UPDATE 2-US FDA advisers back Schering antipsychotic drug

* FDA panel: Saphris OK for schizophrenia, bipolar

* Some panelists say safety profile more favorable

* Advisers seek more data on bipolar dosing

* Agency to weigh advice before making final decision (Adds comments, background, share price, byline)

By Susan Heavey

WASHINGTON, July 30 (Reuters) - A U.S. medical advisory panel on Thursday widely supported Schering-Plough Corp's SGP.N experimental drug, Saphris, as a safe and effective therapy for adults with acute schizophrenia and a more severe type of bipolar disorder.

The Food and Drug Administration's outside advisers unanimously backed the antipsychotic medication's use in treating mania in patients with bipolar I disorder, and most also backed its use for those with schizophrenia.

Schering, which is expected to be acquired by Merck & Co Inc (MRK.N) later this year, is seeking the agency's approval to market the drug as another treatment option for patients with either mood illness and has said Saphris could earn more than $1 billion a year.

Although there are already a number of other available medications, "we still could use more options for treating both these challenging populations," said panel member Andrew Winokur, a psychiatrist at the University of Connecticut School of Medicine.

The FDA will weigh the panel's vote before later making a final decision on whether to approve the drug, also known as asenapine. A company spokeswoman declined to say when it expected the agency to rule.

Saphris is a type of atypical antipsychotic, a class of drugs that target various brain receptors. Such drugs have raised some concerns over their side effects, which can include problems with weight gain, metabolism and blood fat levels.

Those side effects, along with waning effectiveness over time, can cause doctors to have to switch their patients from one drug to another trying to find the best one, Schering officials told the panel.

But company studies showed fewer patients given Saphris gained weight or saw higher cholesterol levels compared to rival drugs, the company said.

Other antipsychotics include Johnson & Johnson's (JNJ.N) Risperdal and Eli Lilly's (LLY.N) Zyprexa, among others.

Panelist Ruth Day, a Duke University professor of medical cognition, echoed other FDA panelists who agreed Saphris was about as safe as its rivals but "also a little bit better in some respects." Overall, panel members said Schering's data was adequate to show it was effective.

BMO Capital Markets analyst Robert Hazlett boosted his sales estimates for the drug following the panel's positive vote, saying he expects Saphris to earn $25 million in 2009, $125 million in 2010 and $200 million in 2011.

About 2 million people in the United States are affected with schizophrenia and about 10 million by more severe bipolar disorder, according to Schering.

Some FDA advisers expressed concern about the proper dosing for use in bipolar patients and urged the company to study a lower 5-milligram dose, saying the 10 milligram dose could be too high in certain cases. Both doses were studied for schizophrenia patients.

Thomas Laughren, head of the FDA's Division of Psychiatry Products, said that such a dosing study would likely be considered as something the company could do after approval.

Schering, which said in a statement it was pleased with the panel's recommendation, saw its shares rise less than one percent to $26.68 in late afternoon trading on the New York Stock Exchange.