US regulators have told Merck & Co that it will need to provide more data before approval is granted for Emend, an experimental injectable drug for nausea caused by chemotherapy.

Merck & Co has received an approvable letter from the US Food and Drug Administration for the company's New Drug Application for Emend (fosaprepitant dimeglumine) for injection, also known as MK-0517, an investigational intravenous therapy for chemotherapy-induced nausea and vomiting.

In the letter, the FDA says that additional manufacturing validation and stability data are required as well as certain, unspecified, additional data. Merck said it is working to provide the information requested and plans to submit it within the next few months.

Merck added that the approvable letter “does not relate in any way to the manufacturing and availability” of the oral formulation of Emend, which uses a completely different production process. The pill form was approved by the FDA in 2003.

Cutbacks on combination vaccine

Meantime, Merck has said that supplies are running low of ProQuad, its combination vaccine against measles, mumps, rubella and chicken pox.

The company told the US Centers for Disease Control in February that because of lower-than-expected amounts of varicella-zoster virus in its recently manufactured bulk vaccine, the firm was prioritising production of Varivax (varicella) for chicken pox and shingles vaccine Zostavax (zoster) vaccines over production of ProQuad. Merck has now told the CDC that current projections of orders indicate ProQuad will be unavailable beginning in July 2007, which might cause extended back orders for the next few months, noting Varivax and Zostavax are its priority because the firm is the sole provider of those vaccines.