NKTR-255, a novel polymer-conjugated rhIL-15 with potent antitumor efficacy

BACKGROUND

NKTR-255 is a novel polyethylene glycol-conjugate of recombinant human interleukin-15 (rhIL-15), which was designed to retain all known receptor binding interactions of the IL-15 molecule. We explored the biologic and pharmacologic differences between endogenous IL-15 receptor α (IL-15Rα)-dependent (NKTR-255 and rhIL-15) and IL-15Rα-independent (precomplexed rhIL-15/IL-15Rα) cytokines.

METHODS

In vitro pharmacological properties of rhIL-15, NKTR-255 and precomplex cytokines (rhIL-15/IL-15Rα and rhIL-15 N72D/IL-15Rα Fc) were investigated in receptor binding, signaling and cell function. In vivo pharmacokinetic (PK) and pharmacodynamic profile of the cytokines were evaluated in normal mice. Finally, immunomodulatory effect and antitumor activity were assessed in a Daudi lymphoma model.

RESULTS

NKTR-255 and rhIL-15 exhibited similar in vitro properties in receptor affinity, signaling and leukocyte degranulation, which collectively differed from precomplexed cytokines. Notably, NKTR-255 and rhIL-15 stimulated greater granzyme B secretion in human peripheral blood mononuclear cells versus precomplexed cytokines. In vivo, NKTR-255 exhibited a PK profile with reduced clearance and a longer half-life relative to rhIL-15 and demonstrated prolonged IL-15R engagement in lymphocytes compared with only transient engagement observed for rhIL-15 and precomplexed rhIL-15 N72D/IL-15Rα Fc. As a consequent, NKTR-255 provided a durable and sustained proliferation and activation of natural killer (NK) and CD8+ T cells. Importantly, NKTR-255 is more effective than the precomplexed cytokine at inducing functionally competent, cytotoxic NK cells in the tumor microenvironment and the properties of NKTR-255 translated into superior antitumor activity in a B-cell lymphoma model versus the precomplexed cytokine.

CONCLUSIONS

Our results show that the novel immunotherapeutic, NKTR-255, retains the full spectrum of IL-15 biology, but with improved PK properties, over rhIL-15. These findings support the ongoing phase 1 first-in-human trial (NCT04136756) of NKTR-255 in participants with relapsed or refractory hematologic malignancies, potentially advancing rhIL-15-based immunotherapies for the treatment of cancer.

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.

Abstract 3265: NKTR-255, a polymer-conjugated IL-15 enhances anti-tumor NK cell responses and synergizes with monoclonal antibodies to provide long-term survival in human lymphoma model

Background: IL-15 is a cytokine that activates and provides survival benefit to NK cells. Exploiting the therapeutic value of native IL-15 has been challenging due to its unfavorable pharmacokinetic properties and tolerability. NKTR-255 is a polymer-conjugated human IL-15 that retains binding affinity to the alpha subunit of IL-15 receptor and exhibits reduced clearance to thereby provide a sustained pharmacodynamics response. NKTR-255 has potential for providing an enhanced immunotherapeutic effect when combined with monoclonal antibodies that mediate tumor killing by antibody dependent cellular cytotoxicity (ADCC). Here we investigate the pharmacological properties of NKTR-255 on NK cells and the therapeutic effect of NKTR-255 when combined with tumor-directed monoclonal antibodies in a B cell lymphoma model.

Methods: KHYG-1 cells (human NK cell line) were used to measure phosphorylated STAT5 (pSTAT5) and cell proliferation. Human PBMCs were stimulated with NKTR-255 and/or daratumumab for in vitro NK cell characterization. In the cytotoxic assay, mice received single IV doses of 0.3 mg/kg of NKTR-255 and splenic NK cells were co-cultured with YAC-1 cells (mouse T lymphoma cell line) to measure cytotoxic function. In the Daudi lymphoma model, 1x107 Daudi cells were inoculated IV on Day 0. NKTR-255 (0.03, 0.1 or 0.3 mg/kg SC) was administered on Days 14, 21 and 28 and antibody treatment was administered on Day 14 (daratumumab 0.5 mg/kg IP) or on Days 14 and 17 (rituximab 40 mg/kg IP). Survival rate was determined by onset of hindlimb paralysis as a surrogate parameter.

