Five patients out of the first forty-four enrolled developed the complication. Participants in the trial, along with their doctors, were informed of the new safety information and given the option to either continue treatment or drop out of the study.

"GI perforations are a known possible adverse event with Avastin, notes Hal Barron, MD, Genentech’s chief medical officer. “However, we chose to discontinue enrollment in this Phase II study due to the observation of a higher rate seen in this study than in other trials of Avastin in ovarian cancer or other tumor types."

Risk Factors Unclear

Genentech will continue studying Avastin for its effectiveness in treating earlier-stage ovarian cancer, according to Barron.

"The limited overall number of GI perforations seen in this study prevent us from ascertaining definitive risk factors for this adverse event. Patients enrolled in this study had more advanced disease, which typically involves the bowel, and had received more prior chemotherapy than in previous clinical trials of Avastin in ovarian cancer," Barron explains.

Evaluation of Potential Continues

Avastin is designed to interfere with the blood supply to tumors, thereby inhibiting their ability to grow and spread to other parts of the body.

The US Food and Drug Association (FDA) approved Avastin in February, 2004 for the treatment of colon cancer. Genentech plans to evaluate the drug’s potential use in treating a broad range of cancers, including those of the kidney, breast, and lung.

In Genentech-sponsored studies, the most serious adverse events associated with Avastin were gastrointestinal perforation, wound healing complications, hemorrhage, arterial thromboembolic events, hypertensive crisis, nephrotic syndrome and congestive heart failure.

Genentech made its decision to halt enrollment in the Avastin study in consultation with the FDA.