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.


OBJECTIVE
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.


CONCLUSIONS
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.
de Vries
M K
MK
VU University Medical Center, Amsterdam, The Netherlands. mk.devries@vumc.nl
van der Horst-Bruinsma
I E
IE
Nurmohamed
M T
MT
Aarden
L A
LA
Stapel
S O
SO
Peters
M J L
MJ
van Denderen
J C
JC
Dijkmans
B A C
BA
Wolbink
G J
GJ
D000328:Adult; D000906:Antibodies / Q000097:blood; D000937:Antigen-Antibody Reactions; D018501:Antirheumatic Agents / Q000097:blood / Q000276:immunology / Q000627:therapeutic use*; D000068800:Etanercept; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology / Q000627:therapeutic use*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018124:Receptors, Tumor Necrosis Factor / Q000097:blood / Q000276:immunology / Q000627:therapeutic use*; D013167:Spondylitis, Ankylosing / Q000188:drug therapy* / Q000276:immunology*; D016896:Treatment Outcome
D000906:Antibodies; D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D000068800:Etanercept