A novel strategy to reduce the immunogenicity of biological therapies

Adeno-associated virus-vectored delivery of HIV biologics: the promise of a "single-shot" functional cure for HIV infection

The ability of immunoglobulin-based HIV biologics (Ig-HIV), including broadly neutralizing antibodies, to suppress viral replication in pre-clinical and clinical studies illustrates how these molecules can serve as alternatives or adjuncts to antiretroviral therapy for treating HIV infection. However, the current paradigm for delivering Ig-HIVs requires repeated passive infusions, which faces both logistical and economic challenges to broad-scale implementation. One promising way to overcome these obstacles and achieve sustained expression of Ig-HIVs in vivo involves the transfer of Ig-HIV genes to host cells utilizing adeno-associated virus (AAV) vectors. Because AAV vectors are non-pathogenic and their genomes persist in the cell nucleus as episomes, transgene expression can last for as long as the AAV-transduced cell lives. Given the long lifespan of myocytes, skeletal muscle is a preferred tissue for AAV-based immunotherapies aimed at achieving persistent delivery of Ig-HIVs. Consistent with this idea, recent studies suggest that lifelong immunity against HIV can be achieved from a one-time intramuscular dose of AAV/Ig-HIV vectors. However, realizing the promise of this approach faces significant hurdles, including the potential of AAV-delivered Ig-HIVs to induce anti-drug antibodies and the high AAV seroprevalence in the human population. Here we describe how these host immune responses can hinder AAV/Ig-HIV therapies and review current strategies for overcoming these barriers. Given the potential of AAV/Ig-HIV therapy to maintain ART-free virologic suppression and prevent HIV reinfection in people living with HIV, optimizing this strategy should become a greater priority in HIV/AIDS research.

Development and characterization of a novel human CD137 agonistic antibody with anti-tumor activity and a good safety profile in non-human primates

CD137 (4-1BB, TNFRSF9), an inducible T-cell costimulatory receptor, is expressed on activated T cells, activated NK cells, Treg cells, and several innate immune cells, including DCs, monocytes, neutrophils, mast cells, and eosinophils. In animal models and clinical trials, anti-CD137 agonistic monoclonal antibodies have shown anti-tumor potential, but balancing the efficacy and toxicity of anti-CD137 agonistic monoclonal antibodies is a considerable hindrance for clinical applications. Here, we describe a novel fully human CD137 agonistic antibody (PE0116) generated from immunized harbor H2L2 human transgenic mice. PE0116 is a ligand blocker, which is also the case for Utomilumab (one of the leading CD137 agonistic drugs); PE0116 partially overlaps with Urelumab's recognized epitope. In vitro, PE0116 activates NF-κB signaling, significantly promotes T-cell proliferation, and increases cytokine secretion in the presence of cross-linking. Importantly, PE0116 possesses robust anti-tumor activity in the MC38 tumor model. In vivo, PE0116 exhibits a good safety profile and has typical pharmacokinetic characteristics of an IgG antibody in preclinical studies of non-human primates. In summary, PE0116 is a promising anti-CD137 antibody with a good safety profile in preclinical studies.

HIV envelope antibodies and TLR7 agonist partially prevent viral rebound in chronically SHIV-infected monkeys

A key challenge for the development of a cure to HIV-1 infection is the persistent viral reservoir established during early infection. Previous studies using Toll-like receptor 7 (TLR7) agonists and broadly neutralizing antibodies (bNAbs) have shown delay or prevention of viral rebound following antiretroviral therapy (ART) discontinuation in simian-human immunodeficiency virus (SHIV)-infected rhesus macaques. In these prior studies, ART was initiated early during acute infection, which limited the size and diversity of the viral reservoir. Here we evaluated in SHIV-infected rhesus macaques that did not initiate ART until 1 year into chronic infection whether the TLR7 agonist vesatolimod in combination with the bNAb PGT121, formatted either as a human IgG1, an effector enhanced IgG1, or an anti-CD3 bispecific antibody, would delay or prevent viral rebound following ART discontinuation. We found that all 3 antibody formats in combination with vesatolimod were able to prevent viral rebound following ART discontinuation in a subset of animals. These data indicate that a TLR7 agonist combined with antibodies may be a promising strategy to achieve long-term ART-free HIV remission in humans.

In a rhesus macaque model for chronic HIV infection where ART was not initiated before 1 year of infection, we demonstrate that the HIV bNAb PGT121 (formatted in three immune cell engager formats) together with the TLR7 agonist vesatolimod can partially prevent viral rebound following discontinuation of ART. Importantly, in most of the animals that did not rebound following the ART discontinuation, CD8+ cell depletion did not result in viral rebound, suggesting that the lack of rebound was not dependent on CD8+ T or NK cells. To the best of our knowledge, no similar study has been performed in the nonhuman primate model with animals that started ART deep into chronic infection. This proof-of-concept study in chronically infected rhesus macaques supports that this treatment regimen may represent a strategy to achieve long-term ART-free HIV remission in humans.

Efficacy and Safety of Ustekinumab in Patients with Active Systemic Lupus Erythematosus: Results Through 2 Years of an Open-Label Extension in a Phase 2 Study

OBJECTIVE

To evaluate long-term efficacy and safety of ustekinumab through 2 years in patients with active systemic lupus erythematosus (SLE).

METHODS

This was a placebo-controlled (Week24) phase 2 study in 102 patients with seropositive active SLE. Patients were randomized to ustekinumab (~6 mg/kg single IV infusion, then 90 mg SC every 8 weeks) or placebo, added to background therapy. Placebo patients initiated ustekinumab (90mg SC Q8W) at Week24. Patients could enter an optional open-label study extension after Week40 (final ustekinumab administration at Week104). Efficacy assessments included SRI-4, SLEDAI-2K, PGA, and CLASI. Observed data are reported for the extension period. The final efficacy assessment was at Week112; safety was monitored through Week120.

RESULTS

In this subset of patients who entered the study extension, 24 in the ustekinumab group and 14 in the placebo-crossover group completed study treatment. At Week112, 79% and 92%, respectively, had an SRI-4 response, 92% in both groups had ≥4-point improvement from baseline in SLEDAI-2K score, 79% and 93%, respectively, had ≥30% improvement from baseline in PGA, 86% and 91%, respectively, had ≥50% improvement in active joint (pain and inflammation) count, and 79% and 100%, respectively, had ≥50% improvement in CLASI activity score. No deaths, malignancies, opportunistic infections, or tuberculosis cases occurred. Safety events were consistent with the known ustekinumab safety profile.

CONCLUSION

In the 46 patients who entered the voluntary extension of this phase 2 study, clinical benefit in global and organ-specific SLE-activity measures was observed with ustekinumab through 2years with no new or unexpected safety findings. clinicaltrials.gov: NCT02349061.

Randomized Controlled Trial: Subcutaneous vs Intravenous Infliximab CT-P13 Maintenance in Inflammatory Bowel Disease

BACKGROUND & AIMS

This study compared pharmacokinetics, symptomatic and endoscopic efficacy, safety, and immunogenicity of a subcutaneous formulation of the infliximab biosimilar CT-P13 (CT-P13 SC) vs intravenous CT-P13 (CT-P13 IV) in patients with inflammatory bowel disease (IBD).

