FDA Rejects AstraZeneca's Exanta  LOS ANGELES (Reuters) - U.S. regulators on Friday turned  down AstraZeneca Plc's  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AZN.L target=/stocks/quickinfo/fullquote"&gt;AZN.L&lt;/A&gt; &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AZN.N target=/stocks/quickinfo/fullquote"&gt;AZN.N&lt;/A&gt; anti-clotting drug  Exanta, following the advice of an advisory panel on which some  members had voiced doubt about the drug's safety and  effectiveness.