It was the best investors in Momenta Pharmaceuticals (Nasdaq: MNTA) could have hoped for. Eleven short words may mean the difference between an approved drug and one that was scrapped.

"The agency has not requested human clinical trials at this time."

That sentence was in a press release about Momenta's generic version of Sanofi-Aventis' (NYSE: SNY) Lovenox for blood clots, which the company is developing with partner Novartis (NYSE: NVS). The Food and Drug Administration rejected their abbreviated new drug application (ANDA) last November because the agency was worried about the drug's potential to cause an immune reaction. Momenta will have to do some additional tests on animals and submit additional information, but no clinical trials are required.

If the FDA had requested clinical trials to prove that the drug worked, the duo might have just scrapped the project. The generic drug isn't expected to fetch as high a price as its branded counterpart, so the return on investment in a clinical trial might have been extremely low.

Lovenox is a pretty complex molecule. It's not as complex as protein-based biologics, but certainly more complex than your average small-molecule drug that's typically approved through the ANDA process. The fact that the FDA is requiring Genzyme (Nasdaq: GENZ) to run clinical trials for its own drug just because it's being made at a different facility now seemed like an ominous sign for Momenta, but I guess the company has convinced the FDA that its knockoff is the same as Sanofi's Lovenox.

No word yet from Teva Pharmaceutical (Nasdaq: TEVA) and Amphastar, which are developing their own generic version of Lovenox, on whether they've also cleared up what they need to do to gain approval.

Momenta expects to submit the additional information to the FDA in the third quarter of this year. Generic-drug makers don't have a Prescription Drug User Fee Act (PDUFA) set up, so there's no way to know how long it could be until the drugmaker hears back from the agency. Last time, it took more than two years to hear that the FDA wanted additional information. It's hoped that Momenta, a Motley Fool Rule Breakers pick, hears back much more quickly this time.