The formation of autoantibodies and antibodies to TNF-α blocking agents in relation to clinical response in patients with ankylosing spondylitis

OBJECTIVES

To investigate the influence of antibody formation to TNF-α blocking agents on the clinical response in AS patients treated with infliximab (IFX), etanercept (ETA), or adalimumab (ADA), and to investigate the development of ANA, ANCA, and anti-dsDNA antibodies in association with the formation of antibodies to TNF-α blocking agents.

METHODS

Consecutive AS outpatients with active disease who started treatment with IFX (n=20), ETA (n=20), or ADA (n=20) were included in this longitudinal observational study. Clinical data were collected prospectively at baseline and after 3, 6, and 12 months of anti-TNF-α treatment. At the same time points, serum samples were collected. In these samples, antibodies to TNF-α blocking agents, serum TNF-α blocker levels, and ANA, ANCA, and anti-dsDNA antibodies were measured retrospectively.

RESULTS

Anti-IFX, anti-ETA, and anti-ADA antibodies were induced in 20%, 0%, and 30% of patients, respectively. Although ANA, ANCA, and anti-dsDNA antibodies were detected during anti-TNF-α treatment, no significant association was found between the presence of these autoantibodies and the formation of antibodies to TNF-α blocking agents. Patients with anti-IFX or anti-ADA antibodies had significantly lower serum TNF-α blocker levels compared to patients without these antibodies. Furthermore, significant negative correlations were found between serum TNF-α blocker levels and assessments of disease activity.

CONCLUSIONS

This study indicates that antibody formation to IFX or ADA is related to a decrease in efficacy and early discontinuation of anti-TNF-α treatment in AS patients. Furthermore, autoantibody formation does not seem to be associated with antibody formation to TNF-α blocking agents.

Clinical response, pharmacokinetics, development of human anti-chimaeric antibodies, and synovial tissue response to rituximab treatment in patients with rheumatoid arthritis

OBJECTIVES

To analyse whether persistence of synovial B lineage cells and lack of clinical response to rituximab treatment in patients with rheumatoid arthritis (RA) are associated with low rituximab serum levels and anti-rituximab antibody (ARA) formation.

METHODS

Fifty-eight patients with RA were treated with rituximab. The clinical response was determined 24 weeks after each treatment course using the Disease Activity Score evaluated in 28 joints (DAS28) and EULAR response criteria. Rituximab serum levels, ARAs and synovial B lineage cell numbers were determined before and after treatment.

RESULTS

Four weeks after treatment rituximab serum levels were highly variable. Low rituximab levels were associated with ARA formation (in five patients (8.6%)) and high baseline erythrocyte sedimentation rate. Interestingly, serum rituximab levels were not related to persistence of synovial B lineage cells or clinical response. Furthermore, response to treatment and re-treatment was similar in ARA-positive and ARA-negative patients.

CONCLUSION

There is clear variability in serum levels after rituximab treatment, but rituximab levels are not lower in patients with persistence of synovial B lineage cells or lack of clinical response. The current treatment schedule suffices to induce and maintain a clinical response, even when ARAs are formed.

Anti-infliximab and anti-adalimumab antibodies in relation to response to adalimumab in infliximab switchers and anti-tumour necrosis factor naive patients: a cohort study

OBJECTIVE

To investigate how antibodies against anti-tumour necrosis factor (anti-TNF) agents influence response after switching from infliximab to adalimumab in rheumatoid arthritis (RA).

METHODS

This cohort study consisted of 235 patients with RA, all treated with adalimumab. At baseline 52 patients (22%) had been previously treated with infliximab ('switchers'), and 183 (78%) were anti-TNF naive. Disease activity (using the 28-joint count Disease Activity Score (DAS28)) and presence of antibodies against infliximab and adalimumab were assessed. Clinical response to adalimumab was compared between switchers and anti-TNF naive patients and their anti-infliximab and anti-adalimumab antibody status.

