There was bad news for Bayer yesterday (Thursday) after the US Food and Drug Administration turned down an additional indication for its Johnson & Johnson-partnered blood thinner Xarelto.

The regulator has issued a complete response letter outlining its objections to approving the drug at this time, though specifics have not been revealed by either company.

The move comes on the back of an assessment by an advisory committee earlier this month, which voted narrowly against recommending the Xarelto (rivaroxaban), in combination with standard antiplatelet therapy, to reduce the risk of secondary cardiovascular events in patients with acute coronary syndrome (ACS).

Committee members expressed serious concerns about the increased risk of major and fatal bleeding associated with the drug, and that 15% of participants enrolled in the 1,500-patient ACS study dropped out of the trial.

The companies, however, remain committed to securing an approval for the drug in this setting.

"We are confident of the safety and efficacy of rivaroxaban in this indication and will work closely with our development partner Janssen Research & Development, LLC, to address the questions set forth by the FDA," said Kemal Malik, Member of the Bayer HealthCare Executive Committee and Head of Global Development.

Xarelto has already racked up three approvals in the US: to reduce the risk of blood clots in the legs and lungs of people who have undergone knee replacement surgery; to reduce this risk hip replacement surgery patients; and to cut the risk of both haemorrhagic and thrombotic strokes (and other blood clots) in people with atrial fibrillation not caused by a heart valve problem.

Bayer has previously said it is expecting peak sales of more than 2 billion euros a year for Xarelto if all goes to plan.