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Ervogastat (PF-06865571) is a small molecule diacylglycerol acyltransferase 2 (DGAT2) inhibitor being developed for the oral treatment of nonalcoholic steatohepatitis (NASH) with liver fibrosis. DGAT2 is a key enzyme in triglyceride synthesis in tissues and in regulating energy metabolism. Fertility and developmental toxicity studies with ervogastat were conducted in female rats and rabbits. There were no effects on female rat fertility or rabbit embryo-fetal development. Administration of ervogastat to pregnant rats during organogenesis reduced fetal weight and caused higher incidences of bent bones in fetuses that were shown to resolve by postnatal day 28 and were therefore considered to be transient variations secondary to developmental delay. Extended dosing in rats through the end of gestation and lactation (pre- and post-natal development study) caused impaired skin development, reduced offspring viability, and growth retardation. The spectrum of developmental effects in rats is consistent with the intended pharmacology (altered triglyceride metabolism) and the transient nature of the skeletal findings, along with the late gestational window of sensitivity for the effects on skin barrier development, reduce the concern for potential adverse developmental effects following unintended early gestational exposure to ervogastat in humans where treatment can be discontinued once pregnancy is determined.

Bococizumab is an anti-PCSK9 monoclonal antibody that was intended for the treatment of hypercholesterolemia. After reviewing the 6-month rat toxicity study data, in which there was a low spontaneous tumor incidence, unrelated to bococizumab administration, the U.S. FDA granted a carcinogenicity waiver request based on a weight-of-evidence assessment of low carcinogenic risk. Subsequently, after reviewing 6-month rat toxicity study data from another anti-PCSK9 antibody, RN317, with a similar low tumor incidence (unrelated to RN317), the U.S. FDA rescinded the bococizumab carcinogenicity study waiver and requested a full 2-year rat carcinogenicity study be conducted. The resulting 2-year carcinogenicity study demonstrated no bococizumab-related increase in tumors, confirming the weight-of-evidence evaluation and alleviating concerns regarding the carcinogenic potential. Here we report the scientific and regulatory background that led to the request for a rat carcinogenicity study, the feedback on the design of the carcinogenicity study, and the results from this study which affirmed the original weight-of-evidence assessment of low carcinogenic risk.

Gynecologic tract origin of inflammatory myofibroblastic tumor (IMT), a receptor tyrosine kinase fusion driven tumor with malignant potential, is uncommon and mostly involves the uterine corpus where misclassification as a smooth muscle tumor may occur due to overlapping morphologic features. With rare exception, uterine IMT involves ALK rearrangements and exhibits ALK immunoexpression. Molecularly confirmed vulvovaginal IMT has not been reported, but several low-grade mesenchymal tumors in this region exhibit myxoid stroma and/or inflammatory infiltrates that may resemble IMT. The aims of this study were to define the diagnostic specificity of ALK immunoexpression for IMT among a broad spectrum (107 cases) of vulvovaginal mesenchymal tumors in the differential diagnosis of IMT and to report the clinicopathologic features of vulvovaginal IMT identified in our archives or via retrospective ALK staining of otherwise classified vulvovaginal tumors. Review of archives from 5 different centers revealed a single case of vulvar IMT in a 62-yr-old woman. The 2.5 cm well-circumscribed tumor exhibited the typical microscopic features of IMT, namely a loose fascicular distribution of bland spindle cells within a myxoid stroma, accompanied by an infiltrate of plasma cells, lymphocytes, and eosinophils. The tumor cells exhibited expression for smooth muscle actin, desmin, h-caldesmon, and ALK. Break-apart fluorescence in situ hybridization confirmed the presence of ALK rearrangement. The patient did not receive any treatment and is alive without disease 32 mo later. No evidence of ALK expression was detected in any of the other 107 vulvovaginal tumors, which included 14 aggressive angiomyxomas, 2 superficial angiomyxomas, 12 angiomyofibroblastomas, 8 cellular angiofibromas, 15 smooth muscle neoplasms, 10 peripheral nerve sheath tumors, 20 fibroepithelial polyps, and a variety of other low grade mesenchymal tumors. Although vulvovaginal ALK- rearranged IMT is exceedingly rare, the behavior remains to be fully understood. ALK immunohistochemistry, which appears specific for IMT in this anatomic site, is advised in the evaluation of vulvovaginal mesenchymal tumors exhibiting myxoid stroma and/or an inflammatory infiltrate.

Achondroplasia is an autosomal disorder caused by point mutation in the gene encoding fibroblast growth factor receptor 3 (FGFR3) and resulting in gain of function. Recifercept is a potential disease modifying treatment for achondroplasia and functions as a decoy protein that competes for ligands of the mutated FGFR3. Recifercept is intended to restore normal bone growth by preventing the mutated FGFR3 from negative inhibitory signaling in pediatric patients with achondroplasia. Here we evaluated the potential effects of twice weekly administration of recifercept to juvenile cynomolgus monkeys (approximately 3-months of age at the initiation of dosing) for 6-months. No adverse effects were noted in this study, identifying the high dose as the no-observed-adverse-effect-level and supporting the use of recifercept in pediatric patients from birth. Considering that juvenile toxicity studies in nonhuman primates are not frequently conducted, and when they are conducted they typically utilize animals ≥9 months of age, this study demonstrates the feasibility of executing a juvenile toxicity study in very young monkeys prior to weaning.

A maternal Group B Streptococcus (GBS) six-valent polysaccharide conjugate vaccine (GBS6) is being developed to protect neonates and infants up to 3 months of age through passive transfer of antibodies from the mother to the infant. Fertility and developmental toxicity studies were conducted in female Sprague Dawley rats and New Zealand White rabbits with GBS6 (20 μg capsular polysaccharide/serotype formulated with or without AlPO4 , the highest clinical dose). Females were administered the full human dose of the GBS6 formulation intramuscularly twice prior to mating and twice during gestation, to ensure that high antibody levels were maintained throughout gestation and lactation. Approximately, half of the rats and rabbits were evaluated at the end of gestation, and the remainder were evaluated at the end of lactation. Maternal blood for GBS6 serology, to measure antibody titers to the GBS6 antigens, was collected prior to the first dose, prior to mating, and at each necropsy. Blood for serology was also collected from offspring at the end of gestation and lactation. In both species, there was no evidence of vaccine-related effects on fertility, embryo-fetal development, or postnatal development of the offspring, supporting regulatory guidance that single-species evaluation would have been sufficient. Functional serum antibodies to all six serotypes in the vaccine were confirmed in maternal animals and functional serum antibodies to one or more of the six serotypes was also confirmed in some rat offspring and most of the rabbit offspring. The results of these studies supported the safety of GBS6 vaccine administration to pregnant women.

