Genentech warns of anemia in Avastin combo trial

WASHINGTON (Reuters) - Genentech Inc has warned doctors about a type of anemia seen in patients treated with the company's blockbuster cancer drug Avastin in combination with Pfizer Inc's Sutent in a clinical trial, U.S. regulators said in a notice issued on Monday.

The cases of microangiopathic hemolytic anemia seen in a Phase 1 kidney cancer study led to the closure of a mid-stage trial of Avastin plus Sutent, Genentech said in a letter to doctors that was posted on the Food and Drug Administration's website.

The combination of Avastin plus Sutent is not approved or recommended, the company's letter said.

Avastin, which is approved to treat colon, lung and breast cancer, is widely considered to be Genentech's most important product. Analysts are looking for second-quarter U.S. Avastin sales of more than $640 million when Genentech announces its quarterly results later on Monday.

The medicine, which works by cutting off the blood supply to tumors, is being tested in combination with numerous other drugs in scores of clinical trials.

Sutent is one of the most widely used medicines for the treatment of advanced kidney cancer.

The letter to doctors noted that five of 12 patients who received the highest dose of Sutent in the study had laboratory findings consistent with microangiopathic hemolytic anemia .

Two of the cases were considered severe with evidence of several adverse side effects, including severe high blood pressure, the letter said. Both cases were reversible within three weeks of discontinuation of the two medicines without additional medical intervention, Genentech said.

Genentech spokeswoman Kimberly O'Campo said other studies combining lower doses of Sutent with Avastin are ongoing.

However, two other mid-stage studies of Avastin in combination with Sutent and chemotherapy were halted due to poor tolerability involving fatigue, gastrointestinal complications and myelosuppression -- a condition in which production of blood cells and platelets is reduced.

Those trials involved patients with breast and lung cancer, O'Campo said.

The letter asks doctors to report cases of microangiopathic hemolytic anemia or any serious adverse events suspected to be associated with Avastin use.

Genentech shares were down $2.36, or 3 percent, to $75.39 on the New York Stock Exchange.

(Additional reporting by Bill Berkrot in New York)

(Reporting by Lisa Richwine; Editing by Andre Grenon, Gary Hill)