| Hu14.18-IL2, an immunocytokine (IC), consists of the humanized 14.18 (hu14.18) monoclonal antibody (mAb) genetically linked to human recombinant interleukin-2 (IL2). This mAb recognizes GD2, a disialoganglioside over-expressed on neuroblastoma and melanoma. Ch14.18, the chimeric form of hu14.18, has been tested as an investigational therapeutic agent, alone and combined with IL-2, in Phase I-III clinical trials. Recently, clinical benefit was proven in a published Phase III trial. Testing directly in tumor-bearing mice, intratumoral (IT) administration of ICs has shown an advantage compared to intravenous (IV) administration. In an A/J mouse model bearing subcutaneous GD2+ NXS2 neuroblastoma, IT hu14.18-IL2 treatment resulted in a greater antitumor response compared to IV hu14.18-IL2. This response was antigen-specific and dose-dependent. These studies indicate that clinical testing of IT hu14.18-IL2 in melanoma patients with measureable disease appears warranted.;To evaluate the antitumor mechanisms of IT-IC, and focus on the degree of tumor-infiltrating leukocytes (TILs), we examined the effects of IT hu14.18-IL2 in A/J mice bearing established GD2+ NXS2 neuroblastoma. We hypothesize that IT-IC administration results in increased and sustained levels of IC within the tumor, augmenting infiltration of immune effector cells into the tumor thereby enhancing antitumor response. We developed methods to evaluate these hypotheses in tumor-bearing mice and demonstrate prolonged IC retention and augmented numbers of activated T and NK cells within tumors. To model patterns of TILs in patients receiving IC in clinical trials, we developed a histological method in mice to identify and quantify TILs. Additionally, we used multicolor flow cytometry to quantify TILs and NKG2D expression on natural killer cells and cytotoxic T cells. We analyzed the profile of hu14.18-IL2 and TILs at the tumor site following IT versus IV delivery of hu14.18-IL2.;Finally, we present a retrospective analysis of parameters predictive of successful immunotherapy in mice. We evaluated levels and distributions of TILs in individual NXS2-bearing mice involved in hu14.18-IL2 administration studies. While differences are seen between treatment groups, substantial heterogeneity is observed within each treatment group. We analyze the immune infiltrate profile of TILs seen shortly after treatment, and demonstrate that there is a correlation between immune infiltration and clinical outcome. |
