From: Reuters

Genzyme Corp (GENZ.O) said on Tuesday that U.S. regulators will not allow the company to market its leukemia drug Clolar to previously untreated older adults unless it completes an additional clinical trial.

Clolar is currently approved for children with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) who have relapsed or who have failed to respond to at least two prior treatment regimes.

Cambridge, Massachusetts-based Genzyme was seeking approval to also market the drug for previously untreated older adults with AML.

The ruling was expected.

In September, an advisory committee to the U.S. Food and Drug Administration voted 9 to 3 that data from a randomized, controlled trial would be needed to establish the drug's safety and efficacy in adults with AML.

Genzyme had tried to win approval based on findings from a less rigorous trial.

Genzyme said it plans to request a meeting with the FDA to discuss the "optimal path forward," including what additional or ongoing studies might be satisfactory.

The company is conducting a late-stage trial comparing Clolar, known generically as clofarabine, in combination with the chemotherapy cytarabine to cytarabine alone in relapsed and refractory adult AML patients 55 years or older.

Results are expected in 2011.