Intermediate-affinity Interleukin-2 Research Articles

ARTISTRY-7: A phase 3, multicenter study of nemvaleukin alfa in combination with pembrolizumab versus chemotherapy in patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer (GOG-3063; ENGOT-OV68).

TPS5612 Background: ARTISTRY-7 will evaluate the novel engineered cytokine nemvaleukin alfa (nemvaleukin, ALKS 4230) in patients (pts) with gynecologic cancers. Ovarian cancer (OC) is the 8th most common cause of cancer mortality in women. OC is an area of high unmet need, as many pts become resistant/refractory to frontline platinum-based chemotherapy. In the platinum-resistant setting, standard of care chemotherapy and anti-PD-1 therapy in clinical trials have modest response rates ranging from ~6% to 20% and ~7% to 12%, respectively. Nemvaleukin was designed to selectively bind to the intermediate-affinity interleukin-2 (IL-2) receptor, preferentially activating antitumor CD8+ T and natural killer cells with minimal regulatory T cell expansion. This selectivity may provide enhanced tumor killing and improved safety/tolerability vs high-dose IL-2. In clinical studies, nemvaleukin, as monotherapy and in combination with pembrolizumab, has shown clinical benefit in multiple tumor types, including OC. In ARTISTRY-1, in 14 evaluable patients with OC, 4 responses were observed with nemvaleukin + pembrolizumab, including 2 complete responses and 2 partial responses (ORR 28.6%; DCR 71.4%; median DOR 53.4 wks). Nemvaleukin monotherapy activity was also observed (6 melanoma and 4 renal cell carcinoma responses). Methods: ARTISTRY-7 (NCT05092360) is an ongoing phase 3, multicenter, randomized study of nemvaleukin and/or pembrolizumab vs chemotherapy. Eligible pts are women (≥18 y) with histologically confirmed epithelial OC (high-grade serous, endometrioid, clear cell), fallopian tube cancer, or primary peritoneal cancer. Pts must have had ≥1 prior line of systemic therapy (platinum-sensitive setting), ≤5 prior lines (platinum-resistant setting), and prior bevacizumab, with radiographic progression on most recent therapy. Pts with primary platinum-refractory disease (progression on first-line platinum therapy) or primary platinum resistance (progression <3 months after first-line platinum therapy completion) are excluded. Approximately 376 pts will be randomized (3:1:1:3) to receive nemvaleukin 6 μg/kg IV (days 1-5) + pembrolizumab 200 mg IV (day 1) of each 21-day cycle, pembrolizumab or nemvaleukin monotherapy, or chemotherapy, and stratified by PD-L1 status, histologic subtype, and chemotherapy (paclitaxel vs other). Pts will continue treatment until disease progression or intolerable toxicity (maximum 35 pembrolizumab cycles; nemvaleukin can be continued). The primary endpoint is investigator-assessed PFS (RECIST v1.1) in the nemvaleukin + pembrolizumab vs chemotherapy arms. Secondary/exploratory endpoints include overall survival, other antitumor measures, safety, health-related quality of life, and PK/PD effects. Clinical trial information: NCT05092360 .

ARTISTRY-6: Nemvaleukin alfa monotherapy in patients with advanced mucosal and cutaneous melanoma.

TPS9592 Background: Despite improved outcomes in melanoma with the introduction of checkpoint inhibitors (CPIs), ≈50% of patients do not respond. A subset of responders ultimately progress and have limited treatment options, underscoring a high unmet need for novel treatments with durable benefit. Patients with mucosal melanoma exhibit response rates and progression-free survival ≈2 times lower than those with cutaneous melanoma. Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds to the intermediate-affinity interleukin-2 receptor complex to preferentially activate CD8+ T and natural killer cells, with minimal expansion of regulatory T cells. Nemvaleukin has been granted Orphan Drug designation for the treatment of mucosal melanoma by the US FDA. In the ARTISTRY-1 study, the intravenous (IV) recommended phase 2 dose (RP2D) for nemvaleukin monotherapy (6 µg/kg on days 1-5 of a 21-day cycle) demonstrated durable antitumor activity in patients with advanced melanoma, including mucosal melanoma, previously treated with a CPI (N = 46, overall response rate [ORR] 13.0% [95% CI 4.9-26.3], median duration of response 8.1 weeks [range 6.1-79.0]). In the ARTISTRY-2 study, the subcutaneous (SC) RP2D was identified as 3 mg every 7 days, which demonstrated pharmacodynamic effects consistent with those of IV delivery. Data from these studies support further evaluation of nemvaleukin monotherapy among patients with advanced mucosal or cutaneous melanoma. Additionally, a less frequent IV nemvaleukin dosing schedule is being evaluated in patients with advanced solid tumors in the ARTISTRY-3 study. Methods: ARTISTRY-6 (NCT04830124) is an ongoing phase 2, global, multicenter, open-label study that is currently enrolling. Eligible patients will have had prior anti–PD-(L)1 therapy with or without anti–CTLA-4 therapy, an Eastern Cooperative Oncology Group performance status of 0 or 1, and adequate hematologic reserve and hepatic and renal function. In Cohort 1, patients with advanced cutaneous melanoma will receive nemvaleukin at the SC RP2D of 3 mg every 7 days. In Cohort 2, patients with advanced mucosal melanoma will receive nemvaleukin at the IV RP2D of 6 µg/kg on days 1-5 of a 21-day cycle. In Cohort 3 (added as a protocol amendment), patients with advanced cutaneous melanoma will receive IV nemvaleukin in 1 of 2 less frequent dosing schedules of 1 or 2 doses per cycle. The dosing schedules for Cohort 3 will be determined when a less frequent IV RP2D has been established in ARTISTRY-3. Patients will receive nemvaleukin until progression or intolerable toxicity. The primary objective is to evaluate the antitumor activity of nemvaleukin monotherapy defined by ORR. Additional objectives include evaluation of safety, health-related quality of life, predictive biomarkers, pharmacokinetics, immunogenicity, and pharmacodynamic effects. Clinical trial information: NCT04830124 .

