Nonclinical safety evaluation of erenumab, a CGRP receptor inhibitor for the prevention of migraine.

Calcitonin gene-related peptide (CGRP) and its receptor have been implicated as a key mediator in the pathophysiology of migraine. Thus, erenumab, a monoclonal antibody antagonist of the CGRP receptor, administered as a once monthly dose of 70 or 140 mg has been approved for the preventive treatment of migraine in adults. Due to the species specificity of erenumab, the cynomolgus monkey was used in the pharmacology, pharmacokinetics, and toxicology studies to support the clinical program. There were no effects of erenumab on platelets in vitro (by binding, activation or phagocytosis assays). Specific staining of human tissues with erenumab did not indicated any off-target binding. There were no erenumab-related findings in a cardiovascular safety pharmacology study in cynomolgus monkeys or in vitro in human isolated coronary arteries. Repeat-dose toxicology studies conducted in cynomolgus monkeys at dose levels up to 225 mg/kg (1 month) or up to 150 mg/kg (up to 6 months) with twice weekly subcutaneous (SC) doses showed no evidence of erenumab-mediated adverse toxicity. There were no effects on pregnancy, embryo-fetal or postnatal growth and development in an enhanced pre-postnatal development study in the cynomolgus monkey. There was evidence of placental transfer of erenumab based on measurable serum concentrations in the infants up to 3 months post birth. The maternal and developmental no-observed-effect level (NOEL) was the highest dose tested (50 mg/kg SC Q2W). These nonclinical data in total indicate no safety signal of concern to date and provide adequate margins of exposure between the observed safe doses in animals and clinical dose levels.

An Enhanced Pre- and Postnatal Development Study in Cynomolgus Monkeys with Tabalumab: A Human IgG4 Monoclonal Antibody.

Tabalumab, a human IgG4 monoclonal antibody (mAb) with neutralizing activity against both soluble and membrane B-cell activating factor (BAFF), has been under development for the treatment of autoimmune diseases. The purpose of this study was to determine the potential adverse effects of maternal tabalumab exposure on pregnancy, parturition, and lactation of the mothers and on the growth, viability, and development of the offspring through postnatal day (PND) 204. Tabalumab was administered by subcutaneous injection to presumed pregnant cynomolgus monkeys (16-19 per group) every 2 weeks from gestation day (GD) 20 to 22 until parturition at doses of 0, 0.3, or 30 mg/kg. Evaluations in mothers and infants included clinical signs, body weight, toxicokinetics, blood lymphocyte phenotyping, T-cell-dependent antibody response (infants only), antitherapeutic antibody (ATA), organ weights (infants only), and gross and microscopic histopathology. Infants were also examined for external and visceral morphologic and neurobehavioral development. There were no adverse tabalumab-related effects on maternal or infant endpoints. An expected pharmacological decrease in peripheral blood B-lymphocytes occurred in adults and infants; however, B-cell recovery was evident by PND154 in adults and infants at 0.3 mg/kg and by PND204 in infants at 30 mg/kg. At 30 mg/kg, a reduced IgM antibody response to T-cell-dependent antigen keyhole limpet hemocyanin (KLH) was observed following primary immunization. Following secondary KLH immunization, all infants in both dose groups mounted anti-KLH IgM and IgG antibody responses similar to control. Placental and mammary transfer of tabalumab was demonstrated. In conclusion, the no-observed-adverse-effect level for maternal and developmental toxicity was 30 mg/kg, the highest dose tested. Exposures at 30 mg/kg provide a margin of safety of 16× the anticipated clinical exposure.

Placental transfer of a fully human IgG2 monoclonal antibody in the cynomolgus monkey, rat, and rabbit: a comparative assessment from during organogenesis to late gestation.

Understanding species differences in the placental transfer of monoclonal antibodies is important to inform species selection for nonclinical safety assessment, interpret embryo-fetal changes observed in these studies, and extrapolate their human relevance. Data presented here for a fully human immunoglobulin G2 monoclonal antibody (IgG2X) revealed that, during organogenesis, in both the cynomolgus monkey (gestation day 35 [gd35]) and the rat (gd10) the extent of IgG2X placental transfer (approximately 0.5% maternal plasma concentration, MPC) was similar to the limited published human data for endogenous IgG. At this early gestational stage, IgG2X placental transfer was approximately 6-fold higher in the rabbit (gd10). By the end of organogenesis, rat embryonic plasma concentrations (gd16) exceeded those in the cynomolgus monkey (gd50) by approximately 3-fold. These data suggest that relative to the cynomolgus monkey, the rabbit (and to a lesser extent the rat) may overestimate potential harmful effects to the human embryo during this critical period of development. Beyond organogenesis, fetal IgG2X plasma concentrations increased approximately 10-fold early in the second trimester (gd50-70) in the cynomolgus monkey and remained relatively unchanged thereafter (at approximately 5% MPC). Late gestational assessment was precluded in rabbits due to immunogenicity, but in rats, fetal IgG2X plasma concentrations increased more than 6-fold from gd16 to gd21 (reaching approximately 15% MPC). In rats, maternal exposure consistent with that achieved by ICH S6(R1) high-dose selection criteria resulted in embryonic plasma concentrations, reaching pharmacologically relevant levels during organogenesis. Furthermore, dose proportional exposure in both mothers and embryos indicated that this was unlikely to occur at the lower therapeutic dose levels used in humans.

