Abstract LB-198: Combination of PEGylated recombinant hyaluronidase PH20 (PEGPH20) with live-attenuated, double-deleted (LADD) Listeria enhances tumor infiltrating CD8+ T cell response and antitumor efficacy in mice

Abstract

Abstract Successful immunotherapy is highly dependent on inducing an efficient CD8+ T cell-mediated antitumor immune response. The trafficking and activation of these effector CD8+ T cells are often inhibited by various immunosuppressive mechanisms in the tumor microenvironment (TME). Hyaluronan (HA), a glycosaminoglycan that accumulates in the TME of many solid tumors, is associated with rapid tumor progression, poor prognosis and increased immunosuppression. We have previously demonstrated in nonclinical models that enzymatic degradation of TME HA by intravenous PEGylated recombinant human hyaluronidase PH20 (PEGPH20) facilitates delivery of chemotherapeutics to tumors and enhances checkpoint inhibitor efficacy. Based on these observations we hypothesized that PEGPH20 may improve current cancer immunotherapies by increasing immune cell infiltration into tumors. To test this hypothesis we used CT26/HAS3 tumors, CT26 murine colon carcinoma cells engineered to over-express hyaluronan synthase-3, and treated them with PEGPH20 in combination with recombinant live-attenuated double-deleted strains of Listeria monocytogenes expressing AH1 (gp70423-431, SPSYVYHQF), the immunodominant CD8+ T cell epitope of CT26 (LADD-AH1). PEGPH20 (1mpk), which results in nearly complete removal of HA at 24hrs, was administered 24hrs prior to LADD-AH1. In this model, LADD-AH1 alone inhibited tumor growth which correlated with an increase in IFNγ+ (p=0.0019) and granzyme B+ CD8+ tumor infiltrating lymphocytes (TILs) (p=0.0006). Tumor-associated macrophages (TAMs) from LADD-AH1 treated tumors were more immunostimulatory with a decrease in MHCIIlow (p=0.0205) and CD206+ TAMs (p=0.0003). Moreover, the combination of PEGPH20 and LADD-AH1 resulted in enhanced anti-tumor activity compared to either PEGPH20 (p=0.0047) or LADD-AH1 alone (p=0.0002). Significant TME changes were observed in the combination treatment with an increase in CD8+ TILs (p=0.0200, of which 88% were granzyme B+), NK cells (p=0.0205) and an increase in CD8:Treg ratio (p=0.0007).These findings were corroborated by immunohistochemical analysis demonstrating an increase in CD3+ T cells with PEGPH20 treatment. Taken together, these data suggest that HA accumulation in tumors may act as a barrier to immune cell access and that reduction of HA by PEGPH20 facilitates increased accumulation of tumor antigen-specific CD8+ effector T cells induced by LADD immunotherapy. Our findings reveal a benefit of PEGPH20 in enhancing tumor infiltration of cytotoxic CD8+ T cells induced by LADD that translate into a significant improvement in efficacy in a murine model of HA-high tumors. Citation Format: Jisook Lee, Meredith Leong, Yujun Huang, Benjamin J. Thompson, Sanna Rosengren, Barbara Blouw, Dirk G. Brockstedt, Curtis B. Thompson. Combination of PEGylated recombinant hyaluronidase PH20 (PEGPH20) with live-attenuated, double-deleted (LADD) Listeria enhances tumor infiltrating CD8+ T cell response and antitumor efficacy in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-198. doi:10.1158/1538-7445.AM2017-LB-198