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Background Calcium release-activated calcium (CRAC) channel inhibitors stabilize the pulmonary endothelium and block proinflammatory cytokine release, potentially mitigating respiratory complications observed in patients with COVID-19. This study aimed to investigate the safety and efficacy of Auxora, a novel, intravenously administered CRAC channel inhibitor, in adults with severe or critical COVID-19 pneumonia. Methods A randomized, controlled, open-label study of Auxora was conducted in adults with severe or critical COVID-19 pneumonia. Patients were randomized 2:1 to receive three doses of once-daily Auxora versus standard of care (SOC) alone. The primary objective was to assess the safety and tolerability of Auxora. Following FDA guidance, study enrollment was halted early to allow for transition to a randomized, blinded, placebo-controlled study. Results In total, 17 patients with severe and three with critical COVID-19 pneumonia were randomized to Auxora and nine with severe and one with critical COVID-19 pneumonia to SOC. Similar proportions of patients receiving Auxora and SOC experienced ≥ 1 adverse event (75% versus 80%, respectively). Fewer patients receiving Auxora experienced serious adverse events versus SOC (30% versus 50%, respectively). Two patients (10%) receiving Auxora and two (20%) receiving SOC died during the 30 days after randomization. Among patients with severe COVID-19 pneumonia, the median time to recovery with Auxora was 5 days versus 12 days with SOC; the recovery rate ratio was 1.87 (95% CI, 0.72, 4.89). Invasive mechanical ventilation was needed in 18% of patients with severe COVID-19 pneumonia receiving Auxora versus 50% receiving SOC (absolute risk reduction = 32%; 95% CI, − 0.07, 0.71). Outcomes measured by an 8-point ordinal scale were significantly improved for patients receiving Auxora, especially for patients with a baseline PaO 2 /FiO 2  = 101–200. Conclusions Auxora demonstrated a favorable safety profile in patients with severe or critical COVID-19 pneumonia and improved outcomes in patients with severe COVID-19 pneumonia. These results, however, are limited by the open-label study design and small patient population resulting from the early cessation of enrollment in response to regulatory guidance. The impact of Auxora on respiratory complications in patients with severe COVID-19 pneumonia will be further assessed in a planned randomized, blinded, placebo-controlled study. Trial registration ClinicalTrials.gov, NCT04345614 . Submitted on 7 April 2020. Graphical abstract

Background Calcium release-activated calcium (CRAC) channel inhibitors block proinflammatory cytokine release, preserve endothelial integrity and may effectively treat patients with severe COVID-19 pneumonia. Methods CARDEA was a phase 2, randomized, double-blind, placebo-controlled trial evaluating the addition of Auxora, a CRAC channel inhibitor, to corticosteroids and standard of care in adults with severe COVID-19 pneumonia. Eligible patients were adults with ≥ 1 symptom consistent with COVID-19 infection, a diagnosis of COVID-19 confirmed by laboratory testing using polymerase chain reaction or other assay, and pneumonia documented by chest imaging. Patients were also required to be receiving oxygen therapy using either a high flow or low flow nasal cannula at the time of enrolment and have at the time of enrollment a baseline imputed PaO 2 /FiO 2 ratio > 75 and ≤ 300. The PaO 2 /FiO 2 was imputed from a SpO 2 /FiO 2 determine by pulse oximetry using a non-linear equation. Patients could not be receiving either non-invasive or invasive mechanical ventilation at the time of enrolment. The primary endpoint was time to recovery through Day 60, with secondary endpoints of all-cause mortality at Day 60 and Day 30. Due to declining rates of COVID-19 hospitalizations and utilization of standard of care medications prohibited by regulatory guidance, the trial was stopped early. Results The pre-specified efficacy set consisted of the 261 patients with a baseline imputed PaO 2 /FiO 2 ≤ 200 with 130 and 131 in the Auxora and placebo groups, respectively. Time to recovery was 7 vs. 10 days ( P  = 0.0979) for patients who received Auxora vs. placebo, respectively. The all-cause mortality rate at Day 60 was 13.8% with Auxora vs. 20.6% with placebo ( P  = 0.1449); Day 30 all-cause mortality was 7.7% and 17.6%, respectively ( P  = 0.0165). Similar trends were noted in all randomized patients, patients on high flow nasal cannula at baseline or those with a baseline imputed PaO 2 /FiO 2  ≤ 100. Serious adverse events (SAEs) were less frequent in patients treated with Auxora vs. placebo and occurred in 34 patients (24.1%) receiving Auxora and 49 (35.0%) receiving placebo (P  = 0.0616). The most common SAEs were respiratory failure, acute respiratory distress syndrome, and pneumonia. Conclusions Auxora was safe and well tolerated with strong signals in both time to recovery and all-cause mortality through Day 60 in patients with severe COVID-19 pneumonia. Further studies of Auxora in patients with severe COVID-19 pneumonia are warranted. Trial registration NCT04345614.

