Genzyme Corp. announced Wednesday that its drug Clolar has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of children with difficult or relapsed acute lymphoblastic leukemia (ALL).

Clolar is the first new leukemia drug approved specifically for children with ALL in more than a decade, the company notes in a press release.

ALL is the most common form of childhood leukemia, with an estimated 3,400 new cases of pediatric acute leukemia expected to be diagnosed in the United States in 2005. Children with ALL who do not respond to existing therapies, or relapse, have a very poor prognosis.

Results from a pivotal phase II trial of 49 heavily pre-treated children with relapsed or unresponsive ALL formed the basis for the accelerated approval of Clolar. In the trial, patients received Clolar intravenously on five consecutive days, with treatment repeated for two to six cycles every 28 days depending on responses.

Twenty percent of children achieved a complete remission and 10 percent achieved a partial response. Fourteen percent of children went on to receive bone marrow or stem cell transplants following treatment with Clolar.

When he reported these data earlier this year at the American Society of Clinical Oncology meeting, Dr. Sima Jeha from St. Jude Children’s Research Hospital, Memphis, Tennessee, told Reuters Health: “In the last 10 years we have really reached a plateau in treating children with unresponsive or relapsed acute leukemias. Clofarabine offers hope to these children, producing durable remissions in some and allowing some to proceed to bone marrow transplant, which offers the best chance for long-term survival.”

In a press statement from Genzyme, Jeha added: “As a pediatric oncologist, I am excited to have a new well-tolerated and effective treatment option for these patients with highly-resistant leukemia.”

Clolar has also shown promise in children with relapsed or refractory acute myeloid leukemia (AML), and earlier this month the Oncologic Drugs Advisory Committee of the FDA called for additional studies in this group of children.

The most common adverse effects of Clolar treatment seen to date include vomiting, nausea, and diarrhea, as well as anemia and infections.