Abstract 1801: STK-012, an a/b-selective IL-2 activates tumor antigen specific CD25+ CD8 T cells to reject tumors without acute vascular toxicity

Abstract High-dose Interleukin-2 (IL-2) monotherapy induces complete responses in cancer patients but its use is limited by acute vascular toxicities including capillary leak syndrome and severe hypotension 1,2. IL-2 activates lymphocytes and NK-cells through the intermediate-affinity dimeric IL-2 receptor, IL-2Rβ/γ (CD122/CD132), while antigen activated T-cells and regulatory T-cells (Tregs) have increased sensitivity to IL-2 by expressing the high-affinity trimeric IL-2 receptor, IL-2Rα/β/γ (CD25/CD122/CD132)3. CD25-independent IL-2s (“non-α-IL-2s”) aim to increase the therapeutic efficacy of IL2 in cancer patients by avoiding Treg activation through selective binding to IL-2Rβ/γ 4. However, those molecules still are reported to induce fever and hypotension and have limited efficacy as a monotherapy or in combination with anti-PD-1 5,6. Here we show that a novel α/β-IL-2 agonist that was designed to preferentially bind to the IL-2Rα/β/γ receptor highly upregulated on antigen activated T-cells can greatly improve on the efficacy of IL-2 while avoiding the vascular toxicity commonly associated with IL-2 treatment. In syngeneic tumor models, this α/β-IL-2 agonist significantly reduced exhaustion of tumor infiltrating T cells compared to WT-IL-2 or a non-α-IL-2 leading to improved expansion of tumor antigen specific CD25+PD-1+CD8+ T cells systemically and in the tumor microenvironment. This resulted in complete responses and tumor immune memory with α/β-IL-2 monotherapy as well as improved outcomes in combination with anti-PD-1 therapy in PD-1 refractory syngeneic tumors. In contrast, WT-IL-2 reduced T cell exhaustion and drove antigen specific T cell responses to a lesser degree, resulting in reduced combinatorial efficacy with anti-PD-1, while the non-α-IL-2 failed to do either. Furthermore, the α/β-IL-2 agonist reduced intratumoral Tregs compared to treatment with WT-IL-2 or PBS improving the intratumoral CD8 to Treg ratio. In non-human primates and mice, WT-IL-2 and a non-α-IL-2 led to broad extravasation of lymphocytes and NK cells and activation of intra-pulmonal T cells resulting in systemic tissue inflammation and NK cell-mediated lethal capillary leak syndrome whereas the α/β-IL-2 agonist, which avoids binding the dimeric IL-2Rβ/γ expressed on NK cells, avoided systemic lymphocyte activation which facilitated continuous treatment without acute vascular toxicities. Overall, through selective engagement of CD25+ T cells, this α/β-IL-2 agonist demonstrated improved efficacy and tolerability of IL-2 in preclinical tumor models. Clinical trials with STK-012, a human α/β-IL-2 agonist, are in progress.1 Atkins, et al.; JCO 1999, 2 Dutcher, et al.; JITC 2014, 3 Liao, et al.; Immunity 2013, 4 Levin, et al.; Nature 2012, 5 Janku, et al.; Cancer Research 2021; 6 Diab, et al.; Cancer Disc. 2020 Citation Format: Martin Oft, Navneet Ratti, Sandro Vivona, Jan Emmerich, Romina Riener, Ievgen O. Koliesnik, Scott McCauley, Michele Bauer, Marie Semana, Deepti Rokkam, Bhargavi Jayaraman, Rene de Waal Malefyt, Paul-Joseph Aspuria, Michael Totagrande, Anita Mehta-Damani, Patrick J. Lupardus, Rob A. Kastelein. STK-012, an a/b-selective IL-2 activates tumor antigen specific CD25+ CD8 T cells to reject tumors without acute vascular toxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1801.

Selective Agonism of Intermediate-Affinity IL-2 Receptor Promotes Systemic Antitumor Responses in Combination with Radiotherapy in Metastatic Lung Cancer

<h3>Purpose/Objective(s)</h3> For immune checkpoint inhibitor-resistant patients, adding interleukin-2 (IL-2) may aid antitumor responses by stimulating effector T cells and NK cells. Unfortunately, high-dose IL-2 therapy has limited clinical utility due to adverse events and stimulation of immunosuppressive regulatory T cells (T_regs). Nemvaleukin alfa (nemvaleukin) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8⁺ T and NK cells, with minimal expansion of T_regs. Thus, Nemvaleukin may be beneficial in combination with radiation therapy (RT) and immunotherapy. This study aimed to evaluate the antitumor activity and mechanism of action of the combination of RDB 1462 (the murine ortholog of Nemvaleukin, a.k.a. mNemvaleukin), RT, and immunotherapy in multiple mouse tumor models. <h3>Materials/Methods</h3> In a bilateral 344SQ lung adenocarcinoma murine model, primary tumors were treated with high-dose RT (HDRT; 12 Gy per fraction for 3 fractions), and secondary tumors were observed for evidence of abscopal effects. In another model for low absolute lymphocyte count (ALC), we used 2 Gy total body irradiation (TBI) three days before HDRT and RDB 1462. In a third MC38-gp100 mouse model, tumors were irradiated with low-dose RT (LDRT; 3 fractions of 1 Gy each) followed by pmel-1 T cell infusion after 24 hours, and RDB 1462 administration 12 hours thereafter. We performed immune phenotyping by flow cytometry; analyzed 770 immune-related genes using a multiplex analysis platform; also performed T cell receptor (TCR) repertoire analysis. Serum pro-inflammatory cytokine markers were analyzed by 23-plex kit. <h3>Results</h3> In 344SQ-parental lung adenocarcinoma, we combined HDRT with escalating doses of RDB 1462 at various timepoints, resulting in significant tumor reduction in both irradiated and unirradiated (abscopal) tumors compared with HDRT or RDB 1462 therapy alone. HDRT+RDB 1462 increased the numbers and activity of tumor-specific CD8⁺ T cells, NK cells, and memory T cells without drastically increasing T_regs, as evidenced by peripheral and tumor-infiltrating immune phenotypic and functional analyses. T cells showed increased receptor clonality and diversity in groups receiving HDRT+RDB 1462. The addition of anti-PD-1 to HDRT+RDB 1462 further increased antitumor control of both irradiated and abscopal tumors, reduced lung metastases, and prolonged survival. The antitumor effects of HDRT and RDB 1462 persisted even in mice with low ALC. The addition of LDRT contributed to increased tumor-specific T cells that were expanded by RDB 1462 with increased infiltration of Thy1.1⁺ CD8⁺ T cells. <h3>Conclusion</h3> The addition of Nemvaleukin therapy may enhance responses to RT alone and in combination with anti-PD-1 or adoptive T cell therapy.