Results: NKTR-255 dose-dependently induced pSTAT5 and proliferation in KHYG-1 cells (EC50 values for pSTAT5: 0.2 ng/ml, proliferation: 5 ng/ml). NKTR-255 also resulted in enhanced pSTAT5 and NKG2D surface expression on human primary NK cells. In addition NKTR-255 increased NK cell degranulation in co-culture experiments with U266 cells (myeloma cell line) with/without daratumumab (anti-human CD38 antibody), as determined by enhanced CD107a surface expression. In vivo pretreatment with NKTR-255 resulted in sustained cytotoxic function of NK cells in both ex vivo and in vivo studies. Finally, NKTR-255 synergistically provided long-term survival benefit in a dose-dependent manner when administered with daratumumab or rituximab (anti-human CD20 antibody) in the Daudi B cell lymphoma model.

Conclusions: NKTR-255 is an immune stimulator of NK cells that provides a dose-dependent effect in the proliferation and activation of NK cells. This property of NKTR-255, when administered with daratumumab or rituximab, translates into enhanced therapeutic efficacies of the antibodies in a B cell lymphoma model. These results indicate that combining NKTR-255 with a tumor-directed antibody having an ADCC mechanism can provide a synergistic effect for treating cancers.

Citation Format: Takahiro Miyazaki, Saul Kivimäe, Rhoneil Pena, Peiwen Kuo, Marlene Hennessy, Murali Addepalli, Neha Dixit, Wildaliz Nieves, Sara Sheibani, Mekhala Maiti, Laurie VanderVeen, Joanna Wilczek, Loui Madakamutil, Jonathan Zalevsky. NKTR-255, a polymer-conjugated IL-15 enhances anti-tumor NK cell responses and synergizes with monoclonal antibodies to provide long-term survival in human lymphoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3265.

Abstract 1603: NKTR-255 engages the IL-15 pathway driving CD8 T cell survival and CD8 memory T cell proliferation

Background: IL-15, an immunostimulatory cytokine, plays an important role in both the innate and adaptive immune system. Notably, this pleiotropic cytokine is a key regulator of homeostasis and survival of CD8 and CD8 memory T cells. Targeting the IL-15 pathway has therefore become a promising therapeutic approach in oncology through the induction of long-term T cell activation and durable memory responses. NKTR-255 is a polymer-engineered IL-15 that as a single-agent reduces tumor burden in various tumor models. Here, we show that the anti-tumor effects of NKTR-255 can be attributed to its modulation of survival and proliferation of CD8 and memory CD8 T cells.

Methods: Immunophenotyping of CD8 T cell subpopulations was performed in naïve and tumor-bearing Balb/c mice treated with NKTR-255. Cell surface staining of CD3, CD8, CD44, CD62L and Sca-1 was conducted to identify effector (Tem), central (Tcm) and stem (Tscm) memory T cells. Intracellular staining of Ki67 and Bcl-2 were also analyzed by flow cytometry. Human whole blood and PBMCs were stimulated with IL-15 (0.0001-1000ng/ml) or NKTR-255 (0.001-10,000ng/ml). At various time points pSTAT5 response in CD3, CD4, CD8 and NK (CD56 bright and dim) cells was monitored by flow cytometry.

Results: In naive mice, single dose NKTR-255 (dose range 0.06-1mg/kg) increased the proliferation of Tem, Tcm and Tscm CD8 T cells in a dose-dependent manner. Treatment at 0.3 and 1mg/kg dose levels increased proliferation at least 4 fold across the CD8 memory populations. The abundance of CD8 and CD8 memory T cells was still apparent 6 days post-treatment unlike single dose IL-15 which was ineffective. In a CT-26 lung metastasis model, NKTR-255 reduced the number of lung nodules in a dose-dependent manner. A 0.3mg/kg dose level increased Bcl-2 MFI 1.5 fold in CD8 T cells. Furthermore, administration of NKTR-255 at 0.3, 1 or 3mg/kg significantly increased CD8 proliferation in a dose-dependent manner in blood (1.7, 4.6 and 5.3 fold) and spleen (2.5, 5.7 and 6.9 fold) compared to vehicle. The enhanced Bcl-2 expression and CD8 proliferation were accompanied by elevated CD8 T cells in blood (1.5, 2.4, and 3.4 fold increase) and spleen (1.3, 1.7 and 2.3 fold increase). Consistent with increased proliferation and increased Bcl-2 levels observed in vivo, both IL-15 and NKTR-255 showed dose-dependent induction of pSTAT5, a modulator of Bcl-2 expression, in CD4 and CD8 T cells from human whole blood and PBMCs.

