The significance of non-human primates as preclinical models of human arthritic disease

Advances in experimental models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by persistent articular inflammation and joint damage. RA was first described over 200 years ago; however, its etiology and pathophysiology remain insufficiently understood. The current treatment of RA is mainly empirical or based on the current understanding of etiology with limited efficacy and/or substantial side effects. Thus, the development of safer and more potent therapeutics, validated and optimized in experimental models, is urgently required. To improve the transition from bench to bedside, researchers must carefully select the appropriate experimental models as well as draw the right conclusions. Here, we summarize the establishment, pathological features, potential mechanisms, advantages, and limitations of the currently available RA models. The aim of the review is to help researchers better understand available RA models; discuss future trends in RA model development, which can help highlight new translational and human-based avenues in RA research.

How to Model Rheumatoid Arthritis in Animals: From Rodents to Non-Human Primates

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease influenced by both genetic and environmental factors. At present, rodent models are primarily used to study the pathogenesis and treatment of RA. However, the genetic divergences between rodents and humans determine differences in the development of RA, which makes it necessary to explore the establishment of new models. Compared to rodents, non-human primates (NHPs) are much more closely related to humans in terms of the immune system, metabolic conditions, and genetic make-up. NHPs model provides a powerful tool to study the development of RA and potential complications, as well as preclinical studies in drug development. This review provides a brief overview of the RA animal models, emphasizes the replication methods, pros and cons, as well as evaluates the validity of the rodent and NHPs models.

MHC class I allele diversity in cynomolgus macaques of Vietnamese origin

Cynomolgus macaques (Macaca fascicularis, Mafa) have been used as important experimental animal models for carrying out biomedical researches. The results of biomedical experiments strongly depend on the immunogenetic background of animals, especially on the diversity of major histocompatibility complex (MHC) alleles. However, there is much less information available on the polymorphism of MHC class I genes in cynomolgus macaques, than is currently available for humans. In this study, we have identified 40 Mafa-A and 60 Mafa-B exons 2 and 3 sequences from 30 unrelated cynomolgus macaques of Vietnamese origin. Among these alleles, 28 are novel. As for the remaining 72 known alleles, 15 alleles are shared with other cynomolgus macaque populations and 32 are identical to alleles previously reported in other macaque species. A potential recombination event was observed between Mafa-A1*091:02 and Mafa-A1*057:01. In addition, the Mafa-A1 genes were found to be more diverse than human HLA-A and the functional residues for peptide binding sites (PBS) or TCR binding sites (TBS) in Mafa-A1 have greater variability than that for non-PBS or non-TBS regions. Overall, this study provides important information on the diversity of Mafa-A and Mafa-B alleles from Vietnamese origin, which may help researchers to choose the most appropriate animals for their studies.

Safety, Biodistribution, and Efficacy of an AAV-5 Vector Encoding Human Interferon-Beta (ART-I02) Delivered via Intra-Articular Injection in Rhesus Monkeys with Collagen-Induced Arthritis

Preclinical studies to assess biodistribution, safety, and initial efficacy of ART-I02, an adeno-associated type 5 (rAAV5) vector expressing human interferon β (hIFN-β), were performed in a total of 24 rhesus monkeys with collagen-induced arthritis. All monkeys were naïve or showed limited neutralizing antibody (Nab) titers to AAV5 at the start of the study. Animals were injected with a single intra-articular dose of ART-I02 or placebo, consisting of 3.2×10(13) vg (Dose A=maximum feasible dose), 4.58×10(12) vg (Dose B), or placebo in the first affected finger joint, the ipsilateral knee, and ankle joint at the same time point. Animals were monitored for clinical parameters and well-being with a maximum of 4 weeks, with the option that the severity of arthritis could necessitate an earlier time point of sacrifice. No adverse events were noted after injection of ART-I02. No abnormalities were observed after histological evaluation of all organs. At both dose levels, immunohistochemical staining indicated expression of hIFN-β. In animals injected with Dose A, we observed stabilization or a reduction in swelling in the finger joint in which vector was administered. The highest copy numbers of vector DNA were detected in synovial tissue of the injected joint and the draining lymph node of the injected knee. High titers of Nab to rAAV5 were observed at the end of the study. Five monkeys developed an rAAV5-specific T-cell response. Two monkeys developed Nab to hIFN-β. In conclusion, intra-articular injection of ART-I02 was well-tolerated and did not induce adverse events. After administration of Dose A of ART-I02, we observed a beneficial effect on joint swelling, substantiated by decreased histological inflammation and bone erosion scores. A GMP vector for clinical application has been manufactured and is currently being tested in GLP rodent studies, with the aim to move forward to a clinical trial.

