris muscle tissue, as little is known about the response to persistent hypoglycemia in these tissues. Histopathologic changes in insulin-infused animals included axonal degeneration and myofibre degeneration. To our knowledge, this is the first study to show that persistent IIH provokes peripheral nerve and skeletal myofiber degeneration within the same animals. This suggests that the model can serve as a nonclinical comparator model during development of long-acting insulin analogues.

Importance of gestational hypoglycaemia for foetal malformations and skeletal development in rats.

The aim was to investigate embryo-foetal effects of continuous maternal insulin-induced hypoglycaemia extending throughout gestation or until gestation day (GD)17 (typical last day of dosing during pre-clinical evaluation) providing comparator data for safety assessment of longer-acting insulin analogues in non-diabetic rats. Pregnant rats received human insulin (HI)-infusion during gestation until either GD20 or GD17 (HI-GD20; HI-GD17). On GD20, foetal abnormalities and skeletal ossification/mineralisation were evaluated. HI-infusion induced continuous hypoglycaemia. Foetal skeletal and eye malformations (e.g. bent ribs, microphthalmia) were common in both groups. Foetal size and skeletal ossification/mineralisation decreased, particularly with infusion throughout gestation. Concluding, insulin-induced hypoglycaemia during gestation in non-diabetic rats is damaging to embryo-foetal growth and skeletal development, particularly after GD17. Three days without HI-infusion after GD17 allows for some developmental catch-up. Eye development is sensitive to HI-infusion before GD17. These results should serve as a benchmark during pre-clinical safety assessment of longer-acting insulin analogues tested in rats.

Hemizygous minipigs produced by random gene insertion and handmade cloning express the Alzheimer's disease-causing dominant mutation APPsw.

In an effort to develop a porcine model of Alzheimer's disease we used handmade cloning to produce seven transgenic Göttingen minipigs. The donor fibroblasts had been stably transfected with a plasmid cassette containing, as transgene, the cDNA of the neuronal variant of the human amyloid precursor protein gene with the Swedish mutation preceded by beta-globin sequences to induce splicing and a human PDGF beta promoter fragment to drive transcription. Transgene insertion had occurred only at the GLIS3 locus where a single complete copy of the transgene was identified in intronic sequences in opposite direction. Similar and robust levels of the transgene transcript were detected in skin biopsies from all piglets and the sequence of full-length transcript was verified. Consistent with PDGF beta promoter function, high levels of transgene expression, including high level of the corresponding protein, was observed in brain tissue and not in heart or liver tissues. A rough estimate predicts that accumulation of the A beta peptide in the brain may develop at the age of 1-2 years.

Assessment of implantable infusion pumps for continuous infusion of human insulin in rats: potential for group housing.

Group housing is considered to be important for rats, which are highly sociable animals. Single housing may impact behaviour and levels of circulating stress hormones. Rats are typically used in the toxicological evaluation of insulin analogues. Human insulin (HI) is frequently used as a reference compound in these studies, and a comparator model of persistent exposure by HI infusion from external pumps has recently been developed to support toxicological evaluation of long-acting insulin analogues. However, this model requires single housing of the animals. Developing an insulin-infusion model which allows group housing would therefore greatly improve animal welfare. The aim of the present study was to investigate the suitability of implantable infusion pumps for HI infusion in group-housed rats. Group housing of rats implanted with a battery-driven pump proved to be possible. Intravenous infusion of HI lowered blood glucose levels persistently for two weeks, providing a comparator model for use in two-week repeated-dose toxicity studies with new long-acting insulin analogues, which allows group housing, and thereby increasing animal welfare compared with an external infusion model.

Reprint of "Potential seminal transport of pharmaceuticals to the conceptus".

