Pfizer Sees Neurontin Exclusivity Through 2002, Pregabalin Filing By Year-End

Pfizer expects at least 30 months of additional exclusivity for the epilepsy agent Neurontin (gabapentin) beyond the expiration of the basic compound patent July 15.

A recently issued patent covering "lactam-free" bulk gabapentin "gives us 30 months of exclusivity" under Waxman/Hatch procedures, Pfizer President Henry McKinnell, PhD, told an investor quarterly earnings conference call July 26.

FDA is prohibited from approving ANDAs that include patent challenges until 30 months have elapsed or a court upholds the challenge. Pfizer said two suits regarding the patent are pending: one against Purepac/Faulding in New Jersey and one against Apotex in Chicago.

"How far beyond [30 months] the patent holds really has to do with whether anybody could convince FDA to register a product with higher levels" of lactam, McKinnell explained. He described lactam as an "impurity which has a toxicity concern."

"Our assumption is it will be beyond 30 months before anybody does the work to convince FDA that the product is safe," McKinnell declared.

An additional 30 months of exclusivity on Neurontin in the U.S. would be worth over $2.5 bil. in revenues to Pfizer. U.S. sales of the product through the first six months of 2000 were $551 mil., an increase of 67%.

Another important benefit to Pfizer of the delay in generic competition will be the opportunity to launch the Neurontin-successor molecule pregabalin before the franchise goes into decline.

Pfizer intends to file an NDA for pregabalin by the end of 2000. "If we were to delay that by one or two months, it would only be to get additional data into the NDA which we think would give us a better shot at expedited approval," McKinnell said. Pfizer will not decide whether to delay the application until the fall.

Prolonged patent life for Neurontin would represent a significant unexpected upside from the Warner-Lambert acquisition.

The potential for generic competition to Neurontin - especially before the launch of pregabalin - was viewed as one of the challenges facing Warner-Lambert when it opted to pursue a friendly merger with American Home Products in November. Pfizer subsequently launched a successful hostile takeover bid for the company.

During the battle to save the AHP merger, Warner-Lambert suggested that generic competition could be delayed past the July expiration of a six-month pediatric exclusivity patent for Neurontin. At the time, nine ANDAs for gabapentin were pending (¹ (Also see "Lipitor Holds Up In Merger Dispute; Warner-Lambert, Pfizer Beat Expectations" - Pink Sheet, 24 Jan, 2000.)).

The "lactam-free" bulk patent (number 6,054,482) did not issue until April 25, after Warner-Lambert had acceded to the Pfizer offer. The Orange Book listing for the patent claims an expiration date of 2017.

The '482 patent was issued to the German company Godecke. The application was filed in 1995.

According to the patent abstract, "lactams display a certain toxicity and must, therefore, be avoided as far as possible. For example, gabapentin has a toxicity (LD50, mouse) of more than 8,000 mg/kg, [but] the corresponding lactam...[has] a toxicity of 300 mg/kg."

"Consequently, these impurities and the potential formation of such decomposition products during storage of pharmaceutical compositions must be reduced to a minimum for reasons of safety," the patent abstract proclaims.

According to Pfizer's McKinnell, the patent "gives us...protection on any Neurontin bulk with very low lactam levels."

In addition to inheriting the Neurontin patent defense via the Warner-Lambert acquisition, Pfizer also inherited an investigation of potential off-label promotions of the drug.

Warner-Lambert has been subpoenaed by the Boston U.S. Attorney's Office in an investigation of Neurontin. The company is also facing a whistleblower suit brought by a former employee (² ).

Neurontin was Pfizer's fourth largest product in the second quarter with $328 mil. in worldwide sales, ahead of Viagra at $304 mil.