The preclinical pharmacology of the high affinity anti-IL-6R Nanobody® ALX-0061 supports its clinical development in rheumatoid arthritis

Introduction

The pleiotropic cytokine interleukin-6 (IL-6) plays an important role in the pathogenesis of different diseases, including rheumatoid arthritis (RA). ALX-0061 is a bispecific Nanobody® with a high affinity and potency for IL-6 receptor (IL-6R), combined with an extended half-life by targeting human serum albumin. We describe here the relevant aspects of its in vitro and in vivo pharmacology.

Methods

ALX-0061 is composed of an affinity-matured IL-6R-targeting domain fused to an albumin-binding domain representing a minimized two-domain structure. A panel of different in vitro assays was used to characterize the biological activities of ALX-0061. The pharmacological properties of ALX-0061 were examined in cynomolgus monkeys, using plasma levels of total soluble (s)IL-6R as pharmacodynamic marker. Therapeutic effect was evaluated in a human IL-6-induced acute phase response model in the same species, and in a collagen-induced arthritis (CIA) model in rhesus monkeys, using tocilizumab as positive control.

Results

ALX-0061 was designed to confer the desired pharmacological properties. A 200-fold increase of target affinity was obtained through affinity maturation of the parental domain. The high affinity for sIL-6R (0.19 pM) translated to a concentration-dependent and complete neutralization of sIL-6R in vitro. In cynomolgus monkeys, ALX-0061 showed a dose-dependent and complete inhibition of hIL-6-induced inflammatory parameters, including plasma levels of C-reactive protein (CRP), fibrinogen and platelets. An apparent plasma half-life of 6.6 days was observed after a single intravenous administration of 10 mg/kg ALX-0061 in cynomolgus monkeys, similar to the estimated expected half-life of serum albumin. ALX-0061 and tocilizumab demonstrated a marked decrease in serum CRP levels in a non-human primate CIA model. Clinical effect was confirmed in animals with active drug exposure throughout the study duration.

Conclusions

ALX-0061 represents a minimized bispecific biotherapeutic of 26 kDa, nearly six times smaller than monoclonal antibodies. High in vitro affinity and potency was demonstrated. Albumin binding as a half-life extension technology resulted in describable and expected pharmacokinetics. Strong IL-6R engagement was shown to translate to in vivo effect in non-human primates, demonstrated via biomarker deregulation as well as clinical effect. Presented results on preclinical pharmacological properties of ALX-0061 are supportive of clinical development in RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0651-0) contains supplementary material, which is available to authorized users.

New drug discovery strategies for rheumatoid arthritis: a niche for nonhuman primate models to address systemic complications in inflammatory arthritis

INTRODUCTION

Despite the tremendous advances made in the treatment of rheumatoid arthritis (RA), there is still excess mortality observed in RA patients, which is mainly caused by cardiovascular disease (CVD). Altered lipid metabolism plays a major role in the etiology of CVD. A second common complication observed in RA patients is anemia. Both conditions are serious, reduce quality of life and are undertreated.

AREAS COVERED

The authors postulate that there is a specific niche for nonhuman primate models of inflammatory arthritis to address these systemic complications that occur in RA. Furthermore, the authors postulate that these nonhuman primate models are a useful platform to unveil the mechanisms underlying dyslipidemia and anemia, which are responsible for the manifestation of these complications.

EXPERT OPINION

The presence of currently untreated systemic complications of RA, such as dyslipidemia and anemia, provides interesting opportunities to include these in the preclinical evaluation of new therapies. In the selection of relevant models for the evaluation of new treatments for RA or the identification of new targets for therapy, we postulate that nonhuman primates should be considered as a valid preclinical model. Because of their closer immunological and physiological proximity to humans, these models in nonhuman primates can be valuable for studying disease-related aspects that cannot be addressed in rodent models.

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.