Momenta Pharmaceuticals announced that it has filed a request for a temporary restraining order and preliminary injunction to prevent Amphastar Pharmaceuticals, Watson Pharmaceuticals and International Medical Systems from launching their enoxaparin sodium product in the United States.

On September 21, 2011 Momenta announced that it had sued Amphastar, Watson, and International Medical Systems in the United States District Court for the District of Massachusetts for infringement of two Momenta patents.

The patents cover the company's methods of producing enoxaparin sodium.