4508 Background: Patients with NMIBC CIS unresponsive to BCG have limited treatment options. N-803 (Anktiva) is a mutant IL-15-based immunostimulatory fusion protein complex (IL15RaFc) that promotes proliferation and activation of natural killer (NK) cells and CD8+ T cells, but not regulatory T cells. Phase 1b data in BCG-naïve patients with NMIBC demonstrate that intravesical administration of N-803 with BCG induced complete response in all patients, without recurrences for the study duration of 24 months. Pembrolizumab was approved in 2020 with a 41% complete response (CR) rate in a single arm phase 2 trial of 96 patients. We report data on 160 subjects from an open-label, 3 cohort multicenter study (QUILT 3.032) of intravesical BCG plus N-803 in patients with BCG-unresponsive high-grade NMIBC (NCT03022825). Methods: All treated patients received intravesical N-803 plus BCG, consistent with the standard induction/maintenance treatment schedule. The primary endpoint for Cohort A (CIS) is incidence of CR of CIS at any time. The primary endpoint for Cohort B (Papillary) is disease-free rate (DFS) at 12 months. Results: To date, we enrolled 160 patients (83 CIS, 77 Papillary). In the overall population, median age is 72.3 years, 81% male, with mean number of prior TURBT = 4. Median number of prior BCG doses = 12. CIS patients have a CR rate of 71% (59/83), with a mediation duration of CR of 24.1 months in responders; 91% avoided cystectomy and 96% 24 month bladder cancer specific progression free survival (defined as progression to MIBC). Papillary patients have a 57% 12 month DFS rate, 48% 24 month DFS rate, and 95% avoided cystectomy. Median time to cystectomy in responders (N = 4) is 12.9 months versus 7.8 in non-responders (N = 8) for a 5.1 month delay in cystectomy. PK data shows no systemic levels of N-803; activity is confined to the bladder. Low grade treatment related AEs (grade 1-2) include dysuria (22%), pollakiurua (19%), hematuria (18%), fatigue (16%), and urgency (12%), all other AEs were seen at 7% or less. No treatment related grade 4 or 5 AE were seen. No SAE's were considered treatment related. No immune related SAE's have been seen. Conclusions: In 160 patients with BCG-unresponsive NMIBC, there is a 99% bladder cancer specific overall survival at 2 years. In CIS patients 71% CR rate with 24.1 months median duration of response, and 53% DFS rate at 18 months in Papillary disease. Cystectomy was avoided in over 90% of patients with 2 years of follow-up. The efficacy and safety profile of N-803+BCG exceeds that of other available intravesical and systemic options for BCG-unresponsive NMIBC. Clinical trial information: NCT03022825.
Allogeneic natural killer (NK) cell transfer is a potential immunotherapy to eliminate and control cancer. A promising source are CD34 + hematopoietic progenitor cells (HPCs), since large numbers of cytotoxic NK cells can be generated. Effective boosting of NK cell function can be achieved by interleukin (IL)-15. However, its in vivo half-life is short and potent trans-presentation by IL-15 receptor α (IL-15Rα) is absent. Therefore, ImmunityBio developed IL-15 superagonist N-803, which combines IL-15 with an activating mutation, an IL-15Rα sushi domain for trans-presentation, and IgG1-Fc for increased half-life. Here, we investigated whether and how N-803 improves HPC-NK cell functionality in leukemia and ovarian cancer (OC) models in vitro and in vivo in OC-bearing immunodeficient mice. We used flow cytometry-based assays, enzyme-linked immunosorbent assay, microscopy-based serial killing assays, and bioluminescence imaging, for in vitro and in vivo experiments. N-803 increased HPC-NK cell proliferation and interferon (IFN)γ production. On leukemia cells, co-culture with HPC-NK cells and N-803 increased ICAM-1 expression. Furthermore, N-803 improved HPC-NK cell-mediated (serial) leukemia killing. Treating OC spheroids with HPC-NK cells and N-803 increased IFNγ-induced CXCL10 secretion, and target killing after prolonged exposure. In immunodeficient mice bearing human OC, N-803 supported HPC-NK cell persistence in combination with total human immunoglobulins to prevent Fc-mediated HPC-NK cell depletion. Moreover, this combination treatment decreased tumor growth. In conclusion, N-803 is a promising IL-15-based compound that boosts HPC-NK cell expansion and functionality in vitro and in vivo. Adding N-803 to HPC-NK cell therapy could improve cancer immunotherapy.
