A billion-dollar "technical revision" added to a patent bill passed by the House last week could provide huge financial benefits to one pharmaceutical company and a law firm.

On the surface, the barely noticed amendment simply clarifies a process by which the Food and Drug Administration approves a patent for a brand-name drug, and gives the manufacturer 60 days to apply for an extension with the U.S. Patent and Trade Office.

In reality, the measure could give a New Jersey drugmaker, The Medicines Co., 2½ more years of patent protection for its lucrative blood thinner Angiomax. It would also save the law firm WilmerHale $214 million it would owe the drug company under a malpractice lawsuit if a generic alternative is sold in the United States before June 15, 2015.

The amendment barely won House approval and it is not a part of the Senate version of the patent system overhaul bill, so it is questionable whether it will ever become law. The amendment would write into law a court decision in favor of the drug company and would pre-empt any appeal.

It shows how, hidden behind the lines of obtuse legislative language, huge fortunes can be at stake, sometimes for specific companies.