Early in the 20th century, it was hypothesized that solid tumors secrete factors, now referred to as angiogenic factors, that induce angiogenesis — the formation of new blood vessels — thereby ensuring the delivery of enough blood to support the growth of the tumor. The idea that inhibiting angiogenesis would have an antitumor effect has been borne out by the startling anticancer activity of some antiangiogenic agents in tumor-bearing mice. For these reasons, perhaps no area of cancer research has attracted as much attention, both on Main Street and on Wall Street, as angiogenesis.

Unfortunately, the dramatic effects of antiangiogenic . . .