UPDATE 1-US drugmaker Alexion to lay off 20 pct of workforce to cut spending

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Sept 12 (Reuters) - U.S. drugmaker Alexion Pharmaceuticals Inc said on Tuesday it would lay off about 20 percent of its global workforce in an effort to cut spending.

The company had about 3,100 full-time employees worldwide as of the end of last year.

As part of the restructuring, Alexion will close some of its manufacturing sites, including its Rhode Island facility, the company said on a call with analysts.

The drugmaker also said it would relocate its headquarters to Boston from New Haven, Connecticut by mid-2018.

Alexion has been roiled in recent months by a sales practices scandal related to its pricey rare disease treatment Soliris as well as senior management resignations.

The company's chief executive officer and chief financial officer resigned in December, a month after Alexion announced it was investigating allegations related to its sales practices.

Alexion named long-time Biogen Inc finance chief Paul Clancy as CFO in June, as newly appointed Alexion CEO Ludwig Hantson stepped up efforts to regain investor confidence.

Alexion said it expects to cut costs by $270 million each year by 2019, on a pre-tax, adjusted basis.

It expects pre-tax expenses of $340 million to $440 million related to the restructuring.

Alexion shares were up 1.8 percent at $145.50 in premarket trading on Tuesday. (Reporting by Manas Mishra in Bengaluru; Editing by Sai Sachin Ravikumar)