Bempegaldesleukin selectively depletes intratumoral Tregs and potentiates T cell-mediated cancer therapy

High dose interleukin-2 (IL-2) is active against metastatic melanoma and renal cell carcinoma, but treatment-associated toxicity and expansion of suppressive regulatory T cells (Tregs) limit its use in patients with cancer. Bempegaldesleukin (NKTR-214) is an engineered IL-2 cytokine prodrug that provides sustained activation of the IL-2 pathway with a bias to the IL-2 receptor CD122 (IL-2Rβ). Here we assess the therapeutic impact and mechanism of action of NKTR-214 in combination with anti-PD-1 and anti-CTLA-4 checkpoint blockade therapy or peptide-based vaccination in mice. NKTR-214 shows superior anti-tumor activity over native IL-2 and systemically expands anti-tumor CD8⁺ T cells while inducing Treg depletion in tumor tissue but not in the periphery. Similar trends of intratumoral Treg dynamics are observed in a small cohort of patients treated with NKTR-214. Mechanistically, intratumoral Treg depletion is mediated by CD8⁺ Teff-associated cytokines IFN-γ and TNF-α. These findings demonstrate that NKTR-214 synergizes with T cell-mediated anti-cancer therapies.

Interleukin-2 can induce an anti-tumour response, but is associated with toxicity. Here, the authors demonstrate that an engineered interleukin-2 promotes intratumoral T regulatory cell depletion while enhancing effective anti-tumour CD8⁺ T cell responses that result in potent tumor suppression.

Cancer vaccine formulation dictates synergy with CTLA-4 and PD-L1 checkpoint blockade therapy

Anticancer vaccination is a promising approach to increase the efficacy of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed death ligand 1 (PD-L1) checkpoint blockade therapies. However, the landmark FDA registration trial for anti-CTLA-4 therapy (ipilimumab) revealed a complete lack of benefit of adding vaccination with gp100 peptide formulated in incomplete Freund's adjuvant (IFA). Here, using a mouse model of melanoma, we found that gp100 vaccination induced gp100-specific effector T cells (Teffs), which dominantly forced trafficking of anti-CTLA-4-induced, non-gp100-specific Teffs away from the tumor, reducing tumor control. The inflamed vaccination site subsequently also sequestered and destroyed anti-CTLA-4-induced Teffs with specificities for tumor antigens other than gp100, reducing the antitumor efficacy of anti-CTLA-4 therapy. Mechanistically, Teffs at the vaccination site recruited inflammatory monocytes, which in turn attracted additional Teffs in a vicious cycle mediated by IFN-γ, CXCR3, ICAM-1, and CCL2, dependent on IFA formulation. In contrast, nonpersistent vaccine formulations based on dendritic cells, viral vectors, or water-soluble peptides potently synergized with checkpoint blockade of both CTLA-4 and PD-L1 and induced complete tumor regression, including in settings of primary resistance to dual checkpoint blockade. We conclude that cancer vaccine formulation can dominantly determine synergy, or lack thereof, with CTLA-4 and PD-L1 checkpoint blockade therapy for cancer.

Abstract B022: Intratumoral CD40 activation and checkpoint blockade induces systemic anti-melanoma immunity that eradicates disseminated tumors

Although surgical resection is a reliable treatment for localized melanoma, treatment options for metastatic melanoma are limited. Melanoma Brain metastasis (MBM) is a major clinical problem in patients with advanced melanoma, and the incidence of brain metastasis is increasing every year. Thus, there is a significant unmet need for effective therapies for metastatic melanoma and MBM patients. Agonistic CD40 antibodies generate strong tumor specific CD8 T cell response and anti-tumor activity; however systemic anti-CD40 therapy has been associated with cytokine release syndrome and liver toxicity. We studied the anti-melanoma activity and mechanism of action of a non-replicating adenovirus encoding a CD40-targeting chimeric immunostimulatory protein (ISF35) by local intratumoral delivery approach to treat local and distant melanoma. Mice bearing established B16 melanomas on both right and left flanks or on right flank and in brain were treated intratumorally with ISF35 or rAd.empty to the right flank tumor and received anti-PD1 plus anti-CTLA-4 systemically. Anti-tumor effects of mono or combination therapies were determined by mice survival and tumor growth measurement. The mechanistic contribution of immune cells to this therapy was determined by using antibody blockades. Immune cell infiltrates in tumor and expression of activation markers on these cells were analyzed by flow cytometry. Intratumoral administration of ISF35 generates systemic anti-tumor immunity mediates by CD8 T cells and suppress both injected and distant uninjected wild-type B16.F10 melanomas. However, tumors did not completely regress after therapy. When combined with checkpoint inhibitors, ISF35 generates synergistic systemic anti-melanoma immunity that eradicates both injected and uninjected distant subcutaneous melanoma and uninjected brain melanoma with 40% of mice cured. The systemic anti-tumor activity of ISF35/anti-PD-1/anti-CTLA-4 was associated with greater production of melanoma-specific CD8 T cells with an activated phenotype. Immunotherapy based on intratumoral CD40 activation is potentiated by PD-1 and CTLA-4 blockade and this combination generates functional and long-lasting anti-tumor CD8 T cell immunity that systemically suppresses melanoma metastases. This approach will be a better option for treatment of patients with metastatic melanoma that does not respond to checkpoint blockage monotherapy.