Acetyl-CoA carboxylase (ACC) is an enzyme within the de novo lipogenesis (DNL) pathway and plays a role in regulating lipid metabolism. Pharmacologic ACC inhibition has been an area of interest for multiple potential indications including oncology, acne vulgaris, metabolic diseases such as type 2 diabetes mellitus, and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. A critical role for ACC in de novo synthesis of long-chain fatty acids during fetal development has been demonstrated in studies in mice lacking Acc1, where the absence of Acc1 results in early embryonic lethality. Following positive predictions of developmental toxicity in the alternative in vitro assays (positive in murine embryonic stem cell [mESC] assay and rat whole embryo culture, but negative in zebrafish), developmental toxicity (growth retardation and dysmorphogenesis associated with disrupted midline fusion) was observed with the oral administration of the dual ACC1 and 2 inhibitors, PF-05175157, in Sprague Dawley rats and New Zealand White rabbits. The results of these studies are presented here to make comparisons across the assays, as well as mechanistic insights from the mESC assay demonstrating high ACC expression in the mESC and that ACC-induced developmental toxicity can be rescued with palmitic acid providing supportive evidence for DNL pathway inhibition as the underlying mechanism. Ultimately, while the battery of alternative approaches and weight-of-evidence case were useful for hazard identification, the embryo-fetal development studies were necessary to inform the risk assessment on the adverse fetal response, as malformations and/or embryo-fetal lethality were limited to doses that caused near-complete inhibition of DNL.

A maternal Group B Streptococcus (GBS) six-valent polysaccharide conjugate vaccine (GBS6) is being developed to protect neonates and infants up to 3 months of age through passive transfer of antibodies from the mother to the infant. Fertility and developmental toxicity studies were conducted in female Sprague Dawley rats and New Zealand White rabbits with GBS6 (20 μg capsular polysaccharide/serotype formulated with or without AlPO

Antibody-like biopharmaceuticals cross the placenta by utilizing existing transport pathways (e.g., FcRn receptor). There are limited data evaluating this transfer during organogenesis in any species. Understanding placental transfer of antibody-like biopharmaceuticals can help to predict risk of developmental toxicity across species, including humans. To complement previously published placental transfer data in the rat with humanized IgGΔ2 (hIgG2), the timing and magnitude of transfer in the cynomolgus monkey and embryo/fetal biodistribution of maternally administered 125 I-radiolabeled hIgG2 was quantified on gestation days (GD) 35, 40, 50, 70, and 140 using gamma counting and whole body autoradiography 24 hr following intravenous injection. Chorioallantoic placental tissues were collected at all time points for Western Blot analysis with anti-FcRn antibody. Maternally administered 125 I-hIgG2 was found in embryo/fetal tissues at all time points, including organogenesis. Embryo/fetal plasma 125 I-hIgG2 concentration increased during gestation, but only slightly up to GD 70 in embryo/fetal tissues, with hIgG2 tissue concentrations generally similar between GD70 and 140. The embryo/fetal:maternal 125 I-hIgG2 plasma concentration ratio was approximately 2.3 fold higher on GD 140, in comparison to ratios on GD 40. Importantly, placental FcRn protein expression was confirmed at all timepoints. These data demonstrate placental transfer of hIgG2 in a nonhuman primate model, and at levels comparable to the rat model, raising the potential for adverse developmental outcomes by direct antibody binding to biological targets.

This review presents a European Federation of Pharmaceutical Industries and Association/PreClinical Development Expert Group (EFPIA-PDEG) topic group consensus on a data-driven approach to harmonized contraception recommendations for clinical trial protocols and product labeling. There is no international agreement in pharmaceutical clinical trial protocols or product labeling on when/if female and/or male contraception is warranted and for how long after the last dose. This absence of consensus has resulted in different recommendations among regions. For most pharmaceuticals, contraception recommendations are generally based exclusively on nonclinical data and/or mechanism. For clinical trials, contraception is the default position and is maintained for women throughout clinical development, whereas appropriate information can justify removing male contraception. Conversely, contraception is only recommended in product labeling when warranted. A base case rationale is proposed for whether or not female and/or male contraception is/are warranted, using available genotoxicity and developmental toxicity data. Contraception is generally warranted for both male and female subjects treated with mutagenic pharmaceuticals. We propose as a starting point that contraception is not typically warranted when the margin is 10-fold or greater between clinical exposure at the maximum recommended human dose and exposure at the no observed adverse effect level (NOAEL) for purely aneugenic pharmaceuticals and for pharmaceuticals that induce fetal malformations or embryo-fetal lethality. Other factors are discussed, including contraception methods, pregnancy testing, drug clearance, options for managing the absence of a developmental toxicity NOAEL, drug-drug interactions, radiopharmaceuticals, and other drug modalities. Overall, we present a data-driven rationale that can serve as a basis for consistent contraception recommendations in clinical trials and in product labeling across regions.

BNT162b2 is a vaccine developed to prevent coronavirus disease 2019 (COVID-19). BNT162b2 is a lipid nanoparticle formulated nucleoside-modified messenger RNA (mRNA) encoding the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein locked in its prefusion conformation. A developmental and reproductive toxicity study was conducted in rats according to international regulatory guidelines. The full human BNT162b2 dose of 30 μg mRNA/dose (>300 times the human dose on a mg/kg basis) was administered intramuscularly to 44 female rats 21 and 14 days prior to mating and on gestation days 9 and 20. Half of the rats were subject to cesarean section and full fetal examination at the end of gestation, and the other half were allowed to deliver and were monitored to the end of lactation. A robust neutralizing antibody response was confirmed prior to mating and at the end of gestation and lactation. The presence of neutralizing antibodies was also confirmed in fetuses and offspring. Nonadverse effects, related to the local injection site reaction, were noted in dams as expected from other animal studies and consistent with observations in humans. There were no effects of BNT162b2 on female mating performance, fertility, or any ovarian or uterine parameters nor on embryo-fetal or postnatal survival, growth, physical development or neurofunctional development in the offspring through the end of lactation. Together with the safety profile in nonpregnant people, this ICH-compliant nonclinical safety data supports study of BNT162b2 in women of childbearing potential and pregnant and lactating women.