For efficient development of an immune response, T lymphocytes require long-lasting calcium influx through calcium release-activated calcium (CRAC) channels and the formation of a stable immunological synapse (IS) with the antigen-presenting cell (APC). Recent RNAi screens have identified Stim and Orai in Drosophila cells, and their corresponding mammalian homologs STIM1 and Orai1 in T cells, as essential for CRAC channel activation. Here, we show that STIM1 and Orai1 are recruited to the immunological synapse between primary human T cells and autologous dendritic cells. Both STIM1 and Orai1 accumulated in the area of contact between either resting or super-antigen (SEB)-pretreated T cells and SEB-pulsed dendritic cells, where they were colocalized with T cell receptor (TCR) and costimulatory molecules. In addition, imaging of intracellular calcium signaling in T cells loaded with EGTA revealed significantly higher Ca²⁺ concentration near the interface, indicating Ca²⁺ influx localized at the T cell/dendritic cell contact area. Expression of a dominant-negative Orai1 mutant blocked T cell Ca²⁺ signaling but did not interfere with the initial accumulation of STIM1, Orai1, and CD3 in the contact zone. In activated T cell blasts, mRNA expression for endogenous STIM1 and all three human homologs of Orai was up-regulated, accompanied by a marked increase in Ca²⁺ influx through CRAC channels. These results imply a positive feedback loop in which an initial TCR signal favors up-regulation of STIM1 and Orai proteins that would augment Ca²⁺ signaling during subsequent antigen encounter.

As the sole Ca 2+ entry mechanism in a variety of non-excitable cells, store-operated calcium (SOC) influx is important in Ca 2+ signalling and many other cellular processes 1 , 2 , 3 . A calcium-release-activated calcium (CRAC) channel in T lymphocytes is the best-characterized SOC influx channel 4 , 5 , 6 and is essential to the immune response, sustained activity of CRAC channels being required for gene expression and proliferation 7 , 8 , 9 , 10 . The molecular identity and the gating mechanism of SOC and CRAC channels have remained elusive. Previously we identified Stim and the mammalian homologue STIM1 as essential components of CRAC channel activation in Drosophila S2 cells and human T lymphocytes 11 . Here we show that the expression of EF-hand mutants of Stim or STIM1 activates CRAC channels constitutively without changing Ca 2+ store content. By immunofluorescence, EM localization and surface biotinylation we show that STIM1 migrates from endoplasmic-reticulum-like sites to the plasma membrane upon depletion of the Ca 2+ store. We propose that STIM1 functions as the missing link between Ca 2+ store depletion and SOC influx, serving as a Ca 2+ sensor that translocates upon store depletion to the plasma membrane to activate CRAC channels.

