AbbVie Inc. filed a patent infringement lawsuit Wednesday against German rival Boehringer Ingelheim Pharmaceuticals Inc., the second case in Delaware that seeks to block sales of a less-expensive biosimilar version of Humira, AbbVie's top-selling drug.

The suit accuses Boehringer of infringing dozens of AbbVie's patents in a bid to bring its copy of the anti-inflammatory treatment to market under a federal law that provides for expedited regulatory approval of drugs that are exceptionally similar to innovative products already being sold in the United States.

Though the Chicago-based drugmaker's 70-page complaint focuses on just eight patents, the company threatened to pursue further litigation on up to 66 patents if Boehringer's copy is approved. Approval from the U.S. Food and Drug Administration—and additional litigation—could mean that it will be years before Boehringer's product launches.