Momenta Pharmaceuticals Inc.'s stock surged more than 62 percent on Thursday, following a judge's ruling to invalidate Paris-based Sanofi-Aventis Group's Lovenox patent.

The decision clears the legal hurdle and opens up the opportunity for Cambridge, Mass.-based Momenta to get its generic version of the blood-thinner product on the market. The company is expected to file an abbreviated new drug application (ANDA) for M-Enoxaparin within the next month.

Momenta's stock (NASDAQ:MNTA) rose $6.36, or 62.7 percent on the news, to close at $16.50.

According to Andrew McDonald, a research analyst with ThinkEquity Partners LLC in San Francisco, Sanofi-Aventis' '618 patent covering Lovenox was critical to that company. The initial patent, '435, expired in late 2004, and Sanofi-Aventis (Aventis SA at the time) evergreened the patent estate until 2010. The company had trouble getting the '618 patent issued initially because it couldn't prove that the new version of Lovenox was any different than the prior art. But the patent was issued, despite protests from Teva Pharmaceuticals Industries Ltd., of Jerusalem, and Amphastar Pharmaceuticals, of Rancho Cucamonga, Calif. - companies that had filed ANDA's for their generic versions of Lovenox. Subsequently, they filed a lawsuit saying that when Sanofi-Aventis "did some critical pharmacokinetic work comparing Lovenox to the prior art," McDonald told BioWorld Today, "that they actually misrepresented data to the patent office, to the patent examiner. So they acted inequitably in order to get the patent issued."

While the court date for that lawsuit was scheduled for Nov. 15, a judge ruled on Thursday that the matter didn't need to go to court, and issued a summary judgment invalidating the patent.

The decision places Momenta in a position in which it could take a large chunk of the $3 billion Lovenox market.

"It's enormous potential here," McDonald said. "Momenta as the sole generic of Lovenox could achieve sales of $1 billion."

Lovenox is a widely prescribed low-molecular-weight heparin. The FDA's decision on Momenta's ANDA could come in 18 to 24 months. M-Enoxaparin is partnered with Sandoz Inc., of Princeton, N.J.

Momenta went public a year ago, pricing its initial public offering of 5.4 million shares at $6.50 apiece for $34.7 million. (See BioWorld Today, June 23, 2004.)