Inflammatory bowel disease (IBD) is characterized by dysregulated intestinal immune responses. Using mass cytometry (CyTOF) to analyze the immune cell composition in the lamina propria (LP) of patients with ulcerative colitis (UC) and Crohn's disease (CD), we observed an enrichment of CD4 + effector T cells producing IL‐17A and TNF, CD8 + T cells producing IFNγ, T regulatory (Treg) cells, and innate lymphoid cells (ILC). The function of these immune cells is regulated by store‐operated Ca 2+ entry (SOCE), which results from the opening of Ca 2+ release‐activated Ca 2+ (CRAC) channels formed by ORAI and STIM proteins. We observed that the pharmacologic inhibition of SOCE attenuated the production of proinflammatory cytokines including IL‐2, IL‐4, IL‐6, IL‐17A, TNF, and IFNγ by human colonic T cells and ILCs, reduced the production of IL‐6 by B cells and the production of IFNγ by myeloid cells, but had no effect on the viability, differentiation, and function of intestinal epithelial cells. T cell‐specific deletion of CRAC channel genes in mice showed that Orai1 , Stim1 , and Stim2 ‐deficient T cells have quantitatively distinct defects in SOCE, which correlate with gradually more pronounced impairment of cytokine production by Th1 and Th17 cells and the severity of IBD. Moreover, the pharmacologic inhibition of SOCE with a selective CRAC channel inhibitor attenuated IBD severity and colitogenic T cell function in mice. Our data indicate that SOCE inhibition may be a suitable new approach for the treatment of IBD. Synopsis The immune cell composition, signaling cascades, and cytokine networks controlling inflammation in therapy‐refractory inflammatory bowel diseases (IBD) remain incompletely understood. The colon lamina propria (LP) of ulcerative colitis (UC) and Crohn's disease (CD) patients is enriched with CD4 + and CD8 + T cells, IL‐17‐producing innate immune cells (ILC) and Treg cells. Pharmacological inhibition of store‐operated Ca 2+ Entry (SOCE) inhibits the production of proinflammatory cytokines and certain activation markers by human LP T cells, B cells, ILCs and myeloid cells. Inhibition of SOCE does not impair the differentiation and function of human or mouse intestinal epithelial cells in colonic organoid cultures. Pharmacologic inhibition of SOCE or T cell‐specific deletion of the SOCE genes Orai1 and Stim1 in T cells ameliorates intestinal inflammation in mouse models of colitis. SOCE is an important regulator of intestinal immune cell function and a potential drug target for the treatment of IBD. Graphical Abstract The immune cell composition, signaling cascades, and cytokine networks controlling inflammation in therapy‐refractory inflammatory bowel diseases (IBD) remain incompletely understood.

As the sole Ca entry mechanism in a variety of non-excitable cells, store-operated calcium (SOC) influx is important in Ca signalling and many other cellular processes. A calcium-release-activated calcium (CRAC) channel in T lymphocytes is the best-characterized SOC influx channel and is essential to the immune response, sustained activity of CRAC channels being required for gene expression and proliferation. The molecular identity and the gating mechanism of SOC and CRAC channels have remained elusive. Previously we identified Stim and the mammalian homologue STIM1 as essential components of CRAC channel activation in Drosophila S2 cells and human T lymphocytes. Here we show that the expression of EF-hand mutants of Stim or STIM1 activates CRAC channels constitutively without changing Ca store content. By immunofluorescence, EM localization and surface biotinylation we show that STIM1 migrates from endoplasmic-reticulum-like sites to the plasma membrane upon depletion of the Ca store. We propose that STIM1 functions as the missing link between Ca store depletion and SOC influx, serving as a Ca sensor that translocates upon store depletion to the plasma membrane to activate CRAC channels.

Recent studies by our group and others demonstrated a required and conserved role of Stim in store-operated $Ca^{2+}$ influx and $Ca^{2+}$ release-activated $Ca^{2+}$ (CRAC) channel activity. By using an unbiased genome-wide RNA interference screen in Drosophila 52 cells, we now identify 75 hits that strongly inhibited $Ca^{2+}$ influx upon store emptying by thapsigargin. Among these hits are 11 predicted transmembrane proteins, including Stim, and one, olf186-F, that upon RNA interference-mediated knockdown exhibited a profound reduction of thapsigargin-evoked $Ca^{2+}$ entry and CRAC current, and upon overexpression a 3-fold augmentation of CRAC current. CRAC currents were further increased to 8-fold higher than control and developed more rapidly when olf186-F was cotransfected with Stim. olf186-F is a member of a highly conserved family of four-transmembrane spanning proteins with homologs from Caenorhabditis elegans to human. The endoplasmic reticulum (ER) $Ca^{2+}$ pump sarco-/ER calcium ATPase (SERCA) and the single transmembrane-soluble N-ethylmaleimide-sensitive (NSF) attachment receptor (SNARE) protein Syntaxin5 also were required for CRAC channel activity, consistent with a signaling pathway in which Stim senses $Ca^{2+}$ depletion within the ER, translocates to the plasma membrane, and interacts with olf186-F to trigger CRAC channel activity.

