Allergan (NYSE:AGN) said this week that it will “vigorously defend” the patents for its Restasis eye drops, after the U.S. Patent and Trademark Office’s Patent Trial and Appeal Board agreed to an inter partes review of 6 patents as requested by generic competitor Mylan (NSDQ:MYL). The patents are valid until August 2024.

“Allergan is disappointed in the PTAB’s decision to institute IPR proceedings regarding the patents that protect Restasis,” the company wrote in a statement yesterday. “Allergan is currently reviewing the grounds for the decision to institute, and will continue to vigorously defend the patents in the IPR proceeding and pursue all legal options available to protect its products and intellectual property rights for this product.”

The board’s review process is expected to take 1 year and a decision due date was set for December 9th next year.

In 2014, Allergan extended its Restasis patents through 2024 to cover the “exact concentrations of active and inactive ingredients used in the commercial embodiment”. The specificity of its claim could help Allergan fight off a challenge to its intellectual property, FiercePharma reported.

The Dublin-based pharmaceutical company’s Restasis eye drops are indicated for the treatment of chronic dry eye. Allergan touts the product as the only eye drop to help increase the eyes’ natural ability to produce tears.