Preclinical safety testing of monoclonal antibodies: the significance of species relevance

Comprehensive approaches to preclinical evaluation of monoclonal antibodies and their next-generation derivatives

Biotherapeutics hold great promise for the treatment of several diseases and offer innovative possibilities for new treatments that target previously unaddressed medical needs. Despite successful transitions from preclinical to clinical stages and regulatory approval, there are instances where adverse reactions arise, resulting in product withdrawals. As a result, it is essential to conduct thorough evaluations of safety and effectiveness on an individual basis. This article explores current practices, challenges, and future approaches in conducting comprehensive preclinical assessments to ensure the safety and efficacy of biotherapeutics including monoclonal antibodies, toxin-conjugates, bispecific antibodies, single-chain antibodies, Fc-engineered antibodies, antibody mimetics, and siRNA-antibody/peptide conjugates.

The Influence of Geographical Origin, Age, Sex, and Animal Husbandry on the Spontaneous Histopathology of Laboratory Cynomolgus Macaques (Macaca Fascicularis): A Contemporary Global and Multisite Review of Historical Control Data

To investigate the influence of geographical origin, age, and sex on toxicologically relevant spontaneous histopathology findings in cynomolgus macaques (Macaca fascicularis), we performed a comparative analysis of historical control data (HCD) from 13 test sites that included 3351 animals (1645 females and 1706 males) sourced from Mauritius, China, Vietnam, and Cambodia, aged from 2 to 9.5 years, and from 446 toxicology studies evaluated between 2016 and 2021. The most common findings were mononuclear infiltrates in the kidney, liver, brain, and lung, which showed highest incidences in Mauritian macaques, and heart, salivary glands, and gastrointestinal tract (GIT), which showed highest incidences of mononuclear infiltrates in mainland Asian macaques. Developmental and degenerative findings were more common in Mauritian macaques, while lymphoid hyperplasia and lung pigment showed higher incidences in Asian macaques. Various sex and age-related differences were also present. Despite origin-related differences, the similarities in the nature and distribution of background lesions indicate that macaques from all geographical regions are suitable for toxicity testing and show comparable lesion spectrum. However, in a toxicity study, it is strongly recommended to use animals from a single geographical origin and to follow published guidelines when using HCD to evaluate and interpretate commonly diagnosed spontaneous lesions.

Nonclinical safety, tolerance and pharmacodynamics evaluation for meplazumab treating chloroquine-resistant Plasmodium falciparum

Meplazumab is an anti-CD147 humanized IgG2 antibody. The purpose of this study was to characterize the nonclinical safety, tolerance and efficacy evaluation of meplazumab treating chloroquine resistant Plasmodium falciparum. Meplazumab was well tolerated in repeat-dose toxicology studies in cynomolgus monkeys. No observed adverse effect level was 12 mg/kg. No difference between genders in the primary toxicokinetic parameters after repeat intravenous injection of meplazumab. No increased levels of drug exposure and drug accumulation were observed in different gender and dose groups. Meplazumab had a low cross-reactivity rate in various tissues and did not cause hemolysis or aggregation of red blood cells. The biodistribution and excretion results indicated that meplazumab was mainly distributed in the plasma, whole blood, and hemocytes, and excreted in the urine. Moreover, meplazumab effectively inhibited the parasites from invading erythrocytes in humanized mice in a time-dependent manner and the efficacy is superior to that of chloroquine. All these studies suggested that meplazumab is safe and well tolerated in cynomolgus monkeys, and effectively inhibits P. falciparum from invading into human red blood cells. These nonclinical data facilitated the initiation of an ongoing clinical trial of meplazumab for antimalarial therapy.

An Anti-hTNF-α Variable New Antigen Receptor Format Demonstrates Superior in vivo Preclinical Efficacy to Humira® in a Transgenic Mouse Autoimmune Polyarthritis Disease Model

Tumor necrosis factor-alpha (TNF-α), an established pro-inflammatory cytokine plays a central role in the induction and progression of several chronic inflammatory and autoimmune diseases. Targeting TNF-α as a treatment modality has shown tremendous success, however there are several limitations associated with the current anti-TNF-α biologic drugs including: immunogenicity, life-threatening infections, resistance to treatment, complexity of manufacture and cost of treatment. Here, we report the in vivo efficacy of novel anti-TNF-α formats generated from molecular engineering of variable new antigen receptors (VNARs), originally derived from the immune system of an immunized nurse shark. Two anti-TNF-α VNAR formats, a tandem multivalent trimer, D1-BA11-C4 and an Fc-fused quadrivalent D1-Fc-C4 (Quad-X™) construct were tested in a clinically relevant, preclinical mouse efficacy model of polyarthritis (Tg197) and compared to the commercial anti-TNF-α "best in class" therapy, Adalimumab (Humira®). Both VNAR formats bind and neutralize TNF-α through an epitope that appears to be different from those recognized by other anti-TNF biologics used clinically. All doses of Quad-X™, from 0.5 to 30 mg/kg, significantly blocked the development of polyarthritis. At 0.5 mg/kg Quad-X™, the arthritis score was improved by 76% and the histopathology score by 63%. At 3 mg/kg Quad-X™, control of disease was almost complete at 90% (arthritis) and 88% (histopathology). In marked contrast, 1 mg/kg Humira® saw profound disease breakthrough with scores of 39 and 16% respectively, increasing to a respectable 82 and 86% inhibition at 10 mg/kg Humira®. We have previously reported the superior potency of anti-TNF-α VNARs in vitro and in these studies translate this superiority into an in vivo setting and demonstrate the potential of VNAR formats to meet the requirements of next-generation anti-TNF-α therapies.