RESULTS

After 28 weeks of adalimumab treatment the decrease in DAS28 (Delta DAS28) for the 235 patients was 1.6+/-1.5 (mean+/-SD). Anti-adalimumab antibodies were detected in 46 patients (20%). Delta DAS28 was 1.8+/-1.4 in patients without anti-adalimumab and 0.6+/-1.3 in patients with anti-adalimumab (p<0.0001). Thirty-three of the 52 switchers (63%) had anti-infliximab antibodies. Patients with anti-infliximab more often developed anti-adalimumab than anti-TNF naive patients (11 (33%) vs 32 (18%); p=0.039). Delta DAS28 was greater for anti-TNF naive patients (1.7+/-1.5) than for switchers without anti-infliximab antibodies (Delta DAS28=0.9+/-1.4) (p=0.009). Delta DAS28 for switchers with anti-infliximab was 1.2+/-1.3 and did not differ significantly from anti-TNF naive patients (p=0.262).

CONCLUSION

Switchers with anti-infliximab antibodies more often develop antibodies against adalimumab than anti-TNF naive patients. Response to adalimumab was limited in switchers without anti-infliximab antibodies, which raises the question whether a second anti-TNF treatment should be offered to patients with RA for whom an initial treatment with an anti-TNF blocker fails, in the absence of anti-biological antibodies.

Improvement of lipid profile is accompanied by atheroprotective alterations in high-density lipoprotein composition upon tumor necrosis factor blockade: a prospective cohort study in ankylosing spondylitis

OBJECTIVE

Cardiovascular mortality is increased in ankylosing spondylitis (AS), and inflammation plays an important role. Inflammation deteriorates the lipid profile and alters high-density lipoprotein cholesterol (HDL-c) composition, reflected by increased concentrations of serum amyloid A (SAA) within the particle. Anti-tumor necrosis factor (anti-TNF) treatment may improve these parameters. We therefore undertook the present study to investigate the effects of etanercept on lipid profile and HDL composition in AS.

METHODS

In 92 AS patients, lipid levels and their association with the inflammation markers C-reactive protein (CRP), erythrocyte sedimentation rate, and SAA were evaluated serially during 3 months of etanercept treatment. HDL composition and its relationship to inflammation markers was determined in a subgroup of patients, using surface-enhanced laser desorption/ionization time-of-flight analysis.

RESULTS

With anti-TNF treatment, levels of all parameters of inflammation decreased significantly, whereas total cholesterol, HDL-c, and apolipoprotein A-I (Apo A-I) levels increased significantly. This resulted in a better total cholesterol:HDL-c ratio (from 3.9 to 3.7) (although the difference was not statistically significant), and an improved Apo B:Apo A-I ratio, which decreased by 7.5% over time (P=0.008). In general, increases in levels of all lipid parameters were associated with reductions in inflammatory activity. In addition, SAA was present at high levels within HDL particles from AS patients with increased CRP levels and disappeared during treatment, in parallel with declining plasma levels of SAA.

CONCLUSION

Our results show for the first time that during anti-TNF therapy for AS, along with favorable changes in the lipid profile, HDL composition is actually altered whereby SAA disappears from the HDL particle, increasing its atheroprotective ability. These findings demonstrate the importance of understanding the role of functional characteristics of HDL-c in cardiovascular diseases related to chronic inflammatory conditions.

Arthritis development in patients with arthralgia is strongly associated with anti-citrullinated protein antibody status: a prospective cohort study

BACKGROUND

Anti-citrullinated protein antibodies (ACPA) are associated with increased risk for rheumatoid arthritis.

OBJECTIVE

To investigate the effect of the presence and levels of ACPA on arthritis development in patients with arthralgia.

METHODS

Patients with arthralgia positive for ACPA or IgM rheumatoid factor (IgM-RF) were tested for the shared epitope (SE) and were prospectively followed up for at least 12 months. Absence of clinical arthritis at inclusion and arthritis development during follow-up were independently confirmed by two investigators. Cox regression hazard analyses were used to calculate hazard ratios (HRs) for arthritis development.

RESULTS

147 patients with arthralgia were included (50 ACPA positive, 52 IgM-RF positive and 45 positive for both antibodies). After a median follow-up of 28 months (interquartile range (IQR) 19-39), 29 patients developed arthritis in a median of 4 (IQR 3-6) joints and 26 (90%) of these were ACPA positive. The presence of ACPA (HR = 6.0; 95% confidence interval (95% CI) 1.8 to 19.8; p = 0.004), but not of IgM-RF (HR = 1.4, 95% CI 0.6 to 3.1) nor the SE (HR = 1.5, 95% CI 0.7 to 3.0), was associated with arthritis development. Within the group of ACPA-positive patients, the risk for arthritis was enhanced by the presence of IgM-RF (HR = 3.0; 95% CI 1.4 to 6.9; p = 0.01) and high ACPA levels (HR = 1.7; 95% CI 1.1 to 2.5; p = 0.008), but not the SE (HR = 1.0; 95% CI 0.5 to 2.1; p = 1.0).

