Background Biologics have been used off-label in treatment of refractory polymyositis (PM) and dermatomyositis (DM) but their role in treating myositis is still unclear.
Objectives In this study we aimed to describe the use of biologics in patients with PM and DM and their effectiveness and safety, based on national registries in Sweden.
Methods Patients were identified by linking the national patient care registers to the prescribed drug register and the Swedish Rheumatology Quality register (SRQ). Effectiveness was based on an overall assessment of clinical outcome in the patient records, and changes in serum levels of creatine phosphokinase (CPK) and prednisolone dose. Clinical data were collected at start of treatment, at last follow up within 3 to 12 months or at discontinuation of treatment. Safety was evaluated by the number of patients stopping treatment due to adverse events within 12 months. Paired t-test was performed on the natural logarithm of CPK and prednisolone dose to compare changes before and after treatment.
Results 63 patients treated with at least one biologic (35 PM, 28 DM, mean age 56 (12), 45 (71%) women,) were identified at 11 different centers between 2001 and 2012. All identified cases were refractory to previous medication with mean 2.5 (1.2) DMARDS beings used prior to start of biologic therapy. Multiple biological treatments were common with 7 patients treated with 2 different biologics and 8 patients treated with 3 different biologics.
Rituximab (RTX) was the most often used biological agent (Table 1). No new treatment with anakinra (ANA) had been started after 2009 and no new treatment with TNF-inhibitors (TNFi) had been started after 2003.
A statistical significant decrease in CPK was observed in the RTX group (p<0,01 [JS1]). No other statistical difference could be found for any of the biologics when comparing CPK level and prednisolone dose before and after treatment.
3 patients stopped their treatment due to disease remission. They were all treated with RTX.
Conclusions We found an increasing use of RTX and ABA in patients with PM and DM. In this population we found an overall favorable response to RTX and ABA in 2/3 of patients but less often to ANA and TNFi. A reduction of elevated CPK was observed in RTX treated patients. RTX and ABA seemed to be well tolerated by patients while more stopped treatment due to side effects in the anakinra- and TNFi-group.
Disclosure of Interest None declared