The Evolving Landscape of Cancer Therapeutics

The last 100 years have seen a dramatic alteration in the treatment of cancer. Aside from small molecule inhibitors of protein tyrosine kinases, monoclonal antibodies have also been found to provide valuable therapeutic approaches for modulating tumour pathophysiology. As our knowledge of cancer biology improves, the specificity of this new generation of drugs is generally delivering an improved therapeutic ratio compared to traditional cytotoxic agents. However, patient selection through the use of biomarkers is key in optimising efficacy and improving cost-effectiveness. The most recent wave of revolutionary new systemic therapy approaches to cancer has arrived in recent years in the form of immune checkpoint inhibitors, now clinically validated as modulators of immune-regulatory pathways. The future of oncology therapeutics includes a combination of cytotoxic agents, targeted therapies and immunotherapy.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Tutorial on Monoclonal Antibody Pharmacokinetics and Its Considerations in Early Development

The tutorial introduces the readers to the fundamentals of antibody pharmacokinetics (PK) in the context of drug development. Topics covered include an overview of antibody development, PK characteristics, and the application of antibody PK/pharmacodynamics (PD) in research and development decision-making. We also discuss the general considerations for planning a nonclinical PK program and describe the types of PK studies that should be performed during early development of monoclonal antibodies.

A methodological review of induced animal models of autoimmune diseases

Autoimmune disorders are characterized by a loss of immune tolerance and consequent autoimmunity-mediated disease manifestation. Experimental models are invaluable research tools helping us to understand disease pathogenesis and to search for novel therapeutics. Animal models of autoimmune diseases consist of two groups, spontaneous and induced models. In this review article, we focus on the induced models of autoimmune diseases. Due to the complex nature of autoimmune disorders, many strategies have been applied for the induction of corresponding experimental models in animals like monkeys, rabbits, rats, and mice. Methodologically, these strategies can be categorized into three categories, namely immunization with autoantigen, transfer of autoimmunity, and induction by environmental factors. In this review article, we aim to provide a comprehensive overview of the field of induced experimental autoimmune diseases. On the one hand, we describe and summarize the different strategies used for induction of experimental autoimmune disease. On the other hand, we discuss how to select a strategy for modeling human disease, including the choice of an appropriate species and method for such an approach.

Challenges and opportunities for the future of monoclonal antibody development: Improving safety assessment and reducing animal use

The market for biotherapeutic monoclonal antibodies (mAbs) is large and is growing rapidly. However, attrition poses a significant challenge for the development of mAbs, and for biopharmaceuticals in general, with large associated costs in resource and animal use. Termination of candidate mAbs may occur due to poor translation from preclinical models to human safety. It is critical that the industry addresses this problem to maintain productivity. Though attrition poses a significant challenge for pharmaceuticals in general, there are specific challenges related to the development of antibody-based products. Due to species specificity, non-human primates (NHP) are frequently the only pharmacologically relevant species for nonclinical safety and toxicology testing for the majority of antibody-based products, and therefore, as more mAbs are developed, increased NHP use is anticipated. The integration of new and emerging in vitro and in silico technologies, e.g., cell- and tissue-based approaches, systems pharmacology and modeling, have the potential to improve the human safety prediction and the therapeutic mAb development process, while reducing and refining animal use simultaneously. In 2014, to engage in open discussion about the challenges and opportunities for the future of mAb development, a workshop was held with over 60 regulators and experts in drug development, mechanistic toxicology and emerging technologies to discuss this issue. The workshop used industry case-studies to discuss the value of the in vivo studies and identify opportunities for in vitro technologies in human safety assessment. From these and continuing discussions it is clear that there are opportunities to improve safety assessment in mAb development using non-animal technologies, potentially reducing future attrition, and there is a shared desire to reduce animal use through minimised study design and reduced numbers of studies.

Safety Profile Based on Concordance of Nonclinical Toxicity and Clinical Adverse Drug Reactions for Blood Cancer Drugs Approved in Japan

BACKGROUND

In drug development, animal toxicology data are very important for the evaluation of clinical safety. We quantitatively assessed the safety profiles of blood cancer drugs approved in Japan from category I (high) to V (low). We examined the ratios of drug exposure in animals at the no observed adverse effect level to those in humans at the expected therapeutic dose. In addition, qualitative analysis of the relationship between toxicological findings and adverse drug reactions (ADRs) is one of the primary approaches for determining the risk-benefit profile of a pharmaceutical. This study thus aimed to evaluate the potential of nonclinical safety assessments for predicting ADRs in humans.

METHODS

We examined toxicological findings at the lowest observed adverse effect level and ADRs in pivotal clinical studies. We calculated concordance rates as the ratio of the number of concordant ADRs to all ADRs.

RESULTS

Twenty-seven drugs were eligible for analysis. Concordance rates ranged from 0 to 84.8%. No significant differences were observed in concordance rates between antibodies (median 14.3%) and small molecules (median 18.5%). There was a significant correlation between concordance rates and quantitative safety profiles (p = 0.047), suggesting that some drugs with low safety profiles (categories III, IV, or V) have high concordance rates.

