64Cu-DOTA-Anti-CTLA-4 mAb Enabled PET Visualization of CTLA-4 on the T-Cell Infiltrating Tumor Tissues

Abstract

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) targeted therapy by anti-CTLA-4 monoclonal antibody (mAb) is highly effective in cancer patients. However, it is extremely expensive and potentially produces autoimmune-related adverse effects. Therefore, the development of a method to evaluate CTLA-4 expression prior to CTLA-4-targeted therapy is expected to open doors to evidence-based and cost-efficient medical care and to avoid adverse effects brought about by ineffective therapy. In this study, we aimed to develop a molecular imaging probe for CTLA-4 visualization in tumor. First, we examined CTLA-4 expression in normal colon tissues, cultured CT26 cells, and CT26 tumor tissues from tumor-bearing BALB/c mice and BALB/c nude mice by reverse transcription polymerase chain reaction (RT-PCR) analysis and confirmed whether CTLA-4 is strongly expressed in CT26 tumor tissues. Second, we newly synthesized 64Cu-1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-anti-mouse CTLA-4 mAb (64Cu-DOTA-anti-CTLA-4 mAb) and evaluated its usefulness in positron emission tomography (PET) and ex-vivo biodistribution analysis in CT26-bearing BALB/c mice. High CTLA-4 expression was confirmed in the CT26 tumor tissues of tumor-bearing BALB/c mice. However, CTLA-4 expression was extremely low in the cultured CT26 cells and the CT26 tumor tissues of tumor-bearing BALB/c nude mice. The results suggested that T cells were responsible for the high CTLA-4 expression. Furthermore, 64Cu-DOTA-anti-CTLA-4 mAb displayed significantly high accumulation in the CT26 tumor, thereby realizing non-invasive CTLA-4 visualization in the tumor. Together, the results indicate that 64Cu-DOTA-anti-CTLA-4 mAb would be useful for the evaluation of CTLA-4 expression in tumor.

Immunotherapy and hypophysitis: clinical presentation, treatment, and biologic insights

“…The high expression levels of CTLA-4 in a subset of pituitary adenomas raises the possibility that CTLA-4 may represent a novel direct therapeutic target for the treatment of aggressive pituitary tumors in selected patients. Additionally, a chelated 64Cu-isotope labeled anti-CTLA-4 monoclonal antibody has recently been developed for use in positron emission tomography [85]. If pituitary CTLA-4 expression levels do correlate with the development of IH, targeted imaging may be able to predict the risk of hypophysitis in patients treated with Ipi or possibly identify candidate patients with aggressive pituitary adenomas for therapeutic treatment with Ipi.…”

In vivo imaging with antibodies and engineered fragments

“…For SPECT imaging of myeloid-specific suppressor cells, which are markers of the inflammatory microenvironment in tumors, Cheng et al used a 99m Tc-labeled anti-CD11b antibody (Cheng et al, 2014). The presence of tumor-infiltrating T cells in subcutaneous colon tumors was analyzed with PET using a 64 Cu-labeled anti-CTLA-4 mAb antibody (Higashikawa et al, 2014), and CD8 + T cells were imaged systemically with a 89 Zr-labeled minibody (Figure 7) (Tavaré et al, 2014a). Griessinger et al used the internalization of the T cell receptor complex to their advantage so that they could stably label T cells for PET imaging (Griessinger et al, 2015).…”

Multiplexed imaging for diagnosis and therapy

“…On the one hand, because of their rapid pharmacokinetic profiles, small-molecule [130][131][132] and many peptide 133 -based tracers are well-suited to procedures involving sequential multiplexing. On the other hand, macromolecules 134 including antibodies and nanoparticles [135][136][137][138][139][140][141][142][143][144] , generally constitute versatile agents for simultaneously multiplexed imaging and therapeutic strategies. Their pharmacokinetics is less sensitive to functionalization, and additional moieties are necessary for contrast generation with an orthogonal technique; also, a chemotoxic component can be included while pursuing a therapeutic strategy.…”