Abstract
The targeted delivery of interleukin-2 to the tumor is gaining attention as an avenue to potentiate the action of T and NK cells at the site of disease. We have previously described the fusion of the L19 antibody, specific to the EDB domain of fibronectin, with human interleukin-2, using a non-covalent homodimeric diabody format. Here, we describe four novel formats for the L19-IL2 fusion, featuring different arrangements of antibody and IL2. A comparative quantitative biodistribution analysis in tumor-bearing mice using radioiodinated proteins revealed that the novel format (L19L19-IL2, with the antibody in single-chain diabody format) exhibited the best biodistribution results. In vitro assays on peripheral blood mononuclear cells showed a decrease activation of regulatory T cells when single IL2 domain was used. In vivo, both L19-IL2 and L19L19-IL2 inhibited tumor growth in immunocompetent mouse models of cancer. T-cell analysis revealed similar levels of CD4+ and FoxP3+ cells, with an expansion of the CD8+ T cell in mice treated with L19-IL2 and L19L19-IL2. The percentage of CD4+ regulatory T cells was markedly decreased with L19L19-IL2 combined with a mouse-specific PD-1 blocker. Collectively, these data indicate that the new L19L19-IL2 format exhibits favorable tumor-homing properties and mediates a potent anti-cancer activity in vivo.
Highlights
There is a growing interest in the use of immunotherapy approaches for the treatment of cancer, which has been promoted by the clinical results obtained against various types of malignancies using anti-PD-1 and anti-PD-L1 antibodies [1,2,3,4]
All immunocytokines were characterized in vitro by SDS PAGE (Figure 1B) where a clean band was observable corresponding to the expected molecular weight
L19-IL2 is an immunocytokine featuring the L19 antibody fused to the cytokine IL2 payload, which is currently being investigated with encouraging results www.oncotarget.com for the treatment of metastatic melanoma in phase II and phase III clinical trials, in combination with targeted TNF
Summary
There is a growing interest in the use of immunotherapy approaches for the treatment of cancer, which has been promoted by the clinical results obtained against various types of malignancies using anti-PD-1 and anti-PD-L1 antibodies [1,2,3,4].Certain pro-inflammatory cytokines (e.g., interleukin-2) may provide a complementary anti-cancer activity and may be ideal combination partners, in addition to immune checkpoint inhibitors [5, 6], and to radiation [7, 8] and cytotoxic agents [9]. IL2 was approved by FDA for metastatic melanoma patients in 1998, based on the observation that a small proportion of subjects enjoyed durable complete responses [10]. Treatments in these dose regimens often lead to severe side effects, including fever and chills, hypotension, fatigue and vascular leak syndrome, which in extreme cases can lead to organ failure with lethal consequences [11]. High dosage treatments are usually reserved to young and physically fit patients only. For this reason, current research efforts aim at the development of IL2 therapeutics with improved therapeutic index. Pegylated forms of IL2 have shown superior properties in mouse models of cancer [12,13,14] and encouraging results in patients as single agents [15]
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