Small molecule pharmaceutical products are assumed to reach concentrations in semen similar to those in blood plasma. Exposure modeling for these small-molecule products in humans assumes a daily dose of 5mL of semen and 100% absorption from the vagina with distribution to the conceptus through the maternal systemic circulation. Monoclonal antibody drugs are present in semen at concentrations about 2% or less of those in blood, and the modeling used for small molecules will over-estimate the possibility of conceptus exposure to immunoglobulins. It is not known whether peptide products reach semen, but in general peptide medications are destroyed by vaginal peptidases, and conceptus exposure is predicted to be minimal. Theoretical exposure routes to pharmaceuticals that might result in exposure of the conceptus greater than that of maternal systemic exposures include direct access through the cervical canal, adsorption to sperm for carriage into the oocyte, and direct delivery from the vaginal veins or lymphatics to the uterine artery. There is some evidence for direct access to the uterus for progesterone, terbutaline, and danazol, but the evidence does not involve exposures during pregnancy in most instances. Studies in mice, rats, rabbits, and monkeys do not suggest that exposure to small molecule pharmaceuticals in semen imposes risks to the conceptus beyond those that can be predicted using modeling of systemic maternal exposure. Monoclonal antibody and peptide exposure in semen does not pose a significant risk to the conceptus.

Potential seminal transport of pharmaceuticals to the conceptus.

Small molecule pharmaceutical products are assumed to reach concentrations in semen similar to those in blood plasma. Exposure modeling for these small-molecule products in humans assumes a daily dose of 5mL of semen and 100% absorption from the vagina with distribution to the conceptus through the maternal systemic circulation. Monoclonal antibody drugs are present in semen at concentrations about 2% or less of those in blood, and the modeling used for small molecules will over-estimate the possibility of conceptus exposure to immunoglobulins. It is not known whether peptide products reach semen, but in general peptide medications are destroyed by vaginal peptidases, and conceptus exposure is predicted to be minimal. Theoretical exposure routes to pharmaceuticals that might result in exposure of the conceptus greater than that of maternal systemic exposures include direct access through the cervical canal, adsorption to sperm for carriage into the oocyte, and direct delivery from the vaginal veins or lymphatics to the uterine artery. There is some evidence for direct access to the uterus for progesterone, terbutaline, and danazol, but the evidence does not involve exposures during pregnancy in most instances. Studies in mice, rats, rabbits, and monkeys do not suggest that exposure to small molecule pharmaceuticals in semen imposes risks to the conceptus beyond those that can be predicted using modeling of systemic maternal exposure. Monoclonal antibody and peptide exposure in semen does not pose a significant risk to the conceptus.

In vitro maturation of bovine cumulus-oocyte complexes in undiluted follicular fluid: effect on nuclear maturation, pronucleus formation and embryo development.

Since resumption of meiosis and cytoplasmic maturation of bovine oocytes takes place in close association with follicular fluid, it would be logical to assume that this might be a perfect maturation medium. To test the hypothesis, abattoir-derived cumulus-oocyte complexes (COCs) were in vitro matured in undiluted (i) mixed follicular fluid (FF) from 3 to 15 mm follicles from abattoir ovaries, (ii) preovulatory follicular fluid (POF) from the dominant follicle from a cyclic unstimulated heifer, (iii) preovulatory follicular fluid (OPU) from synchronised and superovulated heifers 60 h after prostaglandin and 20 h after GnRH treatment, and in (iv) TCM-199 with 5% serum. Subsequent to IVM, the COC were subjected to IVF and IVC, and embryo development was followed until the blastocyst stage at Day 8 after insemination. The MII rates in the TCM-199 (69%), POF (69%) and OPU (72%) groups were not different from each other but different from the FF (41%) group (P<0.05). In spite of the high MII rates, none of the follicular fluids supported embryo development: the FF, POF and OPU blastocyst rates were alike (3%, 3%, 2%) and different (P<0.05) from the rates in the TCM-199 (19%). During IVM in follicular fluids but not in TCM-199, the expanded cumulus masses became trapped in a coagulum. Although it could be prevented by the presence of heparin during IVM, it did not improve the blastocyst rates. In conclusion, undiluted preovulatory follicular fluids supported nuclear maturation but not further embryonic development as judged by the high MII and low blastocyst rates.