BACKGROUND. Monogenic IFN–mediated autoinflammatory diseases present in infancy with systemic inflammation, an IFN response gene signature, inflammatory organ damage, and high mortality. We used the JAK inhibitor baricitinib, with IFN-blocking activity in vitro, to ameliorate disease. METHODS. Between October 2011 and February 2017, 10 patients with CANDLE (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures), 4 patients with SAVI (stimulator of IFN genes–associated [STING-associated] vasculopathy with onset in infancy), and 4 patients with other interferonopathies were enrolled in an expanded access program. The patients underwent dose escalation, and the benefit was assessed by reductions in daily disease symptoms and corticosteroid requirement. Quality of life, organ inflammation, changes in IFN-induced biomarkers, and safety were longitudinally assessed. RESULTS. Eighteen patients were treated for a mean duration of 3.0 years (1.5–4.9 years). The median daily symptom score decreased from 1.3 (interquartile range [IQR], 0.93–1.78) to 0.25 (IQR, 0.1–0.63) (P < 0.0001). In 14 patients receiving corticosteroids at baseline, daily prednisone doses decreased from 0.44 mg/kg/day (IQR, 0.31–1.09) to 0.11 mg/kg/day (IQR, 0.02–0.24) (P < 0.01), and 5 of 10 patients with CANDLE achieved lasting clinical remission. The patients’ quality of life and height and bone mineral density Z-scores significantly improved, and their IFN biomarkers decreased. Three patients, two of whom had genetically undefined conditions, discontinued treatment because of lack of efficacy, and one CANDLE patient discontinued treatment because of BK viremia and azotemia. The most common adverse events were upper respiratory infections, gastroenteritis, and BK viruria and viremia. CONCLUSION. Upon baricitinib treatment, clinical manifestations and inflammatory and IFN biomarkers improved in patients with the monogenic interferonopathies CANDLE, SAVI, and other interferonopathies. Monitoring safety and efficacy is important in benefit-risk assessment. TRIAL REGISTRATION. ClinicalTrials.gov NCT01724580 and NCT02974595. FUNDING. This research was supported by the Intramural Research Program of the NIH, NIAID, and NIAMS. Baricitinib was provided by Eli Lilly and Company, which is the sponsor of the expanded access program for this drug.

Cytokines are key mediators of the development and homeostasis of haematopoietic cells, critical for host defense, but also for the development of autoimmune and inflammatory diseases such as psoriasis or rheumatoid arthritis (RA). Blocking cytokines activity by interfering with the ligand–receptor association has been successfully employed to treat several immune disorders. A subgroup of cytokines signals through receptors requiring the association with a family of cytoplasmic protein tyrosine kinases known as Janus kinases (Jaks). Jaks have recently gained significant attention as therapeutic targets in inflammation and autoimmunity, and several Jak inhibitory small molecules have been developed. The first two Jak inhibitors, tofacitinib and ruxolitinib, have been approved for the treatment of RA and primary myelofibrosis, respectively. Efficacy and safety data suggest that some of these oral Jak inhibitors as well as their topical formulations may soon enter the daily clinical practice for treating patients with psoriasis, lupus erythematosus or other inflammatory skin diseases. While biologics typically target one single cytokine, these new immunomodulators can inhibit signals from multiple cytokines intra‐cellularly and therefore could be useful when other therapies are ineffective. Thus, Jak inhibitors may replace some traditional immunosuppressive agents and help patients not responding to previous therapies.

JAK kinase inhibitors are being investigated as a way of managing cytokine storm in patients with severe COVID-19.