First Treatment Recommended for Rare Immunoglobulin-Related Autoimmune Disease

In September 2025, the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) recommended extending the indication of Uplizna® (inebilizumab) to include treatment of active Immunoglobulin G4-related disease (IgG4-RD) in adults. European Medicines Agency (EMA)

IgG4-RD is a rare, chronic autoimmune disorder in which the body’s immune system attacks its own tissues, leading to inflammation, fibrosis (scarring), and dysfunction in one or more organs. Commonly affected sites include the pancreas, salivary glands, biliary tree, kidneys, lungs, and others. European Medicines Agency (EMA) Patients often present between ages 40 and 60. European Medicines Agency (EMA)

Until now, there were no approved therapies in the EU specifically for IgG4-RD; treatments have relied on off-label use of immunosuppressants and glucocorticoids. European Medicines Agency (EMA)+2Rare Disease Advisor+2

The CHMP’s recommendation is based on a 52-week, randomized, double-blind trial in 135 adults comparing inebilizumab vs placebo. The results were striking: only 7 of 68 patients treated with inebilizumab had flares, versus 40 of 67 patients receiving placebo. Moreover, 58.8% of the inebilizumab group achieved corticosteroid-free, flare-free complete remission at week 52, compared to 22.4% in the placebo group. European Medicines Agency (EMA)

Common side effects observed include infections (upper respiratory, urinary tract), joint pain, back pain, and lymphocyte reductions. The safety profile in IgG4-RD was broadly consistent with that seen in its prior indication (neuromyelitis optica spectrum disorder). European Medicines Agency (EMA)+2Uplizna+2

The CHMP’s positive opinion is an intermediate step toward full EU-wide approval; the final decision now moves to the European Commission, and thereafter national reimbursement and access will be decided in each member state. European Medicines Agency (EMA)

This marks a significant milestone: Uplizna (inebilizumab) would become the first authorised therapy in Europe for IgG4-RD, offering a targeted, steroid-sparing option for patients with this challenging disease.

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Deeper Dive: IgG4-Related Disease & Treatment Landscape

Below is a more in-depth overview to complement the above article.

What is IgG4-Related Disease (IgG4-RD)?

• IgG4-RD is an immune-mediated, fibroinflammatory condition characterized by tissue infiltration of IgG4-positive plasma cells, storiform fibrosis, and often obliterative phlebitis. Rare Disease Advisor+3PMC+3OUP Academic+3
• Clinically, it can mimic malignancies or infections, since it may present as mass‐like lesions in organs or swelling. DermNet®+1
• It often affects multiple organs; up to 60–90% of patients have multiorgan involvement. DermNet®+1
• If untreated or recurrent, the chronic inflammation leads to irreversible fibrosis, organ damage, and dysfunction.

Goals of Therapy

• Induce remission of inflammation and symptoms
• Prevent flares
• Minimize and ideally eliminate long-term dependence on glucocorticoids (steroid sparing)
• Prevent organ damage and functional decline

Conventional / Historical Treatments

Glucocorticoids (Steroids)

• First-line therapy in virtually all symptomatic cases. Merck Manuals+4American College of Rheumatology+4PMC+4
• Typical induction: 0.6 mg/kg (or ~30 mg/day) of prednisone (or equivalent) for 2–4 weeks, followed by gradual tapering over 8–12 weeks or more. PMC+2PMC+2
• Many patients respond well initially. OUP Academic+3American College of Rheumatology+3PMC+3
• Limitations: a substantial proportion relapse during or after tapering (≈40% relapse within a year) American College of Rheumatology+2PMC+2, and long-term steroid use has well-known toxicities (osteoporosis, diabetes, hypertension, infections, muscle weakness, etc.). Rare Disease Advisor+3European Medicines Agency (EMA)+3PMC+3

Conventional Immunosuppressants / “Steroid-Sparing” Agents (DMARDs)

• Agents such as azathioprine, methotrexate, mycophenolate mofetil, tacrolimus, cyclophosphamide, hydroxychloroquine have been used (off-label) to reduce steroid burden. OUP Academic+3PMC+3Rare Disease Advisor+3
• However, evidence is limited, mostly from small case series and retrospective analyses. No robust randomized controlled trials support their efficacy in IgG4-RD. PMC+2ScienceDirect+2
• These agents are often employed when steroids are contraindicated, or after relapse on steroids, or in conjunction with B cell–targeted therapies. PMC+1

B Cell–Targeted Therapies

Because B cells, plasmablasts, and their products appear central to disease activity in IgG4-RD, therapies targeting B cells have gained traction.