Background Children with recurrent and/or metastatic osteosarcoma (OS), neuroblastoma (NB) and glioblastoma multiforme (GBM) have a dismal event-free survival (<25%). The majority of these solid tumors highly express GD2. Dinutuximab, an anti-GD2 monoclonal antibody, significantly improved event-free survival in children with GD2+ NB post autologous stem cell transplantation and enhanced natural killer (NK) cell-mediated antibody-dependent cell cytotoxicity. Thus, approaches to increase NK cell number and activity, improve persistence and trafficking, and enhance tumor targeting may further improve the clinical benefit of dinutuximab. N-803 is a superagonist of an interleukin-15 (IL-15) variant bound to an IL-15 receptor alpha Su-Fc fusion with enhanced biological activity.Methods The anti-tumor combinatorial effects of N-803, dinutuximab and ex vivo expanded peripheral blood NK cells (exPBNK) were performed in vitro using cytoxicity assays against GD2+ OS, NB and GBM cells. Perforin and interferon (IFN)-γ levels were measured by ELISA assays. Multiple cytokines/chemokines/growth factors released were measured by multiplex assays. Human OS, GBM or NB xenografted NOD/SCID/IL2rγnull (NSG) mice were used to investigate the anti-tumor combinatorial effects in vivo.Results N-803 increased the viability and proliferation of exPBNK. The increased viability and proliferation are associated with increased phosphorylation of Stat3, Stat5, AKT, p38MAPK and the expression of NK activating receptors. The combination of dinutuximab and N-803 significantly enhanced in vitro cytotoxicity of exPBNK with enhanced perforin and IFN-γ release against OS, GBM and NB. The combination of exPBNK+N-803+dinutuximab significantly reduced the secretion of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), platelet-derived growth factor-BB (PDGF-BB), and stem cell growth factor beta (SCGF-β) from OS or GBM tumor cells. Furthermore, OS or GBM significantly inhibited the secretion of regulated on activation, normal T cell expressed and presumably secreted (RANTES) and stromal cell-derived factor-1 alpha (SDF-1α) from exPBNK cells (p<0.001) but significantly enhanced monokine induced by gamma interferon (MIG) secretion from exPBNK cells (p<0.001). N-803 combined with dinutuximab and exPBNK cells significantly extended the survival of OS, GBM or NB xenografted NSG mice.Conclusions Our results provide the rationale for the development of a clinical trial of N-803 in combination with dinutuximab and ex vivo exPBNK cells in patients with recurrent or metastatic GD2+ solid tumors.
BackgroundAs heterogeneous tumors develop in the face of intact immunity, tumor cells harboring genomic or expression defects that favor evasion from T-cell detection or elimination are selected. For patients with such tumors, T cell-based immunotherapy alone infrequently results in durable tumor control.MethodsHere, we developed experimental models to study mechanisms of T-cell escape and demonstrated that resistance to T-cell killing can be overcome by the addition of natural killer (NK) cells engineered to express a chimeric antigen receptor (CAR) targeting programmed death ligand-1 (PD-L1).ResultsIn engineered models of tumor heterogeneity, PD-L1 CAR-engineered NK cells (PD-L1 t-haNKs) prevented the clonal selection of T cell-resistant tumor cells observed with T-cell treatment alone in multiple models. Treatment of heterogenous cancer cell populations with T cells resulted in interferon gamma (IFN-γ) release and subsequent upregulation of PD-L1 on tumor cells that escaped T-cell killing through defects in antigen processing and presentation, priming escape cell populations for PD-L1 dependent killing by PD-L1 t-haNKs in vitro and in vivo.ConclusionsThese results describe the underlying mechanisms governing synergistic antitumor activity between T cell-based immunotherapy that results in IFN-γ production, upregulation of PD-L1 on T-cell escape cells, and the use of PD-L1 CAR-engineered NK cells to target and eliminate resistant tumor cell populations.
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