* Cash offer of 232 Swedish crowns/share is 70 pct premium
* Alexion gets late-stage drug for rare Wilson disease
* U.S. company says first step in rebuilding pipeline (Adds latest shares, analyst reaction)
By Ben Hirschler
April 11 (Reuters) - Alexion Pharmaceuticals has agreed to buy Sweden's Wilson Therapeutics for 7.1 billion Swedish crowns ($855 million), boosting its line-up of rare disease drugs as a wave of deal-making in the biotechnology sector continues.
The U.S. group is acquiring the business through a cash tender offer worth 232 crowns per share, a premium of 70 percent compared to the closing share price on April 10.
Alexion was one of the stars of the biotech sector in the first half of this decade, but it has stumbled more recently following an exodus of top management and a sales practices scandal related to Soliris, its pricey rare disease treatment.
Adding Stockholm-based Wilson will give it new therapies to treat unusual copper-mediated disorders and marks a first step by the new executive team in overhauling Alexion's medicine cabinet.
The two companies said on Wednesday that investors holding a total of 73.4 percent of Wilson's shares supported the takeover offer.
Shares in Wilson jumped to 230.50 crowns by 1335 GMT, while Alexion was little changed in early Nasdaq dealings.
The Swedish group's main asset is WTX101, a drug in final-stage Phase III testing for Wilson disease, a rare genetic condition that causes severe liver disease and serious neurological problems. WTX101 works by removing excess copper from the bloodstream.
"The acquisition of Wilson Therapeutics is a strong strategic fit for Alexion given the overlap with our current clinical and commercial focus on metabolic and neurologic disorders, and is an important first step in rebuilding our clinical pipeline," said Alexion Chief Executive Ludwig Hantson.
WTX101 has secured fast-track designation in the United States, which should speed its path to market, and also has orphan drug status in both the U.S. and Europe, which brings certain benefits.
SunTrust Robinson Humphrey analyst Yatin Suneja said the new drug would provide badly needed diversity to Alexion's pipeline, assuming it proves itself in Phase III. Results from the pivotal WTX101 trial here are expected later next year.
RBC Capital Markets said buying Wilson would use up much of Alexion's cash pile but there was still scope for smaller deals.
Wilson disease affects approximately 10,000 patients in the United States and 15,000 in the European Union.
There have been a slew of deals in the biotech sector this year as drugmakers turn to promising drugs from outside to boost sales growth. Highly priced and high-margin treatments for rare diseases have been a particular focus for such acquisitions.
On Monday, Swiss drugmaker Novartis agreed to acquire gene therapy specialist AveXis for $8.7 billion, following similar multibillion-dollar deals by the likes of France's Sanofi and U.S.-based Celgene .
Japan's Takeda Pharmaceutical, meanwhile, is considering a takeover bid for London-listed Shire.
Alexion said its acquisition of Wilson was expected to close in the second quarter of 2018 and that it intended to finance the acquisition through cash on hand.
Lazard is acting as financial adviser to Wilson, while Alexion is being advised by BofA Merrill Lynch, Deutsche Bank and DNB Markets.
$1 = 8.3000 Swedish crowns Editing by Susan Fenton and Jane Merriman