Unprecedented Tumor Shrinkage With Drug

A new drug designed to stop cancer by cutting off its blood supply has surprised experts by showing a tumor shrinkage rate unprecedented for a drug so early in its development.

In the first human trials of the drug, the tumors of one-quarter of the 23 terminal patients shrank by half or more, researchers reported this week. Similar drugs have shown great promise in animals, but proved disappointing in human studies -- prompting no dramatic tumor shrinkage in their early tests.

Tumors shrank by more than 50% in six of the 23 patients. The cancer stabilized in five other people. It is rare for a drug to show more than a 5% regression rate in early human trials, said Dr. Jaap Verweij of Erasmus University in Rotterdam, the Netherlands.

Experts said the new drug attacks from three directions instead of one. As well as blocking a protein involved in blood vessel growth, vascular endothelial growth factor, the new drug also interferes with two other blood vessel growth factors -- basic fibroblast growth factor and platelet-derived growth factor. Scientists suspect those enzymes might do more than just support blood vessel growth.