IL-2K35C-moFA, a Long-Acting Engineered Cytokine with Decreased Interleukin 2 Receptor α Binding, Improved the Cellular Selectivity Profile and Antitumor Efficacy in a Mouse Tumor Model.

Simple SummaryThe application of IL-2 for treating cancer is limited owing to its toxicity and short half-life. Its high binding ability to IL-2 receptor α expands immunosuppressive Treg cells, which represents an undesirable toxicity in cancer immunotherapy. Moreover, its small molecular size is the reason for its short half-life. We solved these problems by using a covalent modification strategy of IL-2 variant IL-2K35C with fatty acid by maleimide chemistry, namely, IL-2K35C-moFA. The experiments performed in vitro and in vivo proved that IL-2K35C-moFA is a novel immunotherapeutic agent with the potential to selectively stimulate CD8+ T cells and NK cells. Compared to IL-2WT, IL-2K35C-moFA showed a specifically reduced potency for the stimulation of Treg cells. Our results also showed that fatty acid conjugation appears to be effective in half-life extension. The combination of selective lymphocyte expansion and its long half-life means IL-2K35C-moFA should be evaluated as a potential human immunotherapeutic in the future.Human interleukin 2 (IL-2) has shown impressive results as a therapeutic agent for cancer. However, IL-2-based cancer therapy is limited by strong Treg amplification owing to its high binding affinity to IL-2 receptor α (IL-2Rα) and its short half-life owing to its small molecular size. In this study, we solved these problems using a covalent modification strategy of the IL-2 variant, i.e., substituting cysteine (C) for lysine (K) at position 35, using octadecanedicarboxylic acid through maleimide chemistry, creating IL-2K35C-moFA. IL-2K35C-moFA was equipotent to human IL-2 wild type (IL-2WT) in activating tumor-killing CD8+ memory effector T cells (CD8+ T) and NK cells bearing the intermediate affinity IL-2 receptors, and less potent than IL-2WT on CTLL-2 cells bearing the high-affinity IL-2 receptors. Moreover, it was shown to support the preferential activation of IL-2 receptor β (IL-2Rβ) over IL-2Rα because of the mutation and fatty acid conjugation. In a B16F10 murine tumor model, IL-2K35C-moFA showed efficacy as a single dose and provided durable immunity for 1 week. Our results support the further evaluation of IL-2K35C-moFA as a novel cancer immunotherapy.

Abstract 4225: IL-2Rβ/IL-2R γsynthetic cytokines induce activation of human T and NK cells

Abstract Introduction: Heterodimerization of the intermediate affinity Interleukin-2 Receptors (IL-2R), IL-2Rβ and IL-2Rγ, initiates a signaling cascade in T and NK cells that ultimately results in proliferation and production of Interferon-gamma (IFN-γ). Binding of IL-2 in a dimeric complex with intermediate affinity or in the high affinity trimeric complex, which also includes IL-2Rα and is predominantly expressed on antigen activated T cells and Tregs leads to trans-phosphorylation of signaling motifs on the IL-2Rβ and IL-2Rγ intracellular domains by the associated JAK kinases. The function of the wild type IL-2 is to bring the receptor chains in close proximity to produce an optimal level of phosphorylation and activation of associated STAT transcription factors. Here we established a way to bring IL-2Rβ and IL-2Rγ chains together in a cytokine-independent manner that results in functional activation. Experimental Procedures: Human IL-2Rβ and IL-2Rγ specific heavy chain single domain antibodies (VHH) were generated by camel immunization and screening of VHH libraries prepared from peripheral blood cells for binding. Ten IL-2Rβ VHH segments and six IL-2Rγ VHH segments, all with low nanomolar affinity, were identified and coupled as IL-2Rβ/IL-2Rγ VHH dimers in all possible combinations in both amino-carboxy and carboxy-amino orientations yielding 120 different proteins that were tested in human T and NK cell functional assays. Results: IL-2Rβ/IL-2Rγ VHH dimers were biologically active and induced pSTAT-5 phosphorylation in the IL-2 dependent NK cell line NKL at various levels. The biological activity of these IL-2Rβ/IL-2Rγ VHH dimers was further confirmed on primary cells. IL-2Rβ/IL-2Rγ VHH dimers induced pSTAT5 phosphorylation on NK cells isolated from human peripheral blood and culture with IL-2Rβ/IL-2Rγ VHH dimers resulted in proliferation and production of high but varied levels of IFN-γ. The activity of IL-2Rβ/IL-2Rγ VHH dimers on primary T cells was also examined. Similar to NK cells, IL-2Rβ/IL-2Rγ VHH dimers induced pSTAT5 phosphorylation, proliferation and IFN-γ production by CD4 positive and CD8 positive T cell blasts generated after CD3/CD28 activation of human PBMC. Conclusions: In conclusion, we have generated a series of functional IL-2Rβ/IL-2Rγ VHH dimers representing surrogate cytokine agonists each with unique signaling strengths that will now be further analyzed for potential therapeutic application in tumor immunology and auto-immunity Citation Format: Rene de Waal Malefyt, PJ Aspuria, Sandro Vivona, Priyanka Balasubrahmanyam, Cindy Buffone, Mahalakshmi Ramadass, Romina Riener, Martin Oft, Patrick Lupardus, Robert Kastelein. IL-2Rβ/IL-2R γsynthetic cytokines induce activation of human T and NK cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4225.

ARTISTRY-3: Effect of nemvaleukin alfa with a less frequent IV dosing schedule as monotherapy and in combination with pembrolizumab and impact on the tumor microenvironment (TME) in patients (pts) with advanced solid tumors.

