Liquidia Technologies, Inc., a late-stage biopharmaceutical company known for its proprietary PRINT technology, announced Wednesday the U.S. Patent Trial and Appeal Board (PTAB) has instituted inter partes review (IPR) against United Therapeutics Corporation’s U.S. Patent No. 9,604,901 (’901).

Liquidia noted that PTAB concurrently denied the institution of an IPR on United Therapeutic’s 9,593,066 (’066) patent.

Both of the products are listed in the Orange Book for Tyvaso (treprostinil).

An inter partes review is a procedure that challenges the validity of a patent before the U.S. Patent Trial and Appeal Board, part of the U.S. Patent and Trademark Office.

According to the release, PTAB stated that “based on the information presented, we institute an inter partes review of claims 1–9 of the ’901 patent.” The PTAB denied said it denied instituting an IPR for ’066 because Liquidia “has not established a reasonable likelihood that it would prevail in showing that at least one of the challenged claims is unpatentable.”

“The PTAB’s decision to institute an IPR proceeding against the ’901 patent for Tyvaso is another important step forward for Liquidia’s ongoing effort to bring LIQ861, a convenient and well tolerated treatment option, to the PAH community,” Liquidia CEO Neal Fowler said in the release.

Liquidia’s LIQ861 product is a dry powder inhaler that uses the same active ingredient as a currently marketed product, treprostinil. The company filed a New Drug Application fora dry powder inhalation of treprostinil, currently under review by the U.S. Food and Drug Administration to treat pulmonary arterial hypertension.

Fowler added that the company believes the decision not to institute IPR on ‘066 “to be in error and while there are options for reconsideration, we remain confident in the arguments of non-infringement and invalidity to be made in district court.”

Liquidia Technologies Inc. (LQDA) was trading down 30 cents near $3.04 on Thursday.