Genzyme Corp has suffered some bad news after advisers to the US Food and Drug Administration recommended that a further study is needed before approval for the firm’s paediatric acute lymphoblastic leukaemia treatment Clolar can be extended to cover older patients.

The FDA’s Oncologic Drugs Advisory Committee voted nine to three that a randomised, controlled trial is needed to support the label expansion for Clolar (clofarabine) to include adult myeloid leukaemia. The panellists found that the single-arm study results showed that the drug was an active agent in acute AML patients, but concluded that a comparative trial “should be necessary to better interpret Clolar’s efficacy and safety in the proposed patient population”.

“I am happy that the three panel members who have significant experience in treating older adults with AML recognised the value of clofarabine in these patients and did not see the need for a randomised trial,” said Harry Erba of the University of Michigan, one of the co-principal investigators of the study reviewed by the committee.

Mark Enyedy, president of Genzyme Oncology and Multiple Sclerosis, said the panel indicated that “it wasn’t an easy decision to vote for a randomised trial as Clolar was clearly active in these patients”. Nevertheless, he added that the company remains committed to the development of the drug “in this patient population with high unmet medical need.”

Indeed, Genzyme is conducting a randomised Phase III trial comparing clofarabine in combination with cytarabine to cytarabine alone in relapsed and refractory adult AML patients aged 55 or older. The trial “continues to exceed patient accrual expectations”, the company said, and results are expected in 2011.

Following the committee’s decision, JP Morgan analyst Geoffrey Meacham issued a research note said that the vote is "an incremental negative as it appears unlikely Clolar will be a meaningful revenue contributor in the near-term." He added that the drug would make up less than 20% of the $550 million expected from Genzyme's haematologic oncology sales in 2010.