DURHAM, N.C., May 17 (UPI) -- A treatment for advanced glioblastoma brain tumors based on poliovirus was granted "breakthrough therapy designation" by the U.S. Food and Drug Administration, according to researchers who developed it.
A phase 1 clinical trial of the drug has been ongoing since 2012 after being developed at Duke University, with researchers saying the FDA designation will allow for a more efficient path of testing and reviewing the drug's efficacy.
Breakthrough designation for a drug does not mean it has been approved for use to cure disease, but rather that it shows the potential to represent a breakthrough in the long run after thorough testing, according to Dr. Richard Moscicki, deputy director for science operations in the FDA's Center for Drug Evaluation and Research.
The treatment is based on a modified version of poliovirus that cannot invade cells, preventing infection by the deadly disease, but is attracted by cancer cells -- which it can invade and kill -- while also motivating the immune system to respond to the tumor.
The university is working to expand its trials of the drug to children with brain cancer, enrollment for which is expected to start by the end of 2016. Additional studies are already being conducted with lab models of breast cancer, and additional federal grants will allow researchers to study the treatment's effects on solid tumors.
"Breakthrough status means that we can work with the highest levels in the FDA to develop the most efficient clinical trial and pathway to fully evaluate the safety and efficacy of the genetically modified poliovirus for treating recurrent glioblastoma," Dr. Darell Bigner, director of the Preston Robert Tisch Brain Tumor Center at Duke University, said in a press release. "Ultimately, we hope the therapy will one day obtain FDA approval."
Researchers tested the drug's safety for seven years, including tests with monkeys showing none contracted polio, before allowing the phase 1 trial with humans.
Early tests showed lower doses of the polio treatment are more effective than higher doses, with 23 patients treated with an optimal dose level and 15 still alive since the start of the trial. Three patients treated with different doses are also still alive 36 months after receiving treatment.
Current therapy for glioblastoma offers a median survival time of 14.6 months, and left untreated researchers say it would be expected to double in size every two to three weeks, though patients in the study who survive have shown shrinking of tumors from the outside and a collapsing on their insides -- suggesting the treatment works.
"You know, I'm very reluctant to use the cure word, the C word as we call it, because we don't know how long it takes to say that a glioblastoma has been cured," Bigner told CBS News. "But I am beginning to think a about it."