Immune-based therapy approved in Europe for pediatric cancer patients

The European Commission, which oversees legislation and regulation for the European Union, has approved a therapy for pediatric patients with non-metastatic, resectable osteosarcoma, a type of bone cancer.

The approval is based on clinical studies led by researchers at The University of Texas M. D. Anderson Cancer Center and a national co-operative group.

MEPACT (mifamurtide, L-MTP-PE) is an immune-based therapy, that when combined with chemotherapy, resulted in approximately a 30 percent decrease in the risk of death with 78 percent of patients surviving more than six years following treatment. This therapy is the first in more than 20 years to improve the long-term survival of osteosarcoma patients.

Eugenie Kleinerman, M.D., head of the Children's Cancer Hospital at M. D. Anderson Cancer Center, was the first investigator to translate the drug from preclinical testing to a Phase I clinical trial in humans. She also led the Phase II clinical trial for pediatric patients with relapsed osteosarcoma, which was followed by a Children's Oncology Group Phase III trial for newly diagnosed patients.

Kleinerman originally proposed the use of this immune therapy for osteosarcoma after Isaiah J. Fidler, D.V.M., Ph.D., professor in M. D. Anderson's Department of Cancer Biology and director of the Center for Metastasis Research, demonstrated that MEPACT induced the regression of melanoma lung metastases in mice.

"When he showed that MEPACT caused the macrophages in the lung to kill tumor cells, I decided that the drug may have therapeutic potential in patients with osteosarcoma, which most often metastasizes to the lungs," says Kleinerman. "From my own preclinical research, we were able to show how MEPACT stimulated human immune cells to react against osteosarcoma cells."

MEPACT works by stimulating certain white blood cells, called macrophages, to kill tumor cells. The drug is shaped in a sphere, also known as a vesical, made up of lipids. Inside the vesical is muramyl tripeptide (MTP). The lipids trigger the macrophages to consume MEPACT. Once consumed, the MTP stimulates macrophages, particularly in the liver, spleen and lungs, to find tumor cells and kill them.

Patients undergo pre-operative chemotherapy followed by surgery to resect the bone tumor and then receive post-operative chemotherapy. While receiving post-operative chemotherapy, patients also are given the immune therapy intravenously twice a week for three months and then once a week for six months. The chemotherapy acts like a bomb sent in to destroy the tumor, while MEPACT acts as a special forces unit sent in to clean out any remaining pockets of microscopic disease.

"Relapsed osteosarcoma is often resistant to chemotherapy," says Kleinerman. "By giving MEPACT to newly diagnosed patients, we hope to prevent relapse by taking care of any remaining tumor cells after chemotherapy."

Currently, only relapsed pediatric patients with osteosarcoma are able to receive treatment with MEPACT through compassionate use in the United States. MEPACT was granted orphan drug status in the United States in 2001 but has not been approved by the Food and Drug Administration for use in newly diagnosed patients. Orphan drug status is given to therapeutic agents that target rare diseases as an incentive for pharmaceutical companies to manufacture these agents.

"We have been working with this therapy for more than two decades, so getting approval in Europe is a huge milestone for those of us fighting pediatric cancer," says Kleinerman. "This drug has made significant strides for long-term survival of children with osteosarcoma."