An assessment of the reliability of 52 enhanced preliminary embryofetal development studies to detect developmental toxicity

BACKGROUND

Preliminary embryofetal development (pEFD) data from two species are currently recommended before inclusion of women of child-bearing potential (WOCBP) in clinical trials in Europe or Japan, but not before trials in the United States. The ICH S5(R3) guideline advises an "enhanced" study design for this purpose.

METHODS

The reliability of pEFD studies was assessed by comparing the outcome of 52 enhanced pEFD studies (25 rat, 23 rabbit, and 4 mouse) with the results of the definitive nonclinical EFD assessment.

RESULTS

Four pEFD studies revealed severe developmental hazard without the need for a main EFD study. Only one pEFD study failed to detect drug-related teratogenicity or pregnancy failure subsequently detected in the main study. There were, however, some false positive and some equivocal pEFD study results. Of the 48 pEFD studies for which a main EFD study was performed, 16 (33%) failed to accurately predict (within two-fold) the no adverse effect level (NOAEL) for developmental toxicity subsequently defined in the main EFD study. Skeletal examination of fetuses in the pEFD study was necessary was to detect drug-induced malformations. One quarter (23%) of EFD investigations revealed malformations and/or pregnancy failure at one dose level or more.

CONCLUSIONS

pEFD studies are effective for the detection of serious or irreversible effects on embryofetal development, provided that full fetal examinations are completed. They are not, however, sufficiently powered to reliably define the NOAEL for developmental toxicity. The regulatory impact of pEFD studies remains obscure since maximum pregnancy prevention precautions are required in clinical trials in all regions until the results of the main EFD studies are available.

Resolution of unexpected pregnancy-related findings in a rat embryofetal development and toxicokinetic study of monoclonal antibodies specific for hCMV

BACKGROUND

Developmental and reproductive toxicity testing is not uniformly warranted for biopharmaceuticals that lack relevant targets in test species. However, RG7667, consisting of two monoclonal antibodies specific for human cytomegalovirus (hCMV), was intended for administration to pregnant women to prevent transmission of CMV to the developing fetus.

METHODS

Considering the target indication, a Pilot Embryo Fetal Development/Toxicokinetic study was conducted to assess toxicokinetics in the dam and fetuses and general tolerability.

RESULTS

RG7667 administered intravenously to presumed pregnant Sprague-Dawley rats was well tolerated with no clinical signs in any dam and comparable litter sizes and viability across groups. However, at cesarean section, hepatic necrosis and pancreatic edema were identified in two dams administered RG7667, with no clear dose relationship. Investigation of total protein, albumin, and transaminase activity in residual serum from TK samples demonstrated striking hypoproteinemia and elevated transaminases limited to these two dams. Overall, these pathology findings in dams were considered of uncertain relationship to RG7667; therefore, a subsequent Pivotal EFD study was conducted, which did not repeat the liver or pancreatic findings.

CONCLUSIONS

The results of the Pivotal study confirmed the lack of overt toxicity, teratogenicity, or effects on litter size and viability when human or humanized monoclonal antibodies that lack an endogenous target are administered IV to rats during pregnancy. With these additional data, we concluded that the unexpected pathology findings in the Pilot study were not specific to RG7667, but rather highlight some clinical pathology and macroscopic/microscopic findings that can occur during pregnancy in rats.

Fertility and Embryo-Fetal Development Assessment in Rats and Rabbits with Evacetrapib: A Cholesteryl Ester Transfer Protein Inhibitor

BACKGROUND

The purpose of these studies was to evaluate the effects of evacetrapib on male and female fertility and on embryo-fetal development (EFD).

METHODS

Evacetrapib, a potent and selective inhibitor of cholesteryl ester transfer protein (CETP), was administered daily by oral gavage starting 2 weeks (for female) or 4 weeks (for male) before mating, during cohabitation, and until necropsy in the male rat fertility study or through gestation day (GD) 17 in the female rat combined fertility/EFD study. For rabbit EFD studies, animals were dosed from GDs 7 to 19 or from 1 week before mating through GD 19. Dose levels of evacetrapib ranged from 60 to 600 mg/kg for rats and from 1 to 100 mg/kg/day for rabbits.

RESULTS

Parental findings in rats included decreased body weight and food consumption and moribund euthanasia in animals given 600 mg/kg/day and decreased food consumption at 300 mg/kg/day. There were no adverse effects on estrus cycling, fertility indices, sperm parameters, maternal reproductive parameters, male reproductive tissue, or fetal viability, growth, or external/visceral morphology. An increase in the incidence of 14th rudimentary ribs, a minor, transient variation considered nonadverse, was the only significant developmental finding in rats given 600 mg/kg/day. Slight decreases in body weight and food consumption at 100 mg/kg/day were the only maternal effects observed in rabbits with no adverse developmental effects noted.

