Protein kinase inhibitors make excellent anti-cancer drugs.
However, because most of these inhibitors are ATP analogs,
achieving specificity is usually challenging (i.e., an inhibitor
designed to inhibit kinase A may also inhibit kinase B, C, etc). In
principle, inhibitors that recognize the inactive conformation of
the A-loop of the target kinase are more likely to be specific than
inhibitors recognizing the active conformation of the A-loop.
Why?