TRENTON, N.J. (AP) -- A federal court invalidated the patent on Friday for Merck & amp; Co.'s second-largest selling drug, the blockbuster osteoporosis treatment Fosamax, in a decision that offers millions of patients hope for a cheaper version sooner, but darkens the company's already clouded outlook.
The company also was hit with news that the federal Securities and Exchange Commission is starting a formal inquiry into its handling of arthritis blockbuster Vioxx, which it withdrew from the market last year after studies showed it increased the risk of heart attacks and strokes.
Merck's shares tumbled in heavy trading.
The U.S. Court of Appeals for the Federal Circuit in Washington, D.C., invalidated the patent for the once-a-week version of Fosamax, which dominates the market for osteoporosis drugs. More than 3 million people in the United States afflicted with the brittle-bone disease take Fosamax.
Under the ruling, generic competition could begin as soon as early 2008, instead of 2018. The main patent for the daily 5 milligram and 10 milligram versions of the drug already was set to expire in February 2008.
Fosamax is the No. 2 drug for Whitehouse Station, N.J.-based Merck. It reported sales of $3.16 billion for Fosamax last year.
Copyright 2005 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.