A clinically meaningful improvement in platelet count was observed in a significantly higher proportion of patients with chronic primary immune thrombocytopenia (ITP) treated with efgartigimod compared with placebo, according to data from a phase 3 trial.
The randomized, double-blind, placebo-controlled ADVANCE trial (ClinicalTrials.gov Identifier: NCT04188379) evaluated the efficacy and safety of efgartigimod in 131 heavily pretreated adults with primary ITP. Patients were randomly assigned 2:1 to receive efgartigimod or placebo via intravenous (IV) infusion for a total of 24 weeks. Patients received weekly infusions from weeks 1 through 4 and were eligible to adjust frequency to biweekly based on platelet count. Administration frequency was fixed from study visits 16 to 24.
The primary endpoint was the proportion of patients with chronic ITP with a sustained platelet count response, defined as achieving platelet counts of at least 50×109/L on at least 4 of the last 6 scheduled visits between weeks 19 and 24.
Findings demonstrated that 21.8% (n=17/78) of patients treated with efgartigimod achieved a sustained platelet response compared with 5% (n=2/40) of those in the placebo group (P =.0316). Statistically significant benefits were also observed in key platelet-derived secondary endpoints, including cumulative number of weeks where platelet counts were at least 50×109/L in the chronic ITP population (P =.0009) and sustained platelet response in the overall population, including both chronic and persistent ITP patients (P =.0108).
Additional findings showed that 51.2% and 27.9% of patients treated with efgartigimod were classified as International Working Group responders and complete responders, respectively, compared with 20% and 4.4% of placebo patients. Efgartigimod was associated with a rapid onset of platelet count improvement with statistically significant separation from placebo observed at week 1 and maintained through 20 out of 24 weeks of the trial.
A greater number of patients in the efgartigimod arm also switched to biweekly dosing after achieving platelet counts of 100×109/L for 3 out of 4 consecutive visits (10 vs 1). Nine out of the ten patients who switched to biweekly dosing achieved a sustained platelet response. The safety profile of efgartigimod was consistent with that observed in previous trials.
“These data are very promising as they show that platelet counts can rapidly improve to clinically meaningful levels following [efgartigimod] treatment in a proportion of a heavily pretreated patient population,” said Catherine Broome, MD, Associate Professor of Medicine at Georgetown University Lombardi Comprehensive Cancer Center, and principal investigator in the ADVANCE study. “We are excited that targeting pathogenic IgG autoantibodies could represent a new, potential approach to help alleviate the disease burden in this patient community.”
Efgartigimod, a neonatal Fc receptor blocker, is marketed under the brand name Vyvgart and is approved for the treatment of generalized myasthenia gravis in adults who are anti-acetylcholine receptor antibody positive.
Subcutaneous administration of efgartigimod is also being evaluated for primary ITP in the phase 3 ADVANCE-SC trial (ClinicalTrials.gov Identifier: NCT04687072). Topline data from this trial are expected in the first quarter of 2023.
Argenx announces positive phase 3 data from ADVANCE trial of Vyvgart® (efgartigimod alfa-fcab) in adults with primary immune thrombocytopenia. News release. argenx SE. Accessed May 5, 2022. https://www.globenewswire.com/news-release/2022/05/05/2436303/0/en/argenx-Announces-Positive-Phase-3-Data-from-ADVANCE-Trial-of-VYVGART-efgartigimod-alfa-fcab-in-Adults-with-Primary-Immune-Thrombocytopenia.html