More testing needed for ridaforolimus

US pharma company Merck & Co has confirmed that marketing approval for its anti-cancer drug ridaforolimus has been held up by the US Food and Drug Administration (FDA). Specifically, the FDA has requested additional clinical trials to further assess safety and effectiveness. Merck says that applications for use in other countries, including Europe, are still ongoing.

Ridaforolimus is a phosphorus-containing analogue of the immunosuppressant drug rapamycin, and was originally developed by Ariad pharmaceuticals. It is an oral small molecule inhibitor of the mTOR protein, known to play an important role in malignancy.

Permission is being sought from the FDA to market it as a maintenance therapy in the treatment of metastatic, or late-stage, soft tissue or bone sarcoma (cancer of the connective tissue). It is only intended for use to stabilise the disease in patients who have had four or more cycles of chemotherapy.

Ariad granted Merck an exclusive license to develop, manufacture and commercialise ridaforolimus in 2010.