Conclusions: NKTR-255 effectively engages the IL-15 pathway as evidenced by its strong induction of CD8 and memory CD8 T cell proliferation and promotion of survival. Combined with sustained activity and potency in human blood and PBMCs, our results support NKTR-255 as a novel tumor immunotherapeutic with great potential.

Citation Format: Peiwen Kuo, Mekhala Maiti, Phi Quach, Murali Addepalli, Arunasree Lanka, Poornachandra Mathamsetti, Christie Fanton, Ping Zhang, Peter Kirk, Takahiro Miyazaki, Jonathan Zalevsky. NKTR-255 engages the IL-15 pathway driving CD8 T cell survival and CD8 memory T cell proliferation [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 1603. doi:10.1158/1538-7445.AM2017-1603

Abstract B057: The CD122-biased immunostimulatory cytokine NKTR-214 combined with checkpoint blockade leads to mobilization of antitumor immunity and synergistic activity

Background: NKTR-214 is a novel immunostimulatory cytokine which provides a sustained and biased activation signal through the heterodimeric IL-2R receptor (IL2Rbg or CD122), resulting in significant expansion of CD8+ T and NK cells relative to regulatory T cells in the tumor microenvironment. As a single agent in preclinical tumor models, NKTR-214 significantly increases the intratumoral CD8T/Treg ratio (>400). Here we examine activity and pharmacodynamic effects of NKTR-214 alone and combined with immune checkpoint blockade in both a murine tumor model and in a human in vitro co-culture system. Methods: Mice bearing subcutaneous CT26 colon tumors were treated with single agent NKTR-214 (q9d), murine anti-CTLA-4 or anti-PD-1 (twice-weekly), or combinations of these agents. Serum cytokines were assessed by multiplex ELISA (Quansys). T cell clonality and infiltration were assessed in tumors 7 days after treatment initiation, with TCR V and J beta usage determined by ImmunoSEQ (Adaptive Biotechnologies). Effects on human cytokine and chemokine expression were examined by the BioMAP Combo ELECT (DiscoverX) in vitro system utilizing human fibroblasts or endothelial cells, PBMCs and either HT29 colon adenocarcinoma or HT1299 NSCLC cell lines. 1-PEG-IL2, the most active species of the NKTR-214 prodrug, or Keytruda (anti-PD-1) was added over a range of concentrations alone or in combination, with biomarkers assessed 48 hours later. Results: In tumor-bearing mice, NKTR-214 led to increases in serum IFNg as well as increases in the chemokine MCP-1 (CCL2), a chemoattractant of CD4 T, CD8 T and NK cells. Single-agent NKTR-214 led to significant tumor growth inhibition and 10% tumor free animals, while single-agents anti-CTLA-4 or anti-PD-1 lacked efficacy. Combination of NKTR-214 with checkpoint blockade was synergistic and led to greater tumor-free animals (67% in combination with anti-CTLA-4, 90% with anti-PD-1). NKTR-214 combined with anti-PD-1 was also more efficacious than the combination of anti-CTLA-4 and anti-PD-1. TCR repertoire analysis demonstrated superior increases in TIL clonality and infiltration with NKTR-214 compared to either anti-CTLA-4 or anti-PD-1 alone. NKTR-214 combined with either mode of checkpoint inhibition led to significant increases in both parameters, with the greatest effect occurring when combined with anti-PD-1. In the human BioMAP system, NKTR-214 active species led to significant increases in granzyme B, IFNg, IL-6, IL-17A and TNFa, while these markers were only modestly induced by Keytruda alone. When NKTR-214 was combined with Keytruda, additive and synergistic increases in these factors were found. In addition, the combination significantly decreased uPA in the fibroblast-HT29 system and MDC in the endothelial-HT1299 system, both factors associated with tumor progression. Conclusions: NKTR-214 delivers sustained signaling of the IL-2 pathway. Analysis of multiple immune markers in mice and human tumor-immune cell cultures provide mechanistic rationale for the increased T and NK cell activation in the tumor microenvironment after treatment with NKTR-214. When combined with anti-PD-1, significant increases in T cell receptor clonality, tumor infiltration and immune activation biomarkers are achieved - a significant finding, given that concomitant increase in clonality and infiltration has been correlated with favorable responses in the clinic. In vitro studies with human cells demonstrate the potentiation of immune activation markers associated with anti-tumor effects in combination with anti-PD-1, further suggesting these findings may be translatable from mouse to human. NKTR-214 is currently in a Phase 1 clinical trial to evaluate the pharmacokinetics, pharmacodynamics and activity in an outpatient setting.