TPS2684 Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds the intermediate-affinity interleukin-2 (IL-2) receptor, preferentially activating and expanding antitumor CD8+ T cells and NK effector cells, with minimal effect on regulatory T cells. Nemvaleukin was designed to leverage antitumor effects of the IL-2 pathway while limiting typical IL-2‒associated toxicity. In ARTISTRY-1, the recommended phase 2 dose (RP2D) for nemvaleukin monotherapy of 6 µg/kg IV on days 1 to 5 of a 21-day cycle elicited durable and deep responses in pts with advanced melanoma and renal cell carcinoma (Boni et al. ASCO 2021:abstr 2513). Responses with nemvaleukin plus pembrolizumab were also observed in platinum-resistant ovarian, breast, cervical, gastrointestinal, and genitourinary cancers. ARTISTRY-3 will investigate the effects of nemvaleukin as monotherapy and in combination with pembrolizumab on the TME in pts with advanced solid tumors, and in an additional cohort (Cohort 2), to further assess a less frequent IV dosing schedule for nemvaleukin. Methods: The phase 1/2, open-label ARTISTRY-3 (NCT04592653) study will enroll adults (≥18 years) with select advanced solid tumors, ≥1 accessible lesion for biopsy, ≥1 target lesion (per RECIST v1.1), ECOG PS of 0 or 1, estimated life expectancy of ≥3 months, adequate hematologic reserve, and adequate hepatic and renal function. Primary objectives: to evaluate effects of nemvaleukin monotherapy on the TME (Cohort 1) and to determine RP2D for less frequent dosing schedule (Cohort 2). Additional objectives are to evaluate: efficacy, safety, immunogenicity, and pharmacokinetics of nemvaleukin monotherapy; effects of nemvaleukin plus pembrolizumab on the TME; and correlative biomarkers of nemvaleukin as monotherapy and combination. Following the protocol amendment, additional pts enrolled in Cohort 1 will receive lead-in monotherapy at a dose selected based on results from Cohort 2, and pre- and on-treatment biopsies will be collected for TME assessments. Subsequent cycles will be administered in combination with pembrolizumab, and a biopsy may be collected at cycle 4 or 5. Tumor types eligible for Cohort 2 are selected based on activity observed in the ARTISTRY-1 study. A quantitative system pharmacology model was applied to identify a less frequent schedule for nemvaleukin monotherapy and combination. Cohort 2 will initially assess safety and tolerability of nemvaleukin at 1 dose per 21-day cycle. Two doses per 21-day cycle may be implemented to achieve optimal PK/PD parameters. Bayesian optimal interval design methodology with open enrollment will be applied to facilitate dose escalation decisions. Clinical trial information: NCT04592653.

Nemvaleukin alfa monotherapy and in combination with pembrolizumab in patients (pts) with advanced solid tumors: ARTISTRY-1.

2500 Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds to the intermediate-affinity interleukin-2 (IL-2) receptor (IL-2R) to preferentially activate antitumor CD8+ T cells and natural killer (NK) cells with minimal expansion of immunosuppressive regulatory T cells. It is sterically occluded from binding to the high-affinity IL-2R, leveraging antitumor effects of the IL-2 pathway but mitigating toxicity associated with preferential binding of IL-2 to the high-affinity IL-2R. Methods: ARTISTRY-1 (NCT02799095) is a 3-part, first-in-human, phase 1/2 study of IV nemvaleukin alone and in combination with pembrolizumab in pts with advanced solid tumors. Parts A (dose escalation to 10 µg/kg/day), B (monotherapy in pts with melanoma or renal cell carcinoma [RCC]), and C (combination) included nemvaleukin 3 or 6 µg/kg/day ´ 5 and pembrolizumab every 21 days. Investigator-assessed antitumor activity (confirmed responses as per RECIST v1.1) and safety are reported as of 29 October 2021. Results: In Part A (N = 46), nemvaleukin recommended phase 2 dose was 6 µg/kg/day IV; maximum tolerated dose not reached. One pt had dose-limiting toxicity (grade 4 acute kidney injury) at 10 µg/kg. Pts in Parts B and C were heavily pretreated (1–9 prior lines of therapy, including prior checkpoint inhibitor therapy). Durable antitumor activity was observed for nemvaleukin monotherapy, including in RCC (objective response rate [ORR], 18.2% [4/22]) and in melanoma (ORR, 8.7% [4/46]), with 2 partial responses (1 unconfirmed) in 30 pts with cutaneous melanoma (ORR, 6.7%) and 2 PRs (1 unconfirmed) in 6 pts with mucosal melanoma (ORR, 33.3%). Durable antitumor activity was also observed for combination therapy (ORR, 16.1% [22/137]; disease control rate [DCR], 59.9%), including in platinum-resistant ovarian cancer (PROC; ORR, 28.6% [4/14]; DCR, 71.4%), with 2 complete responses and 2 PRs (1 unconfirmed) in 14 pts. Forty-three pts remain on therapy. The most frequent grade 3/4 treatment-related adverse events in Parts B and C, respectively, were anemia (9%, 10%), neutropenia (34%, 9%), and decreased neutrophil count (12%, 9%). Safety was consistent with previous reports. In pharmacodynamic studies, nemvaleukin monotherapy induced robust expansion of CD8+ T and NK cells, with minimal effect on regulatory T cells. Conclusions: ARTISTRY-1 showed proof of principle for preferential expansion of CD8+ T cells and NK cells by nemvaleukin. Nemvaleukin was generally well tolerated and demonstrated promising efficacy. Durable responses were observed with monotherapy and combination therapy in heavily pretreated pts across a range of tumors, warranting further investigation. The US FDA granted nemvaleukin Fast Track designation for treatment of mucosal melanoma and PROC, and Orphan Drug designation for mucosal melanoma. Clinical trial information: NCT02799095.

ARTISTRY-7: A phase 3, multicenter study of nemvaleukin alfa in combination with pembrolizumab versus chemotherapy in patients (pts) with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer.