CONCLUSION

The results suggested that ADRs in clinical trials could be predicted based on toxicity data obtained in animal tests, especially for some drugs with a low quantitative safety profile.

Drug Development of Therapeutic Monoclonal Antibodies

Monoclonal antibodies (MAbs) have become a substantial part of many pharmaceutical company portfolios. However, the development process of MAbs for clinical use is quite different than for small-molecule drugs. MAb development programs require careful interdisciplinary evaluations to ensure the pharmacology of both the MAb and the target antigen are well-understood. Selection of appropriate preclinical species must be carefully considered and the potential development of anti-drug antibodies (ADA) during these early studies can limit the value and complicate the performance and possible duration of preclinical studies. In human studies, many of the typical pharmacology studies such as renal or hepatic impairment evaluations may not be needed but the pharmacokinetics and pharmacodynamics of these agents is complex, often necessitating more comprehensive evaluation of clinical data and more complex bioanalytical assays than might be used for small molecules. This paper outlines concerns and strategies for development of MAbs from the early in vitro assessments needed through preclinical and clinical development. This review focuses on how to develop, submit, and comply with regulatory requirements for MAb therapeutics.

Primate autoimmune disease models; lost for translation?

Replacement, reduction and refinement (the 3R's) are the leading principles in translational research with animals. To be useful a model should also be clinically Relevant (the 4th R). Work in a non-human primate model of multiple sclerosis, the experimental autoimmune encephalomyelitis model, reveals an inherent conflict among these 4R principles. The impossibility to harmonize all 4R's forms a major challenge when the model is applied in preclinical drug development.

Waiving in vivo studies for monoclonal antibody biosimilar development: National and global challenges

Biosimilars are biological medicinal products that contain a version of the active substance of an already authorised original biological medicinal product (the innovator or reference product). The first approved biosimilar medicines were small proteins, and more recently biosimilar versions of innovator monoclonal antibody (mAb) drugs have entered development as patents on these more complex proteins expire. In September 2013, the first biosimilar mAb, infliximab, was authorised in Europe. In March 2015, the first biosimilar (Zarxio™, filgrastim-sndz, Sandoz) was approved by the US Food and Drug Administration; however, to date no mAb biosimilars have been approved in the US. There are currently major differences between how biosimilars are regulated in different parts of the world, leading to substantial variability in the amount of in vivo nonclinical toxicity testing required to support clinical development and marketing of biosimilars. There are approximately 30 national and international guidelines on biosimilar development and this number is growing. The European Union's guidance describes an approach that enables biosimilars to enter clinical trials based on robust in vitro data alone; in contrast, the World Health Organization's guidance is interpreted globally to mean in vivo toxicity studies are mandatory. We reviewed our own experience working in the global regulatory environment, surveyed current practice, determined drivers for nonclinical in vivo studies with biosimilar mAbs and shared data on practice and study design for 25 marketed and as yet unmarketed biosimilar mAbs that have been in development in the past 5y. These data showed a variety of nonclinical in vivo approaches, and also demonstrated the practical challenges faced in obtaining regulatory approval for clinical trials based on in vitro data alone. The majority of reasons for carrying out nonclinical in vivo studies were not based on scientific rationale, and therefore the authors have made recommendations for a data-driven approach to the toxicological assessment of mAb biosimilars that minimises unnecessary use of animals and can be used across all regions of the world.

A snapshot of biologic drug development

Since the approval of insulin as the first recombinant therapeutic protein, the prominence of biologic therapies in drug development has grown significantly. Many modalities beyond traditional biologics are now being developed or explored for various indications with significant unmet medical needs. From early traditional replacement proteins to more recent, highly engineered antibodies, oligonucleotides, fusion proteins, and gene constructs, biologic agents have delivered life-changing therapies, despite often having scientifically and technically challenging development programs. This brief review outlines some of the major biotherapeutic classes and identifies the advantages and challenges with the development of these products.

Antibody Drug Conjugates: Nonclinical Safety Considerations

Antibody drug conjugates (ADCs) are biopharmaceutical molecules consisting of a cytotoxic small molecule covalently linked to a targeted protein carrier via a stable cleavable or noncleavable linker. The process of conjugation yields a highly complex molecule with biochemical properties that are distinct from those of the unconjugated components. The impact of these biochemical differences on the safety and pharmacokinetic (PK) profile of the conjugate must be considered when determining the types of nonclinical safety studies required to support clinical development of ADCs. The hybrid nature of ADCs highlights the need for a science-based approach to safety assessment that incorporates relevant aspects of small and large molecule testing paradigms. This thinking is reflected in current regulatory guidelines, where sections pertaining to conjugates allow for a flexible approach to nonclinical safety testing. The aim of this article is to review regulatory expectations regarding early assessment of nonclinical safety considerations and discuss how recent advances in our understanding of ADC-mediated toxicity can be used to guide the types of nonclinical safety studies needed to support ADC clinical development. The review will also explore nonclinical testing strategies that can be used to streamline ADC development by assessing the safety and efficacy of next generation ADC constructs using a rodent screen approach.

Clinical Development Strategies and Outcomes in First-in-Human Trials of Monoclonal Antibodies

PURPOSE

We conducted a comprehensive review of the design, implementation, and outcome of first-in-human (FIH) trials of monoclonal antibodies (mAbs) to clearly determine early clinical development strategies for this class of compounds.

