Graeme J. Moffat

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.

Potential seminal transport of pharmaceuticals to the conceptus

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

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.

Assessment of menstrual cycle length in cynomolgus monkeys as a female fertility endpoint of a biopharmaceutical in a 6 month toxicity study.

According to ICH S6(R1), mating studies are not practical for assessing effects on female fertility of biopharmaceuticals that are pharmacologically active only in non-human primates (NHPs). Instead, fertility should be assessed by evaluating histopathology and organ weights of the reproductive tract in studies of at least 3 months dosing duration using sexually mature NHPs. An assessment of the menstrual cycle in females can be included if there is cause for concern based on pharmacological mode of action or relevant findings in previous studies. However, many factors unrelated to the molecule under evaluation can impact cycle length and thus affect data interpretation. Assessment of a monoclonal antibody in a 6 month repeat dose toxicity study is used as an example in this manuscript to review potential sources of background variability, identify strategies to minimize its impact and recommend optimal ways to collect, present and analyze menstrual cycle data. Experimental variables include the amount of time required for menses to normalize following the transport of animals to the testing facility, stress-related effects on the cycle length due to socialization issues with new cagemates, and the normal background irregularity of cycle length in NHPs. Study related procedures (i.e., animal handling for dosing, blood draws, body weights, ECGs, etc.) did not affect cycle lengths in this study. We show that introducing a number of key experimental control procedures to minimize cycle variability can enable a robust assessment of the effects of a biotherapeutic on menstrual cycling within a chronic toxicity study in NHPs.

Reprint of “Potential seminal transport of pharmaceuticals to the conceptus”

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

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.

Birth Control in Clinical Trials Industry Survey of Current Use Practices, Governance, and Monitoring

The Health and Environmental Sciences Institute (HESI) Developmental and Reproductive Toxicology Technical Committee sponsored a pharmaceutical industry survey on current industry practices for contraception use during clinical trials. The objectives of the survey were to improve our understanding of the current industry practices for contraception requirements in clinical trials, the governance processes set up to promote consistency and/or compliance with contraception requirements, and the effectiveness of current contraception practices in preventing pregnancies during clinical trials. Opportunities for improvements in current practices were also considered. The survey results from 12 pharmaceutical companies identified significant variability among companies with regard to contraception practices and governance during clinical trials. This variability was due primarily to differences in definitions, areas of scientific uncertainty or misunderstanding, and differences in company approaches to enrollment in clinical trials. The survey also revealed that few companies collected data in a manner that would allow a retrospective understanding of the reasons for failure of birth control during clinical trials. In this article, suggestions are made for topics where regulatory guidance or scientific publications could facilitate best practice. These include provisions for a pragmatic definition of women of childbearing potential, guidance on how animal data can influence the requirements for male and female birth control, evidence-based guidance on birth control and pregnancy testing regimes suitable for low- and high-risk situations, plus practical methods to ascertain the risk of drug-drug interactions with hormonal contraceptives.

Comment on “Using Human ‘Experiments of Nature’ to Predict Drug Safety Issues: An Example with PCSK9 Inhibitors”

We read with interest the recent work by Jerome et al. [1] using a phenome-wide association study (PheWAS) approach to predict potentially deleterious effects of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. We agree with the authors’ argument that human genetics provides valuable “experiments of nature” to evaluate drug target safety, and they provide thoughtful discussion of the strengths and caveats of this approach. However, the specific associations that the authors highlight between the PCSK9 loss-of-function variant R46L (rs11591147) and spina bifida and fracture phenotypes are not statistically significant when correcting for multiple hypothesis testing and do not replicate in a larger dataset. When scanning for statistical associations in a large database, it is critical to correct the p value threshold for multiple hypothesis testing [2]. Genome-wide association studies (GWAS) commonly use a Bonferroni-corrected p value threshold of p < 5 × 10−8, because approximately 106 independent loci are tested [3]. Similarly, PheWAS should be interpreted with a corrected p value threshold based on the number of independent phenotypes [4]. The authors do not state the total number of phenotypes tested; however, a recent study that used the same BioVU database for PheWAS on human leukocyte antigen variants [5] reported that 1368 phenotypes were tested. Assuming the same number of phenotypes was tested in this analysis, performing a Bonferroni correction on a threshold of p < 0.05 when testing a variant against 1368 phenotypes would result in a threshold of p < 3.7 × 10−5. Therefore, even the strongest non-cardiovascular result from the Jerome et al. [1] PCSK9 study (spina bifida p = 2.7 × 10−4) is statistically consistent with a chance occurrence, assuming that many phenotypes were tested (for example, p < 2.7 × 10−4 would be expected by chance 5% of the time if at least 186 independent phenotypes are tested). To attempt to replicate the result of Jerome et al. [1] in an independent dataset, we inspected an online portal (the Global Biobank Engine) that provides PheWAS analysis of 337,208 individuals and 1837 phenotypes with genotype–phenotype data from the UK Biobank cohort [6–8]. Using the PheWAS report page for PCSK9 R46L [9], we inspected all associations that surpassed a phenome-wide significance threshold of p < 2.7 × 10−5 and found that all results associated PCSK9 R46L with cardioprotective phenotypes, as previously reported (Table 1). We then found the phenotypes in the UK Biobank that most closely matched the non-cardiovascular associations that Jerome et al. [1] reported, and we tested these for associations (Table 2). Although all of these phenotypes have a much larger sample size in the UK Biobank, none of the associations replicated at p < 0.10. Jerome et al. [1] then examined the medical records of six individuals with both PCSK9 R46L loss-of-function mutation and a classification of spina bifida to define which clinical features had led to this PheWAS classification. These individuals are discussed as being homozygous and having spina bifida, which is very surprising; given the allele frequency, observing even a single homozygous individual with a rare disease such as spina bifida would be extremely unlikely unless the mutation had a highly penetrant, recessive effect on the disease (Table 3). Alternatively, if these six case studies were in fact heterozygous for PCSK9 R46L loss-of-function mutation, this would be consistent with the language the authors use in their This comment refers to the article available at https ://doi. org/10.1007/s4026 4-017-0616-0.