Venous and arterial thromboembolic events in adalimumab-treated patients with antiadalimumab antibodies: a case series and cohort study

Overview of venous thrombosis in inflammatory bowel disease

Thrombosis in inflammatory bowel disease (IBD) is an increasingly noted extraintestinal manifestation with high morbidity and mortality. While controlling the activity of the disease with the appropriate therapy, thromboembolism prophylaxis should be applied to all patients. All common risk factors for thromboembolism are also valid for patients with IBD; however, it is clear that uncontrolled disease and hospitalization are major disease-specific risk factors for venous thromboembolism in patients with IBD. Pharmacological thromboprophylaxis with currently available anticoagulants does not increase the risk of further bleeding in patients with IBD with mild-to-moderate bleeding. In severe bleeding or with increased risk of further bleeding due to other comorbid conditions, thromboprophylaxy with mechanical methods should be the treatment option. Whether thrombosis is the cause or the result of intestinal inflammation remains to be elucidated, and other issues in the etiology, such as the role of intestinal flora in thrombosis pathogenesis, will be the subject of future studies.

Risk of venous thromboembolism in patients with rheumatoid arthritis: initiating disease-modifying antirheumatic drugs

OBJECTIVES

Recent research suggests that rheumatoid arthritis increases the risk of venous thromboembolism. This study compared the risk of venous thromboembolism in patients with newly diagnosed rheumatoid arthritis initiating a biologic disease-modifying antirheumatic drug (DMARD) with those initiating methotrexate or a nonbiologic DMARD.

METHODS

We conducted a population-based cohort study using US insurance claims data (2001-2012). Three mutually exclusive, hierarchical DMARD groups were used: (1) a biologic DMARD with and without nonbiologic DMARDs; (2) methotrexate without a biologic DMARD; or (3) nonbiologic DMARDs without a biologic DMARD or methotrexate. We calculated the incidence rates of venous thromboembolism. Cox proportional hazard models stratified by propensity score (PS) deciles after asymmetric PS trimming were used for 3 pairwise comparisons, controlling for potential confounders at baseline.

RESULTS

We identified 29,481 patients with rheumatoid arthritis with 39,647 treatment episodes. From the pairwise comparison after asymmetric PS trimming, the incidence rate of hospitalization for venous thromboembolism per 1000 person-years was 5.5 in biologic DMARD initiators versus 4.4 in nonbiologic DMARD initiators and 4.8 in biologic DMARD initiators versus 3.5 in methotrexate initiators. The PS decile-stratified hazard ratio of venous thromboembolism associated with biologic DMARDs was 1.83 (95% confidence interval [CI], 0.91-3.66) versus nonbiologic DMARDs and 1.39 (95% CI, 0.73-2.63) versus methotrexate. The hazard ratio of venous thromboembolism in biologic DMARD initiators was the highest in the first 180 days versus nonbiologic DMARD initiators (2.48; 95% CI, 1.14-5.39) or methotrexate initiators (1.80; 95% CI, 0.90-3.62).

CONCLUSIONS

The absolute risk for venous thromboembolism was low in patients with newly diagnosed rheumatoid arthritis. Initiation of a biologic DMARD seems to be associated with an increased short-term risk of hospitalization for venous thromboembolism compared with initiation of a nonbiologic DMARD or methotrexate.

Immunogenicity of Anti-TNF-α Biotherapies: I. Individualized Medicine Based on Immunopharmacological Evidence

Specific inhibition of the cytokine, tumor necrosis factor-α (TNF), has revolutionized the treatment of patients with several autoimmune diseases, and genetically engineered anti-TNF antibody constructs now constitute a heavy medicinal expenditure in many countries. Unfortunately, up to 30% of patients do not respond and about 50% of those who do loose response with time. Furthermore, safety may be compromised by immunogenicity with the induction of anti-drug-antibodies (ADA). Assessment of drug pharmacokinetics and ADA is increasingly recognized as a requirement for safe and rational use of protein drugs. The use of therapeutic strategies based on anti-TNF drug levels and ADA rather than dose-escalation has also proven to be cost-effective, as this allows individualized patient-tailored strategies rather than the current universal approach to loss of response. The objective of the present article – and the accompanying article – is to discuss the reasons for recommending assessments of circulating drug and ADA levels in patients treated with anti-TNF biopharmaceuticals and to detail some of the methodological issues that obscure cost-effective and safer therapies.

