Oct. 18 (Bloomberg) -- Galenica Holding SA, Switzerland's largest drug wholesaler, agreed to buy Canada's Aspreva Pharmaceuticals Corp. for $915 million to hasten development of new treatments and expand into additional markets.

The purchase price values Aspreva at $26 per share, Bern, Switzerland-based Galenica said in an e-mailed statement today. That's a 16 percent premium to Aspreva's closing share price yesterday of $22.50.

The acquisition sent Galenica shares to their biggest gain in 18 years in Zurich trading. Victoria, British Columbia-based Aspreva, which develops treatments for rare diseases from existing drugs, will form a new unit and help market Galenica treatments such as the Ferinject intravenous anemia medicine, Galenica said.

Aspreva shares added $3.11, or 14 percent, to $25.61 as of 12:01 p.m. New York time in Nasdaq Stock Market composite trading, the steepest increase since April 13, 2006. Galenica gained 22 Swiss francs, or 4.7 percent, to close at 494 francs in Zurich, after earlier rising the most since 1989. They have increased 45 percent this year.

Aspreva, which posted 2006 net income of $124.2 million with sales of $214.8 million, will positively affect Galenica profit in its first year, the Swiss company said.

Aspreva shareholders will hold a special general meeting in mid-December to decide whether to approve the sale. The company's directors and officers, as well as the largest shareholder, who collectively hold about 30 percent of the stock agreed to vote in favor of the transaction, Aspreva said.

To contact the reporter on this story: Trista Kelley in London at tkelley2@bloomberg.net.

Last Updated: October 18, 2007 12:02 EDT