Treatment for the polio virus may eventually move into the treatment realm for brain cancer, thanks to a breakthrough therapy designation by the FDA.
The FDA granted the recombinant oncolytic poliovirus PVS-RIPO a breakthrough therapy designation as a potential treatment for patients with recurrent glioblastoma multiforme (GBM), citing evidence from an ongoing phase 1 study that is exploring overall survival rate in patients with grade 4 malignant glioma, according to a statement by the developer of the immunotherapy, Duke Medicine.
According to findings presented at the 2015 ASCO Annual Meeting, the 24-month overall survival (OS) rate was 24 percent among 24 patients treated with the immunotherapy. In updated findings, Duke noted that three patients remained alive 36 months following treatment.
The breakthrough therapy designation is meant to expedite the development of promising medications that have shown preliminary signs of clinical efficacy, typically in phase 1 or 2 trials. Under the program, the FDA will be more accessible, in order to provide advice on the design and conduct of the clinical development program.
“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,” said lead investigator Darell Bigner, director of the Preston Robert Tisch Brain Tumor Center at Duke. “Ultimately, we hope the therapy will one day obtain FDA approval.”
PVS-RIPO, which is manufactured at the NCI’s Frederick facility, consists of a genetically modified nonpathogenic version of the oral poliovirus Sabin type 1. In the therapy, the internal ribosomal entry site (IRES) on the poliovirus was replaced with the IRES from human rhinovirus type 2 (HRV2), thus eliminating neurovirulence. Once administered, the therapy enters and begins duplicating within cells that express CD155/Necl5, which is an onco-fetal cell adhesion molecular that is common across solid tumors.
The phase I study that was the basis for the designation enrolled adult patients with a Karnofsky performance status of at least 70 percent. Patients in the trial received a poliovirus immunization booster two weeks prior to treatment with PVS-RIPO. Treatment was administered directly into the tumor via catheter, which was implanted utilizing stereotactic guidance.
In the trial, treatment was administered in the Neuro-Surgical Intensive Care Unit or neuro step down unit, for safety purposes, at a delivery rate of 0.5 ml/hr over the course of 390 minutes. The study identified a viral load of 5.0 x 107 TCID50 as the ideal dose for PVS-RIPO. Higher doses required prolonged steroid use, according to the ASCO report.
For the 24 patients analyzed for the ASCO poster, the median age was 57.5 years (range 20-70). The KPS was most commonly 90 percent (62.5 percent of patients). Prior therapies included radiation (100 percent), Temodar (temozolomide) (100 percent), and Avastin (bevacizumab) (41.7 percent).
At a data cutoff of May 19, 2015, the median OS across all doses of PVS-RIPO was 12.5 months. The 12-month OS rate was 56 percent and the 18-month rate was 32 percent. At this analysis, 11 patients had failed treatment with PVS-RIPO.
The longest survival durations were seen with two doses that were not selected for further investigation. In these groups, two patients continued to live for more than 35 months, with an additional patient living for more than 23 months. At the recommended dose, eight of nine patients (89 percent) remained on treatment at the time of the analysis. The longest duration of response was over seven months.
The most common grade 3 adverse events (AEs) were hyperglycemia (12.5 percent), lymphopenia (20.8 percent) and hemiparesis (14.3 percent). There was one case of grade 4 lymphopenia, and one dose-limiting grade 4 AE (intracranial hemorrhage during catheter removal). There were no grade 5 events.
The phase 1 study exploring PVS-RIPO continues to enroll participants with recurrent GBM, with a phase 2/3 study being planned, according to Duke. Additionally, given the availability of CD155/Necl5 on solid tumors, trials are anticipated across other types of cancer.