Short-term effect of infliximab is reflected in the clot lysis profile of patients with inflammatory bowel disease: a prospective study

BACKGROUND

Inflammatory bowel disease (IBD) is recognized as an independent risk factor for thrombosis. First, we investigate whether the concentration of fibrinolysis inhibitors is increased in patients with IBD. Second, we investigate the effect of infliximab induction therapy on the hemostatic profile.

METHODS

This prospective study included 103 patients with IBD starting infliximab therapy and 113 healthy controls. Plasma was collected before the first infliximab infusion (wk 0) and after induction therapy (wk 14). Patients not showing a clinical response on induction were considered as primary nonresponders. Fibrinolysis inhibitors were measured by enzyme-linked immunosorbent assay. Using a clot lysis assay, the area under the curve (global marker for coagulation/fibrinolysis), 50% clot lysis time (marker for fibrinolytic capacity), and amplitude (indicator for clot formation) were determined.

RESULTS

Patients with IBD selected for infliximab treatment have higher area under the curve (median 29 [interquartile range, 20-38]) and amplitude (0.4 [0.3-0.5]) compared with healthy controls (18 [13-24] and 0.3 [0.2-0.3], respectively, P < 0.001). Primary nonresponders showed a decrease neither in inflammatory markers nor in hemostatic parameters, whereas in primary responders, a decrease in inflammatory markers was associated with a decrease in both area under the curve (29 [20-38] (wk 0) to 20 [14-28] (wk 14), P < 0.001) and amplitude (0.4 [0.3-0.5] (wk 0) to 0.3 [0.3-0.4] (wk 14), P < 0.001).

CONCLUSIONS

This is the first prospective study demonstrating that the clot lysis profile differs between patients with IBD and healthy individuals. On infliximab induction treatment, this clot lysis profile normalizes in responders suggesting that infliximab treatment is advisable for patients with IBD with an activated hemostatic profile.

Biosimilars in psoriasis: what can we expect?

Biosimilars are biotechnologically processed drugs whose amino acid sequence is identical to the original biopharmaceutical. They are of considerable clinical, economical, and health care interest. As patents for biologicals used to treat psoriasis expire, biosimilars will become more and more important within the field of dermatology. The patents for the two top-selling drugs (adalimumab and etanercept) will terminate in the next few years. Applications for biosimilars will presumably be submitted to the EMA and the FDA for all patent-free biologicals. Both regulatory bodies have issued guidelines on the assessment of bioequivalence, as well as the benefits and risks of biosimilars. While the preclinical requirements of the FDA and EMA are largely comparable, the formal requirements for clinical bioequivalence, including clinical efficacy and safety, differ markedly. Therefore, from a medical and health care perspective before biosimilars enter the market, specific evidence-based regulatory conditions need to be created and fulfilled. Only then biosimilars can be a less expensive option for a large number of patients, providing them with substances of the same value. Adequate, unequivocal proof of their bioequivalence, quality, and related patient safety should have priority over any ostensible economic benefits.

Monitoring drug and antidrug levels: a rational approach in rheumatoid arthritis patients treated with biologic agents who experience inadequate response while being on a stable biologic treatment

Clinical response in patients with rheumatoid arthritis (RA) treated with biologic agents can be influenced by their pharmacokinetics and immunogenicity. The present study evaluated the concordance between serum drug and antidrug levels as well as the clinical response in RA patients treated with biological agents who experience their first disease exacerbation while being on a stable biologic treatment. 154 RA patients treated with rituximab (RTX), infliximab (IFX), adalimumab (ADL), or etanercept (ETN) were included. DAS28, SDAI, and EULAR response were assessed at baseline and reevaluated at precise time intervals. At the time of their first sign of inadequate response, patients were tested for both serum drug level and antidrug antibodies level. At the next reevaluation, patients retreated with RTX that had detectable drug level had a better EULAR response (P = 0.038) with lower DAS28 and SDAI scores (P = 0.01 and P = 0.03). The same tendency was observed in patients treated with IFX and ETN regarding EULAR response (P = 0.002 and P = 0.023), DAS28 score (P = 0.002 and P = 0.003), and SDAI score (P = 0.001 and P = 0.026). Detectable biologic drug levels correlated with a better clinical response in patients experiencing their first RA inadequate response while being on a stable biologic treatment with RTX, IFX, and ETN.