Traditionally, understanding potential developmental toxicity from pharmaceutical exposures has been based on the results of ICH guideline studies in two species. However, support is growing for the use of weight of evidence approaches when communicating the risk of developmental toxicity, where the intended pharmacologic mode of action affects fundamental pathways in developmental biology or phenotypic data from genetically modified animals may increasingly be included in the overall assessment. Since some concern surrounds the use of data from knockout (KO) mice to accurately predict the risk for pharmaceutical modulation of a target, a deeper understanding of the relevance and predictivity of adverse developmental effects in KO mice for pharmacological target modulation is needed. To this end, we compared the results of embryo-fetal development (EFD) studies for 86 drugs approved by the FDA from 2017 to 2019 that also had KO mouse data available in the public domain. These comparisons demonstrate that data from KO mouse models are overall highly predictive of malformations or embryo-fetal lethality (MEFL) from EFD studies, but less so of a negative outcome in EFD studies. This information supports the use of embryo-fetal toxicity data in KO models as part of weight of evidence approaches in the communication of developmental toxicity risk of pharmaceutical compounds.

Mycobacterium avium and Mycobacterium intracellulare are ubiquitous environmental mycobacteria that are frequently isolated from clinical specimens. These mycobacteria may cause significant infections, in immunocompromised patients in particular. Due to similar biochemical characteristics, they are

Toxicity studies in pregnant animals are not always necessary for assessing the human risk of developmental toxicity of biopharmaceuticals. The growing experience and information on target biology and molecule-specific pharmacokinetics present a powerful approach to accurately anticipate effects of target engagement by biopharmaceuticals using a weight of evidence approach. The weight of evidence assessment should include all available data including target biology, pharmacokinetics, class effects, genetically modified animals, human mutations, and a thorough literature review. When assimilated, this weight of evidence evaluation may be sufficient to inform risk for specific clinical indications and patient populations. While under current guidance this approach is only applicable for drugs and biologics for oncology, the authors would like to suggest that this approach may also be appropriate for other disease indications. When there is an unacceptable level of uncertainty and a toxicity study in pregnant animals could impact human risk assessment, then such studies should be considered. Determination of appropriate nonclinical species for developmental toxicity studies to inform human risk should consider species-specific limitations, reproductive physiology, and pharmacology of the biopharmaceutical. This paper will provide considerations and examples of the weight of evidence approach to evaluating the human risk of developmental toxicity of biopharmaceuticals.

Tofacitinib, an oral Janus kinase (JAK) inhibitor for treatment of rheumatoid arthritis, targets JAK1, JAK3, and to a lesser extent JAK2 and TYK2. JAK1/3 inhibition impairs gamma common chain cytokine receptor signaling, important in lymphocyte development, homeostasis and function. Adult and juvenile cynomolgus monkey and rat studies were conducted and the impact of tofacitinib on immune parameters (lymphoid tissues and lymphocyte subsets) and function (T-dependent antibody response (TDAR), mitogen-induced T cell proliferation) assessed. Tofacitinib administration decreased circulating T cells and NK cells in juvenile and adult animals of both species. B cell decreases were observed only in rats. These changes and decreased lymphoid tissue cellularity are consistent with the expected pharmacology of tofacitinib. No differences were observed between juvenile and adult animals, either in terms of doses at which effects were observed or differential effects on immune endpoints. Lymphomas were observed in three adult monkeys. Tofacitinib impaired the primary TDAR in juvenile monkeys, although a recall response was generated. Complete or partial reversal of the effects on the immune system was observed.

Palbociclib is a selective inhibitor of the cyclin-dependent kinase (CDK) 4/6, approved for the treatment of breast cancer. We assessed the potential effects of oral administration of palbociclib on reproduction and development. There were no effects on female or male fertility indices; however, in the male there was seminiferous tubule degeneration in the testes and secondary findings in the epididymides, lower testicular and epididymal weights, sperm density and motility. Palbociclib was not teratogenic in rats or rabbits; however, in the presence of maternal toxicity (lower maternal body weight gain and food consumption), low fetal body weights were observed in rats and small forepaw phalanges were noted in rabbits. There were, however, no adverse effects on the F1 generation in a pre- and post-natal developmental toxicity study in the rat.

As alternative models and scientific advancements improve the ability to predict developmental toxicity, the challenge is how to best use this information to support safe use of pharmaceuticals in humans. While in vivo experimental data are often expected, there are other important considerations that drive the impact of developmental toxicity data to human risk assessment and product labeling. These considerations include three key elements: (1) the drug's likelihood of producing off-target toxicities, (2) risk tolerance of adverse effects based on indication and patient population, and (3) how much is known about the effects of modulating the target in pregnancy and developmental biology. For example, there is little impact or value of a study in pregnant monkeys to inform the risk assessment for a highly specific monoclonal antibody indicated for a life-threatening indication against a target known to be critical for pregnancy maintenance and fetal survival. In contrast, a small molecule to a novel biological target for a chronic lifestyle indication would warrant more safety data than simply in vitro studies and a literature review. Rather than accounting for innumerable theoretical possibilities surrounding each potential submission's profile, we consolidated most of the typical situations into eight possible scenarios across these three elements, and present a discussion of these scenarios here. We hope that this framework will facilitate a rational approach to determining what new information is required to inform developmental toxicity risk of pharmaceuticals in context of the specific needs of each program while reducing animal use where possible.

Standard components of nonclinical toxicity testing for novel pharmaceuticals include clinical and anatomic pathology, as well as separate evaluation of effects on reproduction and development to inform clinical development and labeling. General study designs in regulatory guidances do not specifically mandate use of pathology or reproductive end points across all study types; thus, inclusion and use of these end points are variable. The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology (STP) formed a Working Group to assess the current guidelines and practices on the use of reproductive, anatomic pathology, and clinical pathology end points in general, reproductive, and developmental toxicology studies. The Working Group constructed a survey sent to pathologists and reproductive toxicologists, and responses from participating organizations were collected through the STP for evaluation by the Working Group. The regulatory context, relevant survey results, and collective experience of the Working Group are discussed and provide the basis of each assessment by study type. Overall, the current practice of including specific end points on a case-by-case basis is considered appropriate. Points to consider are summarized for inclusion of reproductive end points in general toxicity studies and for the informed use of pathology end points in reproductive and developmental toxicity studies.

Two intravenous studies with tanezumab, an anti-nerve growth factor monoclonal antibody, were conducted in pregnant cynomolgus monkeys to assess potential effects on pregnancy and pre- and postnatal development. Study 1 evaluated infants up to 12 months of age following weekly maternal dosing (0, 0.5, 4 or 30 mg/kg; 18 per group) from gestation day (GD) 20 through parturition. Study 2 evaluated infants 2 months postnatally following weekly maternal dosing (0, 0.5 or 30 mg/kg; 20-21 per group) from GD 20 through 48. In the absence of maternal toxicity, tanezumab increased stillbirth and post-birth infant mortality/morbidity, decreased infant growth and resulted in microscopic changes in the peripheral sympathetic and sensory nervous system of the infants at all doses. Decreased primary antibody responses and increased incidences in skin changes in infants were also observed. The no-observed-adverse-effect-level for maternal toxicity was 30 mg/kg and0.5 mg/kg for developmental toxicity.