Preclinical safety evaluations supporting pediatric drug development with biopharmaceuticals: strategy, challenges, current practices.

Evaluation of pharmaceutical agents in children is now conducted earlier in the drug development process. An important consideration for this pediatric use is how to assess and support its safety. This article is a collaborative effort of industry toxicologists to review strategies, challenges, and current practice regarding preclinical safety evaluations supporting pediatric drug development with biopharmaceuticals. Biopharmaceuticals include a diverse group of molecular, cell-based or gene therapeutics derived from biological sources or complex biotechnological processes. The principles of preclinical support of pediatric drug development for biopharmaceuticals are similar to those for small molecule pharmaceuticals and in general follow the same regulatory guidances outlined by the Food and Drug Administration and European Medicines Agency. However, many biopharmaceuticals are also inherently different, with limited species specificity or immunogenic potential which may impact the approach taken. This article discusses several key areas to aid in the support of pediatric clinical use, study design considerations for juvenile toxicity studies when they are needed, and current practices to support pediatric drug development based on surveys specifically targeting biopharmaceutical development.

Developmental and reproductive toxicology studies in nonhuman primates.

Developmental and reproductive toxicology testing in nonhuman primates (NHPs) has become more common due to the increasing number of biopharmaceuticals in drug development, since NHPs are frequently the only species to express pharmacologic responses similar to humans. NHPs may also be used to help resolve issues associated with small-molecule reproductive toxicology in traditional species (rodents and rabbits). Adequate designs in NHP are presented for developmental toxicity (embryo-fetal development, pre-postnatal development, enhanced pre-postnatal development), reproductive toxicity (male and female), and juvenile toxicity studies. Optional parameters that may be included in these studies are discussed, as are new study designs that consolidate multiple aspects of the reproductive assessment and thereby conserve the limited supply of sexually mature NHPs available for testing. The details described will assist scientists in pharmaceutical, regulatory, and contract research organizations who are involved in conducting these unique studies to optimize their design based on case-by-case considerations.

Use of barusiban in a novel study design for evaluation of tocolytic agents in pregnant and neonatal monkeys, including behavioural and immunological endpoints.

The oxytocin receptor antagonist barusiban, currently being developed for treatment of preterm labour, was investigated in pregnant cynomolgus monkeys with a 9-month postnatal follow-up of their offspring. The nature of barusiban, its indication, and the potential exposure of pre- and postnatal infants entailed the design of a unique protocol to investigate all aspects of maternal and offspring well-being. Barusiban was administered to the mothers from gestation day 85 until delivery with daily subcutaneous dosages up to 2.5mg/kg body weight/day. There were no test article-related effects seen in the mothers at any time during the study. The postnatal examination of offspring included routine toxicological parameters, as well as specialised investigation of the immune, cardiovascular, renal and central nervous systems, including a full behavioural assessment. A full pathology examination of offspring was performed at the end of the 9-month postnatal period. No adverse infant findings occurred.

Evaluation of early fetal exposure to vaginally-administered metronidazole in pregnant cynomolgus monkeys.

Given concern about potential embryo-fetal harm following seminal exposure to drugs with teratogenic potential, pharmaceutical companies use theoretical calculations to estimate seminal concentrations, maternal exposure, and distribution across the placenta to the embryo-fetal compartment for risk assessment. However, it is plausible that there are additional mechanisms whereby the conceptus is exposed. In order to determine if theoretical calculations are sufficiently conservative to predict embryo-fetal exposure from drugs in semen, pregnant cynomolgus monkeys were given a vaginal dose of metronidazole during the early fetal period and cesarean-sectioned. Maternal, fetal, and amniotic fluid samples were analyzed for metronidazole and 2-hydroxymetronidazole. Exposure to metronidazole and its metabolite were comparable in all matrices. These data demonstrated no preferential transfer mechanism to conceptus following intravaginal administration of a small molecule drug; and therefore, suggest that traditional modeling for embryo-fetal exposure to drugs in semen in support of risk assessment for pharmaceutical agents is sufficiently conservative.

