Elan has agreed to sell the European rights to its chronic pain drug Prialt to Eisai, while retaining the product rights in the US.
Under the terms of the sale, Elan may receive up to $100 million in cash depending on the drug's sales in Europe.
The sum is comprises an upfront payment of $50 million on the closing of the deal, a further $10 million on the earlier of two years from closing or launches of Prialt in key European markets, and an additional $40 million contingent on sales.
The deal which is subject to regulatory approval is expected to be completed in the first quarter of 2006.