Jeanine Bussiere

Differential hepatocyte toxicity of recombinant Apo2L/TRAIL versions.

Our findings not only provide a novel insight into the pathogenesis of the transplant-related atherosclerosis, but also point to a new therapeutic strategy that involves targeting of homing, differentiation and proliferation of putative smooth-muscle progenitor cells derived from the recipient. This is the first report demonstrating that circulating progenitor cells contribute to the development of proliferative diseases. AKIO SAIURA, MASATAKA SATA, YASUNOBU HIRATA, RYOZO NAGAI MASATOSHI MAKUUCHI Department of Surgery, University of Tokyo, Graduate School of Medicine, Tokyo, Japan, Department of Cardiovascular Medicine University of Tokyo, Graduate School of Medicine, Tokyo, Japan A.S. and M.S. supervised this study equally as senior authors Email: sata-2im@h.u-tokyo.ac.jp 1. McKay, R. Stem cells-hype and hope. Nature 406, 361–364 (2000). 2. Asahara, T. et al. Isolation of putative progenitor endothelial cells for angiogenesis. Science 275, 964–967 (1997). 3. Yamashita, J. et al. Flk1-positive cells derived from embryonic stem cells serve as vascular progenitors. Nature 408, 92–96 (2000). 4. Carmeliet, P. One cell, two fates. Nature 408, 43–45 (2000). 5. Clarke, D.L. et al. Generalized potential of adult neural stem cells. Science 288, 1660–1663 (2000).

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.

Receptor Activator of NF-κB Ligand Inhibition Suppresses Bone Resorption and Hypercalcemia but Does Not Affect Host Immune Responses to Influenza Infection

Receptor activator of NF-κB (RANK) and its ligand (RANKL) are essential for osteoclast formation, function, and survival. Osteoprotegerin (OPG) inhibits RANK signaling by sequestering RANKL. This study evaluated the antiosteoclast and immunoregulatory effects of mouse rRANK-Fc, which, similar to OPG, can bind RANKL. The effect of RANKL inhibition by RANK-Fc on osteoclast function was determined by inhibition of vitamin D3 (1,25(OH)2D3)-induced hypercalcemia. Mice were injected with a single dose of 0, 10, 100, 500, or 1000 μg of RANK-Fc; 100 μg of OPG-Fc; or 5 μg of zoledronate 2 h before 1,25(OH)2D3 challenge on day 0, and sacrificed on days 1, 2, 4, 6, 8, 12, 16, and 20. RANK-Fc doses of 100 or 500 μg were tested in a mouse respiratory influenza virus host-resistance model. A single dose of RANK-Fc ≥100 μg suppressed elevation of serum calcium levels and suppressed the bone turnover marker serum pyridinoline at day 4 and later time points, similar to those observed with OPG-Fc and zoledronate (p ≤ 0.01 vs controls). By day 6, both immature and mature osteoclasts were depleted by high doses of RANK-Fc (500 and 1000 μg) or 100 μg of OPG-Fc. RANK-Fc doses of 100 or 500 μg had no detectable effect on immune responses to influenza infection, as measured by activation of cytotoxic T cell activity, influenza-specific IgG response, and virus clearance. RANK-Fc inhibition of RANKL has antiosteoclast activity at doses that have no detectable immunoregulatory activity, suggesting that RANKL inhibitors be further studied for their potential to treat excess bone loss.

Immunogenicity assessment in non-clinical studies.

Recent ICH S6 guidance on preclinical safety evaluation of biotechnology derived biopharmaceuticals indicates that testing for anti-drug antibodies is not always required to establish the safety of a protein therapeutic. Most human protein therapeutics will induce a rapid and robust anti-drug antibody response in preclinical studies and the presence of high levels of circulating drug complicates the detection of anti-drug antibodies. The presence of anti-drug antibodies in preclinical studies does not predict if a protein therapeutic will be immunogenic in the clinic. When testing for anti-drug antibodies is warranted, there are a variety of analytical procedures that can be utilized, although each of these methods has advantages as well as limitations. Immunoassays can be used to identify if antibodies are present that bind to the therapeutic, and when necessary, biological assays can be used to identify if those antibodies neutralize the effect of the therapeutic. Under certain circumstances including intravenous dosing of a mAb therapeutic, anti-drug antibodies can form large immune complexes that can result in a safety issue. The value of immunogenicity data in preclinical studies is to aid in interpretation of other study data when necessary.

Reproductive toxicity of denosumab in cynomolgus monkeys.

Denosumab is a monoclonal antibody that inhibits bone resorption by targeting RANKL, an essential mediator of osteoclast formation, function, and survival. Reproductive toxicity of denosumab was assessed in cynomolgus monkeys in an embryofetal development study (dosing GD20-50) and a pre-postnatal toxicity study (dosing GD20-parturition). In the embryofetal toxicity study, denosumab did not elicit maternal toxicity, fetal harm or teratogenicity. In the pre-postnatal toxicity study, there were increased stillbirths, and one maternal death due to dystocia. There was no effect on maternal mammary gland histomorphology, lactation, or fetal growth. In infants exposed in utero, there was increased postnatal mortality, decreased body weight gain, and decreased growth/development. Denosumab-related effects in infants were present in bones and lymph nodes. There was full recovery at 6 months of age from most bone-related changes observed earlier postpartum. The effects observed in mothers and infants were consistent with the pharmacological action of denosumab.