METHODS

This randomized, multicenter, open-label, parallel-group, phase 1 study enrolled tumor necrosis factor inhibitor-naïve patients with active ulcerative colitis (total Mayo score 6-12 points with endoscopic subscore ≥2) or Crohn's disease (Crohn's Disease Activity Index 220-450 points) at 50 centers. After CT-P13 IV induction at Week (W) 0/W2, patients were randomized (1:1) to receive CT-P13 SC every 2 weeks (q2w) from W6 to W54 or CT-P13 IV every 8 weeks from W6 to W22. At W30, all patients receiving CT-P13 IV switched to CT-P13 SC q2w until W54. The primary endpoint was noninferiority of CT-P13 SC to CT-P13 IV for observed predose CT-P13 concentration at W22 (C_trough,W22), concluded if the lower bound of the 2-sided 90% confidence interval (CI) for the ratio of geometric least-squares means exceeded 80%.

RESULTS

Overall, 66 and 65 patients were randomized to CT-P13 SC and CT-P13 IV, respectively. The primary endpoint of noninferiority was met with a geometric least-squares means ratio for C_trough,W22 of 1154.17% (90% CI 786.37-1694.00; n = 59 [CT-P13 SC]; n = 57 [CT-P13 IV]). W30/W54 clinical remission rates were comparable between arms. Other efficacy, safety, and immunogenicity assessments were also broadly comparable between arms, including after switching.

CONCLUSIONS

The pharmacokinetic noninferiority of CT-P13 SC to CT-P13 IV, and the comparable efficacy, safety, and immunogenicity profiles, support the potential suitability of CT-P13 SC treatment in IBD. ClinicalTrials.gov ID: NCT02883452.

Alemtuzumab scFv fragments and CD52 interaction study through molecular dynamics simulation and binding free energy

Specific antibody-antigen recognition is crucial for the immune response. Knowledge of molecular interaction details in the recognition process is fundamental for the rational design of antibodies with improved properties. We used state-of-the-art computer simulation tools to deepen the molecular-level understanding of the interactions between the monoclonal antibody Alemtuzumab and its antigen, the CD52 membrane receptor, of great biotechnological importance. Thus, we seek such responses by modeling the interaction of native and known mutants single-chain fragment variable (scFv) of Alemtuzumab with CD52 inserted in a membrane model to mimic the physiological conditions of antibody-antigen binding. Extensive molecular dynamics simulations of the interaction between Alemtuzumab's scFvs and CD52 promoted greater understanding of the structural and energetic bases, which can be translated into the biological action and affinity of this antibody. The quantification of the scFv-CD52 complexes binding free energy (ΔG_bind) by Molecular Mechanics-Poisson-Boltzmann Surface Area (MM-PBSA) correlated with the experimental binding energies described before. Thus, the mutants D53K, K54D, and K56D resulted in less attractive ΔG_bind, therefore lower scFv-CD52 affinity than the native scFv. On the other hand, K56D and K54D/K56D showed lower binding to CD52. These Results revealed that the model system mimicking an environment close to the physiological with the presence of the CD52 in a membrane model proved essential for this system's study. The present study allowed to unveil the molecular mechanisms involved in antigen-antibody interaction and the effects of mutations. Thus, these mechanisms may be explored in the Alemtuzumab variants' rational design with enhanced properties.

Innovative approaches to biologic development on the trail of CT-P13: biosimilars, value-added medicines, and biobetters

The biosimilar concept is now well established. Clinical data accumulated pre- and post-approval have supported biosimilar uptake, in turn stimulating competition in the biologics market and increasing patient access to biologics. Following technological advances, other innovative biologics, such as “biobetters” or “value-added medicines,” are now reaching the market. These innovative biologics differ from the reference product by offering additional clinical or non-clinical benefits. We discuss these innovative biologics with reference to CT-P13, initially available as an intravenous (IV) biosimilar of reference infliximab. A subcutaneous (SC) formulation, CT-P13 SC, has now been developed. Relative to CT-P13 IV, CT-P13 SC offers clinical benefits in terms of pharmacokinetics, with comparable efficacy, safety, and immunogenicity, as well as increased convenience for patients and reduced demands on healthcare system resources. As was once the case for biosimilars, nomenclature and regulatory pathways for innovative biologics require clarification to support their uptake and ultimately benefit patients.

Immunogenicity-unwanted immune responses to biological drugs - can we predict them?

INTRODUCTION

Biological agents (BAs) target molecules involved in disease mechanisms and have modified the natural history of several immune-mediated disorders. All BAs are immunogenic, resulting in the formation of antidrug antibodies (ADAs), which can neutralize drug activity leading to loss of response and potential relapse, or serious adverse events such as infusion hypersensitivity reactions. The production of ADAs is the result of a specific adaptive immune response in which T and B cells are involved.

AREAS COVERED

Factors conditioning the immunogenicity of BAs, including drug-, treatment- and patient-related factors are currently the subject of many studies. Among them, a lot of attention is dedicated to define the impact of BAs structure, the effect of targeting (soluble or membrane) molecules, the impact of interruption of therapy as well as the role of genetic (HLA and non-HLA) predisposing factors and disease activity.

EXPERT OPINION

Knowledge of factors capable of influencing the immunogenicity of BAs may help to understand, in a predictive manner and at the single patient level, the presence of risk factors influencing the production of ADAs and their impact on clinical outcomes.

Established and Emerging Immunological Complications of Biological Therapeutics in Multiple Sclerosis

Biologic immunotherapies have transformed the treatment landscape of multiple sclerosis. Such therapies include recombinant proteins (interferon beta), as well as monoclonal antibodies (natalizumab, alemtuzumab, daclizumab, rituximab and ocrelizumab). Monoclonal antibodies show particular efficacy in the treatment of the inflammatory phase of multiple sclerosis. However, the immunological perturbations caused by biologic therapies are associated with significant immunological adverse reactions. These include development of neutralising immunogenicity, secondary immunodeficiency and secondary autoimmunity. These complications can affect the balance of risks and benefits of biologic agents, and 2018 saw the withdrawal from the market of daclizumab, an anti-CD25 monoclonal antibody, due to concerns about the development of severe, unpredictable autoimmunity. Here we review established and emerging risks associated with multiple sclerosis biologic agents, with an emphasis on their immunological adverse effects. We also discuss the specific challenges that multiple sclerosis biologics pose to drug safety systems, and the potential for improvements in safety frameworks.