Citation Format: John L. Langowski, Murali Addepalli, Laurie VanderVeen, Rhoneil Pena, Ravikumar Nutakki, Yolanda Kirksey, Ute Hoch, Jonathan Zalevsky, Stephen K. Doberstein, Deborah H. Charych. The CD122-biased immunostimulatory cytokine NKTR-214 combined with checkpoint blockade leads to mobilization of antitumor immunity and synergistic activity [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 B057.

Abstract B015: Antitumor activity of the CD122-biased immunostimulatory cytokine combined with immune checkpoint blockade requires innate and adaptive immunity

Background: While immune checkpoint blockade is a promising therapeutic approach, combination with agents that modulate complementary pathways may improve responses. Interleukin-2 (IL-2) immunotherapy leads to long-term responses in a small percentage of cancer patients, but systemic toxicity limits its use. In addition, IL-2 expands T regulatory cells, antagonizing antitumor immunity and resulting in a poorer clinical outcome. NKTR-214 is a novel CD122-biased immunostimulatory cytokine which combines biased activation of the IL-2R beta receptor subunit, greatly favoring activation of effector over regulatory T cells, with improved pharmacokinetics and tolerability compared to Proleukin in non-human models. Here we examine the efficacy and mechanism of NKTR-214 combined with anti-CTLA-4 in murine tumor models.

Methods: Mice bearing subcutaneous EMT6 mammary tumors were treated with NKTR-214 q9d, murine anti-CTLA-4 or anti-PD-1 twice-weekly, or both in combination. Immune cell profiling was assessed by flow cytometry following treatment. CD8 or NK cells were depleted in vivo by serial anti-CD8 or anti-asialo-GM1 antibody injections, respectively. Antitumor memory and specificity was assessed in complete responders by challenging with EMT6 or CT26 colon carcinoma implants with no additional treatment.

Results: While NKTR-214 and anti-CTLA-4 were not as efficacious individually, their combination was synergistic and well-tolerated with 83% of test animals tumor-free. Combination treatment increased NK and memory effector CD8 cells in both tumor and spleen. Antitumor immunity by the combination was durable and specific as 70% and 100% of mice remained tumor-free after challenge with a second and third EMT6 implant, but not after a subsequent CT26 implant. NKTR-214 combined with anti-PD-1 also proved synergistic with 40% of animals remaining tumor free following treatment. In vivo depletion of either CD8 effector or NK cells abrogated efficacy suggesting both contribute to the response.

Conclusions: The mechanism of NKTR-214 antitumor immunity is complementary to checkpoint inhibition. Favorable pharmacokinetics of NKTR-214 allows sustained tumor exposure and dosing schedules commensurate with other therapies. This new therapeutic combination of NKTR-214 and checkpoint inhibition may similarly enable durable responses in humans.

Citation Format: John L. Langowski, Seema S. Kantak, Rhoneil Pena, Yolanda Kirksey, Murali Addepalli, Steve Lee, Ute Hoch, Deborah H. Charych, Stephen K. Doberstein. Antitumor activity of the CD122-biased immunostimulatory cytokine combined with immune checkpoint blockade requires innate and adaptive immunity. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B015.

