Recombinant human hyaluronidase-facilitated subcutaneous immunoglobulin (hf-SCIg) for inflammatory myositis: a multicenter retrospective real-world observational study

Background: Subcutaneous immunoglobulin (SCIg) is a promising alternative to intravenous Ig (IVIg) for the treatment of idiopathic inflammatory myositis (IIM), thanks to its more favorable safety profile, reduced costs, and lower impact on patients’ quality of life. We assessed the short- and long-term effectiveness and safety of recombinant human hyaluronidase-facilitated SCIg (hf-SCIg) in patients with IIM treated at different referral centers in Italy. Methods: A multicenter, retrospective, real-life cohort study was conducted on consecutive adult patients diagnosed with IIM according to the EULAR/ACR criteria, treated with hf-SCIg for remission induction or maintenance. Hf-SCIg effectiveness was assessed in terms of variation in the Medical Research Council (MRC) score, serum creatine kinase (CK) values, clinical disease manifestations and daily prednisone dosage. Safety data were also collected. Results: Twenty-six patients with IIM treated with hf-SCIg for remission induction (n = 5) or maintenance (n = 21) were included in the study (18 females; median age at diagnosis of 59 (IQR 42–64) years)). In most patients, hf-SCIg was started following previous IVIg treatment (23, 89 %) and was initiated in combination with oral corticosteroids (21, 81 %) and/or traditional or biologic DMARDs. Short-term use of hf-SCIg for remission induction appeared associated with a corticosteroid-sparing effect, without worsening of MRC score. Long-term hf-SCIg treatment for up to 24 months maintained clinical stability and serum CK levels with further improvement of MRC score. Hf-SCIg was well tolerated, with mild adverse events mostly related to local site reactions. Conclusions: Hf-SCIg seems effective and safe for induce and maintain clinical remission in patients with IIM.