May 2 (Reuters) - Merck & Co Inc and Endocyte Inc said they had stopped a late-stage trial of their experimental ovarian cancer drug because it did not improve survival rates without the cancer worsening.

The trial was testing the drug, vintafolide, in combination with a chemotherapy drug, pegylated liposomal doxorubicin (PLD), compared to PLD plus a placebo.

An independent safety committee reviewing the trial had recommended that it be halted, the companies said in separate statements.

(Reporting by Esha Dey in Bangalore; Editing by Maju Samuel)