Early deterioration of CIDP following transition from IVIG to FcRn inhibitor treatment.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an immune mediated demyelinating neuropathy that can lead to secondary axonal degeneration and irreversible weakness and disability. Early effective treatment is therefore necessary to minimize the degree of axonal degeneration. Prior to 2024 the only FDA approved therapy for CIDP was intravenous immunoglobulin (IVIg). In 2024, efgartigimod (Vyvgart-Hytrulo), a FCRn inhibiting therapy (FIT) was approved for treatment of CIDP based on the phase II Adhere study. In the controlled setting of the phase II clinical study patients who were stable on IVIg were taken off treatment to ensure that their disease was active, and patients who worsened were then treated with efgartigimod. The responders were then randomized (in phase B) to either placebo or continued efgartigimod treatment. In the real world setting it is not feasible to stop IVIg and let patients worsen before starting a FIT, thus the transition from IVIG to efgartigimod in a real world setting was not studied in the pivotal trial. We have treated nine patients with FIT in our practice and report findings of four of those patients who had severe relapse of CIDP after treatment. Five of the other patients neither improved nor declined with FIT. This raises questions about the issues related to transitioning patients from IVIG to efgartigimod.