Abstract 2671: Antitumor activity of NKTR-214 in combination with pmel-1 ACT in an aggressive murine melanoma model
Authors: Parisi Giulia , Saco Justin , Hu-Lieskovan Siwen , Zhang Ruixue , Krystofinski Paige , Saus Cristina Puig , Charych Deborah H. , Ribas Antoni 
Published: July 2017

The adoptive cell transfer (ACT) of genetically engineered T cells expressing cancer-specific T-cell receptors (TCR) has been shown to induce effective anti-tumor response. However, tumors frequently relapse after an initial response. Another strategy towards stimulating the immune system is the use of high-dose interleukin-2 (IL-2) to target the IL-2 receptor (IL2R), leading to immune cell expansion. However, clinically approved IL-2 expands both tumor-killing CD8+ effector T cells (CD8T) as well as regulatory T cells (Tregs) through binding the IL-2Rβγ and IL-2Rαβγ complexes, respectively. Tregs in the tumor lead to immune suppression, which hampers the antitumoral response. NKTR-214 is a CD122-biased cytokine agonist conjugated with multiple releasable chains of polyethylene glycol and designed to provide sustained signaling through the heterodimeric IL-2 receptor pathway (IL-2Rβγ) to preferentially activate and expand effector CD8+ T and NK cells over Tregs. We used the pmel-1 ACT/B16 melanoma tumor model to test the anti-tumor activity of NKTR-214 and evaluate its effects on tumor-specific TCR transgenic T cells. On Day 0 (D0) C57BL/6 mice were implanted with B16-F10 mouse melanoma cells and lymphodepleted with 500 cGy on D6. On D7, mice were treated with either the combination of ACT (T lymphocytes activated in vitro with 1 μg/ml gp100) plus NKTR-214 (0.8 mg/kg, q9dx3, i.v.) or with C57/B6 T cells plus PBS (vehicle control). The tumors of the vehicle control mice (n=12) rapidly grew to the 1500mm3 endpoint in 12 days post-treatment, versus 35 days for the NKTR-214 group (n=12) with only 1 out of 12 mice reaching endpoint. Bioluminescence imaging was used to visualize the in vivo distribution and tumor-homing of antigen-specific T cells. Interestingly, the reporter T cells were retained in the spleen until D7 and could be seen migrating to the tumor at D9 reaching peak of bioluminescence at day 12, a delayed time point compared to the 5 days usually observed in mice treated with standard IL-2. The signal persisted in the NKTR-214 + ACT group until D20 versus D7 in the vehicle-control animals. These data suggest that NKTR-214 + ACT is well tolerated and provides a robust anti-tumor response in the aggressive B16F10 model. Treatment with NKTR-214 + ACT robustly mobilizes T cells into the tumor where they durably persist. The robust and long-lasting effect of NKTR214 supports its potential use in combination with cell-based therapeutics.

Citation Format: Giulia Parisi, Justin Saco, Siwen Hu-Lieskovan, Ruixue Zhang, Paige Krystofinski, Cristina Puig Saus, Deborah H. Charych, Antoni Ribas. Antitumor activity of NKTR-214 in combination with pmel-1 ACT in an aggressive murine melanoma model [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 2671. doi:10.1158/1538-7445.AM2017-2671