METHODS

We performed a PubMed search using appropriate terms to identify reports of FIH trials of mAbs published in peer-reviewed journals between January 2000 and April 2013.

RESULTS

A total of 82 publications describing FIH trials were selected for analysis. Only 27 articles (33%) reported the criteria used for selecting the starting dose (SD). Dose escalation was performed using rule-based methods in 66 trials (80%). The median number of planned dose levels was five (range, two to 13). The median of the ratio between the highest planned dose and the SD was 27 (range, two to 3,333). Although in 56 studies (68%) at least one grade 3 or 4 toxicity event was reported, no dose-limiting toxicity was observed in 47 trials (57%). The highest planned dose was reached in all trials, but the maximum-tolerated dose (MTD) was defined in only 13 studies (16%). The median of the ratio between MTD and SD was eight (range, four to 1,000). The recommended phase II dose was indicated in 34 studies (41%), but in 25 (73%) of these trials, this dose was chosen without considering toxicity as the main selection criterion.

CONCLUSION

This literature review highlights the broad design heterogeneity of FIH trials testing mAbs. Because of the limited observed toxicity, the MTD was infrequently reached, and therefore, the recommended phase II dose for subsequent clinical trials was only tentatively defined.

Drug Development and Nonclinical to Clinical Translational Databases

The International Consortium for Innovation and Quality (IQ) in Pharmaceutical Development is a science-focused organization of pharmaceutical and biotechnology companies. The mission of the Preclinical Safety Leadership Group (DruSafe) of the IQ is to advance science-based standards for nonclinical development of pharmaceutical products and to promote high-quality and effective nonclinical safety testing that can enable human risk assessment. DruSafe is creating an industry-wide database to determine the accuracy with which the interpretation of nonclinical safety assessments in animal models correctly predicts human risk in the early clinical development of biopharmaceuticals. This initiative aligns with the 2011 Food and Drug Administration strategic plan to advance regulatory science and modernize toxicology to enhance product safety. Although similar in concept to the initial industry-wide concordance data set conducted by International Life Sciences Institute’s Health and Environmental Sciences Institute (HESI/ILSI), the DruSafe database will proactively track concordance, include exposure data and large and small molecules, and will continue to expand with longer duration nonclinical and clinical study comparisons. The output from this work will help identify actual human and animal adverse event data to define both the reliability and the potential limitations of nonclinical data and testing paradigms in predicting human safety in phase 1 clinical trials.

Advantages of Papio anubis for preclinical testing of immunotoxicity of candidate therapeutic antagonist antibodies targeting CD28

Antagonist anti-CD28 antibodies prevent T-cell costimulation and are functionally different from CTLA4Ig since they cannot block CTLA-4 and PDL-1 co-inhibitory signals. They demonstrated preclinical efficacy in suppressing effector T cells while enhancing immunoregulatory mechanisms. Because a severe cytokine release syndrome was observed during the Phase 1 study with the superagonist anti-CD28 TGN1412, development of other anti-CD28 antibodies requires careful preclinical evaluation to exclude any potential immunotoxicity side-effects. The failure to identify immunological toxicity of TGN1412 using macaques led us to investigate more relevant preclinical models. We report here that contrary to macaques, and like in man, all baboon CD4-positive T lymphocytes express CD28 in their effector memory cells compartment, a lymphocyte subtype that is the most prone to releasing cytokines after reactivation. Baboon lymphocytes are able to release pro-inflammatory cytokines in vitro in response to agonist or superagonist anti-CD28 antibodies. Furthermore, we compared the reactivity of human and baboon lymphocytes after transfer into non obese diabetic/severe combined immunodeficiency (NOD/SCID) interleukin-2rγ knockout mice and confirmed that both cell types could release inflammatory cytokines in situ after injection of agonistic anti-CD28 antibodies. In contrast, FR104, a monovalent antagonistic anti-CD28 antibody, did not elicit T cell activation in these assays, even in the presence of anti-drug antibodies. Infusion to baboons also resulted in an absence of cytokine release. In conclusion, the baboon represents a suitable species for preclinical immunotoxicity evaluation of anti-CD28 antibodies because their effector memory T cells do express CD28 and because cytokine release can be assessed in vitro and trans vivo.

Polymorphisms and interspecies differences of the activating and inhibitory FcγRII of Macaca nemestrina influence the binding of human IgG subclasses

Little is known of the impact of Fc receptor (FcR) polymorphism in macaques on the binding of human (hu)IgG, and nothing is known of this interaction in the pig-tailed macaque (Macaca nemestrina), which is used in preclinical evaluation of vaccines and therapeutic Abs. We defined the sequence and huIgG binding characteristics of the M. nemestrina activating FcγRIIa (mnFcγRIIa) and inhibitory FcγRIIb (mnFcγRIIb) and predicted their structures using the huIgGFc/huFcγRIIa crystal structure. Large differences were observed in the binding of huIgG by mnFcγRIIa and mnFcγRIIb compared with their human FcR counterparts. MnFcγRIIa has markedly impaired binding of huIgG1 and huIgG2 immune complexes compared with huFcγRIIa (His(131)). In contrast, mnFcγRIIb has enhanced binding of huIgG1 and broader specificity, as, unlike huFcγRIIb, it avidly binds IgG2. Mutagenesis and molecular modeling of mnFcγRIIa showed that Pro(159) and Tyr(160) impair the critical FG loop interaction with huIgG. The enhanced binding of huIgG1 and huIgG2 by mnFcγRIIb was shown to be dependent on His(131) and Met(132). Significantly, both His(131) and Met(132) are conserved across FcγRIIb of rhesus and cynomolgus macaques. We identified functionally significant polymorphism of mnFcγRIIa wherein proline at position 131, also an important polymorphic site in huFcγRIIa, almost abolished binding of huIgG2 and huIgG1 and reduced binding of huIgG3 compared with mnFcγRIIa His(131). These marked interspecies differences in IgG binding between human and macaque FcRs and polymorphisms within species have implications for preclinical evaluation of Abs and vaccines in macaques.

