Four years ago, Boehringer Ingelheim set out to prove that its Aggrenox heart drug could beat a basic dose of aspirin in preventing strokes. The results came back in March, but the drugmaker hasn’t worked very hard to publicize them. Why? The trial was a bust - Aggrenox failed to meet the primary endpoint of reducing the risk of secondary ischemic stroke in 1,294 patients in Japan. The incidence among patients given Aggrenox was 6.9 percent compared with 5 percent for those on aspirin (look here).

This is a problem for Boehringer, which markets Aggrenox to “reduce the risk of a subsequent stroke in patients who have had a transient ischemic attack, or TIA, or stroke due to a blood clot.” After all, Aggrenox is rather pricey, costing about $3 per pill, and it must be taken twice a day (see here and here). Aspirin costs a lot less. The results are unlikely to help Boehringer boost Aggrenox sales, which totaled $404 million in the US through pharmacies last year, according to IMS Health. That was up about 10 percent, but the pill’s 6.7 percent market share was well below the 92.6 percent held by Plavix. (The drugmaker also suffered an unrelated setback last week when its female sexual dysfunction pill was voted down by an FDA advisory panel).

Here’s the rub: The findings not only fail to show a benefit, but a trend toward patient harm, suggesting a further overall review is needed. On the other hand, there were relatively few events and it’s unclear the extent to which this outcome may occur in other populations, given that the risk of stroke can be different among Asians. Nonetheless, Boehringer has instructed its sales reps to avoid discussion with any inquiring doctor and refer all questions to a medical liaison, a source tells us.

When questioned, Boehringer sent a prepared statement, hinting the drugmaker was bracing for questions. Its response, which noted there appeared to be a similar risk of bleeding in both its drug and aspirin, cited an earlier study showing the drug succeeded in reducing the risk of recurrent strokes compared with aspirin. And so the drugmaker stands by its safety and effectiveness. “Because neither non-inferiority nor superiority of either treatment could be demonstrated, we cannot draw conclusions from this study about the relative efficacy of either agent,” the statement says.

Hardly a resounding vote in favor of usage. This isn’t the first time Aggrenox has disappointed. Two years ago, the heart drug failed to meet a primary endpoint in another study that showed Plavix, which is the most widely used blood thinner, was superior in secondary stroke prevention (background). But when will doctors get a chance to actually examine the latest study? A Boehringer spokeswoman informs us that publication is pending. Meanwhile, the bleeding continues.