A federal judge in Texas invalidated four key patents for the dry-eye treatment Restasis on Monday, dealing a blow to its manufacturer, Allergan, which had sought to protect its patents by transferring them to a Native American tribe.

The ruling, by United States Circuit Judge William C. Bryson of the Eastern District of Texas, does not mean that generic versions of the drug will be available soon, however. Allergan said that it would appeal the decision, and the Food and Drug Administration has not yet approved copycat versions of the drug.

Still, the decision was a setback for the company, whose stock dipped more than 5 percent on the news. Restasis is Allergan’s second best-selling product, behind the wrinkle treatment Botox, bringing in nearly $1.5 billion in 2016.

In September, Allergan took the highly unusual step of paying the Saint Regis Mohawk Tribe in upstate New York to take possession of the patents, which then were leased back to the company. The tactic was a way to protect the company from a patent challenge — separate from the federal court case — that is underway in an administrative proceeding before a unit of the United States Patent and Trademark Office.