Norvasc patent ruling favors Pfizer in US court of Appeals for federal circuit

June 17, 2008. United states court of Appeals for Federal Circuit has affirmed the District court's (January 2008) decision in favour of pfizer w.r.t to Norvasc.

A federal appeals court has rejected Synthon IP's challenge of a trial court's decision that two patents Synthon asserted against Pfizer Inc. in a case over the blockbuster blood pressure drug Norvasc are unenforceable due to inequitable conduct.

The federal circuits decision can be read here.

The district court decision can be read here.

In a related case, Pfizer earlier defeated Synthon's efforts to launch a generic version of Norvasc. See Pfizer, Inc. v. Synthon Holdings BV, No. 1:05CV39 (M.D.N.C. 2006).




Earlier at drugresearcher.com it was reported as below:

Synthon originally accused Pfizer of patent infringement of manufacturing processes to produce the hypertension drug, asserting that it infringed patents issued to the company in 2003 and 2005.
The patents related to processes in the drug manufacture, as well as the production of amlodipine besylate, the active ingredient in Norvasc. However, Pfizer maintained that it had not only published the process Synthon was referring to, but had also been using it for 15 years.

The court sided with Pfizer in stating that not only did its method of producing Norvasc not infringe on Synthon's patent, but also that the Dutch firm had obtained the patent by fraudulent means by not disclosing its use of Pfizer's published materials to the US Patent and Trademark Office.

"It's very difficult to meet standards for establishing inequitable conduct," said Alan Waxman, Pfizer's general counsel.

"But in this case it is clear that Synthon improperly used Pfizer's own published material to obtain a patent that it then tried to enforce against us."

Pfizer said it intends to seek attorney's fees from Synthon, who still have the option to appeal against the ruling.

Back in September last year, the company reported that it had successfully defended the patent challenge by Synthon, in a ruling which also prohibited the generics manufacturer from launching a generic version of Norvasc until September this year when the US patent protection for the drug expires.

Norvasc is a widely prescribed mediation for the treatment of hypertension, and in 2006 brought in revenues of $4.71bn for the company. Pfizer has also taken steps to defend the franchise from generic competition by combining Norvasc with its blockbuster drug Lipitor (astorvastatin calcium) for patients with high cholesterol as well as hypertension. The product, Caduet (amlodipine besylate/astorvastatin calcium), achieved revenues of $370m for the year, up 95 per cent from $185m in 2005.

During Norvasc's development in the 1980s, Pfizer originally used amlodipine maleate in its tablet formulation, but decided to switch to amlodipine besylate due to chemical instability observed in the original formulation and the fact that it was sticking to the tabletting machinery.

This was an unprecedented move at the time, as in order to facilitate the scaling up of manufacturing operations, Pfizer had to completely abandon its maleate formulation, which had already reached Phase III clinical studies. Developing the besylate formulation would have required repeated testing to gain approval from the US Food and Drug Administration (FDA) and risked substantially delaying Norvasc's commercial launch.

In the end, however, the move paid off, and Pfizer's formulation scientists were able to produce large commercial batches of amlodipine besylate tablets by direct compression on high-speed tablet presses without disruption, which had proved difficult with the maleate salt of amlodipine.

In 2004 Norvasc held 65.7 per cent of the market for calcium blockers, with Bayer's Adalat (nifedipine) its closest rival with 12.3 per cent.