Barusiban, a new highly potent and long-acting oxytocin antagonist: pharmacokinetic and pharmacodynamic comparison with atosiban in a cynomolgus monkey model of preterm labor.

Preterm labor (PTL) represents a significant unmet clinical need that affects up to 20% of all pregnancies and is a leading cause of preterm delivery and associated neonatal morbidity and mortality. Therapeutic options are limited, with existing drug therapy (tocolytics) compromised by side effects and limited efficacy. Because oxytocin (OT) is likely to be involved causally in PTL, this study compared two OT receptor antagonists, barusiban and atosiban, for their tocolytic effects. OT was given to instrumented pregnant cynomolgus monkeys to induce contractions and simulate PTL. Barusiban or atosiban was then given iv (bolus or infusion) to evaluate inhibitory effects on uterine contractions, measured by telemetric recording of intrauterine pressure. Both antagonists had high efficacy (96-98% inhibition of intrauterine pressure) and rapid onset of action (0.5-1.5 h). Barusiban was three to four times more potent than atosiban, which was attributed to its higher affinity and selectivity for the OT receptor. Barusiban also had a much longer duration of action (>13-15 h, compared with 1-3 h for atosiban). The inhibitory effects of barusiban were reversible within 1.5-2.5 h by high-dose OT infusion. Overall, barusiban's improved potency, long duration of action, and reversibility may provide an improved tocolytic for treatment of PTL.

Telemetric uterine contraction model in preterm cynomolgus monkeys.

A telemetric-based model is presented for evaluation of uterine contractions and preterm labor (PTL) in pregnant cynomolgus monkeys. The model allows continuous monitoring of electromyography (EMG) and intrauterine pressure (IUP) as indicators of uterine activity. A pressure sensor was implanted into the amnion of pregnant monkeys on gestational day (GD) 120 +/- 3 and biopotential sensors were attached to the uterus. A telemetry transmitter was placed in a subcuticular pocket located in the flank. Venous catheters were tethered to the next room for dosing and blood sampling without disturbing the conscious animals. EMG and/or IUP were monitored continuously post-operatively. IUP is a reliable parameter for monitoring intrauterine activity, as demonstrated by a close relationship between bursts of activity in the EMG and increases in IUP. Animals close to term showed a basal level of uterine activity during the daytime, with irregular contractions of <10 mmHg. In the night, spontaneous contractions (10-40 mmHg; maximum between 18:00 and 01:00 h) appeared every 3-6 min. Artificial contractions of 15-40 mmHg that mimicked preterm labor were induced at any time of the day by infusion of 5-60 mU oxytocin (OT) per kilogram per hour. These contractions showed a dose-dependent response to OT, and were stable for up to 14 h of constant infusion of OT. Following withdrawal of oxytocin, contractions returned to baseline within 1h. No desensitization of oxytocin-induced contractions was observed when oxytocin was administered daily for up to several weeks. This telemetric model characterizes uterine contractions in non-human primates and provides an excellent method to evaluate pharmacological characteristics of drug candidates intended to treat PTL.

Investigation of maternal and fetal exposure to an IgG2 monoclonal antibody following biweekly intravaginal administration to cynomolgus monkeys throughout pregnancy.

To assess the potential for male-mediated drug transfer to their female partner and/or developing conceptus, vaginal uptake of a monoclonal antibody (mAb) biotherapeutic was assessed in cynomolgus monkeys. A human IgG2 mAb (IgG2X; bound human and cynomolgus monkey neonatal Fc-receptor, FcRn, with similar high affinity) was administered intravaginally (IvG; 100mg/dose) to 5 pregnant cynomolgus monkeys biweekly from gestation day (gd) 21 to gd133. In all maternal samples collected before gd119, IgG2X plasma concentrations were below the limit of quantification (BLQ; <25ng/mL). After dosing on gd119 and 133, maternal IgG2X plasma concentrations remained BLQ in 3/5 monkeys and were very low in 2/5 (up to 116ng/mL; ∼0.01% of the IvG dose). IgG2X was BLQ in all fetal plasma samples. These data indicate that male-mediated mAb drug transfer via seminal fluid does not present a health risk to the female partner and is not bioavailable to the developing conceptus.

Infant cynomolgus monkeys exposed to denosumab in utero exhibit an osteoclast-poor osteopetrotic-like skeletal phenotype at birth and in the early postnatal period.