The Irony of Humanization: Alemtuzumab, the First, But One of the Most Immunogenic, Humanized Monoclonal Antibodies

Alemtuzumab was designed to reduce the immunogenicity of the parent CD52-specific rat immunoglobulin. Although originally marketed for use in cancer (Mabcampath®), alemtuzumab is currently licensed and formulated for the treatment of relapsing multiple sclerosis (Lemtrada®). Perhaps due to its history as the first humanized antibody, the potential of immunogenicity of the molecule has been considered inconsequential, and anti-drug antibodies (ADA) responses were similarly reported as being clinically insignificant. Nonetheless, despite humanization and depletion of peripheral T and B cells, alemtuzumab probably generates the highest frequency of binding and neutralizing ADA of all humanized antibodies currently in clinical use, and they occur rapidly in a large majority of people with MS (pwMS) on alemtuzumab treatment. These ADA appear to be an inherent issue of the biology of the molecule-and more importantly, the target-such that avoidance of immunogenicity-related effects has been facilitated by the dosing schedule used in clinical practice. At the population level this enables the drug to work in most pwMS, but in some individuals, as we show here, antibody neutralization appears to be sufficiently severe to reduce efficacy and allow disease breakthrough. It is therefore imperative that efficacy of lymphocyte depletion and the anti-drug response is monitored in people requiring additional cycles of treatment, notably following disease breakthrough. This may help inform whether to re-treat or to switch to another disease-modifying treatment.

Infliximab-Tumor Necrosis Factor Complexes Elicit Formation of Anti-Drug Antibodies

BACKGROUND & AIMS

Some patients develop anti-drug antibodies (ADAs), which reduce the efficacy of infliximab, a monoclonal antibody against tumor necrosis factor (TNF), in the treatment of immune-mediated diseases, including inflammatory bowel diseases. ADAs arise inconsistently, and it is not clear what factors determine their formation. We investigated features of the immune system, the infliximab antibody, and its complex with TNF that might contribute to ADA generation.

METHODS

C57BL/6 mice were given injections of infliximab and recombinant human TNF or infliximab F(ab')₂ fragments. Blood samples were collected every 2-3 days for 2 weeks and weekly thereafter for up to 6 weeks; infliximab-TNF complexes and ADAs were measured by enzyme-linked immunosorbent assay (ELISA). Intestinal biopsy and blood samples were obtained from patients having endoscopy who had received infliximab therapy for inflammatory bowel diseases; infliximab-TNF complexes were measured with ELISA. Infliximab-specific plasma cells were detected in patient tissue samples by using mass cytometry. We studied activation of innate immune cells in peripheral blood mononuclear cells (PBMCs) from healthy donors incubated with infliximab or infliximab-TNF complexes; toll-like receptors (TLRs) were blocked with antibodies, endocytosis was blocked with the inhibitor PitStop2, and cytokine expression was measured by real-time polymerase chain reaction and ELISAs. Uptake of infliximab and infliximab-TNF complexes by THP-1 cells was measured with confocal microscopy.

RESULTS

Mice given increasing doses of infliximab produced increasing levels of ADAs. Blood samples from mice given injections of human TNF and infliximab contained infliximab-TNF complexes; complex formation was associated with ADA formation with an area under the curve of 0.944 (95% confidence interval, 0.851-1.000; P = .003). Intestinal tissues from patients, but not blood samples, contained infliximab-TNF complexes and infliximab-specific plasma cells. Incubation of PBMCs with infliximab-TNF complexes resulted in a 4.74-fold increase in level of interleukin (IL) 1β (IL1B) messenger RNA (P for comparison = .005), increased IL1B protein secretion, and a 2.69-fold increase in the expression of TNF messenger RNA (P for comparison = 0.013) compared with control PBMCs. Infliximab reduced only IL1B and TNF expression. Antibodies against TLR2 or TLR4 did not block the increases in IL1B or TNF expression, but endocytosis was required. THP-1 cells endocytosed higher levels of infliximab-TNF complexes than infliximab alone.

CONCLUSIONS

In mice, we found ADA formation to increase with dose of infliximab given and concentration of infliximab-TNF complexes detected in blood. Based on studies of human intestinal tissues and blood samples, we propose that infliximab-TNF complexes formed in the intestine are endocytosed by and activate innate immune cells, which increase expression of IL1B and TNF and production of antibodies against the drug complex. It is therefore important to optimize the infliximab dose to a level that is effective but does not activate an innate immune response against the drug-TNF complex.

Human Monoclonal Antibodies: The Benefits of Humanization

The major reasons for developing human monoclonal antibodies were to be able to efficiently manipulate their effector functions while avoiding immunogenicity seen with rodent antibodies. Those effector functions involve interactions with the complement system and naturally occurring Fc receptors on diverse blood white cells. Antibody immunogenicity results from the degree to which the host immune system can recognize and react to these therapeutic agents. Thus far, there is still no generally applicable technology guaranteed to render therapeutic antibodies antigenically silent. This is not to say that the task is impossible, but rather that we need to train the immune system to help us. This can be achieved if we take advantage of natural mechanisms by which an individual can be rendered tolerant of "foreign" antigens, and as a corollary minimize the potential immunogenicity of any contaminating protein aggregates, or "aggregates" arising from antibodies complexing with their antigen. I here summarize our efforts to engineer antibodies to harness optimal effector functions, while also minimizing their immunogenicity. Potential avenues to achieve the latte are predicted from classical work showing that monomeric "foreign" immunoglobulins are good tolerogens, while aggregates of immunoglobulins ate intrinsically immunogenic. Consequently, I argue that one solution to the immunogenicity problem lies in ensuring a temporal quantitative advantage of tolerogenic non-cell-bound monomer over the cell-binding immunogenic form.

Hypersensitivity to alemtuzumab. A safe and effective desensitization protocol: A case report

We describe a successful desensitization to alemtuzumab in one patient diagnosed with T-cell prolymphocytic leukaemia. Alemtuzumab treatment was initiated during infusion number 18, the patient showed cutaneous eruption with a miliary pattern, despite premedication with corticosteroids and antihistamines. The eruption returned with successive alemtuzumab infusions (infusions 19, 20 and 21), remained present for longer and was more severe with each infusion. The patient was referred to our Allergy Unit as it was necessary to maintain alemtuzumab treatment. Total immunoglobulin E level was 3 UI/ml and specific immunoglobulin E against more common pneumo-allergens, food, latex and hamster were inferior to 0.35 UI/ml. Prick test using the undiluted drug (30 mg/ml) and intradermal tests using serial dilutions (1/10, 1/100) were performed. The result of alemtuzumab skin prick test was 4 mm. The intradermal skin test result was positive at 1/100 dilution (papule: 8 mm; erythema: 12 mm). The basophil activation test with alemtuzumab was performed concluding that 10% of the basophils were activated by alemtuzumab. The patient underwent alemtuzumab desensitization according to a 12-step protocol that resolved to be safe and efficacious. Our experience may be helpful for similar clinical cases where the therapeutic options are very limited and a life-threatening condition such T-cell prolymphocytic leukaemia is present. In addition, a careful risk/benefit ratio should be considered and accurate informed consent is mandatory.

