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596 Combining Bempegaldesleukin (CD122-preferential IL-2 pathway agonist) and NKTR-262 (TLR7/8 agonist) pairs local innate activation with systemic CD8+ T cell expansion to enhance anti-tumor immunity
  1. Annah Rolig1,
  2. Daniel Rose1,
  3. Grace Helen McGee1,
  4. Saul Kivimae2,
  5. Werner Rubas2 and
  6. William Redmond1
  1. 1Earle A. Chiles Research Institute, Portland, OR, USA
  2. 2Nektar Therapeutics, San Francisco, CA, USA


Background Tumor cell death caused by radiation therapy (RT) can trigger anti-tumor immune responses in part because dying cells release adjuvant factors that amplify and sustain DC and T cell responses. We previously demonstrated that bempegaldesleukin (BEMPEG:NKTR-214, a first-in-class CD122-preferential IL-2 pathway agonist), significantly enhanced the anti-tumor efficacy of RT through a T cell-dependent mechanism. Because RT can induce either immunogenic or tolerogenic cell death, depending on a multitude of factors (radiation dose, cell cycle phase, and tumor microenvironment), we hypothesized that providing a specific immunogenic adjuvant, like intratumoral NKTR-262, a novel toll-like receptor (TLR) 7/8 agonist, to the tumor site would further improve systemic tumor-specific immunity by promoting synergistic activation of local immunostimulatory innate immune responses. Therefore, we evaluated whether intratumoral NKTR-262, combined with systemic BEMPEG treatment would result in improved tumor-specific immunity and survival compared to BEMPEG combined with RT.

Methods Tumor-bearing mice (CT26; EMT6) received BEMPEG (0.8 mg/kg; iv), RT (16 Gy x 1), and/or intratumoral NKTR-262 (0.5 mg/kg). Flow cytometry was used to evaluate CD4+ and CD8+ T cell activation status in the blood and tumor (7 days post-treatment). The contribution of specific immune subsets was determined by depletion of CD4+, CD8+, or NK cells. CD8+ T cell cytolytic activity was determined in vitro with an Incucyte assay. Data are representative of 1–2 independent experiments (n=5–14/group) and statistical significance was determined by 1-way ANOVA (p-value cut-off of 0.05).

Results BEMPEG/NKTR-262 resulted in significantly improved survival compared to BEMPEG/RT. Both combination therapies were CD8+ T cell dependent. However, response to BEMPEG/NKTR-262 was characterized by a significant expansion of activated CD8+ T cells (GzmA+; Ki-67+; ICOS+; PD-1+) in the blood, which correlated with reduced tumor size (p<0.05). In the tumor, BEMPEG/NKTR-262 induced higher frequencies of GzmA+ CD8+ T cells exhibiting reduced expression of suppressive molecules (PD-1+, TIM-3+), compared to BEMPEG/RT. Additionally, CD8+ T cells isolated from BEMPEG/NKTR-262-treated tumors had greater cytolytic capacity than those from BEMPEG/RT-treated mice.

Conclusions Combining BEMPEG with NKTR-262 lead to a more robust expansion of activated CD8+ T cells compared to the BEMPEG/RT combination. Enhancement of the activated CD8+ T cell response in mice treated with NKTR-262 in combination with BEMPEG suggests that intratumoral TLR stimulation provides superior antigen presentation and costimulatory activity compared to RT. A clinical trial of BEMPEG/NKTR-262 for patients with metastatic solid tumors is in progress (NCT03435640).

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