Efgartigimod cut relapses in a nerve disease; its long-term data are open-label

Efgartigimod, a drug that lowers circulating antibodies, more than halved the risk of relapse in people with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who had responded to it, in a randomised-withdrawal trial [s1]. A 2026 open-label extension reports that the benefit and a reassuring safety profile hold up over longer treatment — but the extension has no comparison group, so it can describe how patients fared, not prove the drug is why [s2].

CIDP is an autoimmune disease of the peripheral nerves that causes progressive weakness and sensory loss and can be severely disabling [s1]. Standard treatments — corticosteroids, intravenous immunoglobulin and plasma exchange — leave about a third of patients without an adequate response, and many who do respond keep some impairment [s1]. Efgartigimod is an engineered fragment of a human antibody that blocks the neonatal Fc receptor (FcRn), accelerating the breakdown of immunoglobulin G, the antibody class implicated in CIDP [s1]. It was already approved for generalised myasthenia gravis, another antibody-driven neuromuscular disease, before being tested here [s1].

What the randomised trial found

ADHERE enrolled participants across 146 sites in Asia-Pacific, Europe and North America and used a staged design [s1]. In an open-label run-in (stage A), 322 participants received weekly subcutaneous efgartigimod for up to 12 weeks; 214 of them (66%; 95% CI 61.0 to 71.6) showed confirmed clinical improvement [s1]. Those responders then entered the randomised, double-blind withdrawal phase (stage B), where 221 were assigned to continue efgartigimod (111) or switch to placebo (110) for up to 48 weeks [s1].

The design is unusually informative because it asks whether stopping the drug brings the disease back. It did. Efgartigimod cut the risk of relapse by 61% versus placebo (hazard ratio 0.39; 95% CI 0.25 to 0.61; p<0.0001) [s1]. Relapse occurred in 27.9% of the efgartigimod group against 53.6% on placebo [s1]. Serious adverse events were uncommon and balanced between arms (5% on each in stage B), and the three deaths during the trial were judged unrelated or unlikely related to the drug, with the one death in stage B occurring in the placebo group [s1]. The trial was funded by argenx, the manufacturer, and the investigators noted that longer-term data and head-to-head comparisons with existing treatments were still needed [s1].

What the 2026 extension adds — and doesn't

ADHERE+ is the open-label extension, and its interim analysis (data cut-off February 2024) is the new 2026 report [s2]. Of 229 eligible participants, 228 rolled over to receive efgartigimod [s2]. Over a mean treatment duration of 58.0 weeks and a maximum exposure of 187.3 weeks, prolonged dosing did not raise the rate of adverse events (75.0% had a treatment-emergent event; 18.0% a grade 3 or higher event) or of infections, despite the drug's IgG-lowering mechanism [s2]. Stage A responders reported clinically meaningful gains that were sustained to extension week 36: their disability score (aINCAT) fell by 1.2 points, a disability-and-function scale (I-RODS) rose by 8.8 points, and mean grip strength rose by 17.5 kPa from baseline [s2].

The caution is structural. An open-label extension has no placebo arm and enriches for people who already did well, so its efficacy figures cannot separate the drug's effect from natural course, expectation or regression to the mean [s2]. Its real value is safety — the finding that years of FcRn blockade did not produce a creeping infection risk is meaningful, because that was the plausible worry with a therapy that strips out protective antibodies [s2]. On efficacy, the randomised-withdrawal result remains the load-bearing evidence [s1].

Why it matters

For the substantial minority of CIDP patients poorly served by immunoglobulin and steroids, a subcutaneous option with a distinct mechanism is a genuine addition, and the withdrawal design gives more confidence than a simple before-and-after study would [s1]. The honest framing is that this is a single manufacturer-funded trial programme: the RCT is strong within its scope, and the long-term picture rests on uncontrolled follow-up [s1][s2]. Health Newspapers has separately covered the same drug's expansion in myasthenia gravis, where a regulator widened its label.

What to watch

The questions that would move practice are how efgartigimod compares directly with immunoglobulin, its mainstay competitor, and whether the durability seen in the extension holds in patients who did not respond briskly at the start — neither of which the current trials were built to answer [s1][s2].

This article describes research and regulatory status and is not medical advice or a treatment recommendation.

Sources

• Safety, tolerability, and efficacy of subcutaneous efgartigimod in patients with CIDP (ADHERE) — The Lancet Neurology, 19 September 2024
• Long-term safety and efficacy of efgartigimod PH20 in CIDP: ADHERE/ADHERE+ interim analysis — Journal of the Peripheral Nervous System, 16 July 2026