Supreme Court Chief Justice John Roberts on Friday declined to temporarily block a lower court ruling that opens the world's best-selling multiple sclerosis drug to competition from generic rivals next month.

The decision is a victory for rivals challenging the patents of Israel-based Teva Pharmaceutical Industries Ltd., maker of the drug Copaxone.

Teva claims the U.S. Court of Appeals for the Federal Circuit wrongly overturned five of its patents for the drug. That ruling allows rivals Mylan Inc., Momenta Pharmaceuticals Inc. and Sandoz, Inc., to start selling cheaper generic versions in May instead of September 2015.

The Supreme Court has agreed to consider the case, but arguments won't take place until its new term begins in October and it could be next year before a decision is reached. Teva said it would suffer irreparable harm if the appeals court decision was not postponed. Copaxone brought the company $3.2 billion in U.S. sales last year.

In a one-page ruling, Roberts said he was not convinced Teva would suffer such harm. If Teva ultimately prevails in the case, Roberts said, the company would be able to recover damages from the generic rivals for past patent infringement. He acknowledged that Teva has "a fair prospect" of ultimately winning the case at the high court.

Roberts oversees emergency appeals from the U.S. Court of Appeals for the Federal Circuit, which hears appeals in patent cases.