Durable platelet response and immature platelet indices following sequential efgartigimod and eltrombopag therapy in a patient with refractory ITP

Efgartigimod, a neonatal Fc receptor (FcRn) antagonist, represents a novel therapeutic approach for refractory immune thrombocytopenia (ITP). However, its clinical positioning and durability of response in real-world settings remain unclear. We describe a case of refractory ITP in which efgartigimod induced a partial response that was enhanced by the subsequent addition of a thrombopoietin receptor agonist (TPO-RA), resulting in durable remission after efgartigimod discontinuation. Subsequent hematologic workup revealed that platelet recovery was accompanied by a reciprocal shift in immature platelet indices, with immature platelet fraction percentage decreasing and absolute immature platelet fraction increasing. Although there is a paucity of literature on immature platelet indices during ITP treatment, these parameters may serve as useful biomarkers for monitoring therapeutic response. Notably, efgartigimod was discontinued after 22 weeks, with sustained response maintained for an additional 24 weeks on TPO-RA monotherapy. This treatment course highlights the potential of FcRn inhibition to induce durable immunomodulatory effects and demonstrates synergistic benefits with TPO-RAs-insights that extend beyond the scope of conventional clinical trial protocols.