Endo International plc announced that its subsidiaries, Par Pharmaceutical, Inc. and Par Sterile Products, LLC, have received a Notice Letter dated April 16, 2018 advising that Eagle Pharmaceuticals, Inc. (Eagle) has submitted an Abbreviated New Drug Application (ANDA) to the US Food and Drug Administration (FDA) seeking approval from the FDA to manufacture and market a generic version of Vasostrict (vasopressin injection, USP) 1 mL, in the United States.

The Notice Letter also contains "Paragraph IV" certifications alleging invalidity and non-infringement with respect to five patents which Endo has listed in the FDA's Approved Drug Products with Therapeutic Equivalence Evaluations, commonly known as the Orange Book, for Vasostrict.  Endo is assessing the details of the Notice Letter and formulating its legal strategy.  Endo intends to vigorously protect its intellectual property, which may include initiating a patent infringement lawsuit against Eagle within 45 days of receiving the Notice Letter.  If a lawsuit is filed within that timeframe, it will trigger a stay of FDA approval of Eagle's generic version of Vasostrict for up to 30 months pursuant to the Hatch-Waxman Act.

Endo International plc is a highly focused generics and specialty branded pharmaceutical company delivering quality medicines to patients in need through excellence in development, manufacturing and commercialization.