Abstract 5032: Synergy between an engineered cytokine, NKTR-214, and CTLA-4 blockade in murine colon and breast tumor models

Background: Immunotherapy offers the potential for durable responses in a growing list of cancer indications. NKTR-214 is comprised of the cytokine IL2 conjugated o multiple PEG units. Upon in vivo administration some of these PEG molecules are released to leave activated IL2-conjugates that bind selectively at the IL2 receptor beta subunit (IL2Rβ). The active IL-2-conjugates favor proliferation of tumor-killing CD8+ memory T cells (CD8T) over immunosuppressive regulatory T cells (Treg) in the tumor microenvironment (Charych, JCO 2013, 31:15, Suppl. 1).We have also shown that NKTR-214 results in sustained exposure of drug in the tumor and robust immune system activation that translates between rodents and monkeys at safe doses, (AACR; Mol Cancer Ther 2013;12 (11 Suppl): Abstract B296). The receptor selectivity and improved pharmacokinetic profile leads to substantially improved single-agent efficacy and safety over the original IL-2 cytokine. Combinations of different checkpoint blockade antibodies have shown great promise clinically and in preclinical tumor models, highlighting the importance of targeting multiple immune activation pathways. Here we examine the combination of NKTR-214 with anti-CTLA4 antibody in murine breast and colon tumor models to explore the interaction of two mechanisms of action: checkpoint inhibition and direct CD8T cell activation via the IL-2 receptor beta.

Methods: Female BALB/c mice bearing established tumors implanted with CT-26 (Murine Colon Carcinoma) or EMT6 (Murine Mammary Carcinoma) cells were treated with single agent NKTR-214, murine anti-CTLA-4 antibody or the two agents in combination. NKTR-214 was administered at 0.8 mg/kg i.v. and anti-CTLA-4 at 100 μg/mouse i.p.

Results: In both the EMT6 breast and the CT-26 colon models, the combination of NKTR-214 with anti-CTLA-4 yielded significantly better tumor growth inhibition compared to either agent dosed alone. In the EMT6 model 10/12 animals were tumor free by day 20 in the combination arm and stayed tumor free until the end of study (60 days). Similarly in the CT-26 model, 8/12 animals were tumor free by day 25 in the combination arm and stayed tumor free until the end of study (day 60). Single agent anti CTLA-4 or NKTR-214 did not show significant tumor inhibition in either model. No toxicities were observed when NKTR-214 was combined with anti CTLA-4 antibody.

Conclusions: NKTR-214 is a highly differentiated immunotherapy with a new mechanism of action that shows efficacy both as a single agent (as previously shown in a mouse melanoma model) and in combination. Combining NKTR-214 mediated T cell activation with CTLA-4 blockade is highly synergistic in murine models of cancer and holds the promise for durable responses in patients.

Citation Format: Steve Lee, Murali Addepalli, Ute Hoch, Rhoneil Pena, Payal Shirsat, Yolanda Kirksey, Stephen K. Doberstein, Deborah Charych, Seema Kantak. Synergy between an engineered cytokine, NKTR-214, and CTLA-4 blockade in murine colon and breast tumor models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5032. doi:10.1158/1538-7445.AM2014-5032

Abstract B296: NKTR-214: An immunotherapy with altered selectivity at the IL2 receptor; pharmacokinetics (PK) and pharmacodynamics (PD) in animal models

Background: Aldesleukin (IL2) has been successfully used to treat cancer, with the potential for durable responses. However, its efficacy is limited by concomitant enhancement of immunosuppression. An immunostimulatory therapeutic approach that lacks certain immunosuppressive side effects can be achieved by targeting the appropriate subunits of the heterotrimeric interleukin 2 receptor, IL2R. NKTR-214 is a releasable multi-PEGylated conjugate of IL2. Upon in vivo administration, active forms of less conjugated-IL2 are released, which exhibit altered IL2R subunit selectivity. These forms favor proliferation of tumor-killing immune cells (CD8T) over immunosuppressive T cells (Treg) in the tumor (Charych, JCO 2013, 31:15, Suppl. 1). Here we show that polymer conjugation also prolongs exposure and activates known immune pharmacodynamic markers in mice, rats, and monkeys. These combined attributes improve efficacy and tolerability of NKTR-214 compared to the clinically approved cytokine aldesleukin.