Muscle wasting associated with pathologic change is a risk factor for the exacerbation of joint swelling in collagen-induced arthritis in cynomolgus monkeys

BACKGROUND

Not only joint destruction but also muscle wasting due to rheumatoid cachexia has been problem in terms of quality of life of patients with rheumatoid arthritis (RA). In the present study, we performed histopathological examination and assessed relationships between characteristic parameters relating to muscle and joint swelling in a collagen-induced arthritis (CIA) model using cynomolgus monkeys (CMs).

METHODS

Female CMs were used and CIA was induced by twice immunizations using bovine type II collagen with Freund's complete adjuvant. Arthritis level was evaluated from the degree of swelling at the peripheral joints of the fore and hind limbs. Food consumption, body weight, and serum biochemical parameters were measured sequentially. Five or 6 animals per time point were sacrificed at 2, 3, 5 and 9 weeks after the first immunization to obtain quadriceps femoris specimens for histopathology. Pimonidazole hydrochloride was intravenously administered to determine tissue hypoxia in skeletal muscle.

RESULTS

Gradual joint swelling was observed and the maximum arthritis score was noted at Week 5. In histopathology, necrosis of muscle fiber in the quadriceps femoris was observed only at Week 2 and the most significant findings such as degeneration, atrophy, and regeneration of muscle fiber were mainly observed at Week 5. Food consumption was decreased up to Week 4 but recovered thereafter. Body weight decreased up to Week 5 and did not completely recover thereafter. A biphasic increase in serum cortisol was also observed at Weeks 2 and 5. Histopathology showed that muscle lesions were mainly composed of degeneration and atrophy of the muscle fibers, and ATPase staining revealed that the changes were more pronounced in type II muscle fiber than type I muscle fiber. In the pimonidazole experiment, mosaic pattern in skeletal muscle was demonstrated in the intact animal, but not the CIA animal. Increased arthritis score was accompanied by a decrease in serum creatinine, a marker that reflects muscle mass.

CONCLUSIONS

Muscle wasting might exacerbate joint swelling in a collagen-induced arthritis model of cynomolgus monkeys.

The minipig as an alternative non-rodent model for immunogenicity testing using the TNFα blockers adalimumab and infliximab

Immunogenicity is a major issue of concern for monoclonal antibodies used in human diseases and is by default mainly determined in non-human primates (NHP), as target molecules are considered most similar in NHP compared to human. In this manuscript the predictive value of immunogenicity testing in minipigs for human safety is evaluated, as the immune system of the pig is functionally similar to that in other mammalian species. Adalimumab and infliximab (both monoclonal antibodies blocking TNFα) were used as model substances. Female Göttingen minipigs (4/group) were treated every other week with low (0.1 mg/kg), mid (1.0 mg/kg), or high dose (5 mg/kg) adalimumab or 5 mg/kg infliximab subcutaneous (SC) over a period of 8 weeks. After first and last dosing, pharmacokinetic analysis was performed. Anti-drug antibodies (ADAs) were measured on several time points. Furthermore, hematology, clinical chemistry, body weight, clinical signs, and histopathology of several organs were evaluated. No signs of toxicity of the treatments were observed in the limited organs and tissues collected. Eleven out of 12 minipigs treated with adalimumab elicited a detectable ADA response. Induction of ADA was correlated with decreased plasma levels of adalimumab. Infliximab clearance was comparable after first and last dose. Therefore, the presence of ADA directed to infliximab was considered highly unlikely. It was concluded that the minipig and NHP showed comparable suitability for immunogenicity prediction in humans. More studies with other biopharmaceutical products are needed to strengthen the status of the minipig as an alternative model for immunotoxicity testing including immunogenicity.

Novel genetically-humanized mouse model established to evaluate efficacy of therapeutic agents to human interleukin-6 receptor

For clinical trials of therapeutic monoclonal antibodies (mAbs) to be successful, their efficacy needs to be adequately evaluated in preclinical experiments. However, in many cases it is difficult to evaluate the candidate mAbs using animal disease models because of lower cross-reactivity to the orthologous target molecules. In this study we have established a novel humanized Castleman's disease mouse model, in which the endogenous interleukin-6 receptor gene is successfully replaced by human IL6R, and human IL6 is overexpressed. We have also demonstrated the therapeutic effects of an antibody that neutralizes human IL6R, tocilizumab, on the symptoms in this mouse model. Plasma levels of human soluble IL6R and human IL6 were elevated after 4-week treatment of tocilizumab in this mouse model similarly to the result previously reported in patients treated with tocilizumab. Our mouse model provides us with a novel means of evaluating the in vivo efficacy of human IL6R-specific therapeutic agents.

