Background: This case involves Caraco's alleged infringement of one of Novo Nordisk's patents on Prandin, and anti-diabetic drug. Caraco filed for an Abbreviated New Drug Application (ANDA) in 2005, in regards to a Prandin generic. In its ANDA, Caraco notes that it would not be infringing upon Novo Nordisk's patent on the grounds of invalidity and unenforceability. Novo Nordisk responded with a law suit.

Patent: The patent at issue in this case is NIDDM (Non-Insulin Dependent Diabetes Mellitus) regimen, US6677358. This patent covers 1) the regimen of short-acting, oral hypoglycemic agents used to treat type 2 diabetes, and 2) a method improving glycemic control by the combined use of repaglinide (Prandin) and metformin in NIDDM patients. The particular claim at issue is claim 4:

A method for treating non-insulin dependent diabetes mellitus (NIDDM) comprising administering to a patient in need of such treatment repaglinide in combination with metformin. 

In other words, the claim at issue is a claim regarding the method of using repaglinide (Prandin) and metformin in combination to treat NIDDM. 

District Court:

The district court found claim 4 of the '358 patent to be obvious, holding that the patent was unenforceable. This decision was grounded in that 1) it was well known in the art that both drugs had different mechanisms of action for treating diabetes and were hence often used in combination and 2) combination therapy was common at the time of filing the '359 patents and metformin was the most widely used insulin sensitizer. Novo Nordisk appealed this decision to the federal circuit.

Federal Circuit Court:

The circuit court affirmed the district court decision in that claim 4 of the '358 patent is obvious.