The recent case involving United Therapeutics' patent on Tyvaso and Liquidia's Yutrepia sheds light on the complexities of patent law. The Federal Circuit's initial infringement finding, followed by the Patent Trial and Appeal Board's ruling of invalidity, highlights the importance of timing in appeals from both the district court and the PTAB.

The case also raises questions about the practical effects of a PTAB decision on patent infringement cases. United's argument that the patent remains in force until a final decision post-appeals contrasts with Liquidia's stance that the patent's invalidity allows for product launch, as the USPTO's cancellation is deemed ministerial.

As legal professionals, understanding when a PTAB decision formally takes effect is crucial in determining the impact on patent infringement cases. The nuances of Hatch-Waxman Act orders, the role of district court rulings, and the significance of a patent's validity all come into play in such complex intellectual property disputes.

This case serves as a reminder of the intricate interplay between patent infringement and validity proceedings, urging practitioners to stay informed on evolving legal interpretations and the practical implications of PTAB decisions.

The Federal Circuit previously held that United's patent on the hypertension treatment Tyvaso would be infringed by Liquidia's competing drug Yutrepia, and U.S. District Judge Richard Andrews of the District of Delaware initially barred Liquidia from launching its product.

However, he reversed course and vacated the injunction in March, after the appeals court affirmed a PTAB decision finding United's patent to be unpatentable as obvious. The Delaware judge wrote that "invalid patents cannot be infringed."

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