Why does cancer therapy lack effective anti-metastasis drugs?

The suppression of cancer metastasis is an urgent therapeutic need. Yet, most existing drugs inhibit only cancer cell proliferation. Historically, the reason is the much later elucidation of the molecular biology of metastasis versus that of the early steps in transformation. Because the molecules that drive the dissemination of malignant cells are shared among cancers, drugs that inhibit their functions will be broadly beneficial. There are two complementary anti-metastasis strategies, the prevention of cancer cell dissemination and the suppression of already existing metastases. To accelerate the availability of potentially life-saving anti-metastasis agents several adjustments must be made. The risk tolerance in drug trials needs to increase with a worsening prognosis. Clinical trials of drug molecules that prevent cancer dissemination need to be approved for use right after diagnosis, not after failure of standard-of-care therapies. For agents that treat existing metastases, the clinical trial system needs to be modernized. Because cancer metastasis is often fatal, improved and innovative approaches to anti-metastasis drugs are eminently suited to play a lead role in changing the standards of drug development.