The increasing availability of prescription opioid analgesics for the treatment of pain has been paralleled by an epidemic of opioid misuse, diversion, and overdose. The development of abuse-deterrent formulations (ADFs) of conventional opioids such as oxycodone and morphine represents an advance in the field and has had a positive but insufficient impact, as most opioids are still prescribed in highly abusable, non-ADF forms, and abusers can tamper with ADF medications to liberate the abusable opioid within. The abuse liability of mu-opioid agonists appears to be dependent on their rapid rate of entry into the central nervous system (CNS), whereas analgesic activity appears to be a function of CNS exposure alone, suggesting that a new opioid agonist with an inherently low rate of influx across the blood-brain barrier could mediate analgesia with low abuse liability, regardless of formulation or route of administration. NKTR-181 is a novel, long-acting, selective mu-opioid agonist with structural properties that reduce its rate of entry across the blood-brain barrier compared with traditional mu-opioid agonists. NKTR-181 demonstrated maximum analgesic activity comparable to that of oxycodone in hot-plate latency and acetic-acid writhing models. NKTR-181 was distinguishable from oxycodone by its reduced abuse potential in self-administration and progressive-ratio break point models, with behavioral effects similar to those of saline, as well as reduced CNS side effects as measured by the modified Irwin test. The in vitro and in vivo studies presented here demonstrate that NKTR-181 is the first selective mu-opioid agonist to combine analgesic efficacy and reduced abuse liability through the alteration of brain-entry kinetics.

BackgroundNKTR-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.MethodsIn 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.ResultsNKTR-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.ConclusionsOur 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.

Background: NKTR-262 is a novel therapeutic, which delivers intratumoral engagement of the TLR 7/8 pathway, promoting an immune stimulatory environment and local injection site tumor antigen release. When NKTR-262 is administered in combination with NKTR-214, a CD122-biased cytokine agonist currently in clinical trials as a monotherapy and in combination with nivolumab, the combined effect of innate immune stimulation and enhanced antigen presentation with sustained T cell activation leads to systemic tumor immunity. Materials and methods: Ten subcutaneous syngeneic mouse tumor models with diverse histologies were assessed for NKTR-262 and NKTR-214 combination treatment efficacy. Once established, tumors were treated with a single peritumoral dose of NKTR-262, while NKTR-214 was administered i.v. on q9dx3 schedule. A subset of tumor models were inoculated bilaterally to assess abscopal effect of the combination treatment. Regression of injected tumors and the abscopal effect in contralateral untreated tumors was assessed by tumor size measurements. In bilateral models immune cell activation in both tumors was assessed by flow cytometry. Cytokine induction was measured in plasma and tumors in select models. Results: Combination treatment with NKTR-262 and NKTR-214 showed efficacy in all tested tumor models. Efficacy varied from significant tumor growth inhibition to up to 100% complete responses in multiple models. Synergistic efficacy was demonstrated in select models where single agent NKTR-262 or NKTR-214 activity was compared to the combination treatment. Immune cell phenotyping showed that combining NKTR-262 with NKTR-214 induced a two-step immune response in treated and abscopal tumors. At early timepoints, accumulation of activated granulocytes correlated with tumor cell death and dendritic cell activation. The innate response was followed by selective tumor infiltration by CD8 T cells and a reduction of immunorepressive cells. Single agent treatment showed only a subset of the cellular changes observed in the combination. Immune cell activation was shown to correlate with immune stimulatory cytokine release in NKTR-262 treated tumors. Conclusions: We present a designed combination therapy that mimics a natural immune response by activating a broad immune cell network in multiple nonclinical tumor models independent of tissue origin. Combining NKTR-262 and NKTR-214 engages the entire immune activation cascade required for systemic tumor clearance from local tumor antigen production to a sustained systemic T cell response. Unlike treatments that stimulate downstream components of select immune pathways without eliciting systemic tumor immunity, a comprehensive anti-tumor immune activation by coordinated engagement of innate and adaptive immune cells may increase the success of immune therapy for patients. Citation Format: Saul Kivimae, Marlene Hennessy, Rhoneil Pena, Yolanda Kirksey, Wildaliz Nieves, Phi Quatch, Janet Cetz, Zhongxu Ren, Haiying Cai, BoLiang Deng, Wen Zhang, John L. Langowski, Christie Fanton, Neel K. Anand, Werner Rubas, Steve Doberstein, Jonathan Zalevsky. Comprehensive antitumor immune activation by a novel TLR7/8 targeting agent NKTR-262 combined with CD122-biased immunostimulatory cytokine NKTR-214 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3755.

Survival of patients with relapsed/refractory osteosarcoma has not improved in the last 30 years. Several immunotherapeutic approaches have shown benefit in murine osteosarcoma models, including the anti‐programmed death‐1 (anti‐PD‐1) and anti‐cytotoxic T‐lymphocyte antigen‐4 (anti‐CTLA‐4) immune checkpoint inhibitors. Treatment with the T‐cell growth factor interleukin‐2 (IL‐2) has shown some clinical benefit but has limitations due to poor tolerability. Therefore, we evaluated the efficacy of bempegaldesleukin (BEMPEG; NKTR‐214), a first‐in‐class CD122‐preferential IL‐2 pathway agonist, alone and in combination with anti‐PD‐1 or anti‐CTLA‐4 immune checkpoint inhibitors in metastatic and orthotopic murine models of osteosarcoma. Treatment with BEMPEG delayed tumor growth and increased overall survival of mice with K7M2‐WT osteosarcoma pulmonary metastases. BEMPEG also inhibited primary tumor growth and metastatic relapse in lungs and bone in the K7M3 orthotopic osteosarcoma mouse model. In addition, it enhanced therapeutic activity of anti‐CTLA‐4 and anti‐PD‐1 checkpoint blockade in the DLM8 subcutaneous murine osteosarcoma model. Finally, BEMPEG strongly increased accumulation of intratumoral effector T cells and natural killer cells, but not T‐regulatory cells, resulting in improved effector:inhibitory cell ratios. Collectively, these data in multiple murine models of osteosarcoma provide a path toward clinical evaluation of BEMPEG‐based regimens in human osteosarcoma.