Alemtuzumab depletion failure can occur in multiple sclerosis

Alemtuzumab is a lymphocyte-depleting antibody and one of the most effective treatments for relapsing multiple sclerosis. However, it also causes loss of immune-tolerance leading to secondary autoimmunity and marked anti-drug antibody responses. Although these anti-drug responses have been reported to be of no significance, we hypothesized that they will affect the depleting capacity and treatment response in some individuals. This was found following analysis of the regulatory submission of the pivotal phase III trials, which was obtained from the European Medicines Agency. At the population level there was lack of influence of 'ever-positive' alemtuzumab-specific antibody responses on lymphocyte depletion, clinical efficacy and adverse effects during the 2-year trial. This was not surprising as no one before the first infusion, and only 0·6% of people before the second-infusion, had pre-infusion, neutralizing antibodies (NAbs). However, at the individual level, NAbs led to poor lymphocyte depletion. Importantly, it was evident that 31% of people had NAbs and 75% had binding antibodies at the end of treatment-cycle 2, which suggests that problems may occur in people requiring additional alemtuzumab cycles. In addition, we also identified individuals, following 'post-marketing' alemtuzumab use, whose lymphocyte level was never effectively depleted after the first infusion cycle. Hence, although alemtuzumab depletes lymphocytes in most individuals, some people fail to deplete/deplete poorly, probably due to biological-response variation and NAbs, and this may lead to treatment failure. Monitoring depletion following infusion and assessment of the neutralizing response before re-infusion may help inform the decision to retreat or switch therapy to limit treatment failure.

Pharmacokinetics of monoclonal antibodies and Fc-fusion proteins

There are many factors that can influence the pharmacokinetics (PK) of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediated recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic antibodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation. Glycosylation of a mAb or Fc-fusion protein can have a significant impact on the PK of these molecules. mAb charge can be important and variants with pI values of 1-2 unit difference are likely to impact PK with lower pI values being favorable for a longer half-life. Most mAbs display target mediated drug disposition (TMDD), which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody (ADA) response and off-target binding, which require careful consideration during the discovery stage. mAbs are primarily absorbed through the lymphatics via convection and can be conveniently administered by the subcutaneous (sc) route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be reasonably estimated using cynomolgus monkey data and allometric scaling methods.

Interpreting Lymphocyte Reconstitution Data From the Pivotal Phase 3 Trials of Alemtuzumab

Importance

Alemtuzumab, a CD52-depleting monoclonal antibody, effectively inhibits relapsing multiple sclerosis (MS) but is associated with a high incidence of secondary B-cell autoimmunities that limit use. These effects may be avoided through control of B-cell hyperproliferation.

Objective

To investigate whether the data describing the effect of alemtuzumab on lymphocyte subsets collected during the phase 3 trial program reveal mechanisms explaining efficacy and the risk for secondary autoimmunity with treatment of MS.

Design, Setting, and Participants

Lymphocyte reconstitution data from regulatory submissions of the pivotal Comparison of Alemtuzumab and Rebif Efficacy in Multiple Sclerosis I and II (CARE-MS I and II) trials were obtained from the European Medicines Agency via Freedom of Information requests. Data used in this study were reported from June 22 to October 12, 2016.

Main Outcomes and Measures

Tabulated data from T- and B-lymphocyte subset analysis and antidrug antibody responses were extracted from the supplied documents.

Results

Alemtuzumab depleted CD4+ T cells by more than 95%, including regulatory cells (-80%) and CD8+ T cells (>80% depletion), which remained well below reference levels throughout the trials. However, although CD19+ B cells were initially also depleted (>85%), marked (180% increase) hyperrepopulation of immature B cells occurred with conversion to mature B cells over time. These lymphocyte kinetics were associated with rapid development of alemtuzumab-binding and -neutralizing antibodies and subsequent occurrence of secondary B-cell autoimmunity. Hyperrepopulation of B cells masked a marked, long-term depletion of CD19+ memory B cells that may underpin efficacy in MS.

Conclusions and Relevance

Although blockade of memory T and B cells may limit MS, rapid CD19+ B-cell subset repopulation in the absence of effective T-cell regulation has implications for the safety and efficacy of alemtuzumab. Controlling B-cell proliferation until T-cell regulation recovers may limit secondary autoimmunity, which does not occur with other B-cell-depleting agents.

Alemtuzumab for Multiple Sclerosis

Alemtuzumab is a humanised anti-CD52 monoclonal antibody approved for use in active, relapsing multiple sclerosis (MS). Administration results in a rapid depletion of circulating lymphocytes with a subsequent beneficial immune reconstitution. Early open-label experience and recent clinical trials have demonstrated a dramatic effect on relapse rates as well as a positive effect on radiological disease outcomes and disability measures. Despite a mechanism of action that results in profound lymphopaenia, opportunistic infections are rarely seen and no excess association with malignancy has been identified. However, acquired autoimmune disease (AID) is a common adverse event following treatment, necessitating rigorous monitoring in order to facilitate prompt detection and management. Despite this issue, a unique dosing schedule and durability of effect make alemtuzumab a welcome addition to currently available treatment options for MS.

Immunogenicity of Isogenic IgG in Aggregates and Immune Complexes

A paradox in monoclonal antibody (mAb) therapy is that despite the well-documented tolerogenic properties of deaggregated IgG, most therapeutic IgG mAb induce anti-mAb responses. To analyze CD4 T cell reactions against IgG in various physical states, we developed an adoptive transfer model using CD4+ T cells specific for a Vκ region-derived peptide in the hapten-specific IgG mAb 36–71. We found that heat-aggregated or immune complexes (IC) of mAb 36–71 elicited anti-idiotypic (anti-Id) antibodies, while the deaggregated form was tolerogenic. All 3 forms of mAb 36–71 induced proliferation of cognate CD4+ T cells, but the aggregated and immune complex forms drove more division cycles and induced T follicular helper cells (T_FH) development more effectively than did the deaggregated form. These responses occurred despite no adjuvant and no or only trace levels of endotoxin in the preparations. Physical analyses revealed large differences in micron- and nanometer-sized particles between the aggregated and IC forms. These differences may be functionally relevant, as CD4+ T cell proliferation to aggregated, but not IC mAb 36–71, was nearly ablated upon peritoneal injection of B cell-depleting antibody. Our results imply that, in addition to denatured aggregates, immune complexes formed in vivo between therapeutic mAb and their intended targets can be immunogenic.

An observational study of alemtuzumab following fingolimod for multiple sclerosis

Objective:

To describe a series of patients with relapsing multiple sclerosis (MS) who experienced significant and unexpected disease activity within the first 12 months after switching from fingolimod to alemtuzumab.

Methods:

Patients with relapsing MS treated sequentially with fingolimod then alemtuzumab who experienced significant subsequent disease activity were identified by personal communication with 6 different European neuroscience centers.

Results:

Nine patients were identified. Median disease duration to alemtuzumab treatment was 94 (39–215) months and follow-up from time of first alemtuzumab cycle 20 (14–21) months. Following first alemtuzumab infusion cycle, 8 patients were identified by at least 1 clinical relapse and radiologic disease activity and 1 by significant radiologic disease activity alone.

