Off-label use of mycophenolate mofetil in the treatment of rare and complex rheumatic connective tissue diseases.

We aimed to investigate the clinical off-label use of mycophenolate mofetil (MMF), including its safety and efficacy in patients with rare and complex rheumatic connective tissue diseases (rCTDs). A survey was distributed across experts from ERN-ReCONNET reference centres in order to assess the experience with MMF off-label use. Patient-level data of patients with rCTDs under treatment with MMF was also collected for analysis of safety and efficacy. Twelve experts from eleven centres distributed throughout Europe (7 countries) answered the survey. The experience was concordant in that, despite of its off-label use, experts reported opting frequently for this therapeutic alternative with robust confidence on its efficacy and safety. The analysis of 108 patients with rCTDs under MMF revealed a good safety profile, as well as good clinical outcomes, especially for systemic lupus erythematosus and idiopathic inflammatory myopathies. The presence of interstitial lung disease was, as expected, associated with a worse clinical outcome despite use of MMF. MMF is widely used in reference centres for rCTDs. Its safety profile and efficacy seem to be recognised by experts and demonstrated with patient-level analysis. While selected rCTDs will likely remain an off-label indication for MMF, robust data seem to support this therapy as an appropriate alternative for safely and effectively treating many manifestations of rCTDs.