UPDATE 2-U.S. FDA chief Gottlieb resigning

U.S. Food and Drug Administration chief Scott Gottlieb announced his planned resignation on Tuesday, the Department of Health and Human Services said, and plans to step down in one month.

Gottlieb won bipartisan support for his efforts to curb the use of flavored e-cigarettes by youths, speed approval times for cheap generic medicines to increase competition and bring down prescription drug prices and boost the use of cheaper versions of expensive biotech medicines, called biosimilars. "Scott's leadership inspired historic results from the FDA team, which delivered record approvals of both innovative treatments and affordable generic drugs, while advancing important policies to confront opioid addiction, tobacco and youth e-cigarette use," Health and Human Services (HHS) Secretary Alex Azar said in a statement.

The FDA is an agency within HHS. The FDA did not immediately respond to a request for comment. The Washington Post first reported on Tuesday that Gottlieb planned to resign.

The Nasdaq Biotechnology Index turned negative after the report of Gottlieb's resignation. It was last down 0.3 percent. Similarly, shares of Amgen Inc erased their gains and Gilead Sciences Inc shares added to losses. Amgen shares were last down 0.2 percent and Gilead shares were 1.5 percent lower. (Reporting by Yasmeen Abutaleb and Tim Ahmann; editing by Eric Beech and Jonathan Oatis)