Alza Overcomes Obviousness Rejection at Board for its Patented Method for Treating Depression

Scott Daniels | December 8, 2010

Earlier today, the PTO Board reversed the examiner’s obviousness rejection of the sole claim of Alza’s U.S. Patent No. 6,440,457.  The reversal demonstrates the skillful use of declaration evidence to overcome a prima facie case of obviousness. 

The ‘457 patent claims a method of orally administering the anti-depressant drug venlafaxine (Effexor®) in the form of “a sustained-release dosage” or “a controlled-release dosage.”  Administration occurs “over an extended period of time in a therapeutically responsive dose to produce [an] antidepressant therapy.” 

The reexamination examiner rejected the claim as being obvious over a combination of references.  First, he relied on certain primary references for the disclosure venlafaxine for use in treating depression.  The examiner acknowledged that these references failed to disclose administration of the drug in “a sustained-release dosage form” or “a controlled-release dosage form.”  To fill this gap, the examiner cited certain secondary references that disclosed the advantage of controlled drug release and showed that those skilled in the art were familiar with the specifics of controlled and sustained release delivery systems.  The examiner concluded that the references would make the ‘457 claimed invention obvious.

To address the combination of art, the ‘457 patentee submitted two declarations, one by the inventor describing the difficult history of obtaining the claimed method, and one by an expert explaining the shortcomings in the prior art disclosures.  The inventor and his research team initially tested venlafaxine, but were “troubled” because the dosage forms tested resulted in “dose dumping” in which the dosage form readily released the drug upon administration, with poor therapeutic results.  The test results were confusing because “the solubility of venlafaxine was shown not to be pH dependent in preliminary tests, [and yet] the dose dumping was pH dependent.” 

The expert reviewed the inventor’s data in light of the prior art which disclosed that venlafaxine was even more soluble than a related drug that was considered in the art to be unacceptable.  The expert concluded that “one of ordinary skill in the art would have concluded, based on the difference in solubility and the effect of that solubility difference on the osmotic pressure, that dose dumping would have been a more significant problem with venlafaxine.”  Further, there was no disclosure in the art of how one might solve this dose dumping problem. 

The two declarations, in combination, convinced the Board.  It found that despite the disclosure in the art of sustained-release and controlled-release dosage forms, one skilled in the art would have expected dose-dumping to occur.  The Board concluded that without specific guidance on how to solve the dose dumping problem, the prior art cited by the examiner would not have enabled one to create the claimed invention, and therefore, not have rendered that invention obvious. 

Reexamination had been requested by Wyeth in 2006 after Alza had sued Wyeth for infringement of the ‘457 patent (9:06-cv-00156, E.D. Tex.).  That law suit was initially stayed pending completion of the reexamination, but later dismissed without prejudice based on a stipulation of the parties.

Somewhat ironically, it was Wyeth that originally introduced venlafaxine into the market in 1993.

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