TPS5609 Background: ARTISTRY-7 will evaluate the novel engineered cytokine nemvaleukin alfa (nemvaleukin, ALKS 4230) in pts with gynecologic cancers. Epithelial ovarian cancer (OC) is the 7th most common cause of cancer mortality in women. OC is an area of high unmet need, as many pts become resistant or refractory to frontline platinum-based chemotherapy. Nemvaleukin was designed to selectively bind to the intermediate-affinity interleukin-2 (IL-2) receptor, preferentially activating and expanding antitumor CD8+ T and NK cells with minimal expansion of Tregs. This selectivity may provide enhanced tumor killing and improved safety/tolerability compared with high-dose IL-2. In clinical studies, nemvaleukin, as monotherapy and in combination with pembrolizumab, has shown evidence of clinical benefit in multiple tumor types, including OC. In ARTISTRY-1, 4 responses were observed in pts with OC, including 2 complete responses, 1 in a pt with platinum-resistant OC and 5 prior lines of therapy, and 2 partial responses. Methods: ARTISTRY-7 is a phase 3, multicenter, open-label randomized study of nemvaleukin and/or pembrolizumab vs chemotherapy. Eligible pts are women (≥18 y) with histologically confirmed epithelial OC (high-grade serous, endometrioid, clear cell), fallopian tube cancer, or primary peritoneal cancer. Pts must have received ≥1 prior line of systemic therapy in the platinum-sensitive setting, ≤5 prior lines in the platinum-resistant setting, and prior bevacizumab, with radiographic progression on most recent therapy. Primary platinum-refractory disease (progression on first-line platinum therapy) or primary platinum resistance (progression &lt; 3 months after completion of first-line platinum therapy) is exclusionary. Pts must have ECOG performance status of 0 or 1, estimated life expectancy of ≥3 months, and adequate hematologic reserve and hepatic and renal function. Approximately 376 pts will be randomized (3:1:1:3) to receive nemvaleukin 6 μg/kg IV on days 1-5 and pembrolizumab 200 mg IV on day 1 of each 21-day cycle, pembrolizumab monotherapy, nemvaleukin monotherapy, or chemotherapy (pegylated liposomal doxorubicin, paclitaxel, topotecan, or gemcitabine) and stratified according to PD-L1 status, histologic subtype (high-grade vs non–high-grade serous), and chemotherapy (paclitaxel vs other). Pts will continue treatment until disease progression or intolerable toxicity (maximum 35 cycles for pembrolizumab; nemvaleukin can be continued). The primary endpoint is investigator-assessed PFS (RECIST v1.1) in the nemvaleukin/pembrolizumab vs chemotherapy group. Secondary/exploratory endpoints include overall survival, other antitumor measures, safety, health-related quality of life, and pharmacokinetic/pharmacodynamic effects. Clinical trial information: NCT05092360.

ARTISTRY-6: Nemvaleukin alfa monotherapy in patients with advanced mucosal and cutaneous melanoma.

TPS9609 Background: Despite improved outcomes for melanoma patients with the introduction of checkpoint inhibitors (CPIs), ̃50% of patients do not respond. A subset of responders ultimately progress and have limited treatment options, underscoring a high unmet need for novel treatments with durable benefit. Patients with mucosal melanoma exhibit response rates and progression-free survival times ̃2 times lower than those with cutaneous melanoma. Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds the intermediate-affinity interleukin-2 receptor complex to preferentially activate CD8+ T and NK cells with minimal expansion of regulatory T cells. Nemvaleukin has been granted Orphan Drug designation for the treatment of mucosal melanoma by the FDA. In ARTISTRY-1, the intravenous (IV) recommended phase 2 dose (RP2D) of 6 µg/kg nemvaleukin monotherapy demonstrated durable antitumor activity in patients with advanced melanoma, including mucosal melanoma, previously treated with a CPI. In ARTISTRY-2, the subcutaneous (SC) RP2D of 3 mg q7d was identified demonstrating pharmacodynamic effects consistent with IV delivery. Data support further evaluation of nemvaleukin monotherapy among patients with advanced mucosal and cutaneous melanoma. Methods: ARTISTRY-6 is a phase 2, global, multicenter, open-label study. Eligible patients have had prior treatment with an anti–PD-(L)1 therapy with or without anti–CTLA-4 therapy and have an ECOG performance status of 0 or 1 and adequate hematologic reserve and hepatic and renal function. Patients with advanced cutaneous (Cohort 1) and mucosal (Cohort 2) melanoma will receive nemvaleukin at the SC and IV RP2D, respectively. Patients will receive nemvaleukin until progression or intolerable toxicity. The primary objective is to evaluate the antitumor activity of nemvaleukin monotherapy defined by overall response rate. Additional objectives include the evaluation of safety, health-related quality of life, predictive biomarkers, pharmacokinetics, immunogenicity, and pharmacodynamic effects. Clinical trial information: NCT04830124.

A first-in-human, multicenter, phase 1/2, open-label study of XTX202, a masked and tumor-selective recombinant human interleukin-2 (IL-2) protein, in patients with advanced solid tumors.

TPS2697 Background: High-dose interleukin-2 (IL-2) has been approved in metastatic renal cell carcinoma (RCC) and metastatic melanoma, and can result in durable complete responses, including cures. Its use has been limited by life-threatening treatment-related multisystem toxicities, consisting mainly of vascular leak syndrome. XTX202 is a masked, tumor-selective IL-2 that is designed to be pharmacologically inactive in non-tumor tissue when circulating systemically and unmasked by matrix metalloproteases (MMPs) found preferentially in the tumor microenvironment (TME). XTX202 is expected, therefore, to achieve a wider therapeutic index resulting in increased efficacy and lower toxicity compared to existing non-tumor selective IL-2 based-therapies. The IL-2 domain of the XTX202 molecule is modified to reduce binding to the high-affinity IL-2 receptor while maintaining binding to the intermediate-affinity IL-2 receptor, thereby decreasing activation of regulatory T-cells relative to wild-type IL-2, while still activating effector T cells. A masking domain is designed to pharmacologically inactivate IL-2 until it is activated by MMPs that are enriched in the TME. Cleavage at a protease cleavage site in the XTX202 linker by MMPs results in an active IL-2 moiety when the masking domain is released. XTX202 is designed with the goal of producing a localized anti-tumor immune response and limiting exposure of the active form of XTX202 in non-tumor tissue. Preclinically, XTX202 exhibited tumor-selective activity in mice without peripheral toxicities in non-human primates [O’Neil et al. ASCO 2021]. Methods: XTX202-01 trial (NCT05052268) is a first-in-human Phase 1/2 study to determine a recommended Phase 2 dose of XTX202 (Phase 1) and to evaluate the efficacy of XTX202 monotherapy in patients with metastatic RCC and unresectable or metastatic melanoma (Phase 2). Patients with advanced solid tumors are eligible for Phase 1 and will receive XTX202 monotherapy administered every 21 days in an accelerated and standard 3+3 dose escalation design. Phase 2 will consist of 2 parts: Part 2a will enroll patients with metastatic RCC who have received a prior tyrosine kinase inhibitor therapy and have been treated and progressed on an anti-PD-1 therapy. Part 2b will enroll patients with unresectable or metastatic melanoma who have received immune-checkpoint therapy with an anti-PD-1 therapy and an anti-CTLA-4 therapy to determine the efficacy of XTX202 monotherapy in this population. Enrollment to the study began in January 2022. Clinical trial information: NCT05052268.