Citation Format: Manisha Singh, Christina Vianden, Adi Diab, Patrick Hwu, Willem W. Overwijk. Intratumoral CD40 activation and checkpoint blockade induces systemic anti-melanoma immunity that eradicates disseminated tumors [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B022.

Abstract LB-096: Induction of systemic immunity through single-site intratumoral CD40 activation and checkpoint blockade eradicates melanoma in the brain

Background: Melanoma brain metastases (MBM) are a rapidly growing clinical problem with up to 60% of melanoma patients developing MBM over the course of their disease. Locoregional treatment with surgery, radiotherapy, radiosurgery, and newer drug classes such as checkpoint inhibitors and targeted agents against BRAF-mutation melanoma have shown limited effectiveness against MBM (Lancet 2015; 16: e486-97). MBM patients continue to have poor clinical outcomes and life expectancies of only 3-7 months. Thus, there is a significant unmet need for effective therapies for MBM patients. Direct intratumoral administration of a non-replicating adenovirus encoding a CD40-targeting chimeric immunostimulatory protein (ISF35) leads to generation of potent melanoma-specific T cells. When combined with checkpoint inhibitors, ISF35 generates synergistic systemic anti-melanoma immunity that eradicates both injected and uninjected distant melanoma with 40% of mice cured using a B16 model. Based on this evidence of systemic activity, we hypothesized that ISF35/checkpoint inhibitors combination treatment may have systemic activity against MBM.

Methods: A MBM mouse model was developed using luciferase-expressing B16 (B16-Luc). B16-Luc cells were subcutaneously (s.c.) implanted in the right flank of C57BL/6 mice 12 days prior to treatment. B16-Luc cells were then injected into the brain four days prior to treatment. Following tumor establishment at both sites, ISF35 was injected intratumorally in the right flank tumor on days 0, 4, 9, and 14. Simultaneously, anti-PD1 and anti-CTLA-4 antibodies were systemically administered.

Results: Intratumoral administration of ISF35 in combination with anti-PD-1 and anti-CTLA-4 significantly increased (p<0.01) mouse survival compared to untreated mice. Median survival was not reached for the ISF35 plus checkpoint combination, was 10 days for untreated mice, 26 days for ISF35 monotherapy, and 17 days for anti-PD-1/anti-CTLA-4 combination therapy. ISF35/anti-PD-1/anti-CTLA-4 combination treatment of s.c. tumors resulted in complete and durable abscopal regression of brain tumors as assessed by bioluminescent imaging 30 days following initiation of treatment. In contrast, brain melanoma tumors continued to grow in the ISF35 monotherapy or anti-PD-1/anti-CTLA-4 treatment groups. The systemic anti-tumor activity of ISF35/anti-PD-1/anti-CTLA-4 was associated with greater production of melanoma-specific CD8 T cells with an activated phenotype, including upregulated PD-1 surface expression.

Conclusions: These results suggest ISF35 may improve the effectiveness of checkpoint inhibitors therapy for metastatic melanoma, including in the brain.

Citation Format: Manisha Singh, Christina Vianden, Adi Diab, Patrick Hwu, Willem W. Overwijk. Induction of systemic immunity through single-site intratumoral CD40 activation and checkpoint blockade eradicates melanoma in the brain. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-096.