BACKGROUND: Understanding species differences in placental transfer of Fc-containing biopharmaceuticals (particularly monoclonal antibodies) will improve human risk extrapolation from nonclinical embryo-fetal development toxicity data. METHODS: Maternal and fetal concentration data from 10, 15, 8, and 34 Fc-containing biopharmaceuticals in the rabbit, rat, mouse, and cynomolgus monkey, respectively, from an industry survey were analyzed for trends in placental transfer. RESULTS AND CONCLUSIONS: Embryonic (before the end of organogenesis) exposure was assessed in one molecule each in rabbit, rat, and mouse, but detectable levels were present only in rodents. In rodents, fetal levels remained relatively constant from gestation day (GD) 16 and 17 until the end of gestation, while maternal levels decreased or remained constant in rat and decreased in mice. In rabbits, following a last dose on GD 19, fetal levels increased markedly in late gestation while maternal levels decreased. In the cynomolgus monkey, fetal levels increased substantially from GD 50 to 100 and were maintained relatively constant through parturition (approximately GD 165). Based on available data of both the monkey and rabbit, IgG1 molecules appeared to transfer more readily than other isotypes in late gestation. Across all species, there was no differential transfer based on pharmacologic target being soluble or membrane bound. Within each species there was a correlation between maternal and fetal exposure, suggesting it may be possible to predict fetal exposures from maternal exposure data. These nonclinical data (both temporal and quantitative aspects) are discussed in a comparative context relative to our understanding of IgG placental transfer in humans. © 2014 Wiley Periodicals, Inc.

To determine the sensitivity of male reproductive toxicity endpoints in NHPs we performed a power analysis of routine and triggered endpoints using control data from sexually mature Asian and Mauritian NHPs. The power to detect a 50% change from control was 13-30% for male reproductive organ weights, ∼30% for testicular volume, 6-66% for seminal analyses and 10-78% for male hormones. Overall, male reproductive endpoints have poor power (less than 80%) to detect a 50% change from control with a group size of 3 monkeys. Confidently identifying adverse male reproductive effects with these endpoints would likely require specialized study designs with larger group sizes. Triggering of non-routine endpoints in cases where there is special concern for male reproductive toxicity is unlikely to increase sensitivity to detect adverse effects.

The neonatal Fc receptor (FcRn) is a heterodimeric membrane associated protein expressed in a variety of endothelial, epithelial and hematopoietic cells. FcRn regulates pH dependent intracellular trafficking of immunoglobulin G (IgG) and albumin, resulting in enhanced serum persistence and transcellular permeability of these proteins compared to other proteins of similar size. FcRn confers passive immunity during the early stages of life by facilitating maternal transmission of antibodies during gestation, and in some species during the neonatal period. The receptor continues to contribute to immunity beyond the perinatal period and throughout life by providing immunosurveillance in intestinal, pulmonary and genitourinary mucosa. In this capacity, FcRn facilitates bidirectional transport of IgG across mucosa and intracellular trafficking of antigen-antibody complexes in antigen presenting cells. Based on the functional roles of FcRn in regulating serum persistence and transcellular permeability, protein engineers have sought to exploit this receptor as a means of enhancing the absorption, distribution, metabolism and excretion (ADME) of IgG-based therapeutics. In this review, the current state of knowledge regarding the structural, mechanistic and functional properties of FcRn, as they relate to the ADME of IgG-based therapeutics, are discussed.

Langerhans cell histiocytosis is characterized by a localized or systemic proliferation of Langerhans cells. BRAF mutations have been reported in 40-70% of cases and MAP2K1 mutations have been found in BRAF-negative cases, supporting that Langerhans cell histiocytosis is a true neoplasm, at least in mutated cases. In a small subset of patients, Langerhans cell histiocytosis is detected incidentally in a biopsy involved by lymphoma. These lesions are usually minute and rarely have been assessed for mutations. We assessed for BRAF and MAP2K1 mutations in seven cases of Langerhans cell histiocytosis detected incidentally in biopsies involved by lymphoma. We performed immunohistochemical analysis for phosphorylated (p)-ERK. There were four men and three women (median age, 54 years; range, 28-84). The biopsies included lymph nodes (n=6) and chest wall (n=1). The lymphomas included five classical Hodgkin lymphoma, one mantle cell lymphoma, and one angioimmunoblastic T-cell lymphoma. All cases were negative for BRAF V600E and MAP2K1 mutations. Nevertheless, three of seven cases showed ERK activation as shown by expression of p-ERK. We performed mutation analysis using a panel of 134 commonly mutated genes (including BRAF and MAP2K1) by next-generation sequencing on three cases, including two cases positive for p-ERK by immunohistochemistry. No mutations were detected in any of the three cases assessed. Six patients received therapy appropriate for their lymphoma. With a median follow-up of 21 months (range, 6-89), no patients developed disseminated or recurrent Langerhans cell histiocytosis. We conclude that lymphoma-associated Langerhans cell histiocytosis is a clinically benign process that is not associated with BRAF V600E or MAP2K1 mutations and, as suggested by others, the designation Langerhans cell hyperplasia may be more appropriate. Nevertheless, the expression of p-ERK in three cases suggests that the RAS-RAF-MAP2K-ERK pathway is activated, perhaps by non-mutational mechanisms induced by the presence of lymphoma or lymphoma-microenvironment interactions.

As alternative models and scientific advancements improve the ability to predict developmental toxicity, the challenge is how to best use this information to support safe use of pharmaceuticals in humans. While in vivo experimental data are often expected, there are other important considerations that drive the impact of developmental toxicity data to human risk assessment and product labeling. These considerations include three key elements: (1) the drug's likelihood of producing off-target toxicities, (2) risk tolerance of adverse effects based on indication and patient population, and (3) how much is known about the effects of modulating the target in pregnancy and developmental biology. For example, there is little impact or value of a study in pregnant monkeys to inform the risk assessment for a highly specific monoclonal antibody indicated for a life-threatening indication against a target known to be critical for pregnancy maintenance and fetal survival. In contrast, a small molecule to a novel biological target for a chronic lifestyle indication would warrant more safety data than simply in vitro studies and a literature review. Rather than accounting for innumerable theoretical possibilities surrounding each potential submission's profile, we consolidated most of the typical situations into eight possible scenarios across these three elements, and present a discussion of these scenarios here. We hope that this framework will facilitate a rational approach to determining what new information is required to inform developmental toxicity risk of pharmaceuticals in context of the specific needs of each program while reducing animal use where possible.