Conclusions:

We acknowledge the potential for ascertainment bias; however, these cases may illustrate an important cause of reduced efficacy of alemtuzumab in a vulnerable group of patients with MS most in need of disease control. We suggest that significant and unexpected subsequent disease activity after alemtuzumab induction results from prolonged sequestration of autoreactive lymphocytes following fingolimod withdrawal, allowing these cells to be concealed from the usual biological effect of alemtuzumab. Subsequent lymphocyte egress then provokes disease reactivation. Further animal studies and clinical trials are required to confirm these phenomena and in the meantime careful consideration should be given to mode of action of individual therapies and sequential treatment effects in MS when designing personalized treatment regimens.

Depletion of CD52-positive cells inhibits the development of central nervous system autoimmune disease, but deletes an immune-tolerance promoting CD8 T-cell population. Implications for secondary autoimmunity of alemtuzumab in multiple sclerosis

The objective was to determine whether CD52 lymphocyte depletion can act to promote immunological tolerance induction by way of intravenous antigen administration such that it could be used to either improve efficiency of multiple sclerosis (MS) inhibition or inhibit secondary autoimmunities that may occur following alemtuzumab use in MS. Relapsing experimental autoimmune encephalomyelitis was induced in ABH mice and immune cell depletion was therapeutically applied using mouse CD52 or CD4 (in conjunction with CD8 or CD20) depleting monoclonal antibodies. Immunological unresponsiveness was then subsequently induced using intravenous central nervous system antigens and responses were assessed clinically. A dose–response of CD4 monoclonal antibody depletion indicated that the 60–70% functional CD4 T‐cell depletion achieved in perceived failed trials in MS was perhaps too low to even stop disease in animals. However, more marked (~75–90%) physical depletion of CD4 T cells by CD4 and CD52 depleting antibodies inhibited relapsing disease. Surprisingly, in contrast to CD4 depletion, CD52 depletion blocked robust immunological unresponsiveness through a mechanism involving CD8 T cells. Although efficacy was related to the level of CD4 T‐cell depletion, the observations that CD52 depletion of CD19 B cells was less marked in lymphoid organs than in the blood provides a rationale for the rapid B‐cell hyper‐repopulation that occurs following alemtuzumab administration in MS. That B cells repopulate in the relative absence of T‐cell regulatory mechanisms that promote immune tolerance may account for the secondary B‐cell autoimmunities, which occur following alemtuzumab treatment of MS.

Autoimmune Thyroid Diseases in Patients Treated with Alemtuzumab for Multiple Sclerosis: An Example of Selective Anti-TSH-Receptor Immune Response

Alemtuzumab, a humanized anti-CD52 monoclonal antibody, is approved for the treatment of active relapsing-remitting multiple sclerosis (MS). Alemtuzumab induces a rapid and prolonged depletion of lymphocytes from the circulation, which results in a profound immuno-suppression status followed by an immune reconstitution phase. Secondary to reconstitution autoimmune diseases represent the most common side effect of Alemtuzumab treatment. Among them, Graves' disease (GD) is the most frequent one with an estimated prevalence ranging from 16.7 to 41.0% of MS patients receiving Alemtuzumab. Thyrotropin (TSH) receptor (R)-reactive B cells are typically observed in GD and eventually present this autoantigen to T-cells, which, in turn, secrete several pro-inflammatory cytokines and chemokines. Given that reconstitution autoimmunity is more frequently characterized by autoantibody-mediated diseases rather than by destructive Th1-mediated disorders, it is not surprising that GD is the most commonly reported side effect of Alemtuzumab treatment in patients with MS. On the other hand, immune reconstitution GD was not observed in a large series of patients with rheumatoid arthritis treated with Alemtuzumab. This negative finding supports the view that patients with MS are intrinsically more at risk for developing Alemtuzumab-related thyroid dysfunctions and in particular of GD. From a clinical point of view, Alemtuzumab-induced GD is characterized by a surprisingly high rate of remission, both spontaneous and after antithyroid drugs, as well as by a spontaneous shift to hypothyroidism, which is supposed to result from a change from stimulating to blocking TSH-receptor antibodies. These immune and clinical peculiarities support the concept that antithyroid drugs should be the first-line treatment in Alemtuzumab-induced Graves' hyperthyroidism.

How the immune system responds to therapeutic biological agents

Biological agents target disease mechanisms and have modified the natural history of several immune-mediated disorders. Biological agents are structurally immunogenic, and therefore usually elicit a minor, subclinical and transient phenomenon. Occasionally, however, these drugs induce complete cellular and humoral immune responses, with the main clinical consequences being hypersensitivity reactions or loss of treatment response. This article considers the relative pathogenic mechanisms influencing immunogenicity in biological agents and discusses mechanisms of tolerance and adaptive immune response, including adaptive T-regulatory cell induction and immune response induction. Methods of determining cellular and humoral immune response to biological agents are identified and examined. Assays to detect antidrug antibodies and their isotypes can assist in monitoring immunogenicity and in preventing adverse events. Such strategies also enable resource conservation and may provide regulatory authorities with new insights that can be useful during the process of approving new biological or biosimilar agents.

Antidrug Antibody Formation in Oncology: Clinical Relevance and Challenges

: In oncology, an increasing number of targeted anticancer agents and immunotherapies are of biological origin. These biological drugs may trigger immune responses that lead to the formation of antidrug antibodies (ADAs). ADAs are directed against immunogenic parts of the drug and may affect efficacy and safety. In other medical fields, such as rheumatology and hematology, the relevance of ADA formation is well established. However, the relevance of ADAs in oncology is just starting to be recognized, and literature on this topic is scarce. In an attempt to fill this gap in the literature, we provide an up-to-date status of ADA formation in oncology. In this focused review, data on ADAs was extracted from 81 clinical trials with biological anticancer agents. We found that most biological anticancer drugs in these trials are immunogenic and induce ADAs (63%). However, it is difficult to establish the clinical relevance of these ADAs. In order to determine this relevance, the possible effects of ADAs on pharmacokinetics, efficacy, and safety parameters need to be investigated. Our data show that this was done in fewer than 50% of the trials. In addition, we describe the incidence and consequences of ADAs for registered agents. We highlight the challenges in ADA detection and argue for the importance of validating, standardizing, and describing well the used assays. Finally, we discuss prevention strategies such as immunosuppression and regimen adaptations. We encourage the launch of clinical trials that explore these strategies in oncology.

IMPLICATIONS FOR PRACTICE

Because of the increasing use of biologicals in oncology, many patients are at risk of developing antidrug antibodies (ADAs) during therapy. Although clinical consequences are uncertain, ADAs may affect pharmacokinetics, patient safety, and treatment efficacy. ADA detection and reporting is currently highly inconsistent, which makes it difficult to evaluate the clinical consequences. Standardized reporting of ADA investigations in the context of the aforementioned parameters is critical to understanding the relevance of ADA formation for each drug. Furthermore, the development of trials that specifically aim to investigate clinical prevention strategies in oncology is needed.

