Long-term efficacy of MAS825, a bispecific anti-IL1ß and IL-18 monoclonal antibody, in two patients with sJIA and recurrent episodes of MAS.

INTRODUCTION: Systemic juvenile idiopathic arthritis (sJIA), a multifaceted autoinflammatory disorder, can be complicated by life-threatening conditions such as macrophage activation syndrome (MAS) and interstitial lung disease (ILD). The management of these conditions presents a therapeutic challenge, underscoring the need for innovative treatment approaches. OBJECTIVES: to report the possible role of MAS825, a bispecific anti-IL1ß and IL-18 monoclonal antibody, in the treatment of multi-drug-resistant sJIA. METHODS: We report two patients affected by sJIA with severe and refractory MAS and high serum IL-18 levels, responding to dual blockade of IL-1ß and IL-18. RESULTS: The first patient is a 20-year-old man, presenting a severe MAS complicated by thrombotic microangiopathy, following SARS-CoV-2 infection. He was treated with MAS825, with quick improvement. Eighteen months later, the patient is still undergoing biweekly treatment with MAS825, associated with MTX, ciclosporin and low-dose glucocorticoids, maintaining good control over the systemic features of the disease.The second patient, a 10-year-old girl, presented a severe MAS case, complicated by posterior reversible encephalopathy syndrome (PRES), following an otomastoiditis. The MAS was not fully controlled despite treatment with IV high-dose glucocorticoids, anakinra and ciclosporin. She began biweekly MAS825, which led to a prompt amelioration of MAS parameters. After 10 months, the patient continues to receive MAS825 and is in complete remission. CONCLUSION: In light of the pivotal role of IL-1ß and IL-18 in sJIA, MAS and ILD, MAS825 might represent a possible valid and safe option in the treatment of drug-resistant sJIA, especially in the presence of high serum IL-18 levels.

Novel chemotype NLRP3 inhibitors that target the CRID3-binding pocket with high potency.

The NLRP3 inflammasome plays a central role in various human diseases. Despite significant interest, most clinical-grade NLRP3 inhibitors are derived from sulfonylurea inhibitor CRID3 (also called MCC950). Here, we describe a novel chemical class of NLRP3-inhibiting compounds (NIC) that exhibit potent and selective NLRP3 inflammasome inhibition in human monocytes and mouse macrophages. BRET assays demonstrate that they physically interact with NLRP3. Structural modeling further reveals they occupy the same binding site of CRID3 but in a critically different conformation. Furthermore, we show that NIC-11 and NIC-12 lack the off-target activity of CRID3 against the enzymatic activity of carbonic anhydrases I and II. NIC-12 selectively reduces circulating IL-1ß levels in the LPS-endotoxemia model in mice and inhibits NLRP3 inflammasome activation in CAPS patient monocytes and mouse macrophages with about tenfold increased potency compared with CRID3. Altogether, this study unveils a new chemical class of highly potent and selective NLRP3-targeted inhibitors with a well-defined molecular mechanism to complement existing CRID3-based NLRP3 inhibitors in pharmacological studies and serve as novel chemical leads for the development of NLRP3-targeted therapies.

HSP90ß controls NLRP3 autoactivation.

Gain-of-function mutations in NLRP3 are linked to cryopyrin-associated periodic syndromes (CAPS). Although NLRP3 autoinflammasome assembly triggers inflammatory cytokine release, its activation mechanisms are not fully understood. Our study used a functional genetic approach to identify regulators of NLRP3 inflammasome formation. We identified the HSP90ß-SGT1 chaperone complex as crucial for autoinflammasome activation in CAPS. A deficiency in HSP90ß, but not in HSP90α, impaired the formation of ASC specks without affecting the priming and expression of inflammasome components. Conversely, activating NLRP3 with stimuli such as nigericin or alum bypassed the need for SGT1 and HSP90ß, suggesting the existence of alternative inflammasome assembly pathways. The role of HSP90ß was further demonstrated in PBMCs derived from CAPS patients. In these samples, the pathological constitutive secretion of IL-1ß could be suppressed using a pharmacological inhibitor of HSP90ß. This finding underscores the potential of SGT1-HSP90ß modulation as a therapeutic strategy in CAPS while preserving NLRP3's physiological functions.

Pyrin Inflammasome Activation Defines Colchicine-Responsive SURF Patients from FMF and Other Recurrent Fevers.

Syndrome of undifferentiated recurrent fever (SURF) is characterized by recurrent fevers, a lack of confirmed molecular diagnosis, and a complete or partial response to colchicine. Despite the clinical similarities to familial Mediterranean fever (FMF), the underlying inflammatory mechanisms of SURF are not yet understood. We here analyzed the in vitro activation of the pyrin inflammasome in a cohort of SURF patients compared to FMF and PFAPA patients. Peripheral blood mononuclear cells (PBMC) were collected from SURF (both colchicine-treated and untreated), FMF, PFAPA patients, and healthy donors. PBMC were stimulated ex vivo with Clostridium difficile toxin A (TcdA) and a PKC inhibitor (UCN-01), in the presence or absence of colchicine. The assembly of the pyrin inflammasome was evaluated by measuring the presence of apoptosis-associated Speck-like protein containing caspase recruitment domain (ASC) specks in monocytes using flow cytometry. IL-1ß secretion was quantified using an ELISA assay. No differences in TcdA-induced activation of pyrin inflammasome were observed among FMF, PFAPA, and healthy donors. Untreated SURF patients showed a reduced response to TcdA, which was normalized after colchicine treatment. In contrast to FMF, SURF patients, similar to PFAPA patients and healthy donors, did not exhibit pyrin inflammasome activation in response to UCN-01-mediated pyrin dephosphorylation. These data demonstrate that in vitro functional analysis of pyrin inflammasome activation can differentiate SURF from FMF and PFAPA patients, suggesting the involvement of the pyrin inflammasome in the pathophysiology of SURF.