Unituxin (dinutuximab) is the only approved therapy for neuroblastoma, a rare brain cancer that mostly affects children.
United Therapeutics Corporation markets Unituxin. The National Cancer Institute developed it, and the Children’s Oncology Group tested it in clinical trials.
Doctors usually administer the treatment in combination with other therapies after patients have failed to respond to previous treatments.
How Unituxin works
Neuroblastoma cancer cells commonly over-produce a substance called GD2 that appears on the surface of tumors. It’s rare for healthy brain or other types of cancer to produce GD2, making it an ideal target for a neuroblastoma treatment.
Unituxin is an immunotherapy, which means that instead of attacking cancer cells directly, it prompts the immune system to do so. It is an antibody, or protein that goes after a specific target — in this case, GD2.
When Unituxin binds to GD2, it can use one of two pathways to kill tumor cells. One is antibody-dependent cell-mediated cytotoxicity, and the other complement dependent cytotoxicity.
With the antibody-dependent option, Unituxin directs immune cells, such as natural killer cells, to attack a tumor cell. With the complement option, Unituxin’s binding to GD2 triggers a tumor cell process called the complement cascade. It results in tumor cells swelling and bursting.
Doctors usually administer Unituxin with sargramostim (granulocyte-macrophage colony-stimulating factor, or GM-CSF); aldesleukin (interleukin-2); and isotretinoin (13-cis-retinoic acid). Sargramostim and aldesleukin increase the number of immune cells available to fight brain cancer, strengthening Unituxin’s punch. Isotretinoin is a standard therapy that doctors recommend to try to prevent the brain cancer from returning after chemotherapy or a stem cell treatment.
Unituxin in clinical trials
Both the U.S. Food and Drug Administration and European Unon approved Unituxin in 2015 as part of a first-line combo therapy for children with a high-risk form of neuroblastoma. The agencies based their approvals on results of a Phase 3 clinical trial (NCT00026312) that assessed Unituxin’s safety and effectiveness.
All of the 1,449 trial participants had received either chemotherapy or a stem cell treatment before taking part in the study. Researchers compared the treatments of only 226 of the 1,449. Half received a combination of Unituxin, sargramostim, aldesleukin and isotretinoin, and the other half isotretinoin alone. The rest of the 1,449 participants received the Unituxin regimen but were not compared with another treatment group.
The results on the first 226 patients, published in the New England Journal of Medicine, led to the marketing approvals.
The Unituxin group’s overall survival rate was much better after three years than the other group’s. In addition, it took a lot longer for the cancer to progress in the Unituxin group than in the isotretinoin-only group. Seventy-four percent of the Unituxin group was still alive at five years, versus 57 percent of the other group. And 63 percent of the Unituxin group’s cancer had failed to progress, compared with 46 percent of the isotretinoin group’s.
United Therapeutics is also evaluating combinations of Unituxin and other drugs in neuroblastoma trials. One is a Phase 1 trial (NCT03332667) that will identify a recommended dose of Unituxin to be tested in combination with a radiation therapy known as 131I-MIBG . The trial will cover 24 children at multiple U.S. locations. Researchers will assess the optimal dose’s safety and effectiveness in a Phase 2 trial (NCT02914405).
Meanwhile, Britain’s University Hospital Southampton NHS Trust is conducting a Phase 1 trial to evaluate a combination of Unituxin and Bristol-Myers Squibbs’ Opdivo (nivolumab) as a treatment for children’s neuroblastoma.
Other details
The European Commission agreed to United Therapeutics’ request that it withdraw marketing authorization for Unituxin in March 2017 because of difficulty meeting demand for the drug.
Unituxin can cause serious or life-threatening side effects. They include severe pain from irritated nerve cells, upper airway swelling, difficulty breathing, and low blood pressure during or shortly after an infusion of the drug.
More common side effects include lower levels of pain, fever or other signs of infection, blood cell disorders, rash or other allergic reactions, vomiting, diarrhea, and abnormal liver function.
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