ABSTRACT
PURPOSE: Aldesleukin, recombinant human IL2, is an effective immunotherapy for metastatic melanoma and renal cancer, with durable responses in approximately 10% of patients; however, severe side effects limit maximal dosing and thus the number of patients able to receive treatment and potential cure. NKTR-214 is a prodrug of conjugated IL2, retaining the same amino acid sequence as aldesleukin. The IL2 core is conjugated to 6 releasable polyethylene glycol (PEG) chains. In vivo, the PEG chains slowly release to generate active IL2 conjugates. EXPERIMENTAL DESIGN: We evaluated the bioactivity and receptor binding of NKTR-214 and its active IL2 conjugates in vitro; the tumor immunology, tumor pharmacokinetics, and efficacy of NKTR-214 as a single agent and in combination with anti-CTLA-4 antibody in murine tumor models. Tolerability was evaluated in non-human primates. RESULTS: In a murine melanoma tumor model, the ratio of tumor-killing CD8(+) T cells to Foxp3(+) regulatory T cells was greater than 400 for NKTR-214 compared with 18 for aldesleukin, supporting preferential activation of the IL2 receptor beta over IL2 receptor alpha, due to the location of PEG molecules. NKTR-214 provides a 500-fold greater exposure of the tumor to conjugated IL2 compared with aldesleukin. NKTR-214 showed efficacy as a single agent and provided durable immunity that was resistant to tumor rechallenge in combination with anti-CTLA-4 antibody. NKTR-214 was well tolerated in non-human primates. CONCLUSIONS: These data support further evaluation of NKTR-214 in humans for a variety of tumor types, adding to the repertoire of potent and potentially curative cancer immunotherapies.
Subject(s)
Antineoplastic Agents/pharmacology , Interleukin-2/analogs & derivatives , Neoplasms/metabolism , Neoplasms/pathology , Polyethylene Glycols/pharmacology , Prodrugs , Receptors, Interleukin-2/metabolism , Recombinant Fusion Proteins/pharmacology , Animals , Antineoplastic Agents/chemistry , CD8-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , CTLA-4 Antigen/antagonists & inhibitors , Cell Line, Tumor , Disease Models, Animal , Drug Synergism , Female , Humans , Immunologic Memory , Interleukin-2/chemistry , Interleukin-2/pharmacology , Lymphocytes, Tumor-Infiltrating , Male , Melanoma, Experimental , Mice , Models, Molecular , Molecular Conformation , Neoplasms/drug therapy , Neoplasms/immunology , Polyethylene Glycols/chemistry , Protein Binding , Receptors, Interleukin-2/chemistry , Recombinant Fusion Proteins/chemistry , Recombinant Proteins/pharmacology , T-Lymphocytes, Regulatory/drug effects , T-Lymphocytes, Regulatory/immunology , T-Lymphocytes, Regulatory/metabolism , Tumor Burden/drug effectsABSTRACT
Vascular angiogenesis is regulated by a number of cytokines of which vascular endothelial growth factor (VEGF)-A/and its receptor vascular endothelial growth factor receptor 2 (VEGFR2) play an indisputable role. Similarly lymphangiogenesis is regulated by VEGF-C and its receptor VEGFR3. Currently for treating vasculogenesis diseases such as proliferative retinopathies and cancer, a number of anti-VEGF-A therapies are approved for clinical use. Although clinical efficacies achieved are remarkable, they are found to be transitory in nature, followed by restoration of anti-VEGF therapy resistant angiogenesis. Recently the regulatory role of VEGF-C in initiating and potentiating neo-angiogenesis has been uncovered. Although the interactive nature of VEGF-A and C is known, the dynamics of their expression under knockdown conditions is yet to be established. Here in this study we have utilized siRNA to knockdown both VEGF-A and C either independently or in combination. Analysis of VEGF-A and C expression (only in cancer cell lines MCF7, A549 and H460 but not in the ocular cell line RPE19) has shown enhanced expression levels of VEGF-C with increase in knockdown of VEGF-A. However, VEGF-C knockdown has resulted in decreased expression levels of VEGF-A both in RPE19 and MCF7 cells in a dose dependent manner. In addition, VEGF-C knockdown also resulted in decreased expression of RhoA. Further, knockdown studies of RhoA even with supplementation of VEGF-C or A has resulted in decreased endothelial cell proliferation and stress fiber formation, indicating that VEGF-C does promote angiogenesis via RhoA mediated pathway.
