Abstract 3566: Enhanced expansion and tumor targeting of adoptively transferred T cells with NKTR-214
Authors: Parisi Giulia , Saco Justin , Bergara Felix , Krystofinski Paige , Zhang Ruixue , Saus Cristina Puig , Hu-Lieskovan Siwen , Comin-Anduix Begonya , Wu Anna , Charych Deborah H. , Ribas Antoni 
Published: August 2018

Abstract
NKTR-214 is a CD122-biased cytokine agonist designed to provide sustained signaling through the heterodimeric IL-2 receptor pathway (IL-2Rβγ) to preferentially activate and expand CD8 T and natural killer cells (NK) over Tregs in the tumor. We evaluated the tumor immunology, biodistribution and anti-tumor activity of NKTR-214 combined with ACT in the pmel-1 ACT/B16F10 melanoma tumor model. NKTR-214+ACT provides a robust and durable anti-tumor response compared to IL-2+ACT with less frequent dosing in the aggressive B16F10 model. NKTR-214+ACT led to significant tumor growth inhibition at day 14 compared with IL-2+ACT, 174mm3 vs 484mm3 tumor volume, respectively (p&lt;0.05, n=12). Tumors of animals receiving IL-2+ACT grew to the endpoint of 1,500 mm3 18 days after treatment, while NKTR-214+ACT significantly improved the survival to 35 days (p&lt;0.0001). Bioluminescence imaging (BLI) showed that NKTR-214+ACT treatment significantly increased T cells expansion in the spleen from day 5 to day 9 compared to IL-2+ACT (p&lt;0.0001, n=5). At day 5, quantification of BLI of serial images with region of interest analysis at the site of spleen revealed an average radiance 14 folds higher in NKTR+ACT than in IL-2+ACT treated mice (1.3*10^7 vs 9.5*10^5 p/s/cm²/sr). BLI showed a stronger peak of activity of tumor-infiltrating effector T cells in the ACT+NKTR-214 group versus the ACT+IL-2 from day 5 to day 7 (p&lt;0.0001, n =5). The second dose of NKTR-214 at day 9 triggered a second expansion of effector T cells in the spleen and tumor from day 12 to day 17, while no effect in the group treated with 3 doses IL-2 was observed (p&lt;0.0001, n =5). The peak of signal was reached at day 14 with an average radiance 10 folds higher in the NKTR-214+ACT group compared to the IL2+act group (4.7*10^6 vs 4.5*10^5 p/s/cm²/sr). These data are supported by immuno-PET imaging using minibody (Mb) targeting CD8 in vivo. Ex vivo biodistribution analysis showed a signal in the spleen 5-folds higher in the ACT+NKTR-214 group compared with the ACT+IL-2 group on day 5 after treatment, 87% and 17% injected dose per gram, respectively (p&lt;0.05, n=3). Flow cytometry analysis performed at the same time point showed that NKTR-214 treatment significantly increased pmel-1 CD8 T cells and amplified the CD8/Treg ratio compared to IL-2 both in spleen and tumor (3 and 6 folds, respectively, p&lt;0.05, n=3). In conclusion, NKTR-214 + ACT is well tolerated and robustly mobilizes T cells into tumors where they durably persist, supporting NKTR-214 potential use in combination with cell-based therapeutics.
Citation Format: Giulia Parisi, Justin Saco, Felix Bergara, Paige Krystofinski, Ruixue Zhang, Cristina Puig Saus, Siwen Hu-Lieskovan, Begonya Comin-Anduix, Anna Wu, Deborah H. Charych, Antoni Ribas. Enhanced expansion and tumor targeting of adoptively transferred T cells with NKTR-214 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3566.