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  1. Specific Binding

ADC drugs specifically bind to antigenic epitopes of cancer cells through their “guiding” antibodies, and enter into cancer cells through antigen-mediated endocytosis, then release the “warheads” – highly active cytotoxic drugs in special environments (such as lysosomes or low pH values), and finally specifically kill cancer cells. Antibody-drug conjugated are also considered to be more advanced drug delivery systems, and their anticancer mechanisms are completely different from those of antibody drugs. It is known as an upgraded version of antibodies drugs with new mechanisms.

  1. ADCC Effect

ADC drugs enhance antibody-dependent cell-mediated cytotoxicity (ADCC). Its Fab segment binds to the antigenic epitopes of virus-infected cells or tumor cells, and the Fc segment binds to the FcR on the surface of killer cells (NK cells and macrophages, etc.), thus mediating killer cells to kill cancer cells directly.

  1. Inhibition of Downstream Signal Pathways

The antibody of antibody-drug conjugate specifically binds to the antigenic epitope of cancer cell and inhibits the downstream signal transduction. For example, the antibody part of Roche’s ADC Kadcyla can bind to cancer cell HER2 receptor, inhibiting HER2 from forming heterodimer with HER1, HER3 or HER4, and repressing the signal transduction pathway of cell growth. The antibodies of Kadcyla block the normal transduction signal pathways mediated by HER2 (including PI3K and MAPK), and induce cancer cell apoptosis.

  1. Bystander Effect

The drugs (or linker-drug compositions) released by ADC drugs in cancer cells are permeable or transmembrane, and can kill neighboring cancer cells, which is known as bystander effect. The expression of antigens in solid tumor cells is usually heterogeneous, so ADC drugs may not be able to directly and effectively kill neighboring antigen-negative cancer cells. When ADC drugs release cytotoxins outside or inside the target cells, the released small molecular drugs can not only kill antigen-positive cancer cells, but also kill other nearby cancer cells through the bystander effect. At the same time, the bystander effect of these drugs also destroys the environment of tumor growth, such as tumor stromal cells and tumor blood vessels, thus further enhancing the killing effect of cancer cells.