POS0647 DOES TNF INHIBITOR MOLECULAR STRUCTURE MATTER? ANALYSIS OF IMPACT OF BASELINE RHEUMATOID FACTOR TITERS ON DRUG LEVELS IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background

Elevated rheumatoid factor (RF) in patients with rheumatoid arthritis (RA) is associated with higher disease activity and increased risk for disease progression1.

Recent publications indicate significantly lower efficacy of TNF inhibitors (TNFi) in RA patients with high RF levels compared with low/negative RF subgroup2,3. Fab therapy with Certolizumab pegol (CZP), a PEGylated, Fc-free monoclonal antibody (mAb), has shown comparable efficacy and consistent serum levels irrespective of baseline RF4.

RF binds the Fc region of IgG1, the subtype used to engineer the majority of mAbs5. Formation of large immune complexes may likely explain the inceased clearance of mAbs in patients with high RF titers and reported reduced TNFi efficacy.

Objectives

We aimed to evaluate in clinical practice whether RF levels in RA patients influence serum drug levels of 3 TNFi with different molecular structures.

Methods

We evaluated retrospectively a cohort of RA patients from La Paz University Hospital (RA-Paz Registry, 1999-2019) treated with Infliximab (IFX), Adalimumab (ADA) or CZP. Clinical and demographic data were collected at baseline (T0) and after 6 months (T6) of treatment. RF titers and serum drug levels were measured at T0 and T6 using nephelometry and ELISA respectively. Association between baseline RF titers and drug levels was assessed using non-parametric test (Mann-Whitney).

Results

168 patients were evaluated: 90 received IFX, 48 ADA and 32 CZP. Characteristics at T0 are shown in Table 1. All patients had active disease at baseline and 76% were RF positive: ADA subgroup had lower percentage of positive RF than IFX and CZP subgroups. Patients were stratified into quartiles based on baseline RF titers: low (20-57 IU/ml), medium (57-380 IU/ml), high (>380 IU/ml) and seronegative (<20 IU/ml).

Table 1.

Baseline characteristics.

CharacteristicsTotal (n=168)IFX (n=90)ADL (n=48)CZP (n=32)p valueAge, years*55.5(45.3-66)57(46-65)50(42-64)61(47-70)0.08Body mass index, Kg/m2*24.5(21.7-29)24.2(21.8-27.7)24.7(21.5-30.3)24.6(22.2-30.3)0.3Male, n(%)28(17%)14(15%)9(19%)5(17%)0.2Disease duration, years*8.7(4.5-14.3)8.4 (4.4-14.3)8.8 (3.9-16)9.7(5-12)0.06Smoking status, n(%)0.03Currently/ex-smoker66(39%)29(32%)22(48%)16(57%)Non-smoker96(57%)61(68%)24(52%)12(43%)RF, n(%)128(76%)75(83%)28(58%)25(81%)0.002ACPA, n(%)134(80%)73(81%)35(73%)27(84%)0.3DAS28**5.1(1.3)5.4(1.3)4.5(1.3)4.9(1.3)0.002CRP levels*7.8(3-21.8)10.3(3.2-25.2)5.1(1.4-10.1)7.8(2.3-18.2)0.1Prior bDMARDs, n(%)26(15%)10 (11%)10 (21%)6(20%)0.2Monotherapy, n(%)16(10%)8(9%)8(17%)00.2csDMARDS, n(%)152(90%)82(91%)82(91%)32(100%)Methotrexate, n(%)112(67%)64(78%)33(83%)17(53%)0.2Other csDMARDs, n(%)24(24%)18(22%)7(18%)15(50%)0.0008Prednisone, n(%)85(51%)49(54%)21(44%)16(50%)0.6

*Median and interquartile range;**mean and standard deviation

Drug levels of IFX and ADA at T6 were significantly lower in those patients who had higher RF titers at T0 compared to seronegative. In contrast, CZP levels remained stable irrespectively of baseline RF titers, without significant differences among quartiles (Figure 1).

Conclusion

Higher baseline RF titers are associated with lower IFX and ADA levels at T6 in a cohort of RA patients. A concentration-response association has been clearly established for TNFi, and baseline RF levels appear to influence drug levels.

Reduced immune complexes formation with CZP may result in a limited impact of baseline RF titers on drug levels.

