Phase I Study of ¹³¹ I-Metaiodobenzylguanidine With Dinutuximab ± Vorinostat for Patients With Relapsed or Refractory Neuroblastoma: A New Approaches to Neuroblastoma Therapy Trial

PURPOSE We conducted a phase I trial to determine the safety, tolerability, and preliminary antitumor activity of 131 I-metaiodobenzylguanidine (MIBG) combined with the anti-GD2 antibody dinutuximab with or without the histone deacetylase inhibitor vorinostat in patients with relapsed/refractory neuroblastoma (rNBL). METHODS In part A, patients with MIBG-avid rNBL received MIBG intravenously (IV) on day 1 at 12, 15, or 18 mCi/kg per the rolling six design and dinutuximab (17.5 mg/m 2 once daily) IV on days 8-11 and 29-32 and granulocyte-macrophage colony-stimulating factor (250 mcg/m 2 once daily) subcutaneously on days 8-17 and 29-38. Autologous stem cells were infused on day 15. In part B, vorinostat at 180 mg/m 2 once daily was given orally on days 0-13 in combination with the part A recommended phase II dose (RP2D). Patients could receive two courses. RESULTS Forty-five eligible patients enrolled, of whom 31 were evaluable. The median age was 7.5 (range, 2.9-24.1) years. For part A (n = 19), no dose-limiting toxicities (DLTs) occurred across all dose levels and courses, establishing the RP2D of MIBG to be 18 mCi/kg. In part B (n = 12), 1 DLT (grade 3 hypokalemia) occurred during course 1, and 3 of 11 patients who received a second course experienced DLT: grade 3 ALT increase, grade 4 hypoxia and grade 5 pneumonitis, and grade 3 fatigue. The best overall response rate (BORR; complete response [CR] + partial response [PR]) on part A was 42% with a CR/PR/minor response (MR) rate of 46%, and 19% progressive disease (PD) rate. For part B, the BORR was 42% with a CR/PR/MR rate of 75% and 0% PD rate. CONCLUSION MIBG combined with dinutuximab was well tolerated with encouraging antitumor activity. Vorinostat added to this combination may augment responses in this heavily pretreated patient population.