* 38 pct of evaluated patients see tumor shrinkage
* Exelixis shares rise 27 pct after hours
LOS ANGELES, May 14 (Reuters) - An experimental drug being developed by Exelixis Inc (EXEL.O) and Bristol-Myers Squibb Co (BMY.N) was shown to shrink brain tumors in some patients, according to interim results from a mid-stage study of the drug, known as XL184.
Shares of Exelixis rose 27 percent after hours, while shares of Bristol-Myers were unchanged.
Early results from a trial of 46 patients with advanced glioblastoma multiforme, the most common and deadly type of brain cancer, were released on Thursday as part of the American Society of Clinical Oncology’s conference program.
A summary of the findings, called an abstract, said 26 patients have been assessed at four weeks after treatment. Ten of them, or 38 percent, had tumor shrinkage of at least 50 percent, including one patient who had a 100 percent reduction in tumor size.
Nine patients had tumor measurement changes ranging from plus 24 percent to minus 49 percent and seven had at least a 25 percent increase in tumor burden, according to the abstract.
Of 17 patients who had not received prior anti-angiogenic treatment, nine had at least a 50 percent reduction in tumor burden.
Exelixis partnered with Bristol-Myers last year to develop two experimental cancer drugs, including XL184, which is also being tested for thyroid cancer and non-small cell lung cancer.
More details of the study will be released at ASCO’s annual meeting later this month.
Shares of Exelixis, which closed at $4.42 on the Nasdaq, were higher at $5.60 after hours. (Reporting by Deena Beasley, Editing by Steve Orlofsky)