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.

PDADMAC flocculation of Chinese hamster ovary cells: enabling a centrifuge-less harvest process for monoclonal antibodies.

High titer (>10 g/L) monoclonal antibody (mAb) cell culture processes are typically achieved by maintaining high viable cell densities over longer culture durations. A corresponding increase in the solids and sub-micron cellular debris particle levels are also observed. This higher burden of solids (≥15%) and sub-micron particles typically exceeds the capabilities of a continuous centrifuge to effectively remove the solids without a substantial loss of product and/or the capacity of the harvest filtration train (depth filter followed by membrane filter) used to clarify the centrate. We discuss here the use of a novel and simple two-polymer flocculation method used to harvest mAb from high cell mass cell culture processes. The addition of the polycationic polymer, poly diallyldimethylammonium chloride (PDADMAC) to the cell culture broth flocculates negatively-charged cells and cellular debris via an ionic interaction mechanism. Incorporation of a non-ionic polymer such as polyethylene glycol (PEG) into the PDADMAC flocculation results in larger flocculated particles with faster settling rate compared to PDADMAC-only flocculation. PDADMAC also flocculates the negatively-charged sub-micron particles to produce a feed stream with a significantly higher harvest filter train throughput compared to a typical centrifuged harvest feed stream. Cell culture process variability such as lactate production, cellular debris and cellular densities were investigated to determine the effect on flocculation. Since PDADMAC is cytotoxic, purification process clearance and toxicity assessment were performed.

An inter-laboratory retrospective analysis of immunotoxicological endpoints in non-human primates: T-cell-dependent antibody responses

The Immunotoxicology Technical Committee of HESI sponsored a retrospective analysis of T-cell-dependent antibody responses in non-human primates (NHP). Antibody responses to keyhole limpet hemocyanin (KLH), tetanus toxoid (TT), and/or sheep red blood cells (SRBC) in 178 NHP (from 8 sponsors, 13 testing sites, 30 studies) were statistically analyzed. Rates of positive or negative anti-KLH, -TT, and -SRBC primary and secondary IgM and IgG responses were compared. The influence of gender, country of origin, and previous immunization with a different antigen on response rate and kinetics of anti-KLH and anti-TT responses were analyzed. In addition, the magnitude of the antibody responses and the impact of the above-mentioned factors were analyzed. In addition, based upon the inter-individual variability of the peak response values, power calculations were conducted. The analysis demonstrated that the rates of positive responses were similar between the two genders, were high for KLH, SRBC, and TT challenges by 21 days following immunization (87, 100, and 84%, respectively, for IgGs) and did not include statistically significant differences based on NHP country of origin. Mean peak secondary responses were greater than peak primary responses; the magnitude of the response to KLH was increased by incomplete Freund’s adjuvant (IFA). Gender had little effect on the magnitude and variability of these responses. KLH and TT were associated with similar inter-animal variability, whereas in some situations KLH responses were less variable than responses to SRBC. The data suggested that inter-animal variability with KLH was similar with or without IFA. Power analysis illustrated that animal group sizes of typical standard toxicology studies (generally ≤ 4/sex) are likely to detect only fairly large treatment effects. However, combining males and females, when appropriate, will improve the power: an N of 8 to 12 could detect ≤ 3.1-fold differences in anti-KLH IgG responses.

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.

A comparison of effects on reproduction and neonatal development in cynomolgus monkeys given human soluble IL-4R and mice given murine soluble IL-4R

The effects of treatment with a soluble IL-4 receptor (sIL-4R) on reproduction and neonatal development were assessed in pregnant cynomolgus monkeys and mice. When pregnant cynomolgus monkeys were administered a human sIL-4R intravenously twice a week during organogenesis (GD 20-51) at 0, 0.2 or 2.0mg/kg, there was an increase in abortion/embryo-fetal death in the 0.2 (42.9%) and 2.0 (26.3%) mg/kg groups compared to controls (17.6%). All fetuses removed at cesarean sectioning on GD 100-102 were alive and no abnormalities were noted. There were three stillborn neonates (2.0mg/kg group), which were determined to have died before birth. No neonates died after birth and no abnormalities were noted. Due to the unanticipated results in the monkey study, a mouse developmental study with a murine surrogate molecule was conducted. When pregnant Crl:CD-1((R))(ICR)BR mice were administered murine sIL-4R intravenously once daily during the organogenesis period (GD 6-15) at 0, 25, 75, 250, or 625microg/mouse ( approximately 20mg/kg), there were no test-article-related abnormalities in any parameters. Antibody development to the drug did not influence toxicity in the monkey or mouse. In conclusion, evaluation of reproductive effects in mice administered murine soluble IL-4R was not predictive of reproductive effects noted in cynomolgus monkeys administered human soluble IL-4R.