Rozanolixizumab (Rystiggo)

Rozanolixizumab is a second FcRn-blocking antibody for generalized myasthenia gravis, FDA-approved on 26 June 2023 — six days after this site's efgartigimod page's own subcutaneous Vyvgart Hytrulo formulation was approved that same month — but built as a full humanized IgG4 monoclonal antibody rather than an engineered antibody fragment, and approved from day one for both of the disease's two main antibody subtypes rather than just one. Its pivotal trial hit a clean, statistically significant result on the same disability scale efgartigimod's trial used, and by 2025 it had also become the first drug in its class approved for real at-home self-administration in the EU and Japan — a convenience expansion still pending in the US, where it remains a clinic-administered infusion, as of this review.

A second way to clear disease-driving antibodies

This site's efgartigimod page describes generalized myasthenia gravis (gMG) — an autoimmune disease in which antibodies attack the neuromuscular junction, causing muscle weakness — and the first-in-class mechanism of blocking the neonatal Fc receptor (FcRn) to accelerate the breakdown of a patient's own circulating IgG antibodies, including the disease-driving ones. Rozanolixizumab, developed by UCB, works on the same FcRn target but takes a different molecular form: where efgartigimod is an engineered fragment of an antibody's Fc region, rozanolixizumab is a full humanized IgG4 monoclonal antibody, independently developed and unrelated to argenx's molecule beyond sharing the same target. The FDA approved it as Rystiggo (rozanolixizumab-noli, BLA 761286) on 26 June 2023 — six days after Vyvgart Hytrulo's own subcutaneous approval on 20 June 2023 — for adults with gMG who test positive for either anti-acetylcholine-receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibodies, administered as a once-weekly subcutaneous infusion over a defined treatment cycle rather than a continuous regimen.

MycarinG: a clean placebo-controlled result

Rozanolixizumab's approval rested on the Phase 3 MycarinG trial, a randomized, double-blind, placebo-controlled, adaptive study conducted at 81 sites across Asia, Europe and North America. 200 adults with gMG (AChR- or MuSK-antibody-positive) were randomized roughly 1:1:1 to weekly weight-tiered rozanolixizumab (7 mg/kg or 10 mg/kg) or placebo for six weeks. At day 43, the least-squares mean change from baseline in MG-ADL score — the same activities-of-daily-living disability scale efgartigimod's ADAPT trial used — was -3.4 points in both rozanolixizumab dose groups, versus -0.8 with placebo, a placebo-corrected improvement of roughly 2.6 points at both doses (P<0.001), with statistically significant, consistent improvements also seen on the Quantitative Myasthenia Gravis (QMG) and Myasthenia Gravis Composite (MGC) scales (Bril V, Drużdż A, Grosskreutz J, et al., "Safety and efficacy of rozanolixizumab in patients with generalised myasthenia gravis (MycarinG): a randomised, double-blind, placebo-controlled, adaptive phase 3 study," Lancet Neurol 2023;22(5):383-394, PMID 37059507, DOI: 10.1016/S1474-4422(23)00077-7).¹ The most common adverse reactions were headache, diarrhea, pyrexia, nausea, and hypersensitivity reactions; headache was reported more frequently than with efgartigimod's ADAPT trial, a real, if modest, tolerability difference between the two FcRn-blocking drugs.

The real differentiator: MuSK-positive patients from day one

The most concrete practical difference between the two drugs at launch wasn't efficacy — both showed a clear, statistically significant benefit over placebo on the same disability scale — but which patients each was approved to treat. Efgartigimod's original December 2021 approval covered only AChR-antibody-positive gMG, the population its ADAPT trial enrolled; the FDA didn't expand Vyvgart to cover MuSK-positive and antibody-negative patients until 8 May 2026, described on this site's efgartigimod page. Rozanolixizumab's MycarinG trial, by contrast, enrolled both AChR- and MuSK-positive patients from the start, and a dedicated subgroup analysis of the MuSK-positive cohort found a consistent treatment effect in that smaller population too — meaning Rystiggo's original 2023 FDA approval already covered both major antibody subtypes, making it, per UCB's own regulatory materials, the first FDA-approved gMG treatment for MuSK-antibody-positive patients specifically, nearly three years before efgartigimod's label caught up on that front. Antibody-negative ("triple seronegative") gMG patients remain outside rozanolixizumab's approved label as of this review, a population efgartigimod's 2026 expansion does cover.

2025: the EU and Japan approve self-administration, the US hasn't yet

Rystiggo's original US approval required administration by a healthcare professional at an infusion center for every weekly dose — a real practical burden for a chronic weekly therapy, the same limitation efgartigimod's original IV formulation carried before its 2023 subcutaneous Hytrulo version arrived. UCB ran a dedicated Phase 3 study, MG0020, testing whether patients could safely and effectively self-administer rozanolixizumab at home via manual push (a prefilled syringe) or a wearable infusion pump, after a structured training period. Based on that data, the European Commission approved both self-administration routes in January 2025, and Japan's PMDA approved at-home self-administration in May 2025 — real, dated regulatory approvals in two major markets. As of this review, the FDA has not yet approved either self-administration method in the US; Rystiggo's US label continues to require administration by a healthcare professional for every dose.

Current status

Rystiggo remains FDA-approved and actively marketed by UCB for AChR- or MuSK-antibody-positive generalized myasthenia gravis in adults, competing directly with efgartigimod's Vyvgart/Vyvgart Hytrulo and, on a different mechanism, this site's zilucoplan page's complement-blocking approach — all three now UCB or argenx products marketed into the same gMG population. UCB has also secured approval of rozanolixizumab (alongside zilucoplan) in Japan, and the drug carries no boxed warning; its label instead flags a general risk of infection from reduced circulating IgG, consistent with the same mechanism-driven consideration this site's efgartigimod page describes for its own FcRn blocker. As a specialty neurology biologic administered in clinical settings, Rystiggo carries no wellness, bodybuilding or grey-market interest of any kind.