1034TiP ARTISTRY-6: Nemvaleukin alfa monotherapy in patients with advanced mucosal and cutaneous melanoma

Despite improved outcomes for melanoma patients with the introduction of checkpoint inhibitors (CPIs), ∼50% of patients do not respond. A subset of responders ultimately progress and have limited treatment options, underscoring a high unmet need for novel treatments with durable benefit. Patients with mucosal melanoma exhibit response rates and progression-free survival times ∼2 times lower than those with cutaneous melanoma. Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds the intermediate-affinity interleukin-2 receptor complex to preferentially activate CD8+ T and NK cells with minimal expansion of regulatory T-cells.

Pharmacokinetics and Pharmacodynamic Effects of Nemvaleukin Alfa, a Selective Agonist of the Intermediate-Affinity IL-2 Receptor, in Cynomolgus Monkeys.

Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel cytokine created by the fusion of circularly permuted interleukin-2 (IL-2) to the IL-2Rα subunit of the IL-2 receptor (IL-2R) complex that confers selectivity for the intermediate-affinity IL-2R expressed on CD8+ T cells and natural killer (NK) cells. The pharmacokinetics and selective pharmacodynamic properties of nemvaleukin have been demonstrated using in vitro and in vivo mouse models. The pharmacokinetic/pharmacodynamic effects of nemvaleukin on immune cell subtypes were evaluated in cynomolgus monkeys after intravenous and subcutaneous administration to inform dose selection and predict pharmacodynamic effects in humans. Male drug-naïve cynomolgus monkeys (N = 15) were administered either single-dose (0.3 mg/kg i.v.; 0.3 mg/kg or 1.0 mg/kg s.c.) or repeated doses (0.1 mg/kg i.v. on days 1-5 or 0.5 mg/kg s.c. on days 1 and 4) of nemvaleukin. Serial blood samples were collected for pharmacokinetic assessment, immunophenotyping by flow cytometry, and profiling of serum cytokines. Repeat-dose subcutaneous administration of nemvaleukin with less frequent dosing resulted in total systemic exposure and trough serum concentrations comparable to those seen with intravenous administration, with lower peak serum concentrations. Transient elevation of interferon-γ and IL-6 peaked at 2 and 8 hours after intravenous and subcutaneous administration, respectively. Selective expansion of immunoprotective central memory, effector memory, terminal effector CD8+ T cells, and CD56+ NK cells, and minimal expansion of immunosuppressive CD4+CD25+FoxP3+ regulatory T cells was observed after both intravenous and subcutaneous administration. These data support the ongoing clinical evaluation of intravenous and subcutaneous nemvaleukin. SIGNIFICANCE STATEMENT: Administration of the novel interleukin-2 receptor agonist nemvaleukin alfa to cynomolgus monkeys resulted in selective expansion of immune effector cells, including CD8+ T and natural killer cells with minimal effects on immunosuppressive CD4+ regulatory T cells, confirming the design of nemvaleukin and highlighting its potential as a cancer immunotherapy. Subcutaneous administration of nemvaleukin achieved systemic exposure and immunostimulatory effects similar to those observed after more frequent intravenous dosing and may represent a practical alternative in a clinical setting.

ARTISTRY-1: Nemvaleukin alfa monotherapy and in combination with pembrolizumab in patients (pts) with advanced solid tumors.

2513 Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds the intermediate-affinity interleukin-2 (IL-2) receptor complex to preferentially activate CD8+ T cells and natural killer cells with minimal expansion of regulatory T cells, designed to leverage antitumor effects of the IL-2 pathwaywhile mitigating potential toxicity that would limit use. Methods: ARTISTRY-1 (NCT02799095) is a phase 1/2 study. Parts A (dose escalation 0.1-10 µg/kg) and B (6 µg/kg [recommended phase 2 dose]) are monotherapy; pts receive intravenous nemvaleukin for 5 days every 14 or 21 days. In Part C, pts receive nemvaleukin (3 or 6 µg/kg) every 21 days in combination with pembrolizumab (200 mg on day 1). We present safety and antitumor activity (RECIST v1.1, iRECIST) data as of 12/02/2020. Results: In Part A, 39 pts received nemvaleukin. No dose-limiting toxicities were observed; maximum tolerated dose was not reached. Part B enrolled immune checkpoint inhibitor–pretreated pts into melanoma or renal cell carcinoma (RCC) cohorts. 18 pts with melanoma enrolled; 10 were evaluable, 2 (both with metastatic mucosal melanoma) achieved a partial response (PR; 1 unconfirmed). 24 pts with RCC enrolled; 1 of 16 evaluable pts achieved a PR (awaiting confirmation). 12 pts in each cohort continue on study. In Parts A and B, treatment-related adverse events in ≥40% included chills (74.4% and 52.4%, respectively) and pyrexia (74.4% and 47.6%, respectively). In Part C (83 evaluable pts), 12 objective responses (OR) were observed; an additional 5 pts had stable disease (SD) &gt;6 months (1 pt with breast cancer, 2 with ovarian cancer, and 2 with non-small-cell lung cancer). Nemvaleukin did not demonstrate any additive toxicity to that already established with pembrolizumab alone. OR data are summarized in the table. Conclusions: Nemvaleukin was generally well tolerated and demonstrated antitumor activity as monotherapy and in combination with pembrolizumab. Pharmacodynamic studies to identify biomarkers are ongoing. Future research of monotherapy and combination therapy with nemvaleukin is warranted. Clinical trial information: NCT02799095. [Table: see text]

Selection of the recommended phase 2 dose (RP2D) for subcutaneous nemvaleukin alfa: ARTISTRY-2.

