(Adds outlook, tax rate, spending details, share move)
Feb 1 (Reuters) - Amgen Inc on Thursday reported a fourth-quarter profit well below Wall Street estimates, hurt by a steep decline in sales of blockbuster rheumatoid arthritis drug Enbrel and higher-than-expected expenses, and its shares fell 4 percent.
But the world's biggest biotechnology company provided a 2018 earnings forecast range with a midpoint that easily exceeded analysts' estimates and announced a $10 billion share repurchase program and a lower effective tax rate due to U.S. tax reform.
Excluding items, Amgen said it earned $2.89 per share, 14 cents below analysts' average expectations, according to Thomson Reuters I/B/E/S.
For 2018, Amgen forecast adjusted earnings per share of $12.60 to $13.70 and revenue of $21.8 billion to $22.8 billion. Analysts were looking for earnings of $12.71 per share and $22.8 billion in revenue.
Amgen projected a 2018 adjusted tax rate of 14 percent to 15 percent. Some other large drugmakers have announced rates of about 17 percent or 18 percent. AbbVie Inc surprised investors last week by announcing a 9 percent adjusted tax rate, rising to 13 percent over five years.
Amgen said it plans capital investments of about $3.5 billion over the next five years, with 75 percent of that in the United States. The company said it has decided to build a new biomanufacturing plant in the United States and will add jobs to build and run the facility. Amgen expects to announce the plant location in the second quarter.
The company posted a fourth-quarter net loss of $4.26 billion, or $5.89 per share, as it took a $6.1 billion charge related to U.S. tax reform. That compared with a profit of $1.93 billion, or $2.59 per share, in the year-ago quarter.
The company said it incurred $79 million in expenses in Puerto Rico for Hurricane Maria recovery and additional incremental expenses related to tax planning.
Amgen shares fell to $178 in extended trading from a Nasdaq close at $185.56. (Reporting by Bill Berkrot; Editing by James Dalgleish and Leslie Adler)