As we mentioned above, chemotherapy drugs act by killing dividing cells. But cancer cells do not divide constantly. So even if a cancer
cell takes up a chemotherapy drug, the cell may not divide again for a few days, and by that time it may have detoxified the drug, so it
is not killed by the drug. Only the portion of cancer cells that (a) take up the chemotherapy drug and (b) divide shortly after taking up
the drug are killed by the drug.
In our process, many more cancer cells take up the drug, because the IGF-drug conjugate is taken into cancer cells specifically by binding
to the IGF receptor on the surface of the cancer cell. Moreover, once the IGF-drug conjugate is inside the cell, it has an advantage over
conventional chemotherapy because the IGF causes the cancer cell to divide, and the drug can then more easily kill the cancer cell. Thus,
a far larger percentage of cancer cells are killed by the IGF-drug conjugate (Figure 5).
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