Tuesday, November 4, 2008
The most common type of brain tumor, glioblastoma, may be getting a new FDA-approved treatment soon. Yesterday the pharmaceutical firm Genentech announced that it is requesting accelerated approval for its drug Avastin (bevacizumab) as a glioblastoma treatment. Avastin is already approved for use on lung, colon and breast cancers. Promising results in Phase II clinical trials led the company to seek early approval before Phase III trials for glioblastoma, a condition that has high mortality rates and few treatment options. The FDA sometimes grants early approval of treatments for life-threatening conditions when early studies show good results.
| This is a devastating disease and people with glioblastoma desperately need new treatment options | ||
Dr. Hal Barron, chief medical officer for Genentech, told the press “There has been no substantial improvement in the treatment of glioblastoma in more than 20 years… This is a devastating disease and people with glioblastoma desperately need new treatment options.” Glioblastoma is an incurable condition with a median survival time of less than one year. Only about five percent of patients survive for five years. In Phase II clinical trials of Avastin on 167 patients, 43 percent of patients saw no increase in tumor size after six months. Existing tumors decreased in size by at least 50 percent in twenty-eight percent of patients. Phase III clinical trials for Avastin as a brain tumor treatment are scheduled to begin early next year. The trials will evaluate Avastin together with chemotherapy and radiation.
Avastin works by inhibiting angiogenesis: the development of new blood vessels. Fast growing tumors such as glioblastoma need a rapidly growing supply of blood vessels in order to spread. Side effects associated with Avastin include hypertension, convulsion, intestinal perforation, and slow wound healing. There were two patient deaths associated with side effects from the study, yet the study as a whole yielded a significantly longer average life expectancy than glioblastoma patients normally have.
Approximately 19,000 primary brain tumors were diagnosed in the United States last year. 60 percent were gliomas, including glioblastoma. In most of North America and Europe, incidence of glioblastoma each year is 2-3 cases per 100,000 persons.
A single course of Avastin treatment costs approximately US$40,000. News reports gave conflicting information about Avastin sales for the first 9 months of 2008, with figures ranging from US$700 million to US$2 billion. Sales included approved treatments plus off-label use. Genentech shares recently rose 0.8 percent to US$83.64. Relatively few pharmaceutical firms are developing treatments for glioblastoma. Others include Pfizer in collaboration with Avant Immunotherapeudics for vaccine development. Myriad Genetics is developing a drug Azixa for primary and metastatic brain tumors.