Posttranslational Modifications and the Immunogenicity of Biotherapeutics

Whilst the amino acid sequence of a protein is determined by its gene sequence, the final structure and function are determined by posttranslational modifications (PTMs), including quality control (QC) in the endoplasmic reticulum (ER) and during passage through the Golgi apparatus. These processes are species and cell specific and challenge the biopharmaceutical industry when developing a production platform for the generation of recombinant biologic therapeutics. Proteins and glycoproteins are also subject to chemical modifications (CMs) both in vivo and in vitro. The individual is naturally tolerant to molecular forms of self-molecules but nonself variants can provoke an immune response with the generation of anti-drug antibodies (ADA); aggregated forms can exhibit enhanced immunogenicity and QC procedures are developed to avoid or remove them. Monoclonal antibody therapeutics (mAbs) are a special case because their purpose is to bind the target, with the formation of immune complexes (ICs), a particular form of aggregate. Such ICs may be removed by phagocytic cells that have antigen presenting capacity. These considerations may frustrate the possibility of ameliorating the immunogenicity of mAbs by rigorous exclusion of aggregates from drug product. Alternate strategies for inducing immunosuppression or tolerance are discussed.

Cross-reactive and pre-existing antibodies to therapeutic antibodies--Effects on treatment and immunogenicity

The potential for immunogenicity is an ever-present concern during the development of biopharmaceuticals. Therapeutic antibodies occasionally elicit an antibody response in patients, which can result in loss of response or adverse effects. However, antibodies that bind a drug are sometimes found in pre-treatment serum samples, with the amount depending on drug, assay, and patient population. This review summarizes published data on pre-existing antibodies to therapeutic antibodies, including rheumatoid factors, anti-allotype antibodies, anti-hinge antibodies, and anti-glycan antibodies. Unlike anti-idiotype antibodies elicited by the drug, pre-formed antibodies in general appear to have little consequences during treatment. In the few cases where (potential) clinical consequences were encountered, antibodies were characterized and found to bind a distinct, unusual epitope of the therapeutic. Immunogenicity testing strategies should therefore always include a proper level of antibody characterization, especially when pre-formed antibodies are present. This minimizes false-positives, particularly due to rheumatoid factors, and helps to judge the potential threat in case a genuine pre-dose antibody reactivity is identified.

Differential expression of sema3A and sema7A in a murine model of multiple sclerosis: Implications for a therapeutic design

We characterised the expression of semaphorin (sema)3A, sema7A and their receptors in the immune and the central nervous system (CNS) at different stages of experimental autoimmune encephalomyelitis (EAE). We also studied their expression in neonatal and adult oligodendrocyte progenitor cell (OPC) and in mature oligodendrocyte cultures. Our results show that sema3A is increased in the CNS and decreased in the immune system upon EAE induction. However, sema7A expression is increased in both the CNS and the immune system during EAE. We also detected sema3A, sema7A and their receptors in neonatal and adult OPCs and in mature oligodendrocytes. These data suggest that sema3A and sema7A are involved in the pathogenesis of EAE, in the modulation of the immune response and in the neurodegeneration that take place in the CNS. Sema7A may represent an intriguing potential therapeutic target for the treatment of both the neurodegenerative and immune-mediated disease processes in MS.

Characterisation of a Novel Anti-CD52 Antibody with Improved Efficacy and Reduced Immunogenicity

Anti-CD52 therapy has been shown to be effective in the treatment of a number of B cell malignancies, hematopoietic disorders and autoimmune diseases (including rheumatoid arthritis and multiple sclerosis); however the current standard of treatment, the humanized monoclonal antibody alemtuzumab, is associated with the development of anti-drug antibodies in a high proportion of patients. In order to address this problem, we have identified a novel murine anti-CD52 antibody which has been humanized using a process that avoids the inclusion within the variable domains of non-human germline MHC class II binding peptides and known CD4+ T cell epitopes, thus reducing its potential for immunogenicity in the clinic. The resultant humanized antibody, ANT1034, was shown to have superior binding to CD52 expressing cells than alemtuzumab and was more effective at directing both antibody dependent and complement dependent cell cytotoxicity. Furthermore, when in the presence of a cross-linking antibody, ANT1034 was more effective at directly inducing apoptosis than alemtuzumab. ANT1034 also showed superior activity in a SCID mouse/human CD52 tumour xenograft model where a single 1 mg/Kg dose of ANT1034 led to increased mouse survival compared to a 10 mg/Kg dose of alemtuzumab. Finally, ANT1034 was compared to alemtuzumab in in vitro T cell assays in order to evaluate its potential to stimulate proliferation of T cells in peripheral blood mononuclear cells derived from a panel of human donors: whereas alemtuzumab stimulated proliferation in a high proportion of the donor cohort, ANT1034 did not stimulate proliferation in any of the donors. Therefore we have developed a candidate therapeutic humanized antibody, ANT1034, that may have the potential to be more efficacious and less immunogenic than the current standard anti-CD52 therapy.

Alemtuzumab in Multiple Sclerosis: Mechanism of Action and Beyond

Alemtuzumab is a humanized monoclonal antibody against CD52 (cluster of differentiation 52) and is approved for the therapy of relapsing-remitting multiple sclerosis. The application of alemtuzumab leads to a rapid, but long-lasting depletion predominantly of CD52-bearing B and T cells with reprogramming effects on immune cell composition resulting in the restoration of tolerogenic networks. Alemtuzumab has proven high efficacy in clinical phase II and III trials, where interferon β-1a was used as active comparator. However, alemtuzumab is associated with frequent and considerable risks. Most importantly secondary autoimmune disease affects 30%-40% of patients, predominantly impairing thyroid function. Extensive monitoring and early intervention allow for an appropriate risk management. However, new and reliable biomarkers for individual risk stratification and treatment response to improve patient selection and therapy guidance are a significant unmet need. Only a deeper understanding of the underlying mechanisms of action (MOA) will reveal such markers, maximizing the best potential risk-benefit ratio for the individual patient. This review provides and analyses the current knowledge on the MOA of alemtuzumab. Most recent data on efficacy and safety of alemtuzumab are presented and future research opportunities are discussed.

Alemtuzumab treatment of multiple sclerosis: long-term safety and efficacy

OBJECTIVES

Alemtuzumab is a newly licensed treatment of active relapsing-remitting multiple sclerosis (RRMS) in Europe, which in phase II and III studies demonstrated superior efficacy over β-interferon in reducing disability progression over 2-3 years. In this observational cohort study, we sought to describe our longer-term experience of the efficacy and safety of alemtuzumab in active RRMS.

METHODS

Clinical and laboratory data including serial Expanded Disability Status Scale (EDSS) assessments, from all 87 patients treated with alemtuzumab on investigator-led studies in Cambridge, UK, from 1999 to 2012, were collected. The occurrence of adverse events including secondary autoimmunity, malignancy and death, and pregnancy outcomes was recorded. Baseline variables including age, disease duration and relapse rate were compared in univariate and logistic regression analyses between groups with different disability outcomes.

RESULTS

Over a median 7-year follow-up (range 33-144 months), most patients (52%) required just two cycles of alemtuzumab. In the remaining patients, relapses triggered re-treatment to a total of three cycles (36%), four cycles (8%) or five cycles (1%). Using a 6-month sustained accumulation of disability definition, 59/87 (67.8%) of patients had an improved or unchanged disability compared with baseline. By an area under the curve analysis, 52/87 (59.8%) patients had an overall improvement or stabilisation of disability. Higher baseline relapse rate was associated with worse long-term disability outcomes, with trends for longer disease duration and older age at first treatment. Secondary autoimmunity was the most frequent adverse event occurring in 41/86 (47.7%) patients, most commonly involving the thyroid gland.