CONCLUSION

In patients with arthralgia the presence of ACPA (but not of IgM-RF or SE) predicts arthritis development. The risk in ACPA-positive patients may be further increased by the concomitant presence of IgM-RF or high levels of ACPA.

Arthritis development in patients with arthralgia is strongly associated with anti-citrullinated protein antibody status: a prospective cohort study

BACKGROUND

Anti-citrullinated protein antibodies (ACPA) are associated with increased risk for rheumatoid arthritis.

OBJECTIVE

To investigate the effect of the presence and levels of ACPA on arthritis development in patients with arthralgia.

METHODS

Patients with arthralgia positive for ACPA or IgM rheumatoid factor (IgM-RF) were tested for the shared epitope (SE) and were prospectively followed up for at least 12 months. Absence of clinical arthritis at inclusion and arthritis development during follow-up were independently confirmed by two investigators. Cox regression hazard analyses were used to calculate hazard ratios (HRs) for arthritis development.

RESULTS

147 patients with arthralgia were included (50 ACPA positive, 52 IgM-RF positive and 45 positive for both antibodies). After a median follow-up of 28 months (interquartile range (IQR) 19-39), 29 patients developed arthritis in a median of 4 (IQR 3-6) joints and 26 (90%) of these were ACPA positive. The presence of ACPA (HR = 6.0; 95% confidence interval (95% CI) 1.8 to 19.8; p = 0.004), but not of IgM-RF (HR = 1.4, 95% CI 0.6 to 3.1) nor the SE (HR = 1.5, 95% CI 0.7 to 3.0), was associated with arthritis development. Within the group of ACPA-positive patients, the risk for arthritis was enhanced by the presence of IgM-RF (HR = 3.0; 95% CI 1.4 to 6.9; p = 0.01) and high ACPA levels (HR = 1.7; 95% CI 1.1 to 2.5; p = 0.008), but not the SE (HR = 1.0; 95% CI 0.5 to 2.1; p = 1.0).

CONCLUSION

In patients with arthralgia the presence of ACPA (but not of IgM-RF or SE) predicts arthritis development. The risk in ACPA-positive patients may be further increased by the concomitant presence of IgM-RF or high levels of ACPA.

Immunogenicity negatively influences the outcome of adalimumab treatment in Crohn's disease

BACKGROUND

Adalimumab is an effective treatment in patients with Crohn's disease; as it is a humanized anti-tumour necrosis factor monoclonal antibody, immunogenicity is thought not to be of any significance.

AIM

To assess whether antibodies to adalimumab (ATAs) affect adalimumab treatment outcome in patients with Crohn's disease previously treated with infliximab.

METHODS

A retrospective study was performed. Patients with active Crohn's disease and who had lost response or were intolerant to infliximab were treated with adalimumab. Clinical response and side effects were assessed as were serum ATAs and antibodies to infliximab (ATIs).

RESULTS

In total 30 patients [M/F (7/23)], median age 36 years (range 21-73) were treated with adalimumab for 318 days (median range 83-632). Clinical response was 77% (23/30), a dose escalation was necessary in eight (27%) patients and side effects were observed in 47% (14/30). In five patients (17%) ATAs were detected; of these patients, four were nonresponders. The presence of ATAs was related to nonresponse to adalimumab (P = 0.006). ATIs were positive in 57% of patients (17/30) and serum levels were significantly increased in adalimumab nonresponders (P = 0.01).

CONCLUSION

Immunogenicity plays a role in adalimumab treatment because of the development of ATAs.

[The formation of infliximab and anti-infliximab immune complexes as an explanation for non-responding to infliximab treatment of rheumatoid arthritis: observational study in 4 patients]

OBJECTIVE

To investigate the in vivo mechanism of non-responding to infliximab treatment of patients with rheumatoid arthritis (RA) and the role of anti-infliximab antibodies by using radiolabeled infliximab.

