The idiopathic inflammatory myopathies (polymyositis, dermatomyositis) and polymyalgia rheumatica have moved beyond nonspecific immunosuppression toward targeted biologics — including, for polymyalgia rheumatica, its first-ever approved biologic.
Dermatomyositis and polymyositis
Intravenous immunoglobulin is now firmly evidence-based for dermatomyositis: in the placebo-controlled ProDERM trial, 79% of IVIG-treated patients achieved at least minimal improvement versus 44% with placebo, leading to regulatory approval for this indication. Watch for thromboembolic events and infusion reactions. JAK inhibitors (tofacitinib, baricitinib, ruxolitinib) improve muscle strength and skin disease in both dermatomyositis and polymyositis, at the cost of infection, cytopenia, and cardiovascular risk. Rituximab produced improvement in a large majority of refractory myositis patients despite not formally meeting its primary endpoint, and abatacept and anti-interferon approaches (sifalimumab) show early promise. Immunoproteasome inhibitors remain preclinical.
Polymyalgia rheumatica
The landmark change is sarilumab, an IL-6 receptor inhibitor: in the Phase 3 SAPHYR trial, sustained remission at 52 weeks was achieved by 28% of sarilumab-treated patients versus 10% with placebo, with substantially reduced cumulative glucocorticoid exposure. On this basis sarilumab was approved in 2023 (with European endorsement following) as the first and only biologic for polymyalgia rheumatica in patients who relapse or cannot taper steroids — a genuine paradigm shift for a disease long managed with prolonged corticosteroids alone. Looking ahead, secukinumab (IL-17 inhibition) produced positive results in polymyalgia rheumatica and may be a near-term option, and JAK-inhibitor and rituximab trials are adding further depth.
| Disease | Therapy | Key result | Status |
|---|---|---|---|
| Dermatomyositis | IVIG | 79% vs 44% response (ProDERM) | Approved |
| DM/PM | JAK inhibitors | Improved strength and skin | In use / trials |
| DM/PM | Rituximab | Response in most refractory cases | Off-label |
| PMR | Sarilumab | 28% vs 10% sustained remission (SAPHYR) | Approved (2023), first biologic |
| PMR | Secukinumab | Positive results; data maturing | Emerging |
Further reading: ProDERM IVIG (Aggarwal et al., NEJM 2022); SAPHYR sarilumab (Spiera et al., NEJM 2023); JAK inhibitor meta-analysis in myositis (2024).