During scaleup, the growth medium was becoming zinc deficient, they discovered. Without zinc, the proteases chew on the end of the molecule and it lost activity, explained Dr. Folkman. Dr. Folkman, who has a reputation for diligently crediting his co-workers, noted the contributions of Don Wiley and Thomas Boehm. So you can always resume therapy. Tumors don't recur.
Angiogenesis is blocked.
Endostatin is a third-generation angiogenesis inhibitor, said Dr. Folkman. The first generation slows animal tumors but doesn't regress them. The second generation, including inhibitors of integrin, VEGF, and metalloproteinases, produces actual regression. And these are very specific to endothelial cells. Tumor dormancy was originally observed after drug cycling, said Dr. Folkman.