References

[1]Aletaha D. Arthritis Res Ther2015;17(1):229.

[2]Bobbio-Pallavicini F. Ann Rheum Dis 2007;66(3):302–7.

[3]Potter C. Ann Rheum Dis 2009;68(1):69–74.

[4]Tanaka Y. APLAR 2020. Oral Communication.

[5]Levy RA. Immunotherapy 2016;8(12):1427-1436.

Acknowledgements

This study was funded by an anrestricted reserch grant from UCB pharma.

Disclosure of Interests

ANA MARTÍNEZ-FEITO: None declared, Borja Hernández-Breijo: None declared, Marta Novella-Navarro Grant/research support from: UCB, Alejandro Villalba: None declared, Diana Peiteado: None declared, Pilar Nozal: None declared, DORA PASCUAL-SALCEDO Speakers bureau: Abbvie, Pfizer, Novartis, Takeda, Menarini and MSD., Grant/research support from: Abbvie, Pfizer, Novartis, Takeda, Menarini and MSD., Alejandro Balsa Speakers bureau: Pfizer, AbbVie, Galapagos, Lilly, Gilead, UCB, Nordic, Sandoz, Consultant of: Galapagos, Pfizer, AbbVie, Lilly, UCB, Nordic, Grant/research support from: Pfizer, Abbvie, UCB, Chamaida Plasencia Speakers bureau: Abbvie, Pfizer, UCB, Sandoz, Sanofi, Biogen, Lilly, Roche and Novartis, Grant/research support from: Abbvie, Pfizer, UCB, Sandoz, Sanofi, Biogen, Lilly, Roche and Novartis

Early monitoring of infliximab serum trough levels predicts long-term therapy failure in patients with axial spondyloarthritis

Objective: To evaluate whether serum infliximab trough levels (ITL) during the early stages of treatment are predictive of long-term clinical failure in patients with axial spondyloarthritis (axSpA).Method: Longitudinal observational study involving 81 patients with axSpA monitored during infliximab therapy. Serum ITL were measured before starting infliximab treatment and at weeks 2 (W2), W6 and W12 of treatment. Disease activity was assessed by Ankylosing Spondylitis Disease Activity Score (ASDAS) at baseline, W24 and W52, and every 6 months thereafter until treatment discontinuation, regardless of the reason. Non-clinically important improvement was defined by ΔASDAS<1.1. The association between serum levels during the early stages and clinical outcomes (non-clinically important improvement at W52, drug survival and drop-out due to secondary inefficacy) was investigated through logistic regression models and Kaplan Meier curves. Receiver operating characteristic (ROC) curves were employed to determine the best cut-off for serum ITL.Results: Out of the 81 patients, 45 (56%) did not achieve clinical improvement at W52. These patients had lower serum ITL at W12 compared to those who improved: ITL [median (IQR)]: 4.1(0.9-8.3) µg/mL vs 7.1 (4.3-11.3) µg/mL, respectively;p = 0.007). ITL<6.7 µg/mL at W12 was significantly associated with: i) not achieving clinical improvement at W52 (OR: 2.3; 95%CI: 1.3-3.9); ii) shorter drug survival (5.0 years (95% CI 3.8-6.2) vs 7.0 years (95% CI 4.8-6.9; p = 0.04), and iii) higher drop-out rates due to secondary inefficacy (OR: 3.5; 95% CI: 1.2-10.2).Conclusion: Low serum ITL at W12 were associated with long-term clinical failure in patients with axSpA, due to secondary inefficacy.

POS0623 CYTOKINE PRODUCTION BY BLOOD LYMPHOCYTES DEFINES A PROFILE ASSOCIATED WITH NON-REMISSION IN PATIENTS WITH RHEUMATOID ARTHRITIS TREATED WITH TNF INHIBITORS

Background:

In clinical practice no more than 50% of the patients treated with TNF inhibitors (TNFi) achieve remission (REM). Previous investigations suggested that peripheral blood mononuclear cells (PBMC) may be markers associated with the TNFi treatment success1.

Objectives:

This study aims to analyse the intracellular cytokine production by PBMC and its association with REM achievement after 6 months (m) of TNFi treatment in patients with RA.

