Amgen Net Down, Adjusted Earnings Rise  NEW YORK (Reuters) - Amgen Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AMGN.O target=/stocks/quickinfo/fullquote"&gt;AMGN.O&lt;/A&gt;, the world's  biggest biotechnology company, on Wednesday said quarterly net  profit fell on acquisition charges but adjusted earnings rose  21 percent on strong sales of its drugs for anemia and  arthritis.