DESIGN

Descriptive and comparative study.

METHOD

Two responding and two non-responding RA patients were infused with radiolabeled infliximab. Subsequently imaging investigations and serum analysis were performed at set times.

RESULTS

The scintigrams showed that the labelled infliximab was mainly present in the blood until 24 h after infusion. There was a trend of faster blood clearance and higher liver and spleen uptake of 99mTc-infliximab in one non-responding patient. Labelled infliximab was taken up by inflamed joints. The anti-infliximab level was high (1008 and 1641 U/ml) in the non-responders and low or not detectable in the responders. Sucrose gradients of serum revealed antibody complexes in both non-responders. Various sizes of antibody complexes, including very large ones, were observed in one non-responder who developed a serious infusion reaction.

CONCLUSION

Infliximab-anti-infliximab immune complexes were found to form in RA non-responders due to the presence of significant quantities of anti-infliximab. This finding may partly explain the failure of the infliximab treatment.

Preferential decrease in IgG4 anti-citrullinated protein antibodies during treatment with tumour necrosis factor blocking agents in patients with rheumatoid arthritis

Objective:

To investigate the dynamics of IgG1 and IgG4 anti-citrullinated protein antibody (ACPA) subclasses during anti-tumour necrosis factor (TNF) treatment in patients with rheumatoid arthritis (RA).

Methods:

IgG, IgG1 and IgG4 ACPA levels were determined by ELISA on anti-citrullinated fibrinogen (ACF) and IgG1 : IgG4 ACPA ratios were calculated. A pilot study was performed in 28 ACF-positive patients treated with infliximab for one year. Confirmation of the results was obtained using a cohort of 180 consecutive patients treated with adalimumab for 28 weeks.

Results:

The median reduction in ACF levels was 31% for total IgG, 29% for IgG1, 40% for IgG4 and 22% for the IgG4 : IgG1 ACF ratio in the infliximab cohort. In adalimumab-treated patients, ACF levels declined 14% for total IgG and IgG1, and 36% for IgG4 ACF; the IgG4 : IgG1 ratio was reduced by 24% (all percentage values p<0.05). The decrease in antibody levels was correlated with the clinical response; European League Against Rheumatism good responders had the greatest decline in antibody levels and this effect was most pronounced for IgG4 (48% reduction). The IgG4 : IgG1 ACF ratio preferentially decreased in patients with adequate therapeutic adalimumab levels.

Conclusion:

ACPA subclass distribution is modulated by effective anti-inflammatory treatment. The preferential decline of IgG4 ACPA, reflected by the decreased IgG4 : IgG1 ratio, suggests a beneficial effect of anti-TNF treatment on chronic antigenic stimulation by citrullinated proteins. This effect may be directly anti-TNF mediated or the result of effective dampening of the inflammation in the rheumatoid joint.

The role of the shared epitope in arthralgia with anti-cyclic citrullinated peptide antibodies (anti-CCP), and its effect on anti-CCP levels

OBJECTIVES

Patients presenting with both arthralgia and antibodies to cyclic citrullinated peptide (anti-CCP) have an increased risk of developing rheumatoid arthritis (RA). To further characterise this patient group and shed more light on its relationship with clinically manifest early arthritis and established RA, an immunogenetic and serological analysis was performed.

METHODS

In a group of 111 patients with anti-CCP-positive arthralgia, anti-CCP levels and shared epitope (SE) status were determined. Data were compared with 125 and 128 patients with anti-CCP-positive early arthritis and established RA respectively.

RESULTS

In patients with anti-CCP-positive arthralgia, the frequency of SE allele positivity is significantly lower when compared with anti-CCP-positive early arthritis and established RA (58% vs 80%, and 58% vs 92%, respectively, both p<0.001). Median anti-CCP levels were higher in the group of patients with SE-positive arthralgia compared with the group of patients with SE-negative arthralgia (p = 0.02). Median anti-CCP levels were similar in the groups of patients with SE-positive arthralgia and arthritis.

CONCLUSIONS

The lower frequency of SE positivity in patients with arthralgia compared with patients with RA indicates that, compared with patients who were SE positive, patients who were SE negative as a group go through a longer arthralgia phase, or alternatively have a lower risk for transition from anti-CCP positive arthralgia to RA. Furthermore, the present results suggest that in this early stage the effect of the SE on disease risk may be mediated through higher anti-CCP levels.