Methods:

This was a prospective study including 62 patients with RA starting the 1st TNFi. PBMC were isolated from patients at baseline and after 6m of treatment with TNFi and cryopreserved until studied. In vitro stimulation and intracellular cytokine production by PBMC was performed as follow: in the presence of 2µg/mL brefeldin and 2µmol/L monensin monocytes were stimulated with 20ng/mL LPS during 4h whereas lymphocytes were stimulated with 50ng/mL phorbol 12-myristate 13-acetate and 750ng/mL ionomycin for 4h at 37°C. To identify IL10-producing B cells, PBMC were pre-incubated with 3µg/mL of CpG oligonucleotide during 20h at 37°C prior to stimulation. Intracellular cytokine production (TNFα, IL6, GM-CSF, IL10) by the different cell subsets (monocytes, CD4+ and CD8+ T cells, naïve and memory B cells) was analysed by flow-cytometry. Clinical activity at baseline and after 6m was assessed by DAS28-ESR. REM was defined as DAS28≤2.6 at 6m. The association between cytokine production by each PBMC subset and REM was analysed through univariable and multivariable logistic regression models. Receiving operating curve (ROC) analysis was used to select the optimal ratio of cytokine production associated with REM status.

Results:

After 6m of TNFi treatment, 30 (48%) patients achieved REM. No significant differences between REM and non-REM groups were observed for patients’ characteristics at baseline except for DAS28, which was lower in the REM group (non-REM: 5.4±0.9; REM: 4.3±0.9; p<0.0001) (Table 1). Therefore, further analyses were adjusted by baseline DAS28. A lower ratio between calculated with the IL10 and TNFα production by B cells and by CD4+ T cells (IL10 B/TNF CD4) at 6m was found for non-REM patients (non-REM: 0.31 vs REM: 0.54; p=0.007). Based on a ROC analysis, we found that a (IL10 B/TNF CD4)<0.54 at 6 m was significantly associated with a higher probability of non-REM at 6 months (OR: 5.0; 95% CI: 1.1-21.7) (Figure 1).

Table 1.

Baseline predictors of reduction of disease activity at 12 months from start of abatacept. Linear regression.

Baseline patients’ characteristicsTotal patients (n=62)DAS28>2.6(n=32; 52%)DAS28≤2.6(n=30; 48%)p-valueAge (years)53±1253±1352±100.8Female55 (89)30 (94)25 (83)0.2Disease duration (years)8 (4-11)8 (4-12)7 (3-11)0.7RF positive49 (79)23 (72)26 (87)0.1ACPA positive54 (87)26 (81)28 (93)0.2Smoking habit (n=55)0.2Non-smokers26 (47)16 (55)10 (38) Smoker29 (53)13 (45)16 (51)Body mass index (kg/m2)25.9±5.625.8±5.726.0±5.60.9DAS284.9±1.05.4±0.94.3±0.9<0.0001Concomitant csDMARDs60 (97)32 (100)28 (93)0.3MTX [±OD]46 (74)26 (81)20 (67)0.3Only OD14 (23)6 (19)8 (26)0.3Prednisone36 (58)19 (59)17 (57)0.9

Conclusion:

Our results show that the proinflammatory IL10 B/TNF CD4 ratio is associated with non-REM status. It could be useful to analyse the success of TNFi treatment in patients with RA.

References:

[1]Rodríguez-Martín E, et al. Front Immunol. 2020; 11: 1913.

Acknowledgements:

ISCIII (PI16/00474; PI16/01092)

Disclosure of Interests:

Borja Hernández-Breijo: None declared, Eulalia Rodríguez-Martín: None declared, Carlota García-Hoz: None declared, Victoria Navarro-Compán Speakers bureau: Abbvie, Janssen, Lilly, MSD, Novartis, Pfizer and UCB, Grant/research support from: Abbvie, Janssen, Lilly, MSD, Novartis, Pfizer and UCB, Cristina Sobrino: None declared, ANA MARTÍNEZ-FEITO: None declared, Israel Nieto-Gañán: None declared, Javier Bachiller-Corral Speakers bureau: Abbvie, MSD, BMS and Roche, Grant/research support from: Pfizer, Paloma Lapuente-Suanzes: None declared, Gemma Bonilla: None declared, Cristina Pijoán-Moratalla: None declared, Mónica Vázquez: None declared, Alejandro Balsa Speakers bureau: Abbvie, BMS, Nordic, Novartis, Pfizer, Sandoz, Sanofi, Roche and UCB, DORA PASCUAL-SALCEDO: None declared, Luisa María Villar: None declared, Chamaida Plasencia Speakers bureau: AbbVie, Lilly, Novartis, Pfizer, Sanofi, Biogen and UCB

