Pfizer Successfully Defends its Norvasc Patent Again, This Time Against Mylan

Pfizer v. Mylan Labs. et al., No. 02-1628 (W.D. Pa. 2007)

For the third time, Pfizer's patent on Norvasc has withstood a validity challenge from a generic rival. Following a week-long trial held last year, Judge Terrence F. McVerry of the U.S. District Court for the Western District of Pennsylvania ruled yesterday that Pfizer's U.S. Patent No. 4,879,303 patent is valid, enforceable, and infringed by Mylan. As we reported last fall, Pfizer previously defeated challenges of the same patent brought by two other generic drug makers, Apotex and Synthon.

Norvasc, indicated for the treatment of hypertension, is a blockbuster drug for Pfizer, with annual sales of $2.5 billion in the United States. The '303 patent covers the active ingredient in Norvasc, amlodipine besylate. Though the patent will expire next month, the FDA granted six months of pediatric exclusivity for Norvasc, extending Pfizer's protection until September 25, 2007.

In his opinion, Judge McVerry rejected both of Mylan's defenses to infringment: invalidity due to obviousness and unenforceability due to inequitable conduct. With respect to obviousness, Judge McVerry concluded that the asserted prior art expressed a preference for the maleate salt of amlodipine and failed to teach a reason for one skilled in the art to even try to improve upon the maleate salt. Thus, there was no motivation or suggestion to create the besylate salt of amlodipine. With respect to inequitable conduct, Judge McVerry concluded that Mylan failed to prove both elements of the defense--materiality and intent to deceive--and "even if Mylan had proven the required elements, the degree of culpability of Pfizer's representatives would be ever so slight and thus not sufficient to convince this Court that the proper remedy would be to invalidate the '303 patent."

As the first ANDA filer for generic Norvasc, Mylan holds the 180-day exclusivity rights, which could be extremely lucrative. Now, however, Mylan will have to win on appeal before it can launch its product. Moreover, it seems Mylan must win the appeal before Pfizer's pediatric exclusivity expires on September 25, 2007. Otherwise, the FDA will likely grant final approval to other generic companies, including Apotex and Synthon, and Mylan will lose its exclusivity rights. Mylan likely had this in mind when it immediately appealed yesterday's decision to the Federal Circuit.

Finally, yesterday's court decision avoids an interesting problem: if a decision on patent validity were not made before expiration of the '303 patent (March 25, 2007), would Pfizer have had a legal right to the pediatric exclusivity period? In a letter brief to the court, Pfizer acknowledged that the answer was unclear. The district court likely sought to avoid this question entirely by issuing its decision before the '303 patent expires.