The enhanced pre- and postnatal development study for monoclonal antibodies

The enhanced pre- and postnatal (ePPND) study design has been developed in response to new scientific knowledge and subsequent guideline changes [ICH M3(R2) and ICH S6(R1)]. The changes in study design were basically driven by the experiences obtained during preclinical development of biopharmaceuticals. The standard ePPND concept does not apply to conventional small molecule pharmaceuticals. In essence, the ePPND design is a pre- and postnatal development (PPND) study in which key elements of an embryo-fetal development study are investigated in newborns and infants rather than in the fetus. The cynomolgus monkey is the current relevant nonhuman primate model. The ICH S6(R1) guideline reached step 5 in June 2011 and provides detailed recommendations on various parameters and the conduct of an ePPND study. This chapter provides working guidance for monitoring menstrual cycles to generate pregnant animals, ultrasound monitoring of pregnancy, morphometric measurements of fetuses and newborns, in vivo skeletal examination, various protocols for evaluation of infants (e.g., neurobehavioral assessment, learning and memory test, grip strength, immune system evaluation) and a comprehensive list of additional infant evaluation parameters for the cynomolgus monkey.

Embryo fetal development studies in nonhuman primates

Embryo fetal development (EFD) studies in nonhuman primates are frequently conducted in macaques with Macaca fascicularis (cynomolgus monkey, long-tailed macaque, crab-eating macaque) being the most accepted model. EFD studies are also feasible in the marmoset. Due to recent guideline changes (ICH M3(R2) and S6(R1)), EFD studies are largely confined to conventional pharmaceutical compounds rather than biopharmaceuticals. This chapter describes basic study designs and provides working protocols for collecting, processing, and staining fetuses, including collection of amniotic fluid and umbilical cord blood. The chapter also covers the examination and terminology for external, visceral, and skeletal examinations of fetuses. The species covered in this chapter are cynomolgus monkey (long-tailed macaque) and marmoset monkey.

Capture, isolation and release of cancer cells with aptamer-functionalized glass bead array

Early detection and isolation of circulating tumor cells (CTC) can enable better prognosis for cancer patients. A Hele-Shaw device with aptamer functionalized glass beads is designed, modeled, and fabricated to efficiently isolate cancer cells from a cellular mixture. The glass beads are functionalized with anti-epidermal growth factor receptor (EGFR) aptamer and sit in ordered array of pits in polydimethylsiloxane (PDMS) channel. A PDMS encapsulation is then used to cover the channel and to flow through cell solution. The beads capture cancer cells from flowing solution depicting high selectivity. The cell-bound glass beads are then re-suspended from the device surface followed by the release of 92% cells from glass beads using combination of soft shaking and anti-sense RNA. This approach ensures that the cells remain in native state and undisturbed during capture, isolation and elution for post-analysis. The use of highly selective anti-EGFR aptamer with the glass beads in an array and subsequent release of cells with antisense molecules provide multiple levels of binding and release opportunities that can help in defining new classes of CTC enumeration devices.

Functional assessment of sexual maturity in male macaques (Macaca fascicularis)

Selection of suitable criteria for assessing sexual maturity in the male long-tailed macaque (Macaca fascicularis) has yielded conflicting results. The present retrospective work investigates whether the sole presence of sperm in the baseline semen sample unequivocally (i.e. for every animal) hallmarks complete testicular maturation. For 956 animals providing the baseline semen sample, neither age, body weight nor testes volume unequivocally predicted the presence of sperm in that sample, and for 322 animals these parameters failed to predict testicular histology. In contrast, the presence of sperm in the baseline semen sample correlated with mature testis histology at study termination in every single animal (n=197/322). Surprisingly, for the 125/322 animals without sperm in the baseline semen sample, spermatogenesis was also mature in 95 animals. Thus, the mere provision of a semen sample without sperm--implying peripheral reproductive tract maturation--was associated with mature spermatogenesis in approx. 75% of animals. Interestingly, testicular maturation occurred approx. 2 years earlier in Mauritian compared to Asian mainland animals. In conclusion, a single semen sample that contains sperm provides unequivocal evidence for mature spermatogenesis and, thus, is suggested as a functional parameter for sexual maturity assessment in this species.

Different adaptations of IgG effector function in human and nonhuman primates and implications for therapeutic antibody treatment

Safety of human therapeutic Abs is generally assessed in nonhuman primates. Whereas IgG1 shows identical FcγR interaction and effector function profile in both species, fundamental differences in the IgG2 and IgG4 Ab subclasses were found between the two species. Granulocytes, the main effector cells against IgG2- and IgG4-opsonized bacteria and parasites, do not express FcγRIIIb, but show higher levels of FcγRII in cynomolgus monkey. In humans, IgG2 and IgG4 adapted a silent Fc region with weak binding to FcγR and effector functions, whereas, in contrast, cynomolgus monkey IgG2 and IgG4 display strong effector function as well as differences in IgG4 Fab arm exchange. To balance this shift toward activation, the cynomolgus inhibitory FcγRIIb shows strongly increased affinity for IgG2. In view of these findings, in vitro and in vivo results for human IgG2 and IgG4 obtained in the cynomolgus monkey have to be cautiously interpreted, whereas effector function-related effects of human IgG1 Abs are expected to be predictable for humans.

