Accumulation of the COMMD1 protein as a druggable pharmacology event to target cancer cells has not been evaluated so far in cancer animal models. We have previously demonstrated that a second-generation peptide, with cell-penetrating capacity, termed CIGB-552, was able to induce apoptosis mediated by stabilization of COMMD1. Here, we explore the antitumor effect by subcutaneous administration of CIGB-552 in a therapeutic schedule. Outstandingly, a significant delay of tumor growth was observed at 0.2 and 0.7 mg/kg (p < 0.01) or 1.4 mg/kg (p < 0.001) after CIGB-552 administration in both syngeneic murine tumors and patient-derived xenograft models. Furthermore, we evidenced that (131)I-CIGB-552 peptide was actually accumulated in the tumors after administration by subcutaneous route. A typical serine-proteases degradation pattern for CIGB-552 in BALB/c mice serum was identified. Further, biological characterization of the main metabolites of the peptide CIGB-552 suggests that the cell-penetrating capacity plays an important role in the cytotoxic activity. This report is the first in describing the antitumor effect induced by systemic administration of a peptide that targets COMMD1 for stabilization. Moreover, our data reinforce the perspectives of CIGB-552 for cancer targeted therapy.

Hybrid molecules obtained through conjugation of monoclonal antibodies and toxins constitute an approach under exploration to generate potential agents for the treatment of cancer and other diseases. A frequently employed toxic component in the construction of such immunotoxins is ricin, a plant toxin which inhibits protein synthesis at ribosomal level and so requires to be internalized by the cell. A hemolytic toxin isolated from the sea anemone Stichodactyla helianthus, which is active at the cell membrane level, was linked through a disulfide bond to the anti-epidermal growth factor receptor monoclonal antibody ior egf/r3. The resulting immunotoxin did not exhibit hemolytic activity except under reducing conditions. It was toxic for H125 cells that express the human epidermal growth factor receptor, but non-toxic for U1906 cells that do not express this receptor.

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