UPDATE 1-Teva sues Mylan again over Copaxone patents

* Latest suit over characterization of MS drug

* Follows October suit over other Copaxone patents

NEW YORK, Sept 21 (Reuters) - Teva Pharmaceutical Industries Ltd TEVA.TA sued Mylan Inc MYL.O for patent infringement, escalating a fight between the rival drugmakers over Teva's top-selling Copaxone multiple sclerosis treatment.

Teva TEVA.O sued generic drugmaker Mylan in October 2009 for infringement of patents covering the chemical composition of Copaxone and other aspects of the drug. Those patents expire in May 2014 and September 2015.

On Tuesday, Teva said it had filed another complaint in the U.S. District Court for the Southern District of New York asserting infringement of four patents related to the characterization of Copaxone. The latest of these patents expires in February 2020.

Mylan was not immediately available for comment.

The ability for Teva to ward off generic competitors to Copaxone is one of the top concerns for investors in the Israel-based company.

Earlier this month, Teva -- which itself is the world's largest maker of generic drugs -- won a ruling in its battle to protect Copaxone, when a U.S. court denied a motion for summary judgment filed by Novartis' NOVN.VX Sandoz unit and Momenta Pharmaceuticals Inc MNTA.O seeking to invalidate patents.

Reporting by Lewis Krauskopf, editing by Leslie Gevirtz