From the Journals

Drug-inducible gene therapy unlocks IL-12 for glioblastoma



For patients with recurrent, high-grade glioblastoma, localized, drug-inducible gene therapy could unlock the anticancer potential of interleukin-12, based on a phase 1 trial.

In 31 patients who had their tumors excised, intraoperative site injection with an IL-12 vector followed by postoperative administration of veledimex, an oral activator of the transgene, increased IL-12 levels in the brain and appeared to improve overall survival, reported E. Antonio Chiocca, MD, PhD, Harvey W. Cushing Professor of Neurosurgery at Harvard Medical School, Boston, and colleagues. Although some serious adverse events were encountered, the investigators noted that these were less common with lower doses of veledimex and were reversible upon discontinuation. These findings mark a turning point in IL-12 cancer research, which previously encountered prohibitive safety obstacles.

“There was interest in the use of recombinant IL-12 in humans with cancer, and clinical trials of systemic IL-12 were undertaken but had to be stopped because the cytokine, administered as a recombinant soluble protein, was poorly tolerated,” the investigators wrote in Science Translational Medicine.

To overcome this issue, a novel treatment approach was developed. “With the objective of minimizing systemic toxicity, a ligand-inducible expression switch [RheoSwitch Therapeutic System] was developed to locally control production of IL-12 in the tumor microenvironment. In this system, transcription of the IL-12 transgene occurs only in the presence of the activator ligand, veledimex,” they noted.

The primary aim of the study was to evaluate safety and determine the optimal dose of veledimex; four dose levels were tested: 10, 20, 30, and 40 mg. Survival outcomes also were reported.

The protocol-defined maximum tolerated dose was not reached; however, the 20-mg dose was chosen, based on observed tolerability. At this dose level, the most common grade 3 or higher adverse events were lymphopenia (20.3%), thrombocytopenia (13.3%), and hyponatremia (13.3%). Specifically for grade 3 or higher neurologic adverse events, headache was most common, occurring in 13.3% of patients. Grade 2 cytokine release syndrome occurred in about one-fourth of patients (26.7%), whereas grade 3 cytokine release syndrome occurred about half as frequently (13.3%). All adverse events, including cytokine release syndrome, were reversible upon discontinuation of veledimex.

After a mean follow-up of 13.1 months, the median overall survival among patients receiving the 20-mg dose was 12.7 months. The investigators pointed out that this compared favorably with historical controls, who had a weighted median overall survival of 8.1 months. Those who received 30- or 40-mg doses had the poorest survival, which the investigators attributed to intolerability and other subgroup factors.

Data analysis also revealed a negative correlation between dexamethasone use and survival. Among patients in the 20-mg veledimex group who received 20 mg or less of dexamethasone during active veledimex dosing, median overall survival was extended to 17.8 months. The investigators speculated that this was because of reduced immune suppression, although dexamethasone could have induced cytochrome P450 3A4, which may have increased elimination of veledimex.

“In summary, this phase 1 trial reports the use of a transcriptional switch to safely control dosing of [IL-12], highlighting that this can be accomplished across the [blood-brain barrier] to remodel the tumor microenvironment with an influx of activated immune cells,” the investigators wrote.

They noted that this strategy could potentially be applied to other types of cancer, particularly those that are immunologically cold. “These data contribute to our understanding of IL-12 as a ‘master regulator’ of the immune system and highlight that even the transient production of this cytokine may function as a match to turn tumors from cold to hot.”

The study was funded by Ziopharm Oncology and the National Institutes of Health. The investigators reported additional relationships with Advantagene, Stemgen, Sigilon Therapeutics, and others.

SOURCE: Chiocca EA et al. Sci Transl Med. 2019 Aug 14. doi: 10.1126/scitranslmed.aaw5680.

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