Medical Health Encyclopedia

Matrix metalloproteinase Inhibitors. Matrix metalloproteinase is an important enzyme in angiogenesis. Inhibitors of these enzymes, including marimastat, metastat, and prinomastat, are in early trials. Marimastat has been studied and has shown some benefits in early trials for patients with recurrent glioblastoma and anaplastic gliomas, particularly in combination with temozolomide.

Phophoinositide 3-Kinse (Pi3K) Inhibitors. Rapamycin and its analog (CCI-779) inhibit Pi3K, an enzyme involved in cell growth. Early trials using CCI-779 are underway. (Another rapamycin analog, everolimus, has different effects but is also being studied for its actions in inhibiting cell growth.)

Other Drugs that Block Angiogenesis. Thalidomide was one of the first drugs used to inhibit angiogenesis and has undergone several trials. There is some evidence that it may work more effectively for metastasized brain tumors than primary tumors. Other agents in early trials with various effects on tumor growth include suramin, cilengitide, semaxanib, PTK787, and atrasentan.

Other Investigative Agents

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Retinoids. Retinoids are vitamin A derivatives and act as differentiating agents in cancer treatments. That is, they can convert immature, dividing tumor cells into mature cells, stopping tumor growth. Studies suggest that they have little benefits as single agents. Combination with radiotherapy and other drugs may hold promise.

Inactivated Viruses. Investigators are finding that certain genetically inactivated viruses, such as the poliovirus or herpesvirus, may prove to be valuable fighters of brain cancers. Such viruses can enter cells and destroy them but do not pose any danger for infection. For example one specially designed herpes virus targets the enzyme thymidine kinase (an enzyme that promotes tumor growth). Some researchers believe that a combination of this virus with retinoids may be effective with few serious side effects. Other viruses are being investigated. A drug based on this model is years away, however.