In-vitro assessment of JAK inhibitors as precision therapeutics for interferon-driven signaling: A perspective for Indian systemic lupus erythematosus patients

Introduction: Systemic lupus erythematosus (SLE) is a clinically and molecularly heterogeneous autoimmune disease in which aberrant activation of the interferon (IFN) signaling pathway plays a central role in disease pathogenesis. Type I IFN–driven activation of the JAK–STAT pathway results in sustained expression of interferon-stimulated genes (ISGs), contributing to immune dysregulation and tissue damage. Several Janus kinase (JAK) inhibitors, including tofacitinib, baricitinib, and upadacitinib, are approved globally by regulatory agencies such as the United States Food and Drug Administration (US FDA) and the European Medicines Agency for multiple autoimmune diseases. These agents are also approved in India for selected inflammatory indications. However, JAK inhibitors are not yet specifically approved for the treatment of SLE, and their functional efficacy in modulating IFN signaling in SLE patients remains incompletely understood. This study aimed to evaluate the in vitro efficacy of JAK inhibitors as a potential precision medicine approach by assessing their ability to suppress IFN-induced signaling in immune cells derived from patients with SLE Methods: Peripheral blood samples were obtained from clinically diagnosed SLE patients following informed consent. Monocytes were identified using a standardized flow cytometry gating strategy. Cells were stimulated with interferon-α to activate downstream JAK–STAT signaling. To assess pathway inhibition, cells were treated with the JAK inhibitors tofacitinib and baricitinib. IFN signaling activity was quantified by measuring phosphorylation of STAT1 (pSTAT1) using intracellular flow cytometry. Results: Interferon-α stimulation significantly increased pSTAT1 expression in monocytes from SLE patients compared with controls, further confirming hyperactivation of the IFN–JAK–STAT signaling pathway. Treatment with JAK inhibitors resulted in a significant reduction in IFN-induced STAT1 phosphorylation. Both tofacitinib and baricitinib effectively suppressed STAT1 activation, as demonstrated by distinct shifts in mean fluorescence intensity (MFI), indicating functional inhibition of downstream IFN signaling in vitro. Conclusion: Variations in protease and cytokine profiles distinguish fibrotic from non-fibrotic ILD phenotypes and, within CTD-ILD, highlight subgroup-specific inflammatory activity. From a therapeutic perspective, these observations support a dual approach: fibrotic autoimmune ILDs may benefit from anti-fibrotic treatment combined with immunosuppressive therapy, given their protease-dominant and remodeling profile, whereas non-fibrotic inflammatory ILDs may require primarily immunosuppressive strategies aligned with cytokine-driven activity. Combining immunosuppressants with anti-fibrotics in selected patients could represent a rational, precision-based strategy tailored to the biological profile of the disease. Larger longitudinal studies are warranted to validate these preliminary findings and to explore how biomarker-guided treatment can improve ILD management.