Surgery News

Barr Pharmaceuticals confirms patent challenge of Namenda tablets

October 09, 2015

Barr filed its Abbreviated New Drug Application (ANDA) containing a paragraph IV certification for a generic Namenda product with the U.S. Food & Drug Administration (FDA) on October 16, 2007, the first date the FDA could accept an ANDA with a paragraph IV certification for this product. Following receipt of the notice from the FDA that Barr's ANDA had been accepted for filing, Barr notified the New Drug Application (NDA) and patent holder.

On January 10, 2008, Forest Laboratories Holdings, Ltd., Forest Laboratories, Inc., Merz Pharma GmbH & Co. KgaA, and Merz Pharmaceuticals GmbH filed suit in the U.S. District Court for the District of Delaware to prevent Barr from proceeding with the commercialization of its product. This action formally initiates the patent challenge process under the Hatch-Waxman Act.

Namenda (memantine hydrochloride) is indicated for the treatment of moderate to severe dementia of the Alzheimer's type. The product had sales of approximately $824 million in the U.S., based on IMS sales data ending October 2007.

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In the present study, researchers report that memantine has a much more complex pharmacological profile than originally described. It does in fact work rather similar to the originally introduced drugs that affect acetylcholine-related signalling, in addition to weak actions on glutamate, and has negative effects on neuronal communication at high concentrations. At lower concentrations, memantine was able to enhance signalling between neurones of the hippocampus (the main brain area affected in Alzheimer??s disease) and was indeed able to reverse learning and memory deficits. However, a pharmacological analysis showed that this was not due to its ability to block glutamate signalling, but rather to an additional and more potent action on the acetylcholine system.

Therefore, the investigators?? data do confirm that memantine shows promising aspects for the treatment of AD, but only in a narrow concentration range. More importantly, its complex pharmacological profile requires careful considerations concerning suitable doses and suitable patient groups, so that the best use can be achieved for patients suffering from Alzheimer??s disease.

Lead investigator Dr. Bettina Platt, University of Aberdeen, Institute of Medical Sciences, commented, ???Clearly, the claim that memantine??s beneficial action is due to the reduction of glutamate signalling needs to be revised. It is highly unlikely that compounds directly targeting glutamate receptors will be successfully introduced into the clinic, since major side-effects must be expected.???

The article, "Memantine acts as a cholinergic stimulant in the mouse hippocampus" by Benjamin D. Drever, William G.L. Anderson, Helena Johnson, Matthew O??Callaghan, Sangwon Seo, Deog-Young Choi, Gernot Riedel, Bettina Platt, appears in the Journal of Alzheimer??s Disease, Volume 12, Issue 4 published by IOS Press.

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