• Rituximab (anti-CD20 monoclonal antibody): Widely used off-label. Many case reports / open-label series suggest good effectiveness for inducing and maintaining remission, often allowing steroid reduction. Frontiers+4Massachusetts General Hospital+4PMC+4
  • However, rituximab does not target plasmablasts or plasma cells lacking CD20. PMC+2PMC+2
• Inebilizumab (anti-CD19 monoclonal antibody): The new targeted option, recently recommended by EMA and approved by FDA for IgG4-RD. Targets a broader B cell lineage than CD20, including plasmablasts. Uplizna+7New England Journal of Medicine+7PMC+7
• Obexelimab: An experimental bispecific antibody (CD19 + FcγRIIb) currently under investigation for IgG4-RD. Wikipedia
• Other biologic or immune-modulating agents (e.g. abatacept, belimumab, etc.) are being explored, although data in IgG4-RD remain scarce. PMC+2Rare Disease Advisor+2

The MITIGATE Trial & Inebilizumab Efficacy

• The MITIGATE trial was a 52-week, randomized, double-blind, multicenter study of 135 adult patients with active IgG4-RD (some newly diagnosed, others relapsing) comparing inebilizumab vs placebo, as monotherapy. New England Journal of Medicine+6Uplizna+6New England Journal of Medicine+6
• Key findings:
  • 87% reduction in flare risk for inebilizumab vs placebo (hazard ratio ~0.13). AJMC+5Amgen+5New England Journal of Medicine+5
  • Only 7 of 68 patients on inebilizumab had flares vs 40 of 67 in placebo arm. Amgen+5European Medicines Agency (EMA)+5Uplizna+5
  • 58.8% of inebilizumab patients achieved corticosteroid-free, flare-free complete remission at 52 weeks compared to 22.4% of placebo patients. Rare Disease Advisor+3European Medicines Agency (EMA)+3Uplizna+3
  • The safety profile was consistent with known risks: infections, lymphopenia, infusion reactions. New England Journal of Medicine+3Uplizna+3PMC+3
• This is the first randomized, double-blind placebo-controlled trial ever conducted in IgG4-RD. PMC+2PMC+2

Safety and Side Effects of Inebilizumab / Uplizna

• Potential adverse effects include infusion reactions (some severe), infections (upper respiratory, urinary tract), and reductions in lymphocyte counts. AJMC+4Uplizna+4PMC+4
• Patients should be premedicated (with corticosteroid, antihistamine, antipyretic) before infusion to mitigate infusion reactions. Amgen+1
• Contraindications may include active hepatitis B, untreated latent tuberculosis, or prior life-threatening infusion reactions. Uplizna+1
• As with any immunosuppressive therapy, there is a risk of opportunistic infections, and monitoring during therapy is essential.

Challenges, Limitations & Unmet Needs

• Access, cost, and reimbursement: Even once approved, availability may vary by region or country, and pricing may limit access.
• Long-term data: The trial follow-up was 52 weeks; longer monitoring is needed for durability of remission, relapse rates beyond one year, long-term safety.
• Heterogeneity of disease: IgG4-RD can vary widely in organ involvement, severity, and progression; personalized strategies will be needed.
• Biomarkers & disease monitoring: There is a need for reliable biomarkers to monitor disease activity, predict flares, and guide therapy. Plasmablast counts, serum IgG4, imaging metrics are under study. PMC+2OUP Academic+2
• Other therapeutic targets: Research is ongoing into targeting T cells, cytokines, fibrotic pathways, etc. OUP Academic+3advances.massgeneral.org+3PMC+3
• Safety in special populations (elderly, comorbidities) needs further evaluation.

Outlook & Significance

• The EMA recommendation signals that Europe may soon have its first officially approved therapy for IgG4-RD, giving patients a more precise, disease-targeted option beyond steroids and non-specific immunosuppression.
• In the U.S., the FDA has already approved Uplizna (inebilizumab) for IgG4-RD, making it the first approved therapy for this indication in that jurisdiction. Amgen+2AJMC+2
• Clinicians and researchers will likely adopt inebilizumab earlier in the treatment course — especially in patients at high risk of relapse or with contraindications to steroids.
• The success of this trial may stimulate further high-quality trials in IgG4-RD and encourage development of novel therapies targeting various arms of immune dysregulation and fibrosis.