BACKGROUND There is concern about embryo-fetal exposure to antibody-based biopharmaceuticals based on the increase of such therapies being prescribed to women of childbearing potential. Therefore, there is a desire to better characterize embryo-fetal exposure of these molecules. The pregnant rat is a standard model for evaluating the potential consequences of exposure but placental transfer of antibody-based biopharmaceuticals is not well understood in this model. METHODS The relative embryo-fetal distribution of an antibody-based biopharmaceutical was evaluated in the rat. Bevacizumab (Avastin) was chosen as a tool antibody since it does not have significant target binding in the rat that might influence embryo-fetal biodistribution. Avastin was labeled with a fluorescent dye, characterized, and injected into pregnant rats at different gestation ages. Labeled Avastin in fetal tissues was visualized ex vivo using an IVIS 200 (Caliper, A PerkinElmer Company, Alameda, CA). RESULTS Avastin localized to the fetus as early as 24-hr post intravenous injection of the dam, and was taken up by the fetus in a dose-dependent manner. Avastin was detectable in the developing embryo as early as gestation day 13 and continued to be transferred until the end of gestation. Fetal transfer of Avastins mutated in the portion of the antibody that binds the neonatal Fc receptor (FcRn) was tested in late gestation and was found to correlate with affinities of the mutant Avastin antibody to FcRn. CONCLUSIONS The novel application of this imaging technology was used to characterize the onset and duration of Avastin maternal–fetal transfer in rats and the importance of FcRn binding.

An important aspect of the enhanced pre- and postnatal developmental (ePPND) toxicity study in nonhuman primates (NHP) is that it combines in utero and postnatal assessments in a single study. However, it is unclear if NHP ePPND studies are suitable to perform all of the evaluations incorporated into rodent PPND studies. To understand the value of including cognitive assessment in a NHP ePPND toxicity study, we performed a power analysis of object discrimination reversal task data using a modified Wisconsin General Testing Apparatus (ODR-WGTA) from two NHP ePPND studies. ODR-WGTA endpoints evaluated were days to learning and to first reversal, and number of reversals. With α = 0.05 and a one-sided t-test, a sample of seven provided 80% power to predict a 100% increase in all three of the ODR-WGTA endpoints; a sample of 25 provided 80% power to predict a 50% increase. Similar power analyses were performed with data from the Cincinnati Water Maze (CWM) and passive avoidance tests from three rat PPND toxicity studies. Groups of 5 and 15 in the CWM and passive avoidance test, respectively, provided 80% power to detect a 100% change. While the power of the CWM is not far superior to the NHP ODR-WGTA, a clear advantage is the routine use of larger sample size, with a group of 20 rats the CWM provides ~90% power to detect a 50% change. Due to the limitations on the number of animals, the ODR-WGTA may not be suitable for assessing cognitive impairment in NHP ePPND studies.

BACKGROUND Sunitinib (SUTENT, Pfizer Inc., New York, NY) is a multitargeted inhibitor of selected receptor tyrosine kinases, which produces an antiproliferative and antiangiogenic effect by blocking pathways fundamental to tumor growth and survival. We investigated the effects of sunitinib on male and female fertility and early embryonic development in the rat. METHODS In the female fertility and early embryonic development phase, untreated males were paired with treated females dosed at 0 (control), 0.5, 1.5, and 5 mg/kg/day from 14 days premating, through mating, to gestation day 7. In the male fertility phase, the same males were then treated 58 days at doses of 0 (control), 1, 3, and 10 mg/kg/day, mated with untreated females, with continued daily dosing for a total of 74 days. RESULTS There was no systemic toxicity- or treatment-related effects on fertility in female rats. Females exposed at 5 mg/kg/day had an increase in the number of early resorptions with associated decrease in viable embryos. In the males, body weight and food consumption were decreased at 10 mg/kg/day compared to the controls. Male reproductive capacity, as assessed by copulation, fertility, and conception indices, was not impacted at any dose level. Sperm morphology, concentration, and motility were also unaffected by treatment. CONCLUSIONS There were no effects on male reproduction. An increase in corpora lutea and an increase in early resorptions with associated reduction in viable embryos was noted in the females dosed 5 mg/kg/day. Sunitinib at doses up to 1.5 and 10 mg/kg/day had no effects on female and male reproduction, respectively.

The critical periods of axial skeletal development in rats and mice have been well characterized, however the timing of skeletal development in rabbits is not as well known. It is important to have a more precise understanding of this timing of axial skeletal development in rabbits due to the common use of this species in standard nonclinical studies to assess embryo-fetal developmental toxicity. Hydroxyurea, a teratogen known to induce a variety of fetal skeletal malformations, was administered to New Zealand White rabbits as a single dose (500 mg/kg) on individual days during gestation (gestation day, GD 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 19) and fetal external, visceral, and skeletal morphology was examined following cesarean sections on GD 29. A wide range of fetal skeletal effects was observed following hydroxyurea treatment, with a progression of malformations from anterior to posterior structures over time, as well as from proximal to distal structures over time. The sensitive window of axial skeletal development was determined to be GD 8 to 13, while disruption of appendicular and cranio-facial skeletal development occurred primarily from GD 11 to 16 and GD 11 to 12, respectively. The results of this study provide a better understanding of the critical developmental window for different segments of the rabbit skeleton, which will aid in the design of window studies to investigate teratogenicity in rabbits.

Background: Lersivirine is a second-generation nonnucleoside reverse transcriptase inhibitor undergoing clinical development for the treatment of human immunodeficiency virus-1. An embryo-fetal development study was performed to evaluate the potential for maternal and developmental toxicity of lersivirine. Methods: Pregnant New Zealand White rabbits were administered 0, 100, 250, and 500 mg/kg lersivirine by oral gavage once daily on gestation days (GDs) 7 to 19, followed by cesarean section on GD 29 and fetal evaluation. Results: Maternal toxicity was noted at all dose levels (decreased food consumption and body weight gain), with fetal toxicity at 500 mg/kg (decreased fetal weights, increased postimplantation loss). Equivocal findings for axial skeletal malformations were observed in three fetuses at 500 mg/kg. To better understand if these malformations were related to treatment with lersivirine, a follow-up rabbit embryo-fetal development study was performed with 1000 mg/kg/day lersivirine (500 mg/kg BID, 12-hr interdose interval) for two different 3-day windows, GDs 8 to 10 or GDs 11 to 13, which represent the sensitive windows of axial skeletal development in rabbits. Control rabbits were administered vehicle following the same dosing regimen from GDs 8 to 13. Cesarean sections were performed on GD 29, and fetal skeletons were examined for the potential of lersivirine to cause skeletal malformations in rabbits. At maternal exposure levels higher than the initial study, lersivirine did not induce fetal skeletal malformations when administered in the sensitive windows of axial skeletal development. Conclusion: The results of these studies indicate that lersivirine did not exhibit any evidence of teratogenicity in rabbits.

