Jan 14 (Reuters) - Gilead Sciences Inc (GILD.O) on Friday notified the U.S. health regulator of its decision to voluntarily withdraw the use of its drug Zydelig for two types of cancer - follicular lymphoma and small lymphocytic leukemia. The U.S. Food and Drug Administration gave the drug an accelerated approval in 2014 to treat relapsed follicular B-cell non-Hodgkin lymphoma and relapsed small lymphocytic leukemia along with relapsed chronic lymphocytic leukemia (CLL). The approval, however, came with a boxed warning highlighting the risk of serious and potentially fatal toxicities. Two years later, a regulatory review of the drug"s safety was launched by the European and U.S. regulators due to concerns over serious adverse events, including deaths. Gilead said Zydelig will continue to be sold in the U.S. market for treating CLL. It will be available to treat CLL and FL in the European Union, the UK, Canada, Australia, New Zealand and Switzerland.