In the never-ending battle to bring generic versions of sanofi-aventis' (NYSE: SNY) Lovenox to market, Sanofi has a secret weapon: doctors who have asked the Food and Drug Administration not to approve generic versions because of safety concerns. Lovenox is a complex heparin-based molecule, and two doctors groups and a medical researcher think the only way to prove generic versions are the same is to run clinical trials.

There's just one problem. According to The Wall Street Journal, the people advocating on Sanofi's behalf have received financial support from the company in the past. How much the FDA takes their opinion into consideration remains to be seen.

This isn't small potatoes, either; Lovenox registered about $2.2 billion worth of sales in the U.S. last year. With only three companies, Amphastar Pharmaceuticals, Teva Pharmaceutical (Nasdaq: TEVA) and Momenta Pharmaceuticals (Nasdaq: MNTA), vying for approval, the generic-drug price is likely to be fairly close to that of the branded drug.

Of course, that's if the FDA ever signs off on an approval. Unlike for branded drugs, the agency doesn't have any mandated goals for deciding upon generic-drug marketing applications. It's had Teva's and Amphastar's applications since 2003 and Momenta's since 2005. Motley Fool Rule Breakers pick Momenta might seem like the underdog, but it has help from generic-drug giant Novartis (NYSE: NVS), and Momenta helped the FDA sort out Baxter's (NYSE: BAX) contaminated heparin issues back in 2008, which might earn it some brownie points.

The bigger issue for the companies may be whether doctors will prescribe generics. Sure, experts with financial ties to Sanofi probably aren't the most unbiased of sources, but how concerned will other physicians be about the use of generic Lovenox even if the FDA signs off? Pharmacists are generally allowed to substitute generics at will, but most prescription forms have a box to override that power.

That check box could become Sanofi's next secret weapon.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Novartis is a Global Gains selection. The Fool has a disclosure policy.