POS0617 ANTI INFLIXIMAB ANTIBODIES DETECTED BY A DRUG TOLERANT ASSAY ARE FREQUENT BUT, IN MANY CASES, WITHOUT RELEVANT CLINICAL SIGNIFICANCE

Background:

Infliximab (Ifx) has proven effective in treating rheumatoid arthritis (RA) and spondyloarthropathies (SpA), although around 40% of cases fails, mainly due to immunogenicity. Formation of immunocomplexes between antibodies to Ifx (ATI) and Ifx can increase drug clearance, leading to treatment failure. Standard ELISA assays which are drug -sensitive are frequently used, being able to detect only free ATI. Interest in drug-tolerant assays to measure total ATI (free and complexed) is increasing.

Objectives:

To compare the development of ATI using both drug-tolerant and drug-sensitive assays at early stages of Ifx therapy. To analyse the relationship of ATI detected by both assays with the drop-out of treatment.

Methods:

This is a prospective observational study including 45 patients with RA and 61 with axial-SpA treated with standard doses of Ifx (3mg/kg and 5mg/kg, respectively) enrolled at Biological Therapy Unit of Hospital La Paz. Serum samples were obtained at 2, 6, 12 and 22 weeks (W) after Ifx initiation. The data about discontinuation for inefficacy was obtained from the database. ATI presence was evaluated by a drug-sensitive in-house two-site (bridging) ELISA (bELISA) and a drug-tolerant commercial ELISA assay (Immundiagnostik®,IDK). All comparisons were performed throughout non-parametrical test. In SpA group, due to the low number of ATI+ patients at W12 by bELISA the statistical analysis to compare both assays were not performed.

Results:

ATI detection by both assays at early stages (≤22 W) of treatment is shown in Table 1a. ATI were always detected earlier by IDK than bELISA and also in RA than in SpA patients probably reflecting the effect of lower Ifx doses. Three out of 106 (3%) vs 0 (0%) patients had ATI at W 2 and 62 (58%) vs 20 (18%) patients at W22, by IDK and bELISA, respectively.

Table 1.

Patient characteristics of all included patients

W2W6W12W22ARSpAARSpAARSpAARSpAa) ATI+ patients (n, %) at early stagesbELISA003(7%)010(22%)1(2%)13(29%)7(12%)IDK1(2%)2(3%)7(16%)2(3%)16(36%)16(26%)28(62%)34(56%)b) Patients who discontinued (n, %) Ifx therapy considering ATI status at early stagesbELISA+9(90%)*1(100%)*12(92%)4(57%)bELISA-23(66%) 22(37%)20(63%)19(35%)IDK+15(94%)*7(44%)24(86%)13(38%)IDK-17(59%)11(24%)13(77%)10(27%)

*p<0.05 comparing between ATI+ vs ATI- in each assay.

Once ATIs appeared, regardless both methods, they persisted throughout the follow-up, indicating that immunogenicity was not transient.

At W22, only 13/28 (46%) and 7/34 (21%) patients with ATI detected by IDK were also positive by bELISA in RA and SpA, respectively.

ATI levels by IDK were higher in ATI+ by bELISA than in ATI- patients at early stages: ATI levels by IDK at W12: 91[74-348] ng/ml ATI+ vs 21.7[15-59.5] ng/ml ATI- (p<0.01) and at W22: 132 [89-372] ng/ml ATI+ vs 23[13-66] ng/ml ATI- (p<0.001). However, only in 4% (2/45) patients with RA and in 13% (8/61) patients with SpA the detection by IDK was earlier than by bELISA at W12.

Free IFX in serum was not detected in bELISA ATI+ patients. In IDK ATI+ patients low circulating Ifx levels were present as compare to ATI- since W6 to the end of follow-up (p<0.01).