Patients with recurrent acute pancreatitis (RAP) are at significant risk of developing early chronic pancreatitis (CP), which progresses into irreversible, end-stage CP with severe symptoms. There is no specific therapy in RAP or in early CP that may hinder disease progression. The pathogenesis of CP is complex and involves interactions among multiple cell types, including pancreatic acinar, ductal, and stellate cells (PSC). Therefore, it is pivotal to identify common pathogenic pathways in these cells that could be targeted pharmacologically. The Orai1-mediated store-operated Ca 2+ entry (SOCE) is a ubiquitous signaling mechanism that may become overactivated in pathological states resulting in intracellular Ca 2+ overload. In this study, we used ex vivo and in vivo preclinical disease models to demonstrate that Orai1 inhibition prevents progression of RAP and early CP. The selective Orai1 inhibitor CM5480 restored the expression of SOCE-associated regulatory factor in acinar cells, prevented uncontrolled Ca 2+ elevation, protected acinar and ductal functions, mitigated immune cell infiltration, and diminished PSC activation, proliferation, and migration. We suggest that the overactivation of Orai1 is a crucial pathogenetic event in the progression of early CP and that inhibition of Orai1 could prevent the development of end-stage CP.

Recent studies by our group and others demonstrated a required and conserved role of Stim in store-operated Ca 2+ influx and Ca 2+ release-activated Ca 2+ (CRAC) channel activity. By using an unbiased genome-wide RNA interference screen in Drosophila S2 cells, we now identify 75 hits that strongly inhibited Ca 2+ influx upon store emptying by thapsigargin. Among these hits are 11 predicted transmembrane proteins, including Stim , and one, olf186-F , that upon RNA interference-mediated knockdown exhibited a profound reduction of thapsigargin-evoked Ca 2+ entry and CRAC current, and upon overexpression a 3-fold augmentation of CRAC current. CRAC currents were further increased to 8-fold higher than control and developed more rapidly when olf186-F was cotransfected with Stim . olf186-F is a member of a highly conserved family of four-transmembrane spanning proteins with homologs from Caenorhabditis elegans to human. The endoplasmic reticulum (ER) Ca 2+ pump sarco-/ER calcium ATPase (SERCA) and the single transmembrane-soluble N -ethylmaleimide-sensitive (NSF) attachment receptor (SNARE) protein Syntaxin5 also were required for CRAC channel activity, consistent with a signaling pathway in which Stim senses Ca 2+ depletion within the ER, translocates to the plasma membrane, and interacts with olf186-F to trigger CRAC channel activity. capacitative calcium entry (CCE) genome-wide screen CRAC channel RNA interference store-operated calcium (SOC) influx

Ca -dependent repair of plasma membrane breaches is essential for animal cell viability. An initial passive influx of extracellular Ca triggers the formation of a protein plug that rapidly seals breaches. However, the mechanism of extracellular Ca requirement for subsequent repair remains undefined. EHD2 protein stabilizes the plasma membrane caveolae, which sustain membrane repair, and maintains high surface levels of the caveolae-resident Ca channel Orai1. We establish the requirement of both Orai1 and EHD2 for repair of plasma membrane lesions induced by mechanical injury or by a model bacterial pore-forming toxin. We demonstrate rapid EHD2 recruitment and Orai1-mediated Ca entry at plasma membrane sites of localized mechanical stimulus, the latter requiring EHD2 and CAV1. EHD2 and Orai1 are necessary for mechanosensitive YAP/TAZ-TEAD activation and positive feedback for CAV1 expression that promotes membrane repair. Our studies establish EHD2 and Orai1 as novel components of mammalian plasma membrane repair and mechanoadaptation.