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P481. Impact of serum drug level and human anti-drug antibody measurement on management of biologic drugs in inflammatory bowel disease

A. Jauregui-Amezaga1, I. Ordas1, M. Gallego1, A. Ramirez1, S. Pino1, M.C. Masamunt1, M. Juan2, E. Ricart1, J. Yagüe2, J. Panés1, 1Hospital Clínic i Provincial, Gastroenterology, Barcelona, Spain, 2Hospital Clínic i Provincial, Immunology, Barcelona, Spain

Background

The need of implementation of measurement of serum drug levels (sDL) and human anti-drug antibodies (hADA) to guide biological therapy of inflammatory bowel disease (IBD) in clinical practice is still disputed. In this prospective study we determined physicians' management decisions without serum levels and after providing this information.

Methods

sDL and hADA concentration were measured in a cohort of 101 IBD patients under anti-TNF treatment by an enzyme-linked immunosorbent assay (ELISA) technique. The clinician established treatment strategy before and after knowing sDL and hADA results.

Results

sDL and hADA were measured in 59 patients with loss of response and 42 patients with sustained response in whom changes in biological therapy were contemplated (desintensification or withdrawal of treatment). 50% of patients had luminal Crohn's disease, 17% fistulizing disease, 13% perianal disease and 20% ulcerative colitis. 60 patients were receiving infliximab and 41 adalimumab and 50% of cases received concomitant immunosuppressive treatment.

45% of infliximab patients and 73% of adalimumab ones had therapeutic sDL (>2 µg/ml) and non-detectable sDL were found in 28% of infliximab and 12% of adalimumab cases (p = 0.02). hADA were inversely related to sDL, as they were found in 13/22 patients with undetectable sDL, in 1/22 with infra-therapeutic sDL and 2/57 with sDL >2 µg/ml (p < 0.001). 23.5% of patients in monotherapy developed hADA while only 8% of patients under concomitant immunosuppressive therapy had hADA (p = 0.03), with similar proportions in patients treated with infliximab and adalimumab. Patients with loss of response had lower sDL (mean/SD 3.13/4.6 µg/ml vs 6.84/13.8 µg/ml, p = 0.06) and a higher proportion of positive hADA (22% vs 7%, p = 0.04) than patients with sustained response. As shown in Table 1, measurement of sDL and hADA had a significant impact on the management of anti-TNF treatments.

Table 1. Physicians' strategy pre and post-determination of serum drug levels (sDL) and human anti-drug antibodies (hADA)
Physician's strategy before/after measurement of sDL and hADA
BeforeAfter
 No changesDesintensIntensifSwitch BiolStop BiolTotal
No changes10
67%
2
13%
2
13%
1
7%
1
7%
15
100%
Desintens7
35%
13
65%
0
0%
0
0%
0
0%
20
100%
Intensif19
44%
3
7%
14
33%
4
9%
3
7%
43
100%
Switch Biol4
40%
2
20%
0
0%
2
20%
2
20%
10
100%
Stop Biol0
0%
0
0%
0
0%
0
0%
12
100%
12
100%
Total40
40%
20
20%
16
16%
7
7%
17
17%
100
100%

Conclusion

Measurement of sDL and hADA has a significant impact on the management of biologic drugs in clinical practice, with a considerable reduction of drug use resulting from avoiding drug intensification and leading to previously unplanned desintensifications.