Bayer faces setback as Xarelto data highlights increased bleeding risk

Shares of Bayer AG were badly dinged this morning after researchers reported that a large late-stage study of the potential mega-blockbuster Xarelto (rivaroxaban) demonstrated a higher risk of bleeding for patients with acute illnesses.

In the study, which included more than 8,000 patients, investigators compared Xarelto with Lovenox and concluded that they were equally effective in preventing potentially lethal blood clots after 10 days of treatment. After extending treatment for 25 days among the Lovenox group with a placebo and 35 days for the Xarelto arm, the Xarelto group did better with clots but patients experienced a statistically significant increased risk of bleeding.

Magellan investigated the largest and most diverse population of hospitalized, acutely ill patients to date, and managing the risk of blood clots in these patients is extremely complex due to their age, co-morbid conditions and duration of immobilization. There is a continued risk of VTE beyond the initial period of hospitalization or immobilization in acutely ill patients," said Dr. Alexander T. Cohen, the principal investigator. "As observed in a previous study in this area, a consistently positive benefit-risk balance was not seen across the heterogeneous, acutely ill patient population studied. Further analysis is required to identify which groups of patients in Magellan may derive benefit from thromboprophylaxis with rivaroxaban."

Xarelto has consistently outperformed warfarin in late-stage trials, inspiring huge hopes for Xarelto. Bayer CEO Werner Wenning predicted last fall that the market for new blood thinners could reach $12 billion to $15 billion, with his company's drug Xarelto accounting for some $2.6 billion of that. Bayer shares were off more than three percent this morning, a significant drop for a large cap stock.

- check out the Bayer release
- read the Reuters story
- here's the Bloomberg piece