Yesterday, Bausch Health Companies Inc BHC The stock closed 50% lower following reports of the Xifaxan (rifaximin) patent litigation resolution.

The company’s shares gained slightly after it was said contest a decision that would likely invalidate patents related to Xifaxan.

“We are disappointed with today’s development. We expressly disagree with any conclusion that our patents are invalid and intend to appeal any such order,” said Thomas Appio, CEO of Bausch Health.

The US District Court of Delaware entered an oral order in the matter Salix Pharma Ltd, the company’s gastroenterology business, et al. v. Norwich Pharmaceuticals Inc regarding the infringement and validity of Xifaxan’s certain US patents for Irritable Bowel Syndrome with Diarrhea (IBS-D) and reducing the risk of recurrence of overt hepatic encephalopathy (HE).

Court to invalidate Xifaxan patents related to IBS-D while signaling to uphold HE claims.

Related: Why Bausch Health’s market cap will be halved on Thursday: “A near-worst-case scenario”

At the heart of the case is Norwich Pharmaceuticals Abbreviated New Drug Application (ANDA) for a generic xifaxane.

Bausch expects the court to bar Norwich’s ANDA until the HE patents expire in 2029. If Norwich removes HE security data to avoid the patents, the company said it would “strongly oppose” the move.

“The FDA has stated that it plans to substantially revise the product-specific guidance for rifaximin to add an in vivo bioequivalence study,” said Bausch.

“Until approval of a revised ANDA is granted by the FDA and the anticipated injunction is amended by the court, Norwich is not authorized to market a generic equivalent of xifaxane.”

Price promotion: BHC shares are up 8.82% to $5.55 during the premarket session last Check Friday.

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