The class I MHC allele HLA-B27 is highly associated with the human spondyloarthropathies, but the basis for this association remains poorly understood. Transgenic rats with high expression of HLA-B27 develop a multisystem inflammatory disease that includes arthritis and colitis. To investigate whether CD8αβ T cells are needed in this disease, we depleted these cells in B27 transgenic rats before the onset of disease by adult thymectomy plus short-term anti-CD8α mAb treatment. This treatment induced profound, sustained depletion of CD8αβ T cells, but failed to suppress either colitis or arthritis. To address the role of CD8α+β− cells, we studied four additional groups of B27 transgenic rats treated with: 1) continuous anti-CD8α mAb, 2) continuous isotype-matched control mAb, 3) the thymectomy/pulse anti-CD8α regimen, or 4) no treatment. Arthritis occurred in ∼40% of each group, but was most significantly reduced in severity in the anti-CD8α-treated group. In addition to CD8αβ T cells, two sizeable CD8α+β− non-T cell populations were also reduced by the anti-CD8α treatment: 1) NK cells, and 2) a CD4+CD8+CD11b/c+CD161a+CD172a+ monocyte population that became expanded in diseased B27 transgenic rats. These data indicate that HLA-B27-retricted CD8+ T cells are unlikely to serve as effector cells in the transgenic rat model of HLA-B27-associated disease, in opposition to a commonly invoked hypothesis concerning the role of B27 in the spondyloarthropathies. The data also suggest that one or more populations of CD8α+β− non-T cells may play a role in the arthritis that occurs in these rats.

BackgroundThis double-blind, active-controlled, randomized, multinational study evaluated the efficacy, safety, pharmacokinetics (PK), and immunogenicity of PF-06438179/GP1111 (IxifiTM/Zessly®), an infliximab biosimilar, vs infliximab (Remicade®) reference product sourced from the European Union (infliximab-EU) in biologic-naïve patients with moderate to severe active rheumatoid arthritis (RA) despite methotrexate therapy. This paper reports results from the initial 30-week treatment period.MethodsPatients (N = 650) were stratified by geographic region and randomized 1:1 to PF-06438179/GP1111 or infliximab-EU (3 mg/kg intravenous at weeks 0, 2, and 6, then every 8 weeks). Dose escalation to 5 mg/kg was allowed starting at week 14 for patients with inadequate RA response. The primary endpoint was American College of Rheumatology criteria for ≥ 20% clinical improvement (ACR20) response at week 14. Therapeutic equivalence was declared if the two-sided 95% CI for the treatment difference was within the symmetric equivalence margin of ± 13.5%. Statistical analysis was also performed with a two-sided 90% CI using an asymmetric equivalence margin (− 12.0%, 15.0%).ResultsPatients (80.3% female; 79.4% seropositive) had a mean RA duration of 6.9 years, and mean baseline Disease Activity Score in 28 joints, four components based on C-reactive protein was 6.0 in both arms. Week 14 ACR20 in the intention-to-treat population was 62.7% for PF-06438179/GP1111 and 64.1% for infliximab-EU. Week 14 ACR20 using nonresponder imputation was 61.1% for PF-06438179/GP1111 and 63.5% for infliximab-EU, and the 95% (− 9.92%, 5.11%) and 90% (− 8.75%, 4.02%) CIs for the treatment difference (− 2.39%) were entirely contained within the prespecified symmetric and asymmetric equivalence margins, respectively. No differences were observed between arms for secondary efficacy endpoints. Overall postdose antidrug antibody (ADA) rates through week 30 were 48.6% and 51.2% for PF-06438179/GP1111 and infliximab-EU, respectively. Efficacy and immunogenicity were similar between treatments for patients with dose escalation (at or after week 14), as well as between treatments for patients without dose escalation. Safety profiles of PF-06438179/GP1111 and infliximab-EU were similar, with no clinically meaningful differences observed between arms, including after ADA development. Serum drug concentrations were similar between arms at each time point during the initial 30-week treatment period.ConclusionPF-06438179/GP1111 and infliximab-EU demonstrated similar efficacy, safety, immunogenicity, and PK with or without dose escalation in patients with moderate to severe active RA on background methotrexate.Trial registrationClinicalTrials.gov, NCT02222493. Registered on 21 August 2014.EudraCT, 2013-004148-49. Registered on 14 July 2014.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1646-4) contains supplementary material, which is available to authorized users.

The spondyloarthropathy-like disease in rats is specific for HLA-B27 but does not require Cys67. Arthritis but not colitis is particularly sensitive to B27 peptide-binding specificity. Genetic background exerts a strong influence, but some phenotypic differences exist between permissive strains that do not influence disease susceptibility. The data favor a role for B27 peptide presentation in arthritis, but other mechanisms to explain the role of B27 have not been excluded.

CT.gov identifier NCT01844804.

ObjectiveTo investigate the efficacy, safety and immunogenicity of PF-06438179/GP1111 (PF-SZ-IFX) compared with European reference infliximab (Remicade®; ref-IFX) in patients with moderate-to-severe, active rheumatoid arthritis after continued long-term use of PF-SZ-IFX, and in patients who were switched from ref-IFX to PF-SZ-IFX.MethodsREFLECTIONS B537-02 was a double-blind, active-controlled, multinational study in which patients (N=650) were initially randomised to PF-SZ-IFX or ref-IFX for 30 weeks (treatment period [TP] 1). During weeks 30–54 (TP2), the PF-SZ-IFX group (n=280) continued treatment with PF-SZ-IFX (PF-SZ-IFX/PF-SZ-IFX) and patients in the ref-IFX group (n=286) were rerandomised (1:1) to continue ref-IFX (ref-IFX/ref-IFX) (n=143) or switch to PF-SZ-IFX (ref-IFX/PF-SZ-IFX) (n=143) for a further 24 weeks. Efficacy, safety, immunogenicity and pharmacokinetics were evaluated.ResultsDuring TP2, patients in all three treatment groups continued to maintain comparable treatment response. At week 54, the American College of Rheumatology (ACR20) response rates were 71.1% (PF-SZ-IFX/PF-SZ-IFX), 64.3% (ref-IFX/ref-IFX) and 70.6% (ref-IFX/PF-SZ-IFX). Observations for other endpoints, including ACR50/70, Disease Activity Score in 28 Joints Based on High-Sensitivity C Reactive Protein(DAS28-CRP) remission, and mean change in DAS28-CRP and Health Assessment Questionnaire-Disability Index, were also comparable. Treatment-emergent adverse events were reported in 36.8% (PF-SZ-IFX/PF-SZ-IFX), 33.6% (ref-IFX/ref-IFX) and 37.8% (ref-IFX/PF-SZ-IFX) of patients; there were no clinically meaningful differences in the safety profiles between groups. The percentage of patients who were antidrug antibody-positive was generally stable through the treatment period and comparable overall between the PF-SZ-IFX/PF-SZ-IFX (52.1%; neutralising: 80.8%), ref-IFX/ref-IFX (60.1%; neutralising: 84.9%) and ref-IFX/PF-SZ-IFX (58.0%; neutralising 78.3%) groups.ConclusionsThe similar efficacy, safety and immunogenicity of PF-SZ-IFX compared with ref-IFX were maintained for up to 54 weeks and were not affected by blinded treatment switch from ref-IFX to PF-SZ-IFX at week 30.Trial registration numberNCT02222493.