RANKL is a key regulator of bone resorption and osteoclastogenesis. Denosumab is a fully human IgG2 monoclonal antibody that inhibits bone resorption by binding and inhibiting the activity of RANKL. To determine the effects of denosumab on pre- and postnatal skeletal growth and development, subcutaneous injections of 0 (control) or 50 mg/kg/month denosumab were given to pregnant cynomolgus monkeys from approximately gestation day (GD) 20 until parturition (up to 6 doses). For up to 6 months postpartum (birth day [BD] 180/181), evaluation of the infants included skeletal radiographs, bone biomarkers, and oral examinations for assessment of tooth eruption. Infant bones were collected at necropsy for densitometry, biomechanical testing, and histopathologic evaluation from control and denosumab-exposed infants on BD1 (or within 2 weeks of birth) and BD181, and from infants that died or were euthanized moribund from BD5 to BD69. In all denosumab-exposed infants, biomarkers of bone resorption and formation were markedly decreased at BD1 and BD14 and slightly greater at BD91 vs. control, then similar to control values by BD181. Spontaneous long bone fractures were detected clinically or radiographically in 4 denosumab-exposed infants at BD28 and BD60, with evidence of radiographic healing at ≥BD60. In BD1 infants exposed to denosumab in utero, radiographic evaluations of the skeleton revealed decreased long bone length; a generalized increased radio-opacity of the axial and appendicular skeleton and bones at the base of the skull with decreased or absent marrow cavities, widened growth plates, flared/club-shaped metaphysis, altered jaw/skull shape, and reduced jaw length; and delayed development of secondary ossification centers. Densitometric evaluations in these infants demonstrated a marked increase in bone mineral density at trabecular sites, but cortical bone mineral density was decreased. Histologically, long bone cortices were attenuated and there was an absence of osteoclasts. Bones with active endochondral ossification consisted largely of a dense network of retained primary spongiosa with reduced marrow space consistent with an osteopetrotic phenotype. A minimal increase in growth plate thickness largely due to the expansion of the hypertrophic zone was present. Retained woven bone was observed in bones formed by intramembranous ossification, consistent with absence of bone remodeling. These changes in bone tissue composition and geometry were reflected in reduced biomechanical strength and material properties of bones from denosumab-exposed infants. Material property changes were characterized by increased tissue brittleness reflected in reductions in calculated material toughness at the femur diaphysis and lack of correlation between energy and bone mass at the vertebra; these changes were likely the basis for the increased skeletal fragility (fractures). Although tooth eruption was not impaired in denosumab-exposed infants, the reduced growth and increased bone density of the mandible resulted in dental abnormalities consisting of tooth malalignment and dental dysplasia. Radiographic changes at BD1 persisted at BD28, with evidence of resumption of bone resorption and remodeling observed in most infants at BD60 and/or BD90. In 2 infants euthanized on BD60 and BD69, there was histologic and radiographic evidence of subphyseal/metaphyseal bone resorption accompanied by multiple foci of ossification in growth plates that were markedly increased in thickness. In infants necropsied at BD181, where systemic exposure to denosumab had been below limits of quantitation for approximately 3months, there was largely full recovery from all bone-related changes observed earlier postpartum, including tissue brittleness. Persistent changes included dental dysplasia, decreased bone length, reduced cortical thickness, and decreased peak load and ultimate strength at the femur diaphysis. In conclusion, the skeletal and secondary dental effects observed in infant monkeys exposed in utero to denosumab are consistent with the anticipated pharmacological activity of denosumab as a monoclonal antibody against RANKL and inhibitor of osteoclastogenesis. The resulting inhibition of resorption impaired both bone modeling and remodeling during skeletal development and growth. The skeletal phenotype of these infant monkeys resembles human infants with osteoclast-poor osteopetrosis due to inactivating mutations of RANK or RANKL.

Developmental immunotoxicity (DIT) testing of pharmaceuticals: current practices, state of the science, knowledge gaps, and recommendations.

