By Ransdell Pierson NEW YORK, Jan 21 (Reuters) - Wyeth could win U.S. approval on Monday for a depression drug derived from the company's widely used Effexor XR, but its launch will be delayed by factory problems and issues with nausea, according to Wyeth and industry analysts. The experimental drug, called Pristiq, is the successor to Effexor XR, Wyeth's $3.5 billion-a-year flagship product that in July 2010 will begin facing competition from a cheaper generic to be sold by Teva Pharmacueticals Industries Ltd <TEVA.O>. Wyeth said in July, however, that it will not introduce Pristiq until it completes tests of a low 50-milligram dose of the drug, following trials of higher dosages in which about half the patients experienced nausea. Company Chief Executive Officer Bob Essner said at the time he hoped a smaller dose would also prove effective, but with a "more tolerable profile." "We will wait for the results of the low-dose trials, which we've said we expect in early 2007, before making a decision" on when to launch Pristiq, company spokeswoman Gwen Fisher told Reuters on Friday. She said nausea seen in the earlier trials was mild to moderate and generally went away within a week after treatment began. Fisher said the launch will also likely be delayed by quality-control problems at a company plant in Puerto Rico that must be fixed to the satisfaction of the U.S. Food and Drug Administration. "We're awaiting an FDA inspection of the plant," Fisher said, declining to speculate when the agency will conduct it. Pristiq is also awaiting approval as a non-hormonal treatment for so-called vasomotor symptoms -- including hot flashes -- in women experiencing menopause. An FDA decision on that use is expected by April. Wyeth has predicted Pristiq will garner annual sales of more than $1 billion, helping to preserve company earnings growth once Effexor XR is slammed by copycats and when Wyeth's blockbuster Protonix ulcer drug faces generics in early 2011. "Pristiq is an important product for Wyeth because it can offset some of the sting of Effexor and Protonix going generic within six months of each other," said A.G. Edwards analyst Joseph Tooley. Tooley forecast Pristiq will fetch annual global sales of $1.4 billion by 2011 -- about $1 billion from use against depression and the remainder for post-menopausal symptoms. But he said the estimate assumes Wyeth will aggressively try to switch depression patients from Effexor XR to Pristiq long before generic forms of Effexor XR come to market -- a strategy that Wyeth has not yet announced. "What they're waiting for evidently is to see if they can get the same effectiveness at a low dose," Tooley said. In the meantime, he added, "perhaps it's the side effects -- the nausea -- that is preventing Wyeth from (announcing) a full switching strategy." He speculated Wyeth may be more confident of the drug's potential against post-menopausal symptoms, because lower doses might do the job -- with minimal nausea risk. Wyeth's Fisher said it would be "premature" to comment on a possible switching campaign and declined to cite what advantages, if any, Pristiq has over Effexor XR in treating depression. "When the FDA gives us its decision, we will be able to answer these questions more fully," she said. "The drug's trial data suggest to us it probably will be a moderate product -- not a huge drug -- because it will be more focused on vasomotor symptoms (of menopause) than for depression," said Jason Fox, an analyst with H&R Block Financial Advisors.
