They have developed a drug production process that ensures purity. They are developing tests for each drug for its action on body chemistry and organ systems. These studies of the chemistry of the purified drug products will help predict the drugs' effects on human body processes and organ systems. Required safety testing will follow. Currently, research on angiostatin and endostatin has only been done in animals.
Humans are very different than animals.
Also, in the published work with mice, scientists have been treating tumors that were transplanted into the mice rather than tumors that developed naturally in mice, as they do in people. Tumors transplanted into mice have a different biology than naturally occurring tumors and are often not accurate predictors of what will happen in natural human cancers. Laboratory animals such as mice metabolize drugs very differently than humans, which can affect the success of treatments with proteins. Moreover, the relative size of humans compared to mice would require much more drug to treat a human. For reasons such as these, scientists follow a systematic process to move drugs from the laboratory to clinical trials.