Lersivirine is a second-generation nonnucleoside reverse transcriptase inhibitor undergoing clinical development for the treatment of HIV-1. An embryo-fetal developmental toxicity study was performed to evaluate the maternal and developmental toxicity of lersivirine in pregnant mice. Mated Crl:CD1(ICR) mice were administered 0, 150, 350, and 500 mg/kg lersivirine once daily by oral gavage on gestation days 6 to 17, followed by cesarean section on gestation day 18. The first 2 days of dosing for the high-dose group were done at 250 mg/kg to allow induction of hepatic metabolizing enzymes, after which the dose was increased to 500 mg/kg/day. This dosing paradigm allowed for maintenance of exposure in the high-dose group despite the considerable autoinduction that occurs in rodents following lersivirine treatment. Lersivirine did not cause an increase in external, visceral, or skeletal malformations. Intrauterine growth retardation, demonstrated by reduced fetal body weights and increased variations associated with delayed skeletal ossification, was noted at 350 and 500 mg/kg/day. The results of these studies indicate that lersivirine is not teratogenic in mice.

The changing environment of monoclonal antibody (mAb) development is impacting on the cost of drug development and the use of experimental animals, particularly non-human primates (NHPs). The drive to reduce these costs is huge and involves rethinking and improving nonclinical studies to make them more efficient and more predictive of man. While NHP use might be unavoidable in many cases because of the exquisite specificity and consequent species selectivity of mAbs, our increasing knowledge base can be used to improve drug development and maximise the output of experimental data. Data on GLP regulatory toxicology studies for 58mAbs were obtained from 10 companies across a wide range of therapeutic indications. These data have been used to investigate current practice and identify study designs that minimise NHP use. Our analysis shows that there is variation in the number of animals used for similar studies. This information has been used to develop practical guidance and make recommendations on the use of science-based rationale to design studies using fewer animals taking into account the current regulatory guidance. There are eight recommendations intended to highlight areas for consideration. They include guidance on the main group size, the inclusion of recovery groups and the number of dose groups used in short and long term chronic toxicology studies.

Anatomical and developmental differences of the parental-offspring interface among experimental animals and humans throughout gestation are reviewed focusing on biodistribution of immunoglobulins (IgG). The formation of the extraembryonic membranes, uteroplacental circulation, and characteristics of the placenta (gross shape, modes of implantation, surface modifications that increase surface area, and extent of embryonic invasion into maternal tissue) are reviewed. Placental physiology and function are covered with attention to transfer of xenobiotics. Placental transfer of immunoglobulins in the human, non-human primate (NHP), rodent, and rabbit is discussed and the transfer of human fragment crystallizable (Fc)-containing biopharmaceuticals and potential impact on developmental toxicity risk assessment are specifically addressed. Safety assessment is often limited to the NHP as the only pharmacologically relevant model, despite poor statistical power as employed in current experimental designs. Although data are limited, the gestational timing of placental IgG transfer in rabbits appears to be more consistent with that of humans (i.e. occurring at the very end and after completion of organogenesis) than that of rodents, making the rabbit a reasonable choice assuming it is pharmacologically relevant. The rodent is not considered the most appropriate model for human placental transfer of Fc-containing biopharmaceuticals because it is currently believed to overestimate exposure during organogenesis. Nevertheless, the rodent may provide a conservative approach for hazard identification. It is clear that additional experimentation is needed to further clarify the timing of prenatal transfer of Fc-containing biopharmaceuticals in various species.

Bococizumab is a humanized monoclonal IgG2Δa antibody against proprotein convertase subtilisin/kexin type 9 (PCSK9) for the treatment of hyperlipidemia. The evaluation of potential effects on embryo-fetal development was conducted in the rat. In a pharmacokinetic/pharmacodynamic study bococizumab was administered intravenously to pregnant Sprague–Dawley (SD) rats (n = 8/group) at 0, 10, 30, and 100 mg/kg during organogenesis. Maternal and fetal bococizumab, total cholesterol and HDL concentrations were determined. Bococizumab was well tolerated and there were no effects on ovarian or uterine parameters. Maternal and fetal bococizumab exposure increased with increasing dose, with a corresponding dose-dependent decrease in fetal cholesterol levels. Maternal cholesterol levels were decreased significantly, with reductions that were of a similar magnitude regardless of dose. In the definitive embryo-fetal development study bococizumab was administered to pregnant SD rats (n = 20/group) at 0, 10, 30, and 100 mg/kg and no adverse maternal or developmental effects were observed up to 100 mg/kg. These studies have provided an appropriate and relevant safety assessment of bococizumab in pregnant rats to inform human risk assessment, demonstrating no adverse effects on embryo-fetal development at magnitudes greater than anticipated clinical exposure and in the presence of maximal reductions in maternal cholesterol and dose-dependent reductions in fetal cholesterol.

Nonhuman primates (NHPs) are an important model for evaluating the potential effects of new biopharmaceuticals on male and female reproduction and pre- and postnatal development. Toxicity testing for these parameters should be conducted in NHPs only when they are the only relevant species or are critical for the human risk assessment. In general, evaluation of potential effects on male and female reproduction can be included in general toxicity studies using sexually mature animals, and effects on development can be assessed in a single, well-designed developmental toxicity study. In the case of specific concerns about effects on the reproductive system, additional studies may be considered. Although the concepts of standard toxicity testing for development and reproduction still apply, the NHP model requires different considerations and in most cases must be tailored based on the type of molecule, the intended patient population, and the expected pharmacology to enable the optimal use of these animals.