2552 Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds the intermediate-affinity interleukin-2 receptor to preferentially activate CD8+ T and natural killer (NK) cells with minimal expansion of regulatory T cells (Tregs),designed for use as a cancer immunotherapy. ARTISTRY-2 (NCT03861793) is an ongoing phase 1/2 study evaluating the safety, efficacy, and pharmacokinetic and pharmacodynamic (PD) responses of subcutaneous (SC) nemvaleukin in combination with pembrolizumab in patients (pts) with advanced solid tumors. Methods: In phase 1, cohort-specific doses of SC nemvaleukin are administered on an every-7-day (q7d) or every-21-day (q21d) schedule during a 6-week monotherapy lead-in period, followed by combination with pembrolizumab 200 mg q21d. We present safety, PD effects, and preliminary clinical activity outcomes as of 12/02/2020. Results: 57 pts received nemvaleukin doses ranging from 0.3 mg to 6 mg q7d or 1 mg to 10 mg q21d. The most frequent tumor types (&gt; 5 pts) were colorectal, pancreatic, ovarian, and lung; median number of prior therapies was 4. Treatment-related adverse events (TRAEs) in &gt; 30% pts overall were pyrexia (43.9%), chills (38.6%), injection site erythema (33.3%), injection site reaction (33.3%), and fatigue (31.6%). 3 mg q7d (n = 7) had no drug-related dose reductions, discontinuations, or deaths during the monotherapy or combination periods. 6 mg was declared the maximum tolerated dose (MTD) for q7d dosing as 2 of 8 pts experienced dose-limiting toxicities (DLTs). For 6 mg q21d (n = 7), no drug-related dose reductions, discontinuations, or deaths have occurred during the monotherapy period; combination period data are not mature. 10 mg was declared the MTD for q21d dosing as 1 of 9 pts experienced DLTs and 3 had TRAEs leading to dose reductions. Systemic exposure to nemvaleukin increased with increasing dose. Increases in NK cells and CD8+ T cells of approximately 16-fold and 3-fold, respectively, at 3 mg q7d, and approximately 8-fold and 3-fold, respectively, at 6 mg q21d were observed, with minimal change in Tregs. 46 pts had at least 1 on-treatment scan as of the data cutoff date, and 30 (65%) had stable disease (SD) on the first scan. Of the 30 pts with ≥2 scans, 13 (43%) had 2+ consecutive scans of SD. 16 of 57 pts remain on therapy. Antitumor activity data for more recent cohorts are still maturing. Based on the totality of the safety, PD effects, and antitumor activity data, 3 mg q7d was selected as the RP2D for SC nemvaleukin. Conclusions: SC nemvaleukin 3 mg q7d was generally well tolerated as monotherapy and in combination with pembrolizumab, and demonstrated robust PD effects on NK cells and CD8+ T cells with minimal expansion of Tregs. These PD effects are similar to or greater than those observed with intravenous nemvaleukin. Thus, 3 mg q7d was selected as RP2D; phase 2 expansion cohorts for combination with pembrolizumab are enrolling. Clinical trial information: NCT03861793.

Abstract 591: Efficacy of ALKS 4230, a novel immunotherapeutic agent, in murine syngeneic tumor models alone and in combination with immune checkpoint inhibitors

Abstract ALKS 4230 is a novel immunotherapeutic agent being tested in an ongoing phase 1 study to evaluate safety and tolerability in the treatment of patients with refractory solid tumors. ALKS 4230 is a selective agonist of the intermediate-affinity interleukin 2 (IL-2) receptor that when administered to mice results in a significant increase in numbers of memory CD8+ T cells and NK cells with no expansion of CD4+ regulatory T cells (Tregs). The selectivity achieved by ALKS 4230 is due to the fact that the molecule is a fusion of circularly permuted IL-2 to the extracellular portion of the IL-2 receptor α, and the resulting fusion protein is sterically prevented from binding to the high-affinity IL-2 receptor expressed on Tregs. The efficacy of ALKS 4230 was compared to recombinant human IL-2 in a B16F10 lung tumor metastasis model. ALKS 4230 treatment resulted in dose-dependent reduction of lung tumor colonization, with 100% inhibition at the highest dose tested. In contrast, while IL-2 was able to reduce lung tumor colonization, the maximal level of inhibition achieved was 60-70% at multiple dose levels such that increasing doses did not result in greater inhibition. Thus, the activation and expansion of effector cells without expansion of Tregs in response to ALKS 4230 treatment correlates with its improved efficacy over IL-2, which non-selectively expands both effector cells and Tregs. The antitumor efficacy mediated by ALKS 4230 was further evaluated in several murine subcutaneous syngeneic tumor models, including B16F10, MC38 and EMT6. Treatment with ALKS 4230 or its murine ortholog resulted in inhibition of tumor growth and improved survival in multiple models. When dosed in combination with anti-CTLA-4 or anti-PD-1 antibodies, ALKS 4230 resulted in further improvement of tumor growth inhibition and survival. These results demonstrate the murine antitumor efficacy of ALKS 4230 alone and in combination with immune checkpoint inhibitors and support the ongoing clinical evaluation of ALKS 4230 as an immunotherapy for cancer. Citation Format: Heather C. Losey, Jared E. Lopes, Reginald L. Dean, Michael R. Huff, Rosemarie A. Moroso, Juan C. Alvarez. Efficacy of ALKS 4230, a novel immunotherapeutic agent, in murine syngeneic tumor models alone and in combination with immune checkpoint inhibitors [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 591. doi:10.1158/1538-7445.AM2017-591

Adverse Effects of Denileukin Diftitox and Their Management in Patients With Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma (CTCL) is a rare non-Hodgkin lymphoma with predominant skin manifestations and a relatively indolent course at early stages, but it can be fatal in advanced settings. In the absence of cure, the goal of therapy for CTCL is to induce long-term remissions without further compromising a patient's immune system or quality of life. Denileukin diftitox (DD) is a fusion protein chemotherapeutic agent used for the treatment of persistent or recurrent CTCL. It binds selectively to the high- and intermediate-affinity interleukin-2 receptor (CD25+) on lymphocytes and is internalized by these cells. Inside the cells, the diphtheria toxin portion of fusion protein is cleaved by proteolytic enzymes, causing cell death. DD produces durable responses and may forestall disease progression. This article reviews DD phase III clinical trial data and summarizes one institution's clinical experience in the management of the most frequent and clinically significant adverse effects of DD (e.g., acute infusion reactions, capillary leak syndrome, hypoalbuminemia, visual changes, constitutional symptoms, rash, hepatobiliary disorders). Many DD-associated adverse effects can be managed effectively without dose reduction or interruption of treatment with prudent use of supportive care measures.