More ATI+ patients dropped out Ifx at W12 and W22 regardless de assay (Table 1.b), being statistically significant for both assays in patients with RA and only for bELISA in patients with SpA.

Conclusion:

ATI measured by a drug-tolerant assay are always detected earlier than ATI detected by bELISA, indicating that immunogenicity, at least with Ifx, is usually an early event. High levels of ATI by IDK are associated with an earlier detection by bELISA in case of RA patients. ATI detected only by drug tolerant assays are associated with low levels of circulating Ifx but not with a complete drug neutralization and may do not have clinical relevance compared to ATI detected by bELISA. Many patients have low levels of ATI which can only be detected by drug tolerant assays after long-term of follow-up.

The reasons why ATI levels rise rapidly in some patients while in others remain low are currently unknown but may be relevant if the clinical effect of immunogenicity is to be minimized.

Acknowledgements:

We are grateful to all the rheumatologists and nurses of the Daycare Department for Biologics and to the laboratory technicians of the Immunological Unit

Disclosure of Interests:

ANA MARTÍNEZ-FEITO: None declared, Borja Hernández-Breijo: None declared, Marta Novella-Navarro: None declared, Victoria Navarro-Compán Grant/research support from: AbbVie, Janssen, Lilly, Novartis, Pfizer, and UCB, Cristina Diego: None declared, Irene Monjo: None declared, Laura Nuño: None declared, Alejandro Villalva: None declared, Diana Peiteado: None declared, DORA PASCUAL-SALCEDO: None declared, Pilar Nozal: None declared, Alejandro Balsa Grant/research support from: Abbvie, Pfizer, Novartis, Roche.Amgen, Sandoz, Lilly, UCB. Personal fees and non- financial support from BMS. Grants, personal fees and non- financial support from Nordic., Chamaida Plasencia Grant/research support from: AbbVie, Lilly, Novartis, Pfizer,Sanofi, Biogen and UCB.

SAT0084 SERUM ADIPOKINES PROFILE IN PATIENTS WITH RHEUMATOID ARTHRITIS TREATED WITH TNF-INHIBITORS

Background:

In recent years, the relationship between obesity and autoimmune diseases has taken interest, since adipose tissue has been identified as an endocrine organ that secretes cytokines (adipokines), among which leptin stands out as a soluble pro-inflammatory mediator associated with the body mass index (BMI).

Objectives:

The main objectives of this study are: i) to analyse the influence of BMI on clinical response in Rheumatoid Arthritis (RA) patients who initiate TNF-inhibitor (TNFi) therapy; ii) to analyse the differences in the serum profile of adipokines (leptin and adiponectin) according to BMI and their association with response to treatment.

Methods:

Observational study of a prospective cohort of 73 RA patients who initiated biological treatment with TNFi from the Complex Therapy Unit (CTU) of our Hospital. Patients were classified according to their BMI in normal-weight (BMI<25) and overweight/obesity (O/O) (IMC≥25). Demographic, clinical and laboratory variables were collected at baseline and at 6 months. Our outcome measures were DAS28-VSG remission (DAS28<2.6) at 6 months after TNFi initiation. Serum leptin and adiponectin levels were measured by Enzyme-Linked Immuno Sorbent Assay (ELISA) at baseline and 6 months. A descriptive sample analysis comparing the characteristics of both patient subgroups was performed using Chi-square, T-test for independent samples and U-Mann Whitney. Likewise, a bivariate analysis was carried out by means of binary logistic regression to assess the probable association of the parameters studied with remission.

Results:

Of the 73 patients studied, 51% were classified in O/O group. The O/O patients presented higher levels of baseline CRP (16.69±6.16 vs 8.74±3.81, p=0.01). No statistically significant differences were observed in the remaining variables (sex, age at the beginning of the TNFi, disease duration, baseline DAS-28), as well as therapeutic variables (use of previous DMARDs and doses of methotrexate and/or steroids). Patients with overweight/obesity presented higher DAS28-ESR values at 6 months of treatment (3.59±1.14 vs 2.93±1.27, p=0.02) and achieved remission less frequently (18.9% vs 48.6%, p=0.007). Serum leptin levels were significantly higher in O/O patients, both baseline (29.39±21.50 vs 13.49±8.78, p<0.001) and 6 months (33.06±22.03 vs 14.77±9.50, p<0.001) after TNFi initiation. In addition, O/O patients were less likely to reach remission at 6 months than normal-weight patients. [OR= 4.04 IC95% (1.40-11.64); p=0.009]. Lower frequency of remission was associated to greater leptin levels at 6 months [OR=0.94 CI95% (0.90-098); p=0.012]. No differences in serum adiponectin were found between both subgroups of patients.