Finasteride is a specific inhibitor of type II 5alpha-reductase, the enzyme that converts testosterone (T) to the more potent androgen receptor agonist dihydrotestosterone (DHT). In utero exposure to androgen receptor antagonists and T biosynthesis inhibitors have induced permanent effects on androgen-sensitive end points such as anogenital distance (AGD), nipple retention, and malformations of the male rat reproductive tract. The objectives of this study were to (1) characterize the dose response of finasteride-mediated alterations in androgen-dependent developmental end points, (2) determine whether prenatal exposure to finasteride permanently decreases AGD or results in nipple retention, and (3) evaluate whether AGD or nipple retention is predictive of adverse alterations in the male reproductive tract. Pregnant Crl:CD(SD)BR rats (n=5-6/group) were gavaged with either vehicle or finasteride at 0.01, 0.1, 1.0, 10, or 100 mg/kg/day on gestation days 12 to 21. All male offspring were monitored individually until necropsy on postnatal day (PND) 90. The present study design has been used previously for other antiandrogens and is sensitive to perturbations of the male rat reproductive tract. Decreases in AGD on PND 1 and increases in areolae-nipple retention on PND 13 were significantly different from controls in all finasteride-exposed male rats. Finasteride-induced changes in AGD and nipple retention were permanent in male rats exposed to finasteride at and above 0.1 mg/kg/day. On PND 90, dorsolateral and ventral prostate lobes were absent in 21 to 24% of rats exposed to 100 mg/kg/day finasteride and weighed significantly less at and above 10 mg/kg/day. In the highest dose group, 73% of animals had ectopic testes, much higher than previously reported. The most sensitive malformation other than decreased AGD and nipple retention was the dose-dependent increase in hypospadias. The lowest observed adverse effect level (LOAEL) for finasteride-induced permanent effects in this study was 0.1 mg/kg/day based on permanent changes in AGD and nipple retention. Finasteride-induced changes in AGD and retention of nipples were highly predictive of hypospadias, ectopic testes, and prostate malformations even though some animals with retained nipples or decreased AGD may not have had other reproductive tract malformations. In summary, prenatal exposure to finasteride specifically inhibited DHT-mediated development with little to no change in T-mediated development.

Delayed-type hypersensitivity (DTH) is a T-cell-mediated immune response that may be used for immunotoxicity testing in non-clinical species. However, in some cases DTH assays using T-dependent antigens may be confounded by the production of antibodies to the antigen. The authors have previously modified a DTH assay, initially validated in the mouse, for use in juvenile rats to assess the effect of immunosuppressive drugs on the developing rat immune system. The assay measures footpad swelling induced by subcutaneous footpad injection of Candida albicans (C. albicans) derived-chitosan in rats previously sensitized with C. albicans. Antibodies to chitosan are not produced in this model. However, considerable inter-animal variability inherent in the footpad swelling assay can make it difficult to precisely quantify the magnitude of the immune response and inhibition by immunosuppressants, particularly if complete suppression is not observed. This report describes the development of an ex vivo assay to assess DTH in rats using interferon (IFN)-γ production by splenocytes, obtained from rats sensitized with C. albicans, as the quantifiable measure of the DTH response. Adult and neonatal rats administered dexamethasone (DEX), a known immunosuppressant, exhibited immunosuppression as evidenced by a reduction in ex vivo IFNγ production from splenocytes challenged with C. albicans-derived chitosan. Current data indicate that the ex vivo based DTH assay is more sensitive than the conventional footpad swelling assay due to a lower background response and the ability to detect a response as early as post-natal day (PND) 12. The ex vivo based rat DTH assay offers a highly sensitive and quantitative alternative to the footpad swelling assay for the assessment of the immunotoxic potential of drugs. The increased sensitivity of the ex vivo DTH assay may be useful for identifying smaller changes in response to immunotoxic drugs, as well as detecting responses earlier in animal development.

Tanezumab, an antibody to nerve growth factor, was administered to pregnant cynomolgus monkeys at 0, 0.5, 4, and 30 mg/kg weekly, beginning gestation day (GD) 20 through parturition (� GD165). Maternal tanezumab administration appeared to increase stillbirths and infant mortality, but no consistent pattern of gross and/or microscopic change was detected to explain the mortality. Offspring exposed in utero were evaluated at 12 months of age using light microscopy (all tissues), stereology (basal forebrain cholinergic and dorsal root ganglia neurons), and morphometry (sural nerve). Light microscopy revealed decreased number of neurons in sympathetic ganglia (superior mesenteric, cervicothoracic, and ganglia in the thoracic sympathetic trunk). Stereologic assessment indicated an overall decrease in dorsal root ganglion (thoracic) volume and number of neurons in animals exposed to tanezumab 4 mg/kg (n ¼ 9) and 30 mg/kg (n ¼ 1). At all tanezumab doses, the sural nerve was small due to decreases in myelinated and unmyelinated axons. Existing axons/ myelin sheaths appeared normal when viewed with light and transmission electron microscopy. There was no indication of tanezumab-related, active neuron/nerve fiber degeneration/necrosis in any tissue, indicating decreased sensory/ sympathetic neurons and axonal changes were due to hypoplasia or atrophy. These changes in the sensory and sympathetic portions of the peripheral nervous system suggest some degree of developmental neurotoxicity, although what effect, if any, the changes had on normal function and survival was not apparent. Overall, these changes were consistent with published data from rodent studies.

The recent interest in hormonally active environmental contaminants has sparked a drive to find sensitive methods to measure their effects on wildlife. A molecular-based assay has been developed to measure the induction of gene expression in sheepshead minnows ( Cyprinodon variegatus ) exposed in vivo to the natural and pharmaceutical estrogens 17β-estradiol, ethinylestradiol, and diethylstilbestrol. This method used differential display reverse transcriptase polymerase chain reaction assays to compare the expression of individual mRNAs from control and estrogen-exposed fish. Forty-eight differentially expressed cDNAs were isolated by this method, including cDNAs for vitelline envelope proteins and vitellogenin. The mRNA expression patterns for fish injected with a pharmacological dose of estradiol (5 mg/kg) were identical to those obtained in fish receiving constant aqueous exposure to 212 ng estradiol/liter. Further, the cDNA “fingerprint” pattern observed in the estradiol-treated fish also matched that obtained in fish receiving continuous-flow aqueous exposures to 192 ng ethinyl estradiol/liter and a nominal concentration of 200 ng diethylstilbestrol/liter. The results demonstrate a characteristic expression pattern for genes upregulated by exposure to a variety of natural and anthropogenic estrogens and suggest this approach may be valuable to examine the potential effects of environmental contaminants on other endocrine-mediated pathways of reproduction, growth, and development.

