The U.S. Supreme Court on Monday for the second time did not announce whether it would hear an appeal by Teva Pharmaceutical Industries Ltd. in a patent fight with generic competitors over a top-selling multiple sclerosis drug.

The case is closely watched because, if the court declines to take it, cheaper versions of the drug Copaxone could go on the market as soon as May.

The nine justices are considering whether to review a July 2013 ruling by the U.S. Court of Appeals for the Federal Circuit in favor of two teams developing cheaper generic forms of Copaxone. Novartis AG's Sandoz Inc. and Momenta Pharmaceuticals Inc. are developing one drug and Mylan Inc. and Natco Pharma Ltd. are working on the other.

The appeals court upheld some of nine patents involved in the drug, or parts of them, but declared several invalid, meaning patent protections expire this May instead of September 2015.

The Supreme Court was first scheduled to act on the case on March 10. On Monday, the case was again absent from the list of cases on which the court took action. The court does not give reasons for why consideration of cases is delayed.