The development and regulatory approval of immunomodulatory pharmaceuticals to treat many human diseases has increased significantly over the last two decades. As discussed by FDA and ICH guidelines, all human pharmaceuticals in development should be evaluated for potential adverse effects on the immune system. Developmental immunotoxicology (DIT) focuses on the concern that early-life (during pre-/post-natal development) exposure to agents which target the immune system may result in enhanced susceptibility to immune-related disease (e.g., infection, autoimmunity, and cancer, particularly leukemia) compared to adults, unique effects not observed in adults, or more persistent effects in comparison to those following adult exposure. This article provides a substantive review of the literature and presents detailed considerations for DIT testing strategies with a specific focus on pharmaceuticals and biopharmaceuticals. In this regard, differences between small molecule and large molecule therapeutics will be considered, along with recommendations for best practices in the assessment of DIT during drug development. In addition, gaps in the DIT knowledge base and current testing strategies are identified. Finally, a summary of an ILSI-HESI-ITC sponsored Workshop conducted in 2010, entitled 'Developmental Immunotoxicity Testing of Pharmaceuticals' will be presented. This Workshop consisted of participants from the pharmaceutical, biotechnology, academic, and regulatory sectors, where many of the issues relating to DIT outlined in this review were discussed, key points of consensus reached, and current gaps in the science identified.

Developmental and peri-postnatal study in cynomolgus monkeys with belimumab, a monoclonal antibody directed against B-lymphocyte stimulator.

Belimumab is a fully human monoclonal antibody antagonist for soluble B-lymphocyte stimulator, and is a potential therapeutic for various autoimmune disorders. To support clinical use, belimumab was administered intravenously to pregnant cynomolgus monkeys every 2 weeks throughout gestation at dosages of 5 and 150 mg/kg. Fetuses were delivered by C-section on Gestation Day 150 from one-half of the mothers, and evaluated for teratologic effects (external, visceral, skeletal, and heart), pharmacodynamics (PD) and toxicokinetics (TK). Remaining mothers delivered their infants naturally, enabling extensive assessment of PD and TK during a 1-year postnatal period. Effects attributed to belimumab were limited to the expected pharmacology, primarily decreased numbers of B-lymphocytes in peripheral blood of mothers and infants, and in fetal lymphoid tissues. Infants demonstrated full recovery upon cessation of exposure. In conclusion, belimumab was well tolerated at pharmacologically active dose levels in pregnant cynomolgus monkeys and their infants after exposure throughout pregnancy.

Barusiban, an effective long-term treatment of oxytocin-induced preterm labor in nonhuman primates.

Preterm labor (PTL) affects up to 25% of human pregnancies in developing countries, but there are few therapeutic options. Based on the key role of oxytocin (OXT) in labor and parturition, OXT antagonists are a potentially useful class of drugs for PTL. Barusiban is a new selective, potent, and long-acting OXT receptor antagonist. In this study barusiban was given by continuous i.v. infusion to monkeys during the last 3 wk of pregnancy; the monkeys were also given daily doses of OXT to induce uterine contractions and simulate PTL. Barusiban effectively suppressed OXT-induced PTL-like contractions and prevented early delivery. In contrast, fenoterol (a beta2-adrenoceptor [beta2-AR] agonist used as a comparative control) did not inhibit uterine contractions in this model. Barusiban was particularly effective in maintaining low intrauterine pressure (IUP) near the end of pregnancy, which is when IUP in both OXT controls and fenoterol-treated females increased substantially. Although barusiban delayed the onset of labor, it did not prevent normal delivery. These data demonstrate the safety and efficacy of barusiban in reducing uterine contractility in response to repeated OXT challenge, and suggest that barusiban may be therapeutically effective in long-term treatment of PTL.

Methods for the prediction of breeding success in male cynomolgus monkeys (Macaca fascicularis) used for reproductive toxicology studies.

The cynomolgus monkey (Macaca fascicularis) may be the species of choice for nonclinical reproductive toxicology studies because of the comparability of its reproductive processes to man, similarity of pharmacologic response to various test substances, and decreased probability of immunogenic response to biological therapeutic products. For success in conducting these studies, the male and female monkeys used need to be characterized thoroughly. This study focused on the evaluation of 42 male cynomolgus monkeys as potential breeders for reproductive toxicology studies. Parameters evaluated included age, body weight, testicular volume, serum testosterone levels, ejaculate volume, and sperm parameters (count, motility, and morphology). The results showed that physical parameters (age, body weight, testicular volume) were a good starting point for selection of potential breeder males. However, additional endpoints (testosterone; ejaculate volume; sperm count, motility and morphology; mating behavior) were also helpful as part of an overall "weight of evidence" approach to optimize selection of breeder males. In light of the data obtained in this study, 29 of 42 of the males evaluated were used with excellent success as breeder males for reproductive toxicology studies, resulting in an overall pregnancy rate of 36% when mated with sexually mature females. The successful breeder males were at least 6 y old, weighed at least 5 kg, had testicular volumes of at least 25 ml and serum testosterone levels of 1 to 10 ng/ml, and produced ejaculates with large numbers of sperm (median: 502 x 10(6) per ejaculate) of high quality (few morphologic defects and most sperm highly motile).