Exelixis Pill Slows Prostate Cancer and Ovarian Tumors in Study

Exelixis Inc.’s experimental pill reduced malignant growths in the bones of 86 percent of men with prostate cancer and cut the spread of tumor cells in one-fourth of women with ovarian cancer in a company study.

The research sought to gauge the effect of the drug called XL184 on nine cancer types. Based on the findings released today, Exelixis plans to conduct larger studies in ovarian and prostate cancer, said Michael Morrissey, the South San Francisco-based company’s chief executive officer.

Shares of Exelixis, which doesn’t have any marketed products, have more than doubled since researchers announced on Nov. 17 that the pill at least partly cleared bone masses in 19 of 20 men with prostate cancer. Slowing the spread of cancer may lengthen their lives and ease their pain, Morrissey said.

“We have a lot to learn about this drug but it does have an extremely exciting property -- it appears to resolve bone metastases,” said Eric Schmidt, an analyst for Cowen & Co. in New York, in a phone interview “That’s not something that’s ever been observed in prostate cancer patients before.”

XL184, also known as cabozantinib, aims to halt the growth or spread of tumors by blocking three enzymes that fuel cancer cell growth and help bring blood to the tumor. A previous study showed the drug reduced tumor size in 30 percent of patients with thyroid cancer, Gisela Schwab, the company’s chief medical officer, said in a telephone interview.

Year-End Application

Exelixis plans to release results from a larger trial in thyroid cancer patients in the middle of the year and to file an application for U.S. regulatory approval by the end of the year, Schwab said.

Today’s findings will be presented in greater detail at a meeting of the American Society for Clinical Oncology starting June 4 in Chicago.

Among 65 prostate tumor patients who took XL184 for 12 weeks and received bone scans, cancerous bone growths were gone or reduced in 56 of them, the study found.

“The benefit we’re seeing to individual patients with prostate cancer is very exciting,” said Michael Gordon, a medical oncologist at Pinnacle Oncology Hematology in Scottsdale, Arizona, and the study leader.

Ovarian cancer tends to spread from the ovaries to nearby soft tissue and small tumor deposits begin to appear on the intestine and in the stomach, Gordon said. About a quarter of 51 patients had at least a 30 percent shrinkage of their growths, a result he called “impressive” because the spread of ovarian cancer is very hard to control.

Exelixis plans to stop testing XL184 in small-cell lung, gastric and pancreatic cancers and to keep evaluating the therapy against melanoma, breast, liver and non-small-cell lung cancers, Gordon said.

Side effects included diarrhea, fatigue and redness and tenderness on hands and feet, each in fewer than 10 percent of patients.

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