Conclusion:

In this RA patient cohort, overweight/obesity is associated with i) a reduced response to TNFi therapy and ii) a lower short-term remission rate. Within the adipokine profile, leptin seems to play a relevant role in the maintenance of pro-inflammatory activity with a negative influence on the response to TNFi therapy in O/O patients.

References:

[1] Versini M. et al. Autoimmun Rev. 2014; 13, 981-1000

[2] Toussirot E et al. Life Sci. 2015;140: 29-36.

Disclosure of Interests:

Marta Novella-Navarro: None declared, Borja Hernández-Breijo: None declared, Fernanda Genre: None declared, Leticia Lera-Gómez: None declared, Verónica Pulito-Cueto: None declared, Laura Nuño: None declared, Alejandro Villalba: None declared, Alejandro Balsa Grant/research support from: BMS, Roche, Consultant of: AbbVie, Gilead, Lilly, Pfizer, UCB, Sanofi, Sandoz, Speakers bureau: AbbVie, Lilly, Sanofi, Novartis, Pfizer, UCB, Roche, Nordic, Sandoz, Chamaida Plasencia: None declared

FRI0582 GM-CSF PRODUCED BY CD4+ T CELLS AS A MARKER OF CLINICAL REMISSION IN PATIENTS WITH RHEUMATOID ARTHRITIS TREATED WITH TNF INHIBITORS

Background:

According to the EULAR recommendations, the therapeutic target in patients with RA should be remission (REM). However, no more than 50% of the patients treated with TNF inhibitors (TNFi) attains this outcome. Previous investigations suggested the peripheral blood mononuclear cells (PBMC) as markers associated with the TNFi treatment success1,2. Granulocyte-monocyte colony-stimulating factor (GM-CSF) plays a relevant role in the pathogenesis of rheumatoid arthritis (RA) because it promotes the macrophage differentiation, survival and activation3.

Objectives:

To analyse the intracellular cytokine production by PBMC and its association with REM attainment after 6 months (m) of TNFi treatment in patients with RA.

Methods:

This was a prospective bi-center pilot study including 36 patients with RA. PBMC were isolated from patients at baseline and after 6m of treatment with TNFi and cryopreserved until studied. Intracellular cytokine production by PBMC was stimulated in the presence of 2µg/mL brefeldin as follow: monocytes were stimulated with 20ng/mL LPS during 4h; and simultaneously lymphocytes were stimulated with 50ng/mL phorbol 12-myristate 13-acetate (PMA) and 750ng/mL ionomycin during 4h at 37°C. To identify IL-10-producing B cells, PBMC were pre-incubated with 3µg/mL of CpG oligonucleotide during 20h at 37°C prior to stimulation in presence of 2µmol/L monensin. Intracellular cytokine production (TNFα, IL6, GM-CSF, IL10) by the different cell subsets (monocytes, CD4+and CD8+T cells, naïve and memory B cells) was analysed by flow-cytometry. Clinical activity at baseline and after 6m was assessed by DAS28. REM was defined as DAS28≤2.6 at 6m. The association between REM and the change in cytokine production (Δ, 6m-0m) by each PBMC subset was analysed through univariable and multivariable logistic regression models.

Results:

Seventy-eight percent of the patients were female. After 6m of TNFi treatment, 47% patients attained REM. Univariable analyses was performed to investigate the association between REM and the baseline variables. Male sex (OR: 12.6; 95% CI: 1.35-117.57; p=0.03) and having lower baseline DAS28 (OR: 0.4; 95% CI: 0.19-0.85; p=0.02) were independently associated with attaining REM after 6m of TNFi. In the multivariable analysis, only being male (OR: 19.7; 95% CI: 1.4-273.9; p=0.03) remained independently associated with REM after 6m of treatment. Therefore, further analyses were adjusted by sex. Decreased production of GM-CSF by CD4+T cells percentage was found after 6m of TNFi treatment in REM patients (0m: 6.07%; 6m: 3.87%; p=0.007) while no-REM patients did not show differences with the baseline (0m: 3.70%; 6m: 3.75%; p=0.9). The decrease was significantly associated with attaining REM (OR: 0.56; 95% CI: 0.33-0.95; p: 0.03). No significant association was found between any other analysed intracellular cytokine produced by the different PBMC subsets and REM.