CONCLUSIONS

Alemtuzumab is associated with disease stabilisation in the majority of patients with highly active RRMS over an average seven-year follow-up. No new safety concerns arose over this extended follow-up.

Comparative efficacy of alemtuzumab and established treatment in the management of multiple sclerosis

Alemtuzumab is the newest disease-modifying therapy approved for the treatment of relapsing multiple sclerosis. Alemtuzumab is an anti-CD52 targeted antibody that causes lysis of T and B lymphocytes, monocytes, natural killer cells, macrophages, and dendritic cells. Following its administration, a prolonged T-cell lymphopenia results with emergence of a reconstituted immune system that differs in its composition from that pretreatment. In clinical trials, alemtuzumab has shown impressive efficacy with regard to clinical and radiological outcomes in relapsing multiple sclerosis, along with sustained long-term beneficial effects, and it is attractive for its once-yearly administration. Despite this, the occurrence of serious secondary autoimmune disorders, infections, and a potential risk of malignancy necessitates a careful evaluation of risks versus benefits for an individual patient prior to its use. The requirement of patient commitment to the intense mandatory monitoring program is also a factor to be considered when incorporating alemtuzumab into the treatment regimen.

Drug safety evaluation of alemtuzumab for multiple sclerosis

INTRODUCTION

Alemtuzumab is a humanised anti-CD52 mAb which has recently been licensed for the treatment of relapsing multiple sclerosis in Europe.

AREAS COVERED

The efficacy and safety of alemtuzumab from open label, Phase II and Phase III trials is reported.

EXPERT OPINION

Alemtuzumab causes rapid and profound complement mediated lysis of circulating lymphocytes and allows beneficial modulation of the immune system during a subsequent reconstitution phase. Clinical trials have demonstrated superior efficacy against an active comparator, with reduction in annualised relapse rates and sustained accumulation of disability at 3 years and sustained efficacy at 5 years. The main adverse effects are mild to moderate infusion reactions, an increased incidence of mild to moderate infections and autoimmune adverse events. Thyroid disorders are the most common form of autoimmune adverse events, occurring in approximately one third of patients. Overt Graves' hyperthyroidism represents approximately half of these cases. Careful patient selection and structured monitoring programs allow for effective patient management resulting in a favourable risk benefit profile.

Monoclonal antibodies as disease modifying therapy in multiple sclerosis

Multiple sclerosis (MS), a demyelinating disease of the central nervous system, was untreatable until the mid-1990s when beta-interferons and glatiramer acetate were introduced. These agents, while effective, were relatively nonspecific in action. Over the last 10 years, research has focused toward developing more targeted therapies for the disease. Monoclonal antibodies (mAbs) have been central to these efforts and many of the mAbs studied in MS have been singularly effective. We review here the 6 monoclonal antibodies that have been approved for MS or are in late-stage clinical trials, focusing on the drugs' efficacy and safety. Additionally, we review several monoclonal antibodies that were studied in MS but were found to be ineffective or even deleterious in this patient population.

Human monoclonal antibodies: the residual challenge of antibody immunogenicity

One of the major reasons for seeking human monoclonal antibodies has been to eliminate immunogenicity seen with rodent antibodies. Thus far, there has yet been no approach which absolutely abolishes that risk for cell-binding antibodies. In this short article, I draw attention to classical work which shows that monomeric immunoglobulins are intrinsically tolerogenic if they can be prevented from creating aggregates or immune complexes. Based on these classical studies two approaches for active tolerization to therapeutic antibodies are described.

The outlook for alemtuzumab in multiple sclerosis

Alemtuzumab is a humanized anti-CD52 monoclonal antibody. Treatment in humans results in a rapid, profound, and prolonged B- and T-cell lymphopenia. Subsequently, lymphocyte reconstitution by homeostatic mechanisms alters the composition, phenotype, and function of T-cell subsets, thus allowing the immune system to be 'reset'. One phase II and two phase III randomized, multicenter, single-blinded (outcomes assessor) clinical trials of alemtuzumab in relapsing-remitting multiple sclerosis have now been completed. Against an active comparator and the current first-line therapy for relapsing-remitting multiple sclerosis (interferon-beta), alemtuzumab showed a significant reduction in annualized relapse rate as well as a significant reduction in the accumulation of disability. These outcomes are sustained over at least 5 years following treatment. The most common adverse effects are mild infusion reactions, an increased incidence of mild-to-moderate severity infections and secondary autoimmunity. The latter is observed in a third of treated patients, commonly thyroid disease but other target cells have been described including cytopenias. Marketing authorization applications have been submitted for the use of alemtuzumab in multiple sclerosis to the Food and Drug Administration and the European Medicines Agency, with licensing expected in 2013. Here, we discuss the outlook for alemtuzumab in multiple sclerosis in light of the currently available therapies, outcomes of and lessons learnt from clinical trials, and the overall position of monoclonal antibodies in modern treatment strategies.

Beyond humanization and de-immunization: tolerization as a method for reducing the immunogenicity of biologics

Immune responses to some monoclonal antibodies (mAbs) and biologic proteins interfere with their efficacy due to the development of anti-drug antibodies (ADA). In the case of mAbs, most ADA target 'foreign' sequences present in the complementarity determining regions (CDRs). Humanization of the mAb sequence is one approach that has been used to render biologics less foreign to the human immune system. However, fully human mAbs can also drive immunogenicity. De-immunization (removing epitopes) has been used to reduce biologic protein immunogenicity. Here, we discuss a third approach to reducing the immunogenicity of biologics: introduction of Treg epitopes that stimulate Treg function and induce tolerance to the biologic protein. Supplementing humanization (replacing xeno-sequences with human) and de-immunization (reducing T effector epitopes) with tolerization (introducing Treg epitopes) where feasible, as a means of improving biologics 'quality by design', may lead to the development of ever more clinically effective, but less immunogenic, biologics.

Challenges and approaches for the development of safer immunomodulatory biologics

Immunomodulatory biologics are a class of biotechnology-derived therapeutic products that are designed to engage immune-relevant targets and are indicated in the treatment and management of a range of diseases, including immune-mediated inflammatory diseases and malignancies.

Despite their high specificity and therapeutic advantages, immmunomodulatory biologics have been associated with adverse reactions such as serious infections, malignancies and cytokine release syndrome, which arise owing to the on-target or exaggerated pharmacological effects of these drugs. Immunogenicity resulting in the generation of antidrug antibodies is another unwanted effect that leads to loss of efficacy and — rarely — hypersensitivity reactions.

For some adverse reactions, mitigating and preventive strategies are in place, such as stratifying patients on the basis of responsiveness to therapy and the risk of developing adverse reactions. These strategies depend on the availability of robust biomarkers for therapeutic efficacy and the risk of adverse reactions: for example, seropositivity for John Cunningham virus is a risk factor for progressive multifocal leukoencephalopathy. The development of effective biomarkers will greatly aid these strategies.