Intermediate-affinity interleukin-2 receptor expression predicts CD56bright natural killer cell expansion after daclizumab treatment in the CHOICE study of patients with multiple sclerosis

Objective: The objective of this study was to evaluate whether interleukin-2 (IL-2) receptor expression on CD56bright natural killer (NK) cells predicted CD56bright NK cell expansion and therapeutic response to daclizumab (DAC) in multiple sclerosis (MS). Methods: DAC exposure, CD56bright NK cell counts, IL-2 receptor alpha (CD25) and beta (CD122) subunits, and new or enlarged lesions on brain MRI were measured in 64 subjects in a pharmacokinetic/pharmacodynamic substudy of the phase 2 CHOICE trial at multiple time points. Peripheral blood mononuclear cell (PBMC) samples were obtained from healthy subjects to assess the relationship among DAC treatment, intermediate affinity IL-2 signaling, and CD56bright NK cell expansion. Results: Increased CD56bright NK cell counts in DAC/interferon beta (IFNβ)-treated subjects were observed by day 14, the first post-dosing time point (mean [SD] ln{CD56bright NK cell count}: DAC high/IFNβ, 2.01 [1.25]; DAC low/IFNβ, 2.29 [1.06]; placebo/IFNβ, 1.01 [1.03]; adjusted p = 0.003), and persisted throughout the treatment period. Higher DAC dose predicted a faster rate of CD56bright NK cell expansion (p < 0.001), but individual subjects’ increases in CD56bright NK cells from baseline levels were only weakly correlated with DAC exposure (r2 = 0.167). Higher expression of the intermediate-affinity IL-2 receptor subunit (CD122) on CD56bright NK cells at baseline predicted fewer new gadolinium-enhanced (Gd+) lesions during the treatment period (1.77 vs. 0.62 adjusted mean new Gd+ lesions during weeks 8–24, lowest vs. highest quartile of percentage CD122+ CD56bright NK cells; p = 0.033) and a greater increase in CD56bright NK cell counts at the end of DAC dosing (p = 0.029). Conclusion: CD56bright NK cell expansion after DAC treatment appears to reflect individual differences in the capacity for intermediate-affinity IL-2 signaling and could provide a basis for predicting clinical response to DAC in MS.

The interleukin-2 antagonizing antibody MT204 delays allogeneic skin graft rejection in non-human primates and is well tolerated

MT204 is a humanized IgG1 antibody specific for interleukin-2 (IL-2) of human and rhesus monkey origin. It potently antagonizes IL-2 signaling in both CD25+ and CD25− cells by a unique mode of action. MT204 can not only prevent soluble IL-2 from binding to the intermediate affinity IL-2 receptors but can also antagonize IL-2 that is already bound to the CD25 subunit of high affinity IL-2 receptors on the cell surface. As initial steps toward development of a therapeutic antibody, pharmacokinetics (PK) and tolerability of MT204, as well as efficacy were investigated in rhesus monkeys. MT204 was infused by single escalating (2, 10 and 50mg/kg) or repeat dose administrations (50mg/kg, 1×/week for 3weeks). Over the course of the experiment, the animals were regularly observed for clinical adverse reaction and bled for laboratory investigations (PK, hematology, chemical chemistry and leukocyte subset analysis). For the efficacy study, six rhesus monkeys were grafted with MHC-mismatched rhesus skin and infused with MT204 (50mg/kg), on the day of transplantation and again on days 5 and 12 post grafting. Efficacy was determined by assessment of graft necrosis at different time-points. No obvious adverse effects were observed clinically after single infusion, or after three repeated infusions of 50mg/kg and no MT204-related toxic effects were revealed by hematology or clinical chemistry. In the efficacy study, MT204-treated animals showed a significant delay in graft rejection versus control animals (p=0.025 by Log-rank test). The characteristics of MT204, displaying linear pharmacokinetics, half-life in the range expected for a human IgG, benign safety profile and signs of efficacy, warrant further development of this antibody for therapy.

A Low-Toxicity IL-2–Based Immunocytokine Retains Antitumor Activity Despite Its High Degree of IL-2 Receptor Selectivity

The goal of the study was to engineer a form of interleukin 2 (IL-2) that, when delivered as a tumor-specific antibody fusion protein, retains the ability to stimulate an antitumor immune response via interaction with the high-affinity IL-2 receptor but has lower toxicity because of the reduced activation of the intermediate-affinity IL-2 receptor. We investigated changes in the proposed toxin motif of IL-2 by introducing a D20T mutation that has little effect on the activity of free IL-2. We expressed this IL-2 variant as a fusion protein with an antibody (NHS76) that targets the necrotic core of tumors and characterized this molecule (NHS-IL2LT) in vitro and in vivo. NHS-IL2LT was shown to have near normal biological activity in vitro by using T-cell lines expressing the high-affinity IL-2 receptor, but little or no activity by using cell lines expressing only the intermediate IL-2 receptor. Relative to the control antibody fusion protein containing wild-type IL-2, NHS-IL2LT retained antitumor activity against established neuroblastoma and non-small cell lung cancer metastases in syngeneic mouse tumor models but was much better tolerated in immune-competent mice and in cynomolgus monkeys. The qualities of low toxicity and single-agent efficacy shown suggest that NHS-IL2LT is a good candidate for therapeutic approaches combining standard cytotoxic and immune therapies. In fact, this molecule (also known as Selectikine or EMD 521873) is currently in phase I clinical trial.