Conclusion:

GM-CSF intracellular production by CD4+T cells was significantly decreased by TNFi treatment only in patients who attained REM. Therefore, our results suggest that GM-CSF production by CD4+T cells may be a useful marker of REM to TNFi in RA.

References:

[1] Sobrino C, et al. Ann Rheum Dis. 2019; 78 (S2): A1665.

[2] Hernández-Breijo B, et al. Ann Rheum Dis. 2019; 78 (S2): A711.

[3] Avci AB, et al. Clin Exp Rheumatol. 2016; 34 (S98), 39-44.

Figure. 1:

Association between the change in intracellular cytokine production (Δ, 6m-0m) by each PBMC subset and REM. Adjusted logistic regression analyses were performed for each cytokine.

Acknowledgments:

ISCIII (PI16/00474; PI16/01092)

Disclosure of Interests:

Borja Hernández-Breijo: None declared, Chamaida Plasencia: None declared, Carlota García-Hoz: None declared, Cristina Sobrino: None declared, Victoria Navarro-Compán Consultant of: Abbvie, Lilly, Novartis, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Lilly, Novartis, Pfizer, UCB, ANA MARTÍNEZ-FEITO: None declared, Israel Nieto-Gañán: None declared, Paloma Lapuente-Suanzes: None declared, Javier Bachiller-Corral: None declared, Gemma Bonilla: None declared, Cristina Pijoan Moratalla: None declared, Garbiñe Roy: None declared, Mónica Vázquez Díaz: None declared, Alejandro Balsa Grant/research support from: BMS, Roche, Consultant of: AbbVie, Gilead, Lilly, Pfizer, UCB, Sanofi, Sandoz, Speakers bureau: AbbVie, Lilly, Sanofi, Novartis, Pfizer, UCB, Roche, Nordic, Sandoz, Luisa María Villar: None declared, DORA PASCUAL-SALCEDO Grant/research support from: Pfizer, Novartis & Progenika, Speakers bureau: Pfizer, Merck, Novartis, Takeda, Menarini & Grifols, Eulalia Rodríguez-Martín: None declared

Standardization of the homogeneous mobility shift assay protocol for evaluation of anti-infliximab antibodies. Application of the method to Crohn's disease patients treated with infliximab

BACKGROUND

The availability of a quantitative method to measure anti-infliximab (IFX) antibodies (ATI) would facilitate the implementation of therapeutic drug monitoring in clinical decision-making. Our aim was to standardize the homogeneous mobility shift assay (HMSA) used in the measure of ATI levels.

METHODS

In this prospective longitudinal multicenter study, 50 IFX-treated Crohn's disease (CD) patients were followed up for 54weeks. During this period 360 human serum samples were analysed. Monomeric ATI levels were measured by a quantitative HMSA-method using an anti-IFX calibrator. IFX trough levels measured by ELISA were correlated with ATI levels.

RESULTS

Using HMSA and a pure anti-idiotypic monoclonal antibody specific for IFX (anti-IFX calibrator), we measured the levels of monomeric ATI generated in Crohn's disease patients treated with IFX. Anti-IFX calibrator allowed to quantify monomeric antibodies against IFX with a low limit of quantification (3nM). The threshold level of ATI in order to classify the immunogenicity of the patients was 10nM. We observed that 24% (12/50) of IFX-treated patients developed ATI (>10nM) during the observation period (54weeks). Serum concentration of ATI higher than 10nM dramatically increased the probability (OR=51.1; 95% CI: 20.4-128.0; p<0.0001) of presenting low levels of IFX (⩽1.5nM) in serum, as observed in some CD patients treated with standard doses of the drug.

CONCLUSIONS

The HMSA-method described here allows an accurate quantification of ATI concentration in international units (IU) and therefore it could be useful in the study of the relationship between ATI concentration, infliximab level and the clinical response to the drug.