FOSTER CITY (CBS/AP) — Drugmaker Gilead Sciences Inc. has halted several patient studies of its cancer drug, Zydelig, because of increased risk of death and serious side effects.

The company told The Associated Press the “adverse events” were spotted during an ongoing review of late-stage testing in patients with chronic lymphocytic leukemia, a blood cancer, and patients with relapsed non-Hodgkin’s lymphoma, a cancer of the infection-fighting lymphatic system.

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Nathan Kaiser, a spokesman for the Foster City company, wouldn’t disclose details, including how many patients died or suffered serious side effects.

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“We are conducting a comprehensive review of all ongoing studies and are consulting with regulatory authorities,” Kaiser wrote in an email Tuesday.

Zydelig is approved for treating follicular B-cell non-Hodgkin’s lymphoma and chronic lymphocytic leukemia in patients who have failed other treatments.

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