Immunogenicity does not influence treatment with etanercept in patients with ankylosing spondylitis

BACKGROUND

Immunogenicity, specifically the onset of antibodies against tumour necrosis factor (TNF) blocking agents, seems to play an important role in non-response to treatment with these drugs.

OBJECTIVES

To assess the relation of clinical response of ankylosing spondylitis (AS) to etanercept with etanercept levels, and the presence of antibodies to etanercept.

METHODS

Patients with AS were treated with etanercept 25 mg twice weekly, according to the international Assessment in Ankylosing Spondylitis (ASAS) working group consensus statement. Sera were collected at baseline and after 3 and 6 months of treatment. Clinical response was defined as a 50% improvement or as an absolute improvement of 2 points on a (0-10 scale) Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score. Functional etanercept levels were measured by a newly developed ELISA, measuring the binding of etanercept to TNF. Antibodies against etanercept were measured with a two-site assay and antigen binding test. Clinical data were used to correlate disease activity with serum etanercept levels.

RESULTS

In all, 53 consecutive patients were included. After 3 months of treatment 40 patients (76%) fulfilled the response criteria. Mean etanercept levels were 2.7 mg/litre and 3.0 mg/litre after 3 and 6 months respectively. Characteristics and etanercept levels of responders and non-responders were similar. No antibodies to etanercept were detected with any of the assays.

CONCLUSION

Etanercept levels of responders and non-responders were similar and no antibodies to etanercept were detected with any of the assays. This study indicates that etanercept is much less immunogenic compared with the other TNF-blocking agents.

The clinical response to infliximab in rheumatoid arthritis is in part dependent on pretreatment tumour necrosis factor alpha expression in the synovium

OBJECTIVE

To determine whether the heterogeneous clinical response to tumour necrosis factor (TNF)alpha blocking therapy in rheumatoid arthritis (RA) can be predicted by TNFalpha expression in the synovium before initiation of treatment.

METHODS

Prior to initiation of infliximab treatment, arthroscopic synovial tissue biopsies were obtained from 143 patients with active RA. At week 16, clinical response was evaluated using the 28-joint Disease Activity Score (DAS28). Immunohistochemistry was used to analyse the cell infiltrate as well as the expression of various cytokines, adhesion molecules and growth factors. Stained sections were evaluated by digital image analysis. Student t tests were used to compare responders (decrease in DAS28 > or =1.2) with non-responders (decrease in DAS28 <1.2) and multivariable regression was used to identify the independent predictors of clinical response.

RESULTS

Synovial tissue analysis confirmed our hypothesis that the baseline level of TNFalpha expression is a significant predictor of response to TNFalpha blocking therapy. TNFalpha expression in the intimal lining layer and synovial sublining were significantly higher in responders than in non-responders (p = 0.047 and p = 0.008, respectively). The numbers of macrophages, macrophage subsets and T cells (all able to produce TNFalpha) were also significantly higher in responders than in non-responders. The expression of interleukin (IL)1beta, IL6, IL18, IL10, E-selectin, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) was not associated with response to anti-TNFalpha treatment.

CONCLUSION

The effects of TNFalpha blockade are in part dependent on synovial TNFalpha expression and infiltration by TNFalpha producing inflammatory cells. Clinical response cannot be predicted completely, indicating involvement of other as yet unknown mechanisms.

Changes in lipid profile during infliximab and corticosteroid treatment in rheumatoid arthritis

OBJECTIVE

To evaluate the effects of infliximab and corticosteroid treatment on the lipid profile in patients with active rheumatoid arthritis (RA).

METHODS

Infliximab infusions were given at weeks 0, 2, 6 and then every 8 weeks. Before each infusion, disease activity parameters (Disease Activity Index 28-Joint Score (DAS28)) C reactive protein (CRP) and lipid levels (total cholesterol, high-density lipoprotein (HDL)-cholesterol, triglycerides, apolipoprotein A1 (apo A1) and apolipoprotein B) were measured in 80 consecutive patients with RA, who completed the study period of 48 weeks. Longitudinal analyses were used to investigate (1) the course of lipid levels over a period of time and (2) the relationship between lipids, prednisone dose and disease activity.