Possible association of etanercept, venous thrombosis, and induction of antiphospholipid syndrome

Tumor necrosis factor α (TNF α) inhibitors are commonly used for treatment of aggressive rheumatoid arthritis and other rheumatic diseases. Etanercept is one of the medications approved for treatment of rheumatoid arthritis. Though many studies have documented the safety and efficacy of these medications, evidence for adverse effects is emerging including cancer, infections, and cardiovascular disease. There have been studies showing that these medications induce autoantibody production, including antinuclear antibodies and anti-dsDNA antibodies. Limited data exists, however, regarding induction of antiphospholipid antibodies (APLs) by TNF α inhibitors, including anticardiolipin antibodies (ACLs), lupus anticoagulant (LAC), and anti-β₂-glycoprotein I (anti-β₂ GPI), or an association between antibody development and clinical manifestations. In this case series, we describe five patients who developed venous thromboembolism (VTE) and APLs while receiving etanercept therapy. All five of our patients met the criteria for diagnosis of APS after receiving etanercept. Our case series supports the association between etanercept, APLs, and VTE. We believe that testing for APLs prior to initiation of anti-TNF therapy is reasonable, given this relationship and the risks associated with VTE.

Assessment and reporting of the clinical immunogenicity of therapeutic proteins and peptides-harmonized terminology and tactical recommendations

Immunogenicity is a significant concern for biologic drugs as it can affect both safety and efficacy. To date, the descriptions of product immunogenicity have varied not only due to different degrees of understanding of product immunogenicity at the time of licensing but also due to an evolving lexicon that has generated some confusion in the field. In recent years, there has been growing consensus regarding the data needed to assess product immunogenicity. Harmonization of the strategy for the elucidation of product immunogenicity by drug developers, as well as the use of defined common terminology, can benefit medical practitioners, health regulatory agencies, and ultimately the patients. Clearly, understanding the incidence, kinetics and magnitude of anti-drug antibody (ADA), its neutralizing ability, cross-reactivity with endogenous molecules or other marketed biologic drugs, and related clinical impact may enhance clinical management of patients treated with biologic drugs. To that end, the authors present terms and definitions for describing and analyzing clinical immunogenicity data and suggest approaches to data presentation, emphasizing associations of ADA development with pharmacokinetics, efficacy, and safety that are necessary to assess the clinical relevance of immunogenicity.

Unexpected hematologic effects of biotherapeutics in nonclinical species and in humans

Biotherapeutics are expanding the arsenal of therapeutics available for treating and preventing disease. Although initially thought to have limited side effects due to the specificity of their binding, these drugs have now been shown to have potential for adverse drug reactions including effects on peripheral blood cell counts or function. Hematotoxicity caused by a biotherapeutic can be directly related to the activity of the biotherapeutic or can be indirect and due to autoimmunity, biological cascades, antidrug antibodies, or other immune system responses. Biotherapeutics can cause hematotoxicity primarily as a result of cellular activation, cytotoxicity, drug-dependent and independent immune responses, and sequelae from initiating cytokine and complement cascades.  The underlying pathogenesis of biotherapeutic-induced hematotoxicity often is poorly understood. Nonclinical studies have generally predicted clinical hematotoxicity for recombinant cytokines and growth factors.  However, most hematologic liabilities of biotherapeutics are not based on drug class but are species specific, immune-mediated, and of low incidence. Despite the potential for unexpected hematologic toxicity, the risk-benefit profile of most biotherapeutics is favorable; hematologic effects are readily monitorable and managed by dose modification, drug withdrawal, and/or therapeutic intervention.  This article reviews examples of biotherapeutics that have unexpected hematotoxicity in nonclinical or clinical studies. 

Risk of venous thromboembolism in patients with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is associated with cardiovascular disease (CVD), but little is known about its association with another form of vascular disorder, venous thromboembolism (VTE).

METHODS

A retrospective cohort study was conducted using US insurance claims. RA and non-RA patients were matched on age, sex, and index date. Incidence rates (IRs) and rate ratios (RRs) of VTE, defined as the composite of deep vein thrombosis (DVT) or pulmonary embolism (PE), were calculated. Cox proportional hazards models compared VTE risks between RA and non-RA patients, adjusting for VTE risk factors such as CVD, surgery, hospitalization, medications, and acute-phase reactants.

