Merck & Co. and Endocyte Inc. said Tuesday that European Union regulators will review their drug vintafolide as a treatment for ovarian cancer.

The companies said the European Medicines Agency will review vintafolide as a treatment for ovarian cancer that is resistant to platinum-based chemotherapy. The agency will also review their application for a diagnostic agent that is intended to help identify patients who could benefit from the drug.

Vintafolide is designed to target a folate receptor that appears on cancer cells but doesn't exist on most other cells. Endocyte, based in West Lafayette, said the receptor is found on 80 percent to 90 percent of ovarian and lung cancers.

Vintafolide and the diagnostic agent both have orphan drug status, which means competing products will be barred from the market for up to 10 years if they are approved.

Whitehouse Station, N.J.-based Merck will pay Endocyte $5 million because the application was accepted.

Merck stock fell 9 cents, to $44.10 per share, and Endocyte shares lost 15 cents, to $8.99, in midday trading Tuesday.