FDA Approval Summary: Eflornithine for High-Risk Neuroblastoma Following Prior Multiagent, Multimodality Therapy

On December 13, 2023, the U.S. Food and Drug Administration (FDA) approved eflornithine (IWILFIN, US WorldMeds) to reduce the risk of relapse in adult and pediatric patients with high-risk neuroblastoma who have demonstrated at least a partial response to prior multiagent, multimodality therapy including anti-GD2 immunotherapy. The approval was based on an externally controlled trial (ECT) consisting of a single-arm trial, Study 3(b), compared to an external control derived from a National Cancer Institute (NCI)/Children’s Oncology Group (COG)-sponsored clinical trial (Study ANBL0032) and supported by confirmatory evidence. In the protocol-specified primary analysis, the event-free survival (EFS) hazard ratio (HR) was 0.48 (95% confidence interval [CI]: 0.27, 0.85) and overall survival (OS) HR was 0.32 (95% CI: 0.15, 0.70). The most common adverse reactions (≥5%) were hearing loss, otitis media, pyrexia, pneumonia, and diarrhea. Notably, this is the first oncology drug approval which relies on an ECT as the primary clinical data to support substantial evidence of effectiveness. This was made possible by a distinctly high-quality, comparable external control dataset with consistent treatment effect estimations demonstrated in multiple sensitivity and supportive analyses. Eflornithine's manageable safety profile and strong nonclinical and mechanistic data provided further support for the approval, and the evidentiary package was evaluated in the context of high unmet need in a rare, life-threatening cancer.