RESULTS

Over the mean followup of 2 years, the IR for VTE among RA patients was 6.1 per 1,000 person-years, 2.4 times higher (95% confidence interval [95% CI] 2.1-2.8) than the rate of non-RA patients. The IRs for both DVT (RR 2.2, 95% CI 1.9-2.6) and PE (RR 2.7, 95% CI 2.2-3.5) were higher in RA patients compared with non-RA patients. After adjusting for risk factors of VTE, the VTE risk remained elevated in RA patients (hazard ratio 1.4, 95% CI 1.1-1.7) compared to non-RA patients. The result was similar after further adjustment for elevated acute-phase reactants (hazard ratio 1.5, 95% CI 0.3-6.5). One-third of patients who developed VTE had at least 1 major VTE risk factor 90 days before and after the VTE event.

CONCLUSION

Our results showed an increased risk of developing VTE for RA patients compared with non-RA patients. The risk was attenuated but remained elevated even after adjusting for various risk factors for VTE.

Adverse effects of golimumab in the treatment of rheumatologic diseases

INTRODUCTION

A number of new biological immune modulators have become available as treatments for inflammatory diseases over the past two decades. Most prominent among them are TNF-α inhibitors (TNFi) which have been available in the clinic since the late 1990s. TNFi have demonstrated efficacy in various rheumatologic diseases as well as in inflammatory bowel disease and psoriasis. Golimumab is one of the most recently introduced TNFi.

AREAS COVERED

Although golimumab is generally well tolerated, as is the case with other TNFi and indeed with most of the marketed immunomodulatory drugs, potential adverse events may be associated with its use. Herein, we the potential adverse effects associated with golimumab therapy are reviewed. Adverse effects are divided into target-related and agent-related categories.

EXPERT OPINION

Golimumab has been demonstrated to be generally safe and well tolerated. Its safety profile seems to be very comparable to the other available TNFi. Long-term studies of golimumab and other TNFi will help establish the durability of response to golimumab as well as identify any potential delayed or cumulative adverse effects.

The role of DMARDs in reducing the immunogenicity of TNF inhibitors in chronic inflammatory diseases

The management of RA, SpA, psoriasis and inflammatory bowel disease has significantly improved over the last decade with the addition of tumour necrosis factor inhibitors (anti-TNFs) to the therapeutic armamentarium. Immunogenicity in response to monoclonal antibody therapies (anti-drug antibodies) may give rise to low serum drug levels, loss of therapeutic response, poor drug survival and/or adverse events such as infusion reactions. To combat these, the use of concomitant MTX may attenuate the frequency of anti-drug antibodies in RA, SpA and Crohn's disease. Although a similar effect to methotrexate has been observed with AZA usage in the management of Crohn's disease, there is insufficient evidence to suggest that other DMARDs impact immunogenicity. In this article we review the evidence to date on the effect of immunomodulatory therapy when co-administered with anti-TNFs. We also discuss whether such a strategy should be employed in SpA and psoriasis, and if optimization of the MTX dose could improve biologic drug survival and thereby benefit disease management.

Acute renal artery occlusion following infliximab infusion

We report the case of a 44-year-old male patient who presented with acute renal artery occlusion, 3 d after first injection of infliximab for steroid refractory attack of ulcerative colitis. Extensive work-up provided no evidence of predisposing factors for arterial thrombosis. Infliximab was thus suspected in the genesis of thrombosis, based on both intrinsic and extrinsic criteria. At month 3 after thrombosis with ongoing anticoagulation, angio-tomodensitometry showed complete revascularization of the left renal artery with renal atrophy. Renal function remained normal and the patient was still in steroid free remission on mercaptopurin monotherapy at maximal follow-up. Few thromboembolic events have been described with anti- tumor necrosis factor (TNF) agents, but it is the first case reported of renal artery thrombosis after infliximab infusion. In addition, we review thrombosis associated with anti-TNF agents.

Immunogenicity in biologic therapy: implications for dermatology

It is now known that all biologic drugs, even those that are fully human, are immunogenic, that is, they have the ability to induce an immune response in the treated patient. Since the presence of antidrug antibodies may influence the levels and function of the drug in the body, this immune response can alter the efficacy of the biologic treatment and even its safety profile, depending on the mechanism of action (neutralizing or nonneutralizing) and/or an accelerated clearance of the drug. Immunogenicity is a dynamic factor that should be taken into account when prescribing biologic therapy in psoriasis, especially in the case of long-term treatment and when assessing secondary loss of response. An understanding of the immunogenicity of biologic therapies and how this can be managed is useful not only for optimizing the treatment strategy used with each drug, but also for designing predictive models of response and even for tailoring therapy on a case-by-case basis.

