Combining Immunotherapies with Conventional Cancer Therapies in a Preclinical Model of Treatment-Resistant, High-Risk Neuroblastoma

Abstract Patients diagnosed with neuroblastoma (NBL) are segmented into categories, with ~50% considered high-risk and ~40% of those patients eventually succumbing to disease. Our group published a regimen (“CAIR”) combining adaptive and innate immunotherapies with radiotherapy (RT) to treat an immunologically cold, treatment-resistant model of NBL (9464D-GD2). Despite CAIR being our most effective treatment, it only cures ~40% of tumors and lacks clinical relevance due in part to toxicities. Here we aimed to test if the clinically-approved salvage therapy of temozolomide and irinotecan (T/I) and αGD2-based therapy replicated human trials and to test if CAIR can be reduced to improve relevance. For chemo studies, mice were treated T/I and αGD2 immunocytokine (Hu14.18-IL2). T/I or Hu14.18-IL2 alone did not extend survival of 9464D-GD2-bearing mice (p=0.596 and p>0.999). T/I and Hu14.18-IL2 together extended survival (p=0.036 and p=0.004) but none of these treatments resulted in cures. To test CAIR reductions, mice were treated with RT, αCD40, αCTLA4, CpG, and Hu14.18-IL2. The full regimen cured 36% of mice (8/22), CAIR minus αCTLA cured 43% (9/21), CAIR minus αCD40 cured 50% (8/16), and CAIR minus CpG cured 44% (7/16). CAIR minus RT or Hu14.18-IL2 cured no mice (0/8 each). Demonstrating similarity to human NBLs that do not respond to salvage treatment of T/I and αGD2 therapy, 9464D-GD2 tumors are not cured by T/I and αGD2 immunocytokine (Hu14.18-IL2). In contrast, CAIR can cure 9464D-GD2 bearing mice, and our data indicate that this regimen can be further reduced without decreasing efficacy. A reduced regimen enhances both clinical relevance and our ability to add additional agents to further improve survival. Fellowship support provided by the Hartwell Foundation.