Blocking T cell co-stimulation in primary Sjögren's syndrome:rationale, clinical efficacy and modulation of peripheral and salivary gland biomarkers

There is accumulating evidence that patients with primary Sjögren's syndrome (pSS) display aberrant CD4+ T cell responses, both in the peripheral compartment and in the inflamed salivary glands. CD4+ T cell abnormalities are also critically associated with B cell hyper activation, one of the hallmarks of disease, which is linked with disease severity and evolution to lymphoma. T cell activation and the cross-talk between T and B cells are tightly regulated by the balance between co-stimulatory pathways, such as the interactions between CD80/CD86:CD28, CD40:CD40L and ICOS:ICOSL, and co-inhibitory signals, including the immunoregulatory CTLA-4 protein. Evidence from patients with pSS as well as data from animal models of the disease suggests that these pathways play a critical role in pSS pathogenesis and their targeting could be exploited for therapeutic purposes. In this review, we first summarise the evidence implicating aberrant T cell co-stimulation and co-inhibition in driving the disease before focusing on the results of recent randomised controlled trials (RCTs) with compounds able to block T cell co-stimulation and enhance T cell co-inhibition. Despite a clear biological effect on downstream B cell activation has been observed in patients treated with CTLA-4-Ig (abatacept) and with monoclonal antibodies targeting CD40 and ICOSL, the clinical efficacy of this approach has so far yielded mixed results; while the anti-CD40 monoclonal antibody iscalimab showed significant improvement in systemic disease activity compared to placebo, two large RCTs with abatacept and a phase IIa RCT with an anti-ICOSL monoclonal antibody (prezalumab) failed to reach their primary endpoints. Although the discrepancies between biological and clinical efficacy of targeting T cell co-stimulation on pSS remain unresolved, several factors including drug bioavailability and receptor occupancy, patient stratification based on T-cell related biomarkers and the choice of study outcome are likely to play an important role and form the basis for further work towards the quest for a disease-modifying biologic therapy in pSS

Blocking T cell co-stimulation in primary Sjögren's syndrome:rationale, clinical efficacy and modulation of peripheral and salivary gland biomarkers

There is accumulating evidence that patients with primary Sjögren's syndrome (pSS) display aberrant CD4+ T cell responses, both in the peripheral compartment and in the inflamed salivary glands. CD4+ T cell abnormalities are also critically associated with B cell hyper activation, one of the hallmarks of disease, which is linked with disease severity and evolution to lymphoma. T cell activation and the cross-talk between T and B cells are tightly regulated by the balance between co-stimulatory pathways, such as the interactions between CD80/CD86:CD28, CD40:CD40L and ICOS:ICOSL, and co-inhibitory signals, including the immunoregulatory CTLA-4 protein. Evidence from patients with pSS as well as data from animal models of the disease suggests that these pathways play a critical role in pSS pathogenesis and their targeting could be exploited for therapeutic purposes. In this review, we first summarise the evidence implicating aberrant T cell co-stimulation and co-inhibition in driving the disease before focusing on the results of recent randomised controlled trials (RCTs) with compounds able to block T cell co-stimulation and enhance T cell co-inhibition. Despite a clear biological effect on downstream B cell activation has been observed in patients treated with CTLA-4-Ig (abatacept) and with monoclonal antibodies targeting CD40 and ICOSL, the clinical efficacy of this approach has so far yielded mixed results; while the anti-CD40 monoclonal antibody iscalimab showed significant improvement in systemic disease activity compared to placebo, two large RCTs with abatacept and a phase IIa RCT with an anti-ICOSL monoclonal antibody (prezalumab) failed to reach their primary endpoints. Although the discrepancies between biological and clinical efficacy of targeting T cell co-stimulation on pSS remain unresolved, several factors including drug bioavailability and receptor occupancy, patient stratification based on T-cell related biomarkers and the choice of study outcome are likely to play an important role and form the basis for further work towards the quest for a disease-modifying biologic therapy in pSS

Checkpoint inhibition-induced sicca:a type II interferonopathy?

The advent of immune checkpoint inhibitor (ICI) therapy for treatment of cancers is unfortunately coupled with a broad panoply of side effects, related to non-specific activation of the immune system. One such side effect is the development of sicca complaints. This culminates in a proportion of patients who, according to the ACR-EULAR 2016 criteria, can be classified as suffering from the autoimmune disease primary Sjögren's syndrome (pSS). Although salivary gland (SG) loss of function is often seen after ICI therapy, the similarities with 'classical' pSS patients would appear to end there. Despite the presence of focal lymphocytic sialadenitis typical for SS in salivary gland biopsies from patients receiving ICI therapy, the nature of the immune infiltration (foci) following ICI use (T-cell dominated) is starkly different to that in pSS (B-cell dominated). The SG parenchyma post-ICI use does not present with germinal centres, lymphoepithelial lesions or IgG plasma cells, which are frequently found in the SG in pSS. Here we review the functional deterioration of SGs following ICI use, the SG parenchyma phenotype associated with this, and ultrasound abnormalities. We conclude by suggesting that ICI-induced SG dysfunction may represent a new interferonopathy, driven by IFNγ, and that this 'pSS' patient cohort may require a different management than classical pSS patients

Checkpoint inhibition-induced sicca:a type II interferonopathy?

The advent of immune checkpoint inhibitor (ICI) therapy for treatment of cancers is unfortunately coupled with a broad panoply of side effects, related to non-specific activation of the immune system. One such side effect is the development of sicca complaints. This culminates in a proportion of patients who, according to the ACR-EULAR 2016 criteria, can be classified as suffering from the autoimmune disease primary Sjögren's syndrome (pSS). Although salivary gland (SG) loss of function is often seen after ICI therapy, the similarities with 'classical' pSS patients would appear to end there. Despite the presence of focal lymphocytic sialadenitis typical for SS in salivary gland biopsies from patients receiving ICI therapy, the nature of the immune infiltration (foci) following ICI use (T-cell dominated) is starkly different to that in pSS (B-cell dominated). The SG parenchyma post-ICI use does not present with germinal centres, lymphoepithelial lesions or IgG plasma cells, which are frequently found in the SG in pSS. Here we review the functional deterioration of SGs following ICI use, the SG parenchyma phenotype associated with this, and ultrasound abnormalities. We conclude by suggesting that ICI-induced SG dysfunction may represent a new interferonopathy, driven by IFNγ, and that this 'pSS' patient cohort may require a different management than classical pSS patients