The patent litigation surrounds Roquette's US patent no. 5,573,777 (the '777 patent') which relates to a relatively pure, dry mannitol that is readily crumbled and has a density between 300 and 525 g/l for a particle size cut of between 100 and 200 microns.
The patent states that this 'pulverulent' mannitol posses "remarkable functional properties which make its use particularly recommended as sweetening agent, texturizing agent or additive excipient or vehicle in the food and pharmaceutical industries" .
Roquette filed the lawsuit against SPI Pharma in a Delaware federal district court in August 2006 alleging that SPI Pharma's Mannogem EZ spray dried mannitol infringes the patent.
SPI Pharma has now denied infringing the patent and is challenging the legitimacy of the '777 patent saying that the Mannogem EZ product will continue to be available for purchase, and that the company will defend itself vigorously against Roquette's allegations.
Mannitol has become a popular excipient for chewable tablets as it gives a cool taste sensation on dissolving due to its negative heat of solvation.
The excipient is also used in conventional tablets because it does not absorb water and can protect water sensitive molecules from degradation.
Roquette was granted a US patent in 2004 (no. 6,743,447) for the production of mannitol as a suitable excipient which had been thought impossible.
Mannitol's crystal structure favours the creation of large particles which made it difficult to produce a version with the desired particle size control and flowability.
Roquette overcame these problems by starting with crystalline mannitol and modifying its physical properties through continuous mixing and granulation steps