There was a mixed bag of news about the latest generation of bloodthinners emanating from the American Heart Association meeting in Florida this weekend. But the biggest headlines were generated by a study showing Xarelto, which is made by Bayer and Johnson & Johnson, succeeded in reducing deaths following a heart attack.

The results, which were published in The New England Journal of Medicine, examined 15,526 patients and found that lower doses of Xarelto were effective in reducing heart attacks, strokes and cardiovascular deaths by 16 percent, without creating unacceptable levels of bleeding (here is the abstract and an accompanying editorial). In the study, Xarelto was combined with Plavix, which is the standard of care.

The drugmakers, which recently received FDA approval to use Xarelto to treat atrial fibrillation (see this), now plan to seek regulatory endorsement for acute coronary syndrome. ACS leads to nearly 1.2 million hospitalizations annually, and Xarelto would compete with Brilinta from AstraZeneca and Efficent from Eli Lilly, although adoption has been slow.

Analyst reactions to the trial, known as ATLAS-2, were largely positive. Xarelto “appears to have hit the sweet spot for efficacy with an acceptable safety profile,” wrote Leerink Swann analyst Seamus Fernandez in a research note, in which he opined that the lowest dose “can be a meaningful competitor in an increasingly crowded space that has been relatively slow to develop commercially.”

Similarly, Larry Biegelsen of Wells Fargo Securities wrote that the positive date and the recent Afib approval for Xarelto “marks a significant turnaround” for the bloodthinner, “which was viewed by many investors as nearly dead when the FDA advisory committee briefing documents were released in September,” prior to the subsequent agency approval that includes a Black Box warning. He estimates the ACS population studied in the trial represents a $2 billion market in the US alone.

But how might Xarelto fare against rival bloodthinners, notably Brilinta? He points out that Brilinta showed a mortality benefit of 22 percent over Plavix in ACS patients, while Xarelto showed a 32 percent reduction with the low 2.5 mg dose when adding Plavix, “which is a higher bar,” he writes, adding that Brilinta is also associated with side effects such as shortness of breath.

As a plus, Biegelsen adds that Xarelto would have the ACS indication to itself among the new group of bloodthinners, because a recent trial for Eliquis, which was developed by Pfizer and Bristol-Myers Squibb and showed strong results for Afib (see here), was stopped recently due to excess bleeding rates. Overall, he believes the latest findings will yield a “modest” commercial opportunity.

However, some reactions were more muted, given that real-world bleeding rates may prove to be higher. For this reason, Deutsche Bank analyst Barbara Ryan wrote in her own investor note this morning that Xarelto does not yet appear ready to trump the competition. In her view, there are still “significant bleeding liabilities” found by combining Xarelto with Plavix and aspiring.

“Alternative antiplatelet regimens, especially with AstraZeneca’s Brilinta, may be perceived as more viable and safer options for most high risk ACS patients and we believe will be used preferentially over (Xarelto plux Plavix and aspirin) in high risk and recurrent ACS. The increased risk of major bleeding associated with the combo is a significant deterrent and will impede its uptake in ACS,” she wrote.