Biologics in organ transplantation

The last two decades have witnessed a pandemic in antibody development, with over 600 entering clinical studies and a total of 28 approved by the FDA and European Union. The incorporation of biologics in transplantation has made a significant impact on allograft survival. Herein, we review the armamentarium of clinical and preclinical biologics used for organ transplantation--with the exception of belatacept--from depleting and IL-2R targeting induction agents to costimulation blockade, B-cell therapeutics, BAFF and complement inhibition, anti-adhesion, and anti-cytokine approaches. While individual agents may be insufficient for tolerance induction, they provide possibilities for reduction of steroid or calcineurin inhibitor use, alternatives to rejection episodes refractory to conventional therapies, and specialized immunosuppression for highly sensitized patients.

Minipig as a potential translatable model for monoclonal antibody pharmacokinetics after intravenous and subcutaneous administration

Subcutaneous (SC) delivery is a common route of administration for therapeutic monoclonal antibodies (mAbs) with pharmacokinetic (PK)/pharmacodynamic (PD) properties requiring long-term or frequent drug administration. An ideal in vivo preclinical model for predicting human PK following SC administration may be one in which the skin and overall physiological characteristics are similar to that of humans. In this study, the PK properties of a series of therapeutic mAbs following intravenous (IV) and SC administration in Göttingen minipigs were compared with data obtained previously from humans. The present studies demonstrated: (1) minipig is predictive of human linear clearance; (2) the SC bioavailabilities in minipigs are weakly correlated with those in human; (3) minipig mAb SC absorption rates are generally higher than those in human and (4) the SC bioavailability appears to correlate with systemic clearance in minipigs. Given the important role of the neonatal Fc-receptor (FcRn) in the PK of mAbs, the in vitro binding affinities of these IgGs against porcine, human and cynomolgus monkey FcRn were tested. The result showed comparable FcRn binding affinities across species. Further, mAbs with higher isoelectric point tended to have faster systemic clearance and lower SC bioavailability in both minipig and human. Taken together, these data lend increased support for the use of the minipig as an alternative predictive model for human IV and SC PK of mAbs.

Considerations regarding nonhuman primate use in safety assessment of biopharmaceuticals

Selection of a pharmacologically responsive species can represent a major challenge in designing nonclinical safety assessment programs for many biopharmaceuticals (eg, monoclonal antibodies (mAbs)). Frequently, the only relevant species for nonclinical testing of mAbs is the non-human primate (NHP). This situation, coupled with a rapidly increasing number of mAb drugs in development, has resulted in a significant increase in the number of NHPs used in nonclinical safety assessment. Apart from ethical considerations related to responsible animal use, there is a clear need for more efficient and innovative approaches to drug discovery and development; these factors drive the need to investigate alternative approaches and strategies for the safety assessment. This review summarizes important scientific and regulatory perspectives derived from presentations and audience discussions in an educational forum at the 2010 annual American College of Toxicology meeting regarding opportunities for employing alternative approaches to minimize NHP use in mAb drug development.

The design of chronic toxicology studies of monoclonal antibodies: implications for the reduction in use of non-human primates

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.

Pre-clinical strategies and safety issues in developing therapeutic monoclonal antibodies

Although mAbs present a different set of challenges from other product classes, and the pre-clinical safety evaluation may need to be more extensive than for other medicinal products to overcome the limited predictive value of conventional pre-clinical test systems, the level of risk associated with first administration to human subjects can be effectively mitigated. This article seeks to provide a systematic approach to identifying and addressing the pertinent risks relative to the characteristics of the particular mAb product before the first administration to human subjects.

A novel preclinical model for rheumatoid arthritis research

Based on increasing knowledge on the pathogenesis of rheumatoid arthritis (RA), more and more potential therapeutics have been developed. To evaluate their therapeutic efficacy, safety and toxicity, appropriate animal models are required. Although rodent models of RA have been extensively used for preclinical evaluation, the differences between rodents and humans limit their usability for some species-specific therapeutics. Therefore, autoimmune arthritis developed in a non-human primate with essential hallmarks of RA will be an alternative model for preclinical studies.

Collagen-induced arthritis in common marmosets: a new nonhuman primate model for chronic arthritis

INTRODUCTION

There is an ever-increasing need for animal models to evaluate efficacy and safety of new therapeutics in the field of rheumatoid arthritis (RA). Particularly for the early preclinical evaluation of human-specific biologicals targeting the progressive phase of the disease, there is a need for relevant animal models. In response to this requirement we set out to develop a model of collagen-induced arthritis (CIA) in a small-sized nonhuman primate species (300 to 400 g at adult age); that is, the common marmoset (Callithrix jacchus).

METHODS

Twenty-two animals divided into three experiments were immunized with collagen type II (CII) of either bovine or chicken origin with different immunization strategies. The animals were analyzed for clinical manifestation of arthritis, hematology and clinical chemistry, immunological responses against CII and histopathological features of the arthritis.

RESULTS

Clinically manifest arthritis was observed in almost 100% (21 out of 22) of the animals. Fifty percent of the animals developed semi-acute CIA while the other 50% displayed a more chronic disease. Both cellular (CD3/CD4 and CD3/CD8) and humoral responses (IgM and IgG) against CII were involved in the development of the disease. Besides mild histopathological changes in bone and cartilage, severe inflammation in extraarticular tissues like periosteum and subcutaneous tissues was observed.

