Shares for San Diego-based Sequenom Inc. plunged 23 percent after it reported in a regulatory filing that it received an unfavorable ruling in a patent infringement case against San Jose-based Ariosa Diagnostics Inc.

Sequenom’s stock (Nasdaq: SQNM) closed at $1.92, down 56 cents in day trading.

The U.S. District Court for the Northern District of California found that the science behind one of Sequenom’s prenatal genetic testing patents couldn’t actually be filed as intellectual property because it was based on “a natural phenomenon.”

Sequenom said it “vigorously disagrees” with the ruling and plans to appeal the decision in the Federal Circuit Court of Appeals.

— SDBJ Staff Report