UPDATE 2-U.S. FDA to review Mylan's generic of Teva MS drug

* Mylan: agency accepts application for Copaxone version

* Teva shares fall 2.4 percent in U.S. (Adds Teva comment, updates shares)

NEW YORK, Sept 14 (Reuters) - U.S. regulators have accepted for review Mylan Inc's (MYL.O) application to market a generic version of Teva Pharmaceutical Industries Ltd's (TEVA.TA) (TEVA.O) blockbuster Copaxone multiple sclerosis drug, Mylan said on Monday, sending Teva shares down more than 2 percent.

Mylan's application brings a new threat to Teva's product, which is known scientifically as glatiramer acetate. Although Israel-based Teva is the world's largest generic drugmaker, Copaxone amounted to about 20 percent of Teva's $11.1 billion in sales last year.

Teva has maintained that Copaxone is an extremely challenging product to manufacture, and has cast doubt on the ability of rivals to make an equivalent version.

Mylan in June 2008 signaled its intent to sell a Copaxone generic when it announced a supply deal with India's Natco Pharma Ltd (NATP.BO).

Teva is also contending with a potential generic Copaxone from Momenta Pharmaceuticals Inc (MNTA.O), which said in July 2008 that the U.S. Food and Drug Administration had accepted its application for review. Teva sued Momenta and partner Novartis AG (NOVN.VX) the following month for patent infringement.

In a statement on Monday, Teva said it had "serious doubts" about any the ability of any generic applicant to demonstrate its product is identical to Copaxone. Full-scale clinical trials -- more extensive than is required for generic drugs in general -- must be performed, Teva said.

Teva also said it "remains committed to vigorously defending its property rights against infringement."

Teva shares were down $1.26, or 2.35 percent, to $51.44 in afternoon trading on the Nasdaq. Mylan rose 8 cents, or 0.6 percent, to $15.25. (Reporting by Lewis Krauskopf; Editing by Maureen Bavdek, Bernard Orr)