CONCLUSIONS

This new model in marmosets more closely resembles chronic RA with respect to the chronic disease course and pathomorphological presentation than the more acute monophasic and destructive CIA model in macaques. This model can therefore fill a niche in preclinical testing of new human specific therapeutics.

The cynomolgus monkey as a model for developmental toxicity studies: variability of pregnancy losses, statistical power estimates, and group size considerations

BACKGROUND

This work evaluates pregnancy and infant loss in 1,069 vehicle-treated cynomolgus monkeys from 78 embryo-fetal development (EFD) studies and 14 pre-postnatal development (PPND) studies accrued during 1981-2007.

METHODS

Losses were analysed by survival function and hazard ratio using logistic regression for influence of year, study type (e.g., dose duration), and test item route of administration (ig, im, iv, sc).

RESULTS

Neither study type nor route of dosing affected pregnancy outcome. Losses were higher pre-1990 (104 losses/347 pregnancies) compared to 1990 onwards (94 losses/722 pregnancies). Losses were greatest before gestation day 50 and at parturition. Using post-1989 data, Monte-Carlo simulations of pregnancy outcomes were created. The power associated with the comparison of vehicle survival curves and simulated adverse survival curves was examined. This showed that EFD studies with initial vehicle group sizes of 16 and 20 have an 80% probability of having 13 and 16 ongoing pregnancies at gestational day 100, respectively. For PPND studies with initial vehicle group sizes of 16, 20, or 28, there is an 80% likelihood of having 9, 11, or 16 infants at day 7 post-partum, respectively. A PPND study initiated with group size 20 could detect a threefold increase of test item-related pregnancy or infant loss.

CONCLUSIONS

For designing and managing primate developmental toxicity studies, this type of analysis provides an objective tool to facilitate decisions either by supplementing groups with additional pregnant animals or stopping a group because an adverse effect on offspring survival has already been adequately revealed.

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

Overview of known non-human primate pathogens with potential to affect colonies used for toxicity testing

The increased demand for non-human primates (NHPs) in biomedical research has resulted in alternative sources of animals being used, which has allowed for importation of animals with varying background incidences of bacterial, viral, parasitic, and fungal pathogens. This can be of minimal consequence when animals from different sources are kept isolated. However, when NHPs from different sources with varying incidences of primary and opportunistic pathogens are mixed, there can be a rapid spread of these pathogens and an increase in the seroconversion of susceptible animals. If this process occurs during the conduct of a study, interpretation of that study can be confounded. Furthermore, NHPs imported from areas enzootic for pathogens such as Plasmodium or with high incidences of human diseases such as measles and tuberculosis can introduce diseases that can be a threat to colony health, have zoonotic risk, and can severely impact study outcome. Thus, knowledge of the common primary and opportunistic NHP infections, as well as reemerging pathogens, enables the toxicologist to use information on disease status for pre-study animal selection and intelligent study design. This is particularly important when immunomodulatory compounds are being investigated. Moreover, the toxicologic pathologist well versed in the common spontaneous infections, opportunistic pathogens, and background lesions in NHPs is able to assess possible drug-related effects in drug safety studies. This review identifies the common primary and opportunistic pathogens, as well as newly emerging infections of NHPs, that can directly or indirectly affect colony health and the interpretation of drug safety studies.

Application of quantitative pharmacology in development of therapeutic monoclonal antibodies

The advancement of therapeutic monoclonal antibodies during various stages of the drug development process can be effectively streamlined when appropriate translational strategies are applied. Design of successful translational strategies for development of monoclonal antibodies should allow for understanding of the dose- and concentration-response relationships with respect to both beneficial and toxic effects from early phases of drug development. Evaluation of relevant biomarkers during early stages of drug development should facilitate the successful design of safe and effective dosing strategies. Moreover, application of quantitative pharmacology is critical for translation of exposure-response relationships early on.

The safety and side effects of monoclonal antibodies

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Immunotoxicity testing in nonhuman primates

Biological relevance is generally the major justification for using nonhuman primates (NHP) during preclinical safety assessment. This holds particularly true for the evaluation of biopharmaceuticals with NHP often being the species of choice. For safety assessment of small molecules, NHP are used in case of a higher degree of metabolic similarity, to detect the highly specific immunotoxic side effects and to discriminate toxicity from efficacy of immunomodulatory drugs. Unlike for rodent immunotoxicity studies, standardized tests and protocols are generally less available for NHP. The immunotoxicity testing protocols described in the present chapter have been adapted for application to NHP samples. In principle, rodent protocols can be transferred to NHP. Fortunately, most of the immunotoxicity parameters delineated in the ICH S8 guideline can be applied to NHP specimens. Exceptions are the host resistance assay and the delayed type hypersensitivity test. Owing to the close structural and physiological similarity between NHP and human, human test kits or reagents are often well suited for application to NHP samples. For data evaluation it should be noted that no inbred strains of NHP are available, resulting in a large inter-animal variability for most immunotoxicity assay results. The experimental protocols and reagents described in this chapter were developed specifically for the cynomolgus monkey (Macaca fascicularis), currently the most commonly used NHP species in toxicology. In many instances, these protocols will also be applicable to rhesus monkeys (M. mulatta) and potentially to other Old World macaques. For the marmoset (Callithrix jacchus), a New World monkey also used in toxicology, the choice of available immunotoxicity testing protocols is much reduced when compared to macaques.