Methods: NKTR-214 PK and PD were assessed after single IV bolus doses in mice bearing B16F10 melanoma (2 mg/kg), rats (1 mg/kg), and monkeys (0.1 mg/kg). Aldesleukin was assessed in mice bearing B16F10 melanoma after 3 mg/kg IP qdx5. For assessment of PK, serial plasma samples were assayed for IL2 by ELISA. For NKTR-214, conjugated-IL2 was chemically released prior to ELISA. Immune system activation was monitored in plasma by sequential measurement of sCD25, C-reactive protein (CRP), lymphocyte counts, IFNγ, and TNFα.

Results: The half-life of NKTR-214 was 20 hr in mice, which is considerably longer than the 5 hr half-life for aldesleukin, contributing to a 600-fold greater dose-normalized exposure. Consistent with the sustained exposure, altered receptor selectivity and favorable immune cell response, a single 2 mg/kg dose of NKTR-214 maintained greater suppression of tumor growth compared to daily 3 mg/kg doses of aldesleukin. NKTR-214 half-life was similar in rats and monkeys. In addition, NKTR-214 triggered a robust activation of known systemic immune system markers. For example, after a single efficacious dose of NKTR-214 in mice (2 mg/kg), sCD25 increased 25-fold compared to 5-fold for 5 daily doses of aldesleukin. In monkeys, an equally robust activation of sCD25 was observed at a single dose of 0.1 mg/kg (MTD) of NKTR-214. The kinetic profiles of CRP and lymphocyte counts following NKTR-214 were similar to that of sCD25 in monkeys, while the inflammatory cytokines IFNγ and TNFα remained undetectable.

Conclusions: A single dose of NKTR-214 results in sustained exposure, robust immune system activation, and favorable immune cell changes in the tumor microenvironment. Based on NKTR-214 PK and PD in animals, infrequent dosing is feasible in humans, allowing convenient combination with other immunotherapies.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B296.

Citation Format: Ute Hoch, Paul Sims, Murali Addepalli, Yuan Song, Chunmei Ji, Peter Kirk, Theresa Sweeney, Deborah Charych, Seema Kantak. NKTR-214: An immunotherapy with altered selectivity at the IL2 receptor; pharmacokinetics (PK) and pharmacodynamics (PD) in animal models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B296.

An engineered immunotherapy (NKTR-214) with altered selectivity toward the IL2 receptor: Efficacy and tolerability in a murine tumor model

3060

Background: Cytokine-based immunotherapy has been successful for the treatment of cancer, with potential for durable responses in multiple indications. One approach towards stimulating the immune system is to target the heterotrimeric interleukin2 receptor, IL2R. NKTR-214 uses polymer technology to alter receptor subunit selectivity to favor expansion of CD8+ memory effector T cells (CD8T) in the tumor over CD4+ regulatory T cells (Treg). In addition, polymer conjugation is designed to improve exposure and enhance tumor localization, significantly improving efficacy, modulating vascular leak syndrome (VLS) and allowing flexible dosing regimens. Methods: C57BL/6 mice bearing established subcutaneous B16F10 melanoma were treated with NKTR-214 at a variety of doses (0.25-4.0 mg/kg) and schedules (q5dx3 to q14dx2). Mice treated with clinically validated IL2 were administered 3mg/kg, bidx5 for 2 cycles. Efficacy was measured by monitoring tumor volumes. Tolerability was evaluated by survival. VLS was measured by injection of Evans Blue dye followed by colorimetry in lungs. Tumor immunotyping, by flow cytometry. Results: Tumors from mice receiving NKTR-214 had a CD8/Treg ratio of over 1,000 versus 14 for IL2. NKTR-214 administered at 2 mg/kg, q9dx3 was identified as the optimal regimen and showed tumor growth delay of 26 days compared to 9 days for optimally dosed IL2. 90% of NKTR-214 treated mice tolerated treatment compared to 67% for IL2. VLS was completely resolved prior to administration of the next dose of NKTR-214, unlike IL2. NKTR-214 was well tolerated in rats at two schedules, at MTD. Conclusions: NKTR-214 is a highly differentiated cytokine with a new mechanism of action that may provide options for cancer immunotherapy. Polymer conjugation of a clinically validated cytokine alters the IL2R selectivity to favor expansion of tumor killing immune cells (CD8T) over regulatory immune cells (Treg) in the tumor. The conjugate is also designed to improve exposure and enhance tumor localization, offering more options of dose and schedule. The optimal dose and schedule is cytokine-sparing, provides substantial tumor growth delay, and reduces toxicity.

