LONDON (AP) — GlaxoSmithKline PLC said Wednesday it is selling full commercial rights to antidepressant Wellbutrin XL in the United States to Canadian drug developer Biovail Corp. for $510 million. The drug was developed by Biovail and has been distributed in the United States by Glaxo since September 2003, but has since been hit by generic competition. Once Biovail's top earner, U.S. sales of Wellbutrin XL in the first quarter of 2009 were 45 million pounds ($67.9 million), down 70 percent from a year ago. "We are actively reshaping our U.S. business and managing the transition occurring in our product portfolio," said Deirdre Connelly, president of North American pharmaceuticals. "This transaction is one of a series of actions we are taking to maximize the value of our current assets and to enable us to resource and invest in new products and upcoming launches." Glaxo, the world's second largest drug maker by revenues, will retain existing rights to Wellbutrin XL for countries outside the United States, excluding Canada, where sales were 7 million pounds in the first quarter. Glaxo signaled its intention to continue to "re-engineer" its U.S. operations when it reported a 13 percent drop in first quarter net profit last week, dragged down by a poor performance in its U.S. pharmaceutical business. The company had earlier in the week announced it was buying American dermatology business Stiefel Laboratories Inc. in a $2.9 billion deal.