Anti-IFX antibodies of Remicade-treated patients cross-react with either Inflectra or Remsima. Although additional epitopes may be present in the biosimilar, results suggest that epitopes influencing the immune response to IFX are also present in the biosimilar. Antibody-positive patients treated with Remicade should not be switched to the biosimilar, since antibodies will interact with the new drug and potentially lead to loss of response. This finding supports the utility for therapeutic drug monitoring before a switching strategy is considered.

Patients treated with adalimumab (ADL) can induce anti-ADL antibodies (AAA) formation that is associated with low drug levels and clinical non-response. But, in the majority of the assays, the measurement of AAA is hampered by the presence of the drug itself. In support of immunogenicity assessment in clinical samples with subtherapeutic ADL levels, we proved acid pre-treatment for AAA detection with the Promonitor-enzyme-linked immunosorbent assay (ELISA). Were measured AAA after acidification in 32 serum samples with a subtherapeutic ADL trough level. ADL and AAA concentrations were measured by ELISA (Promonitor). The impact of drug concentration on AAA recovery (with or without acidification) was also evaluated by mixing known amounts of ADL (0.25, 0.5 and 1 mg/L) and AAA (100, 200, 300 and 400 AU/mL) from clinical samples in pooled serum. The drug significantly inhibited the detection of AAA in untreated samples. And progressively higher levels of ADL cause increasing inhibition of signal. Acid pre-treatment carried a significant increase in assay response, particularly at lower free ADL concentrations. AAA were detected in the 53 % of the samples after acid dissociation. In seven patients, the positive AAA after dissociation was detected in the first monitoring of ADL and five patients were positive 3 months later for AAA with the standard assay. Monitoring AAA using acid dissociation in patients with subtherapeutic circulating level of ADL could detect precocious problems of bioavailability, assess the immunogenicity of ADL and may be used to optimise dose regimens, thereby preventing prolonged use of inadequate therapy and guide change of treatment.

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MMF was effective in the majority of patients with uveitis with an acceptable profile of side-effects. TDM of MMF in patients with uveitis is clinically practicable and may help to optimize individual immunosuppressive therapy. We estimated that MMF dosages in the range of 0.5-1.5 g/day might be sufficient for treating uveitis and we recommend an initial target range of 2-4 microg/mL, which included 50% of our results. Randomized controlled trials are essential to confirm the efficacy of MMF in uveitis.

Objectives To assess the clinical relevance of serum levels of Golimumab (GLM) and the prevalence of antibodies anti-Golimumab (anti-GLM-Ab), in patients with rheumatic diseases. Methods We included 49 test of serum level of GLM and anti-GLM-Ab in 27 consecutives patients, on treatment with GLM at least 6 months, diagnosed of rheumatoid arthritis (RA), peripheral psoriatic arthritis (PsA) (18 test in 9 patients), or ankylosing spondylitis (AS) (31 test in 18 patients). Clinical characteristics, clinical activity index (DAS in 28 joints or SDAI, for RA and PsA; BASFI, BASDAI for AS, were recorded. Serum levels of GLM and anti-GLM-Ab was evaluated by a new ELISA kit developing: Promonitor®-GLM y Promonitor®-anti-GLM-Ab (Proteomika, Derio. Vizcaya. Spain). Cut-off level for serum level of GLM was >32 ng/mL and for anti-GLM-Ab was >20 UA/mL. Serum samples were collected before injection of GLM, and stored frozen -80°C, until analysis. Results We enrolled 27 patients, 56% were women; mean age 50±12 years. The diagnosis of patients was: RA/PsA in 33% (37% of total test) and AS in 67% (63% of tests). The average time of treatment for the whole population was 14±13 years; but lower in AR/PsA patients respect to AS patients (9.5 vs 17 years; p=0.08). In patients with RA/PsA, the mean DAS28 and SDAI was 2.03±1 and 4.2±5.8 respectively; in AS patients the mean BASDAI and ASDAS was 6.7 and 3.5, respectively. The mean time on treatment with GLM was 12±9 months (range: 1-28). 65% of patients was treated with some DMARD (100% of patients with RA/PsA) and 65% have treated before with some anti-TNF drugs: adalimumab: 40%, etanercept: 35%, infliximab: 25% (1 anti-TNF: 18%; 2 anti-TNF: 31%; 3 anti-TNF: 16%). The mean serum level of GLM was 1.006 ng/mL (RA/PsA: 889 ng/mL vs AS: 986 ng/mL). Three (11%) patients had developed anti-TNF antibodies previously: 2 patients against infliximab and 1 patient against adalimumab. One patient with AS on GLM treatment as the third anti-TNF (adalimumab and etanercept), and with previously ant-adalimumab antibodies, developed anti-GLM-Ab (773 UA/mL), in the sixth month of treatment, losing efficacy (prevalence of anti-GLM-Ab in the total patients: 4%). In the group of patients who had been developed anti-adalimumab antibodies, 20% of them developed anti-GLM-Ab. Conclusions 1. Immunogenicity induced by GLM is scarce. The prevalence of anti-GLM-Ab was of 4% of patients in this study. 2. In 20% of patients with previous anti-adalimumab antibodies, developed anti-GLM-Ab. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.3862