Abstract 482: Tipping the balance in the tumor microenvironment: An engineered cytokine (NKTR-214) with altered IL2 receptor binding selectivity and improved efficacy

Introduction

Immunotherapy offers the potential for durable responses in a growing list of cancer indications.1 One approach towards stimulating the immune system is to target the heterotrimeric interleukin2 receptor, IL2R. Binding of ligand to the β subunit leads to expansion of tumor killing memory effector T cells, whereas engagement of the α subunit expands undesirable regulatory T cells, promoting immune suppression in the tumor.2 NKTR-214 uses polymer technology to engineer a cytokine that has reduced affinity for the IL2Rα subunit, diminishing the expansion of regulatory T cells in the tumor, while maintaining affinity for the β subunit expands memory effector T cells. The selective immunological profile in the tumor tips the balance towards tumor killing and results in superior efficacy and tolerability in a resistant mouse melanoma model.

Methods

The affinity of NKTR-214 to IL2Rα and IL2Rβ was measured directly by SPR and compared to that of clinically available IL2 (Aldesleukin). C57BL/6 mice bearing subcutaneous B16F10 melanoma were treated with NKTR-214 (IV, Q9dx3), Aldesleukin (BIDx5, 2 cycles) or vehicle. Immune cell populations in the tumor microenvironment were characterized by flow cytometry. Anti-tumor efficacy was measured by monitoring tumor volumes over time.

Data

The affinity of the activated form of NKTR-214 to IL2Rα was reduced by ∼8x compared to clinically available Aldesleukin. Mice receiving NKTR-214 showed an increase of ∼8-fold in CD8 memory effector T cells in the tumor compared to Aldesleukin .Conversely, mice receiving NKTR-214 showed a ∼6-fold decrease of CD4 regulatory T cells in the tumor compared to Aldesleukin. Improved survival and substantial tumor growth delay were observed in the NKTR-214 treated mice as compared to Aldesleukin, despite using 10-fold fewer moles of protein. The mice in the NKTR-214 treated group were not moribund, did not shiver, and showed an 84% decrease in mortality as compared to the Aldesleukin treated group.

Conclusions

Engineering a cytokine through polymer modification leads to a differential IL2 receptor binding profile and an improved tumor infiltrating T cell profile. The modification increases CD8 memory effector T cells and decreases suppressive regulatory T cells in the tumor compared to a clinically available IL2 (Aldesleukin). The reduced level of immune suppression in the tumor may explain the substantially improved therapeutic index observed for NKTR-214, despite using 10-fold fewer moles of protein, and infrequent dosing (Q9Dx3). The drug was well tolerated by the mice, with an 84% decrease in mortality compared to Aldesleukin. The results demonstrate that polymer engineering of a cytokine can have a profound differentiating effect on its in vitro and in vivo behavior.

1L. Calabro, Semin Oncol 2010 37 460-467

2O. Boyman, J. Sprent Nature Reviews Immunology 2012 12 180

Citation Format: Deborah Charych, Steven Lee, Murali Addepalli, Thomas Chang, Peter Kirk, Marina Konakova, Laurie Vanderveen, Rupesh Kanhere, Dennis Fry, Cherie Ali, Stephen Harrison, Seema Kantak, Stephen Doberstein. Tipping the balance in the tumor microenvironment: An engineered cytokine (NKTR-214) with altered IL2 receptor binding selectivity and improved efficacy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 482. doi:10.1158/1538-7445.AM2013-482