RESULTS

Infliximab treatment causes a significant reduction in disease activity and a concomitant decrease in prednisone dose. Although they initially improved significantly, all lipid levels had returned to baseline levels after 48 weeks, except for apo A1. Longitudinal analyses revealed significant yet opposite associations between lipid levels and disease activity and between lipid levels and prednisone dose. DAS28 improvement by 1 point was associated with an increase of 0.016 mmol/l (0.618 mg/dl) total cholesterol and 0.045 mmol/l (1.737 mg/dl) HDL-cholesterol. Reduction of 10 mg prednisone was associated with a decrease of 0.04 mmol/l (1.544 mg/dl) total cholesterol and 0.16 mmol/l (6.177 mg/dl) HDL-cholesterol.

CONCLUSION

Overall, no changes in serum lipid levels were observed after 48 weeks of infliximab treatment. The initial beneficial effects of infliximab on the lipid profile, by means of a reduction of disease activity, are attenuated by a concomitant decrease in prednisone dose.

Rituximab treatment in patients with primary Sjögren's syndrome: An open-label phase II study

OBJECTIVE

To investigate the safety and efficacy of B cell depletion treatment of patients with active primary Sjögren's syndrome of short duration (early primary SS) and patients with primary SS and mucosa-associated lymphoid tissue (MALT)-type lymphoma (MALT/primary SS).

METHODS

Fifteen patients with primary SS were included in this phase II trial. Inclusion criteria for the early primary SS group were B cell hyperactivity (IgG >15 gm/liter), presence of autoantibodies (IgM rheumatoid factor, anti-SSA/SSB), and short disease duration (<4 years). Inclusion criteria for the MALT/primary SS group were primary SS and an associated MALT-type lymphoma (Ann Arbor stage IE) localized in the parotid gland. Patients were treated with 4 infusions of rituximab (375 mg/m2) given weekly after pretreatment with prednisone (25 mg) and clemastine. Patients were evaluated, using immunologic, salivary/lacrimal function, and subjective parameters, at baseline and at 5 and 12 weeks after the first infusion.

RESULTS

Significant improvement of subjective symptoms and an increase in salivary gland function was observed in patients with residual salivary gland function. Immunologic analysis showed a rapid decrease of peripheral B cells and stable levels of IgG. Human anti-chimeric antibodies (HACAs) developed in 4 of 15 patients (27%), all with early primary SS. Three of these patients developed a serum sickness-like disorder. Of the 7 patients with MALT/primary SS, complete remission was achieved in 3, and disease was stable in 3 and progressive in 1.

CONCLUSION

Findings of this phase II study suggest that rituximab is effective in the treatment of primary SS. The high incidence of HACAs and associated side effects observed in this study needs further evaluation.

Relationship between serum trough infliximab levels, pretreatment C reactive protein levels, and clinical response to infliximab treatment in patients with rheumatoid arthritis

OBJECTIVE

To investigate the relationship between serum trough infliximab levels and clinical response to infliximab treatment in patients with rheumatoid arthritis (RA).

METHODS

Disease activity and serum trough infliximab levels before and 2, 6, and 14 weeks after initiation of infliximab treatment at a dose of 3 mg/kg in a cohort of 105 patients with RA were assessed. Serum trough infliximab levels in responders and non-responders were compared. Additionally, the clinical responses of patients with high, intermediate, and low serum trough infliximab levels at 14 weeks were compared.

RESULTS

After 14 weeks of treatment non-responders had lower serum trough levels of infliximab than responders (median (interquartile range) 0.5 (0.2-2.2) v 3.6 (1.4-8.2) mg/l; p<0.01)). Patients with low serum trough infliximab levels at 14 weeks had significantly less improvement in the 28 joint count Disease Activity Score (DAS28) score than patients with intermediate or high serum trough infliximab levels at 14 weeks. Pretreatment C reactive protein (CRP) levels correlated negatively with serum trough infliximab levels at 14 weeks after the start of treatment (Spearman rank correlation r(s) = -0.43, p<0.001).

CONCLUSION

Serum trough levels of infliximab correlate with the clinical response to treatment with infliximab and pretreatment CRP levels. This study indicates that patients with high pretreatment CRP levels might benefit from higher dosages of infliximab or shorter dosing intervals.