CONCLUSION

No adverse effects on fertility or EFD were observed in rats at doses up to 600 mg/kg/day and no adverse effects on EFD were noted in rabbits at doses up to 100 mg/kg/day. Birth Defects Research 109:513-527, 2017. © 2017 Wiley Periodicals, Inc.

mtDNA mutations variously impact mtDNA maintenance throughout the human embryofetal development

Mitochondria are the largest generator of ATP in the cell. It is therefore expected that energy-requiring processes such as oocyte maturation, early embryonic or fetal development, would be adversely impacted in case of mitochondrial deficiency. Human mitochondrial DNA (mtDNA) mutations constitute a spontaneous model of mitochondrial failure and offer the opportunity to study the consequences of energetic defects over fertility and embryofetal development. This review provides an update on the mtDNA metabolism in the early preimplantation embryo, and compiles data showing the impact of mtDNA mutations over mtDNA segregation. Despite convincing evidences about the essential role of mitochondria in oogenesis and preimplantation development, no correlation between the presence of a mtDNA mutation and fertilization failure, impaired oocyte quality, or embryofetal development arrest was found. In some cases, mutant cells might upregulate their mitochondrial content to overcome the bioenergetic defects induced by mtDNA mutations, and might escape negative selection. Finally we discuss some of the clinical consequences of these observations.

Short and long-term repercussions of the experimental diabetes in embryofetal development

BACKGROUND

Diabetic pregnancy have increased rates of congenital malformation and neonatal mortality. In vitro studies suggest hyperglycemia associated with diabetes impair embryogenesis but in vivo investigations on maternal hyperglycemic insult and early embryo development are scarce. We evaluated the embryofetal development on experimental diabetes models to assess whether hyperglycemia at preimplantation period impairs the progression of pregnancy.

METHODS

Different hyperglycemic intensities were obtained by two experimental diabetes models. Female Sprague Dawley rats received streptozotocin at birth (mild diabetes) or at day 90 of life (severe diabetes). For both diabetic groups hyperglycemia was confirmed 5 days after diabetes induction and the mating was performed around 100 day of life. For preimplantation analysis, embryos were recovered at D4 of pregnancy. Another group of animals was submitted to laparotomy at D21 to assess contents of the uterus and fetal viability.

RESULTS

Mild (i) and Severe (ii) diabetes modified the early development. Degenerating embryos percentage was higher compared to control (11%) (i) 30.7%, (ii) 37.3%. Cell number mean dropped according to hyperglycemic intensity (control 30.57, (i) 21.42, (ii) 13.42). Pre and post-implantation loss rates were higher in diabetic groups. The fetal viability also decreased from 96% in the control group to (i) 78.7% and (ii) 80.6%.

CONCLUSION

Our results show that during diabetic pregnancy, preimplantation embryos present decreased cell number due to higher apoptosis rates, which are dependent of the hyperglycemic intensity. Moreover, fetal viability was also decreased suggesting that the quality of these embryos at long-term may be questioned.

Considerations for the nonclinical safety evaluation of antibody drug conjugates for oncology

Antibody drug conjugates (ADCs) include monoclonal antibodies that are linked to cytotoxic small molecules. A number of these agents are currently being developed as anti-cancer agents designed to improve the therapeutic index of the cytotoxin (i.e., cytotoxic small molecule or cytotoxic agent) by specifically delivering it to tumor cells. This paper presents primary considerations for the nonclinical safety evaluation of ADCs and includes strategies for the evaluation of the entire ADC or the various individual components (i.e., antibody, linker or the cytotoxin). Considerations are presented on how to design a nonclinical safety assessment program to identify the on- and off-target toxicities to enable first-in-human (FIH) studies. Specific discussions are also included that provide details as to the need and how to conduct the studies for evaluating ADCs in genetic toxicology, tissue cross-reactivity, safety pharmacology, carcinogenicity, developmental and reproductive toxicology, biotransformation, toxicokinetic monitoring, bioanalytical assays, immunogenicity testing, test article stability and the selection of the FIH dose. Given the complexity of these molecules and our evolving understanding of their properties, there is no single all-encompassing nonclinical strategy. Instead, each ADC should be evaluated on a case-by-case scientifically-based approach that is consistent with ICH and animal research guidelines.