62MO Naxitamab pivotal clinical trial planned interim analysis of PFS and OS in patients with relapsed or refractory high-risk neuroblastoma

Naxitamab (NAX) is a humanized GD2-binding monoclonal antibody approved in the US with granulocyte-macrophage colony-stimulating factor (GM-CSF) under accelerated approval based part on ad hoc analysis of data from registrational phase II 201 trial (NCT03363373). We report progression free (PFS) and overall survival (OS) results prespecified interim analyses. This ongoing evaluating NAX+GM-CSF patients (pts) relapsed/refractory high-risk neuroblastoma residual disease bone/bone marrow (BM). Pts progressive or soft tissue were excluded. NAX was given intravenously days 1/3/5 at 3mg/kg/day GM-CSF subcutaneously -4 to 5; cycles repeated every 4 weeks (wks). Efficacy evaluated centrally by independent pathology radiology review per International Neuroblastoma Response Criteria (Park et al 2017). Kaplan-Meier (KM) estimated duration response (DoR), OS PFS. At cutoff (Dec 31, 2021), 52 pts evaluable baseline eligible for efficacy assessment. Analyses showed 50% rate (ORR; [95% CI 36-64%], 30% complete (CR) 25-53%] 12 partial (PR) 4-23%]. Median number onset CR PR (n=26) 2 (range 2-4), same only (n=20) 2-8). wks 6.7 5.4-30.7). DoR not estimable (NE; CI, 24.9-NE]), i.e., 20 26 responders had response. See table PFS results. Frequent CTCAE grade 3 adverse events (AEs; safety population n=74) included hypotension (58%) pain (54%); 6.8% discontinued due AEs.Table: 62MOKM estimatesPFS (N=52)OS (N=52)Median CI]30.3 [18.4 – NE]NE* [140 NE]At [95%CI]59.8% [43.8 72.7]95.7% [84, 98.9]At CI]34.9% [17.3 53.2]93.2 [80.3, 97.8] Open new tab provided durable clinically significant ORR CR, promising With manageable profile an option outpatient administration treatment addresses unmet medical need.