In the 1980s and early 1990s, huge resources were put into the development of MMP inhibitors (MMPIs) for treatment of cancer patients. At this time, MMPs were simply thought of as matrix-degrading enzymes, and MMPIs were believed to be
able to greatly reduce the invasive and metastatic potential of cancer cells. In clinical trials, however, the drugs generally offered no survival benefit to patients or sometimes even decreased survival compared to patients in control groups. In
addition, severe side effects were reported.