Drugmakers Bleeding Out

Editor's note: A previous version of this article misidentified Momenta Pharmaceuticals' partner. The Fool regrets the error.

The battle to replace warfarin as the go-to treatment for atrial fibrillation is about to reach a climax. Pfizer (NYSE: PFE  ) and Bristol-Myers Squibb (NYSE: BMY  ) said yesterday that the Food and Drug Administration had accepted their marketing application for Eliquis.

The review is of the priority variety, so the companies will get a six-month review rather than the standard 10 months. The FDA issues a priority review only for drugs that it thinks are major advances or provide a treatment for an unmet need.

I'm a little surprised that Eliquis fits that definition, but it does seem as if the agency has been a little more generous with the priority reviews recently. Regeneron Pharmaceuticals (Nasdaq: REGN  ) and Bayer's Eylea got a priority review, and the only major advantage that the macular-degeneration treatment has over Roche's Lucentis is that it can be injected half as often.

Assuming no delays -- Eylea's decision was subsequently pushed by three months -- Pfizer and Bristol-Myers should hear back from the FDA on March 28.

The cat's meow of a drug market
A generic drug called warfarin is the current standard of care for atrial fibrillation. The drug is also an active ingredient in some rat poisons. Use a little, and it'll help with your the irregular heartbeat. Use too much and you'll bleed internally, just like the unsuspecting rat.

And it's not just overdoses that doctors have to worry about. Taking just a little too much of the drug increases the risk of internal bleeding and dosing is complicated by the fact that a patient's diet changes the effective dose of warfarin. To say the least, warfarin is a drug that most doctors would be happy to get out of their medicine bag.

Eliquis seems to have the advantage over Boehringer Ingelheim's Pradaxa and Xarelto from Bayer and Johnson & Johnson (NYSE: JNJ  ) , which were both recently approved for the indication. In a recent trial, Eliquis was shown to be superior to warfarin in both efficacy and safety, potentially granting it a better label than its competitors.

Other indications, same issue
Atrial fibrillation isn't the only indication where anti-blood-clotting drugs are used, but it's always the same issue: Thin the blood enough so that it doesn't clot and cause a heart attack or stroke, but not so much that it causes internal bleeding. It's not an easy balance, for sure.

Xarelto cut the risk of death in patients with acute coronary syndrome, but the drug also significantly increased the amount of internal bleeding. That's not going to cut it when drugs such as Brilinta from AstraZeneca work just as well with less bleeding.

Even if the advantages outweigh the bleeding issues -- for instance, if it saves five heart attacks but causes four bleeding issues -- doctors will be hesitant to use the product because explaining that the patient died of a heart attack because of their heart problems is easier than explaining that the patient died of bleeding caused by a drug.

The prospects for Merck's (NYSE: MRK  ) vorapaxar has also diminished substantially for the same reason. The company stopped one trial and scaled back another to exclude patients who have previously had a stroke because of bleeding seen in patients taking the experimental medicine.

Blockbuster generic
Blood thinners are also used to prevent clots in patients after hospitalization, but both Xarelto and Eliquis failed to beat the current standard of care, Sanofi's (NYSE: SNY  ) Lovenox.

Patents on Lovenox have already expired, but Lovenox is a complex mixture of heparin molecules, which makes it difficult to manufacture. So far, Momenta Pharmaceuticals (Nasdaq: MNTA  ) and Novartis' copycat version is the only one that's made it to market.

The exclusivity allowed Momenta and Novartis to capture a large chunk of the market, gaining blockbuster status as a generic. Unfortunately, competition is on its way. Amphastar Pharmaceuticals and Watson Pharmaceuticals recently gained approval for their generic version of Lovenox. So far, Momenta and Novartis have kept the Amphasta/Watson product off the market, claiming the drug impedes on Momenta's patents for characterizing the drug, but the threat of additional competition pushed Sanofi to launch an authorized generic.

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