Assessing immunogenicity of biosimilar therapeutic monoclonal antibodies: regulatory and bioanalytical considerations

This article reflects on methodological limitations for interpretation of relative immunogenicity of biosimilar and reference therapeutic monoclonal antibodies, in emphasizing the relevance of correlation of bioanalytical signals with appropriate clinical end points, and the possible need for post-marketing observational studies to indicate the impact of detected differences in anti-drug antibody incidence and magnitude on sustainability of treatment benefit. Given the current uncertainty regarding the longer term clinical impact of undesirable immunogenicity for reference products, there can be no predefined margin for an acceptable difference based on incidence and magnitude of detected anti-drug antibodies. Any detected differences should be assessed in relation to clinical parameters; and the designation of biosimilarity made with reference to the similarity demonstrated in the directly comparative quality, nonclinical and clinical evaluations. Application of this ‘totality of evidence’ approach is illustrated for infliximab and adalimumab.

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.

Long-term measurement of anti-adalimumab using pH-shift-anti-idiotype antigen binding test shows predictive value and transient antibody formation

BACKGROUND AND OBJECTIVES

Therapeutic monoclonal antibodies are effective drugs for many different diseases. However, the formation of anti-drug antibodies (ADA) against a biological can result in reduced clinical response in some patients. Measurement of ADA in the presence of (high) drug levels is difficult due to drug interference in most assays, including the commonly used antigen binding test (ABT).

METHODS

We recently published a novel method which enables the measurement of complexed antibodies against adalimumab (an anti-TNF antibody) in the presence of drug. Here we use this pH-shift-anti-idiotype ABT (PIA) to measure anti-adalimumab antibodies (AAA) in 99 rheumatoid arthritis (RA) patients treated for up to 3 years with adalimumab.

RESULTS

53 out of 99 RA patients produced AAA. In 50 of these PIA positive patients, AAA could be detected within the first 28 weeks of treatment. Patients in which AAA could be detected in the PIA after 28 weeks of treatment were more prone to declining adalimumab levels (<5 µg/ml) (p<0.01) and high AAA levels which could be detected in the ABT (p<0.05) at later time points. We observed transient AAA formation in 17/53 patients.

CONCLUSIONS

Results show that AAA develop early in treatment. However, levels that completely neutralise the drug may be reached much later in treatment. Furthermore, the patients positive for PIA at 28 weeks have an increased chance to develop clinical non-response due to immunogenicity. In some of the patients, AAA formation is transient.

The immunogenicity of anti-TNF therapy in immune-mediated inflammatory diseases: a systematic review of the literature with a meta-analysis

BACKGROUND

Immunogenicity of aTNFs is one of the mechanisms behind treatment failure.

OBJECTIVE

To assess the effect of anti-drug antibodies (ADA) on drug response to infliximab, adalimumab and etanercept, and the effect of immunosuppression on ADA detection, in patients with Rheumatoid Arthritis, Spondyloarthritis, Psoriasis and Inflammatory Bowel Diseases.

DATA SOURCES

PubMed, EMBASE, Cochrane databases, article reference lists (through August 19 2012).

STUDY SELECTION

Out of 2082 studies, 17 were used in the meta-analysis (1RCT; 16 observational studies).

DATA EXTRACTION

Two reviewers extracted data. Risk ratios (RR), 95% CI, using random-effect models, sensitivity analysis, meta-regressions and Egger's test were calculated.

DATA SYNTHESIS

Of 865 patients, ADA against infliximab or adalimumab reduced drug response rate by 68% (RR=0.68, 95% CI=0.12 to 0.36), an effect attenuated by concomitant methotrexate (MTX): <74% MTX+: RR=0.23, 95% CI=0.15 to 0.36; ≥74% MTX+: RR=0.32, 95% CI=0.22 to 0.48. Anti-etanercept antibodies were not detected. Of 936 patients, concomitant MTX or azathioprine/mercaptopurine reduced ADA frequency by 47% (RR=0.53, 95% CI=0.42 to 0.67), particularly when ADA were assessed by RIA (RR=0.36, 95% CI=0.23 to 0.55) compared with ELISA (RR=0.63, 95% CI=0.53 to 0.74).

CONCLUSIONS

ADA reduces drug response, an effect that can be attenuated by concomitant immunosuppression, which reduces ADA frequency. Drug immunogenicity should be considered for the management of patients receiving biological therapies.