The development and design of safer immunomodulatory biologics is reliant on a detailed understanding of the nature of the disease, target biology, the interaction of the target with the immunomodulatory biologic and the inherent properties of the biologic that elicit unwanted effects.

The availability of in vitro and in vivo models that can be used to predict adverse reactions associated with immunomodulatory biologics is central to the development of safer immunomodulatory biologics. Some progress has been made in developing in vitro and in silico tests for predicting cytokine release syndrome and immunogenicity, but there is still a lack of models for effectively predicting infections and malignancies.

Two pathways can be followed in designing and developing safer immunomodulatory biologics. The first pathway involves generating a biologic that engages an alternative target or mechanism to produce the desired pharmacodynamic effect without the associated adverse reaction, and is followed when the adverse reaction cannot be dissociated from the target biology. The second pathway involves redesigning the biologic to 'engineer out' components within the biologic structure that trigger adverse effects or to alter the nature of the target–biologic interactions.

Owing to their specificity, immunomodulatory biologics generally have better safety profiles than small-molecule drugs. However, adverse effects such as an increased risk of infections or cytokine release syndrome are of concern. Here, Park and colleagues discuss the current strategies used to predict and mitigate these adverse effects and consider how they can be used to inform the development of safer immunomodulatory biologics.

Immunomodulatory biologics, which render their therapeutic effects by modulating or harnessing immune responses, have proven their therapeutic utility in several complex conditions including cancer and autoimmune diseases. However, unwanted adverse reactions — including serious infections, malignancy, cytokine release syndrome, anaphylaxis and hypersensitivity as well as immunogenicity — pose a challenge to the development of new (and safer) immunomodulatory biologics. In this article, we assess the safety issues associated with immunomodulatory biologics and discuss the current approaches for predicting and mitigating adverse reactions associated with their use. We also outline how these approaches can inform the development of safer immunomodulatory biologics.

Immunogenicity of anti-TNF biologic therapies for rheumatoid arthritis

Currently, five anti-TNF biologic agents are approved for the treatment of rheumatoid arthritis (RA): adalimumab, infliximab, etanercept, golimumab and certolizumab pegol. Formation of anti-drug antibodies (ADA) has been associated with all five agents. In the case of adalimumab and infliximab, immunogenicity is strongly linked to subtherapeutic serum drug levels and a lack of clinical response, but for the other three agents, data on immunogenicity are scarce, suggesting that further research would be valuable. Low ADA levels might not influence the efficacy of anti-TNF therapy, whereas high ADA levels impair treatment efficacy by considerably reducing unbound drug levels. Immunogenicity is not only an issue in patients treated with anti-TNF biologic agents; the immunogenicity of other therapeutic proteins, such as factor VIII and interferons, is well known and has been investigated for many years. The results of such studies suggest that investigations to determine the optimal treatment regimen (drug dosing, treatment schedule and co-medication) required to minimize the likelihood of ADA formation might be an effective and practical way to deal with the immunogenicity of anti-TNF biologic agents for RA.

Alemtuzumab therapy for multiple sclerosis

Alemtuzumab is a humanized monoclonal antibody that is administered daily for 5 days, and then no further therapy is required for 12 months. It causes rapid and prolonged lymphocyte depletion; the consequent homeostatic reconstitution leads to a radically reformed lymphocyte pool with a relative increase in regulatory T cells and expansion of autoreactive T cells. Although previously licensed for the treatment of B-cell chronic lymphocytic leukemia, it is now been considered for licensing in the treatment of multiple sclerosis (MS). From a disappointing experience with alemtuzumab in progressive MS, Alastair Compston and I argued that immunotherapies should be given early in the course of the disease. In a unique program of drug development in MS, alemtuzumab has been compared in 1 phase 2 trial and 2 phase 3 trials with the active comparator interferon beta-1a. In all trials, alemtuzumab was more effective in suppressing relapses than interferon beta-1a. In one phase 2 and one phase 3 trial, alemtuzumab also reduced the risk of accumulating disability compared with interferon beta-1a. Indeed, alemtuzumab treatment led to an improvement in disability and a reduction in cerebral atrophy. The safety issues are infusion-associated reactions largely controlled by methylprednisolone, antihistamines, and antipyretics; mild-to-moderate infections (with 3 opportunistic infections from the open-label experience: 1 case each of spirochaetal gingivitis, pyogenic granuloma, and Listeria meningitis); and autoimmunity. Usually autoimmunity is directed against the thyroid gland, but causes (1 %) immune thrombocytopenia, and in a few cases antiglomerular basement membrane syndrome. Alemtuzumab is an effective therapy for early relapsing-remitting MS, offering disability improvement at least to 5 years after treatment. Its use requires careful monitoring so that potentially serious side effects can be treated early and effectively.

Development of resistance to biologic therapies with reference to IFN-β

All biotherapeutics have the potential to generate anti-drug antibodies (ADAs) in patients. The main factors leading to an immune response are thought to be product, treatment and patient related. In this review, reasons for the formation of ADAs, and particularly neutralizing antibodies (NAbs), are considered, with a focus on IFN-β as a well-studied example. The time course for the production of NAbs, the measurement of NAbs, the defining of IFN-β responders and non-responders, the implications for disease progression in patients, and future methods for avoiding the production of ADAs and of tolerizing patients are considered.

Aggregation, immune complexes and immunogenicity

The development of an immune response to a protein therapeutic may nullify its beneficial activity or result in adverse events. Immunogenicity is, therefore, a major concern for clinicians, regulatory authorities and the biopharmaceutical industry. These concerns are particularly acute for the treatment of chronic diseases, as opposed to cancer, that may require repeated exposure to therapeutic over extended cycles of remission/relapse. There are many parameters that may be contributory to immunogenicity; however, the "bête noire," for the past decade has been aggregation. ( 1-3).

Have we overestimated the benefit of human(ized) antibodies?

The infusion of animal-derived antibodies has been known for some time to trigger the generation of antibodies directed at the foreign protein as well as adverse events including cytokine release syndrome. These immunological phenomena drove the development of humanized and fully human monoclonal antibodies. The ability to generate human(ized) antibodies has been both a blessing and a curse. While incremental gains in the clinical efficacy and safety for some agents have been realized, a positive effect has not been observed for all human(ized) antibodies. Many human(ized) antibodies trigger the development of anti-drug antibody responses and infusion reactions. The current belief that antibodies need to be human(ized) to have enhanced therapeutic utility may slow the development of novel animal-derived monoclonal antibody therapeutics for use in clinical indications. In the case of murine antibodies, greater than 20% induce tolerable/negligible immunogenicity, suggesting that in these cases humanization may not offer significant gains in therapeutic utility. Furthermore, humanization of some murine antibodies may reduce their clinical effectiveness. The available data suggest that the utility of human(ized) antibodies needs to be evaluated on a case-by-case basis, taking a cost-benefit approach, taking both biochemical characteristics and the targeted therapeutic indication into account.