Long-term effects of combined B-cell immunomodulation with rituximab and belimumab in severe, refractory systemic lupus erythematosus: 2-year results.

BACKGROUND: Anti-CD20 B-cell depletion has not shown superior efficacy to standard immunosuppression in patients with systemic lupus erythematosus (SLE). Besides trial design, potential explanations are incomplete B-cell depletion in relation to substantial surges in B-cell-activating factor (BAFF). To improve B-cell targeting strategies, we conducted the first study in SLE patients aimed at investigating immunological effects and feasibility of combining rituximab (RTX; anti-CD20) and belimumab (BLM; anti-BAFF). METHODS: Reported is the long-term follow-up of a Phase 2 proof-of-concept study in 15 patients with SLE including 12 (80%) with lupus nephritis (LN). RESULTS: In 10/15 (67%) patients, a clinical response was observed by achievement of lupus low disease activity state, of which 8 (53%) continued treatment (BLM + ≤7.5 mg prednisolone) for the complete 2 years of follow-up. Five patients (33%) were referred to as 'non-responders' due to persistent LN, major flare or repetitive minor flares. Out of 12 LN patients, 9 (75%) showed a renal response including 8 (67%) complete renal responders. All anti-dsDNA+ patients converted to negative, and both anti-C1q and extractable nuclear antigen autoantibodies showed significant reductions. CD19+ B cells showed a median decrease from baseline of 97% at 24 weeks, with a persistent reduction of 84% up to 104 weeks. When comparing responders with non-responders, CD20+ B cells were depleted significantly less in non-responders and double-negative (DN) B cells repopulated significantly earlier. CONCLUSIONS: Combined B-cell targeted therapy with RTX and BLM prevented full B-cell repopulation including DN B cells, with concomitant specific reduction of SLE-relevant autoantibodies. The observed immunological and clinical benefits in a therapy-refractory SLE population prompt further studies on RTX + BLM.

The NET-effect of combining rituximab with belimumab in severe systemic lupus erythematosus.

OBJECTIVE: In systemic lupus erythematosus (SLE) patients, excessive formation of neutrophil extracellular traps (NETs) is observed and their degradation is impaired. In vitro, immune complexes (ICx) trigger NET formation while NET-derived DNA is a postulated autoantigen for anti-nuclear autoantibodies (ANAs), found in SLE. Based on these self-perpetuating mechanisms in SLE, this study investigates whether interfering with ICx formation using a combination of rituximab (RTX) and belimumab (BLM) could decrease NET formation and ameliorate disease. METHODS: A phase 2A, open-label, single arm proof-of-concept study was performed wherein 16 SLE patients with severe, refractory disease were treated with a combination of CD20-mediated B-cell depletion with rituximab and sustained inhibition of B-cell activating factor BlyS with belimumab. Besides safety, the study's endpoints were chosen to address the concept of autoantibodies in relation to excessive NET formation. RESULTS: We demonstrated a surge of BlyS levels upon RTX-mediated B-cell depletion which was abrogated by subsequent BLM treatment. As such, therapeutic intervention with RTX + BLM led to specific reductions in ANAs and regression of excessive NET formation. RTX + BLM appeared to be safe and achieved clinically significant responses: low lupus disease activity state was achieved in 10 patients, renal responses in 11 patients and concomitant immunosuppressive medication was tapered in 14 out of the 16 patients. CONCLUSIONS: This study provides novel insights into clinical beneficence of reducing excessive NET formation in SLE by therapeutic targeting ANA production with RTX + BLM. Altogether putting forward a new treatment concept that specifically ameliorates underlying SLE pathophysiology. TRIAL REGISTRATION: ClinicalTrials.gov NCT02284984.

Update on autoantibodies to modified proteins.

PURPOSE OF REVIEW: This article provides an update on the recent findings on autoantibodies to modified proteins in rheumatoid arthritis (RA). RECENT FINDINGS: In the past few years, the knowledge on the autoantibodies to citrullinated antigens has expanded considerably. More specifically, it is now clear that many different citrullinated protein antigens present in the synovial compartment can be recognized by anticitrullinated protein antibody (ACPA). This is most likely a consequence of the cross-reactivity the ACPA response displays to citrullinated proteins. It is now also clear that the isotype usage and the citrullinated epitope repertoire recognized by ACPA expands before the manifestation of full-blown RA and that this goes hand in hand with a rise in ACPA level. Next to ACPA, several other autoantibody systems directed against other posttranslationally modified proteins, such as proteins containing a homocitrulline residue resulting from protein carbamylation, have been identified. On the whole, the evolution of these autoantibody systems in time mimics the evolution of the ACPA response, indicating that the break of tolerance underlying different autoimmune responses present in RA occurs before disease onset, with a further maturation of these responses shortly before or concurrent with the manifestation of clinical symptoms. SUMMARY: Since the discovery of rheumatoid factor over 65 years ago, our knowledge on autoantibodies and their relevance for rheumatic disease has expanded enormously. Especially, the realization that next to rheumatoid factor, also other autoantibodies recognizing posttranslationally modified proteins are present in RA patients has contributed significantly to the understanding of disease. In the past few years, several new autoantibody systems to differentially modified proteins have been identified and their relation to clinical outcome has been scrutinized. Here, we provide an update on the recent developments in our knowledge on the presence and consequences of autoantibodies to modified proteins in RA.

Fine-mapping the human leukocyte antigen locus in rheumatoid arthritis and other rheumatic diseases: identifying causal amino acid variants?

PURPOSE OF REVIEW: To provide an update on and the context of the recent findings obtained with novel statistical methods on the association of the human leukocyte antigen (HLA) locus with rheumatic diseases. RECENT FINDINGS: Novel single nucleotide polymorphism fine-mapping data obtained for the HLA locus have indicated the strongest association with amino acid positions 11 and 13 of HLA-DRB1 molecule for several rheumatic diseases. On the basis of these data, a dominant role for position 11/13 in driving the association with these diseases is proposed and the identification of causal variants in the HLA region in relation to disease susceptibility implicated. SUMMARY: The HLA class II locus is the most important risk factor for several rheumatic diseases. Recently, new statistical approaches have identified previously unrecognized amino acid positions in the HLA-DR molecule that associate with anticitrullinated protein antibody-negative and anticitrullinated protein antibody-positive rheumatoid arthritis. Likewise, similar findings have been made for other rheumatic conditions such as giant-cell arteritis and systemic lupus erythematosus. Interestingly, all these studies point toward an association with the same amino acid positions: amino acid positions 11 and 13 of the HLA-DR ß chain. As both these positions influence peptide binding by HLA-DR and have been implicated in antigen presentation, the novel fine-mapping approach is proposed to map causal variants in the HLA region relevant to rheumatoid arthritis and several rheumatic diseases. If these interpretations are correct, they would direct the biological research aiming to address the explanation for the HLA-disease association. Here, we provide an overview of the recent findings and evidence from literature that, although relevant new insights have been obtained on HLA-disease associations, the interpretation of the biological role of these amino acids as causal variants explaining that such associations should be taken with caution.