Anti-TNF-α biotherapies: perspectives for evidence-based personalized medicine

This article discusses the rationale behind recommending immunopharmacological guidance of long-term therapies with genetically engineered anti-TNF-α immunoglobulin constructs. Arguments why therapeutic decision-making should not rely on clinical outcome alone are presented. Central to this is that the use of theranostics (i.e., monitoring circulating levels of functional anti-TNF-α drugs and antidrug antibodies) would markedly improve treatment because therapies can be tailored to individual patients and provide more effective and economical long-term therapies with minimal risk of side effects. Large-scale immunopharmacological knowledge of how patients ‘handle’ TNF-α biopharmaceuticals would also help industry develop more effective and safer TNF-α inhibitors.

Thromboembolic events and anti-tumor necrosis factor therapies

Thromboembolic (TE) events have been observed in about 4.5% of patients treated with TNF antagonists. It has been suggested that anti-drug antibodies could be involved. However, another mechanism fits more with the available immunochemical data and could lead to practical measures to prevent TE events during anti-TNF therapies. Adverse effects are not related to the type of antagonist, but well to the combination of the inhibition of TNF and the predisposition of some patients to lupus-like reactions, including antiphospholipid syndrome. The overproduction of interferon-α, caused by the inhibition of TNF in these individuals would foster the development of lupus-like syndrome. Therefore, seeking conventional markers of systemic lupus erythematosus (e.g. anti-dsDNA, anti-phospholipid, anti-β(2)-glycoprotein antibodies) before the administration of an anti-TNF could be a prudent measure.

Review article: non-malignant haematological complications of anti-tumour necrosis factor alpha therapy

BACKGROUND

Tumour necrosis factor-alpha (TNF-α) is an important mediator of the molecular cascade leading to chronic inflammation. TNF-α inhibitors have proven their safety and efficacy in the treatment of inflammatory diseases.

AIM

To review the non-malignant haematological adverse events, such as thrombocytopaenia, neutropaenia, hypercoagulability, pancytopaenia and aplastic anaemia in patients receiving TNF-α inhibitors.

METHODS

We reviewed the literature by searching MEDLINE and EMBASE databases as well as references of all retrieved articles for the following terms: anti-tumour necrosis factor, anti-TNF, infliximab, adalimumab, certolizumab, etanercept, haematological complications, thrombocytopaenia, neutropaenia, anaemia, bone marrow and thrombosis.

RESULTS

Thombocytopaenia is a very rare phenomenon and was associated with no serious adverse events. However, transient neutropaenia developed in up to 16% of cases. Patients with a previous history of neutropaenia on other therapies or baseline neutrophil count <4 × 10(9) /L are at a particularly higher risk. The association between anti-TNF-α therapy and thrombosis is very nebulous due to the multitude of potential confounders. Only one case of primary eosinophilia has been reported with anti-TNF-α therapy.

CONCLUSION

Regular monitoring of the white blood cell count at baseline and with each infusion is recommended for patients on anti-TNF-α. Further studies to elucidate their interaction with the immune system are warranted.

Anti-TNF therapy

There are now five anti-tumour necrosis factor (TNF) drugs licenced for use in rheumatoid arthritis. This chapter examines the similarities and differences between the drugs and looks for clues with regard to their rational prescribing. The major difference is between the monoclonal antibody-based drugs and the soluble receptor etanercept. Etanercept exhibits the best drug survival and is also associated with a lower risk of opportunistic infections, particularly tuberculosis. Immunogenicity should explain some of the differences between the different drugs but the lack of standardised assays has hindered this area of research. The optimal approach to the patient who has failed their first anti-TNF remains unclear and awaits appropriate clinical trials. The safety profile of anti-TNFs has become clearer, largely through registry data. There is a small increase in serious and opportunistic infections but there does not appear to be a heightened cancer risk, and cardiovascular risk is probably reduced.

Are we ready for therapeutic drug monitoring of biologic therapeutics?

In the previous issue of Arthritis Research & Therapy, Ducourau and colleagues report that they retrospectively detected anti-infliximab antibodies in 21% of patients with rheumatic diseases. Patients with anti-infliximab antibodies had lower serum drug concentrations. These findings contribute to the existing evidence of immunogenicity of biologicals and its clinical relevance. We argue for therapeutic drug monitoring to optimize treatment response.