Temporal and dose-response relationships of vitellogenin (VTG) mRNA induction and subsequent plasma VTG accumulation were established for sheepshead minnows (Cyprinodon variegatus) treated with p-nonylphenol (an alkylphenol) and the organochlorine pesticides methoxychlor and endosulfan. Thirty-two adult male fish per treatment were continuously exposed to measured concentrations of 0.64, 5.4, 11.8, 23.3, and 42.7 micrograms/L p-nonylphenol; 1.1, 2.5, 5.6, 12.1, and 18.4 micrograms/L methoxychlor; and in two separate tests, 15.9, 36.3, 68.8, 162, 277, 403, 590, and 788 ng/L endosulfan using an intermittent flow-through dosing apparatus. Separate triethylene glycol (50 microliters/L) and 17 beta-estradiol (65.1 ng/L) treatments served as the negative and positive controls, respectively. Four fish were randomly sampled from each test concentration on days 2, 5, 13, 21, 35, and 42 of exposure, and levels of hepatic VTG mRNA induction and serum VTG accumulation were determined for each individual. Overall, fish exposed to p-nonylphenol or methoxychlor demonstrated a rapid, dose-dependent synthesis of VTG mRNA up to day 5 of exposure, followed by a relatively constant dose-dependent expression through day 42. Both chemicals showed a dose-dependent increase in plasma VTG over the entire time course of exposure, with significantly elevated VTG levels by the fifth day of exposure to p-nonylphenol at concentrations of 5.4 micrograms/L or greater and to methoxychlor at concentrations of 2.5 micrograms/L or greater. Exposure to 0.64 microgram/L p-nonylphenol resulted in highly variable plasma VTG levels of less than 6 mg/ml. Exposures with endosulfan failed to induce measurable levels of either hepatic VTG mRNA or serum VTG at the chemical concentrations tested. Our results demonstrate that the sheepshead minnow bioassay is a suitable estuarine/marine teleost model for in vivo screening of potentially estrogenic substances.

Many environmentally persistent xenobiotic chemicals appear to disrupt normal endocrine function by acting as ligands for endogenous steroid receptors, including the estrogen receptor. Xenobiotics that bind to the estrogen receptor may elicit several effects, one of which is activating estrogen-responsive genes, such as vitellogenin (Vtg). Primers to vitellogenin mRNA have been used to amplify a portion of the coding sequence in sheepshead minnow (SHM) (Cyprinodon variegatus). Two Vtg cDNA fragments from SHM were isolated exhibiting 72% sequence homology and corresponding to the two Vtg genes identified in the mummichog, Fundulus heteroclitus. Using these Vtg cDNA fragments as sensitive genetic probes, we evaluated the initial estrogenic response of fish exposed to natural or anthropogenic chemicals. These probes were used to study in vivo gene induction in SHM exposed to 17beta-estradiol (E(2)) and ethinylestradiol (EE(2)) under controlled laboratory conditions. Hepatic Vtg mRNA was upregulated and plasma Vtg synthesis in estrogen-induced SHM was assessed. Two in vivo time-course experiments were conducted; a single injection of E(2) followed over 72 h and a double E(2) injection examined for 12 days. These two protocols provided evidence for differential hepatic Vtg mRNA regulation resulting from a single or a double injection. In a separate experiment using an aqueous flowthrough system, constant exposures to low doses of E(2) (200 ng/L) and EE(2) (100 ng/L) induced hepatic Vtg mRNA and plasma Vtg to levels comparable with the E(2) injections. Larger aqueous exposure doses (2000 ng/L E(2) or 1000 ng/L EE(2)) in the flowthrough experiment resulted in greater responses of hepatic Vtg mRNA and plasma Vtg at 7 days. Constant aqueous exposure to E(2) (2000 ng/L) or EE(2) (1000 ng/L) may thus be more effective than a single large-dose injection (5 mg/kg) to stimulate Vtg gene activation and synthesis.

An in vivo bioasssay for vitellogenin (VTG) synthesis was developed to screen individual chemicals or mixtures of chemicals for potentially estrogenic effects in a marine teleost model. An enzyme-linked immunosorbent assay (ELISA) was used to quantitate VTG synthesis in male sheepshead minnows (Cyprinodon variegatus) exposed to five concentrations of the natural estrogen (17beta-estradiol), a synthetic, steroidal pharmaceutical estrogen (17alpha-ethynyl estradiol), or a synthetic, non-steroidal, pharmaceutical estrogen (diethystilbestrol) for 16 days. At an exposure concentration of 20 ng/l, only diethystilbestrol elicited a vitellogenic response. At all test concentrations greater than 100 ng/l, VTG appeared in the plasma in a dose-dependent manner for the three estrogen treatments. Liver VTG mRNA measurements were also made, exhibiting no clear correlations between quantities, nor temporal appearance of the message and mature protein were apparent. This assay is short-term, relatively inexpensive, shows a direct response, and easily quantitated.

The main focus of environmental endocrine disruption is understanding how hormone mimics may be affecting reproduction and development. The principle mode of action for hormones is to regulate gene expression. The vitellogenin mRNA assay described in this paper was developed to study the specific mechanisms of action by proposed xenoestrogens. The establishment of this method is widely applicable to different species and to different genes. This gene specificity is what makes it such a good method to characterize a particular mechanism of action. Vitellogenin was chosen due to its current value as a plasma protein biomarker for estrogen exposure. The vitellogenin mRNA assay serves as a valuable complement to plasma vitellogenin, as it increases the sensitivity of detection as well as its potential to detect an earlier estrogenic response. Once validated, it can be used in biomonitoring as an effective method to detect a specific mechanism of action in samples exposed to xenoestrogens.

Understanding species differences in placental transfer of Fc-containing biopharmaceuticals (particularly monoclonal antibodies) will improve human risk extrapolation from nonclinical embryo-fetal development toxicity data.Maternal and fetal concentration data from 10, 15, 8, and 34 Fc-containing biopharmaceuticals in the rabbit, rat, mouse, and cynomolgus monkey, respectively, from an industry survey were analyzed for trends in placental transfer.Embryonic (before the end of organogenesis) exposure was assessed in one molecule each in rabbit, rat, and mouse, but detectable levels were present only in rodents. In rodents, fetal levels remained relatively constant from gestation day (GD) 16 and 17 until the end of gestation, while maternal levels decreased or remained constant in rat and decreased in mice. In rabbits, following a last dose on GD 19, fetal levels increased markedly in late gestation while maternal levels decreased. In the cynomolgus monkey, fetal levels increased substantially from GD 50 to 100 and were maintained relatively constant through parturition (approximately GD 165). Based on available data of both the monkey and rabbit, IgG1 molecules appeared to transfer more readily than other isotypes in late gestation. Across all species, there was no differential transfer based on pharmacologic target being soluble or membrane bound. Within each species there was a correlation between maternal and fetal exposure, suggesting it may be possible to predict fetal exposures from maternal exposure data. These nonclinical data (both temporal and quantitative aspects) are discussed in a comparative context relative to our understanding of IgG placental transfer in humans.