"For vilaprisan we have just some days ago put clinical development of our ongoing trials on hold," said drug development head Joerg Moeller, speaking at the group's capital markets day in London.

"That is due to very recent safety findings in long-term toxicology studies ... We have therefore decided as a precautionary measure to stop enrolment into our ongoing programme and evaluate the data," he added.

The toxicology data were from pre-clinical long-term testing of the drug on rodents, carried out in parallel with late stage testing on humans, a spokeswoman said.