UPDATE 2-Solvay loses U.S. partner Wyeth for psychosis drug

(Adds details, analyst views)

By Philip Blenkinsop

BRUSSELS, Feb 29 (Reuters) - Belgium's Solvay (SOLB.BR: Quote, Profile, Research, Stock Buzz) lost its U.S. partner Wyeth (WYE.N: Quote, Profile, Research, Stock Buzz) for planned schizophrenia drug bifeprunox on Friday, adding fresh doubt to the would-be blockbuster's future.

Solvay's shares immediately dropped 5 percent to 81.02 euros. At 1100 GMT, they were down 3.2 percent at 82.57 euros, making them the second worst performers in Belgium's benchmark Bel-20 index .BFX.

Wyeth said it was ending its collaboration with Solvay Pharmaceuticals on bifeprunox as well as other compounds in earlier stages of development for the potential treatment of schizophrenia and other psychiatric conditions.

"Wyeth terminated the collaboration with Solvay after assessing the opportunity for bifeprunox and determining it would not have sufficient commercial value for the two companies to share," Wyeth said in a statement.

All development and commercialisation rights in North America would revert to Solvay.

Solvay said in a statement it would evaluate all options regarding bifeprunox for which it had initially seen peak annual sales of $500 million to $1 billion.

"The commercial potential now appears to be below that for a number of reasons, including that an additional study is required by the FDA, leading to a delay," a spokesman said.