A Trojan Horse for Brain Cancer: First-in-Human Gene Therapy Trial Shows Promise in Glioblastoma
Key Insights
A first-in-human phase 1 trial of Temferon, a gene therapy using patients' own engineered blood stem cells, met its safety primary endpoint in 24 patients with newly diagnosed, treatment-resistant glioblastoma (search).
The therapy reprograms the immunosuppressive tumor microenvironment by delivering interferon-α (search) locally via tumor-infiltrating macrophages, avoiding the severe systemic toxicity that previously limited this cytokine's use.
Median overall survival reached 16.7 months in patients with unmethylated MGMT (search) promoter, a population with among the worst prognosis, and two patients achieved late partial responses more than a year after treatment.
A first-in-human phase 1 clinical trial published in Nature Medicine has demonstrated that a novel gene therapy approach can safely and durably reprogram the immunosuppressive tumor microenvironment in glioblastoma (search) (GBM), one of the most aggressive and universally fatal cancers. The therapy, called Temferon, uses patients' own genetically engineered blood stem cells as "Trojan horses" to deliver the immune-stimulating protein interferon-α (search) (IFN-α) directly into the tumor, achieving what the researchers describe as proof-of-mechanism in humans for an entirely new therapeutic concept.
The study, designed and conducted at San Raffaele Hospital and the Carlo Besta Neurological Institute in Milan under the scientific leadership of Prof. Bernhard Gentner (now at Lausanne University Hospital and the Ludwig Institute for Cancer Research) and Prof. Luigi Naldini (SR-TIGET, Milan), enrolled 24 patients with newly diagnosed, treatment-resistant GBM. The trial was sponsored by Genenta Science.
A 'Living Drug' Approach
Temferon works by harvesting patients' own hematopoietic stem cells, genetically engineering them with a lentiviral vector to produce IFN-α under the control of a tumor-specific promoter, and reinfusing them after conditioning chemotherapy. The engineered cells home to the bone marrow and, over time, their progeny infiltrate the tumor where they differentiate into macrophages—immune cells that GBM normally corrupts into allies that suppress anti-tumor immunity. By forcing these macrophages to release IFN-α locally and only locally within the tumor microenvironment, the therapy aims to reactivate the immune system precisely where it matters most, while avoiding the severe systemic side effects that historically made IFN-α too toxic for widespread use in oncology.
Safety and Engraftment
The trial met its primary endpoint: Temferon was safe and well tolerated at all dose levels tested, with no dose-limiting toxicities. Engineered cells engrafted durably in patients' bone marrow and blood, and were detected in tumor samples years after treatment. Critically, IFN-α levels in the blood remained minimal, confirming that the genetic control mechanism was functioning as designed. Meanwhile, analysis of cerebrospinal fluid showed measurable interferon activity over time, consistent with progressive infiltration of Temferon progeny into the tumor.
Reprogramming the Tumor Microenvironment
Analysis of tumor tissue from patients who underwent a second surgery revealed that the therapy had successfully reprogrammed the immunosuppressive tumor microenvironment. Inflammatory macrophages increased, tumor-killing CD8+ T cells accumulated, and hallmarks of immunological activation were detected throughout the tumor. These findings represent the first demonstration in patients that the myeloid compartment of the GBM microenvironment—the very machinery that suppresses immunity—can be durably reprogrammed by a single treatment with genetically engineered stem cells.
Survival and Clinical Activity
Median overall survival was 16.7 months, an encouraging result for patients whose tumors carried a genetic feature—unmethylated MGMT (search) promoter—that makes standard chemotherapy with temozolomide largely ineffective. This population has among the worst prognosis in oncology. Two patients achieved late partial responses more than a year after treatment without additional therapy, suggesting durable immune control in a subset of cases.
Long-term tumor control correlated with higher abundance of TIE2 (search)+ macrophages, the tumor-associated macrophage population in which the IFN-α antitumor gene is activated, and reprogramming of the tumor microenvironment toward an immunologically active state. Conversely, absence of IFN-α release was correlated with a change in the macrophage population, suppression of T cells, and tumor progression.
Beyond Glioblastoma (search)
The significance of this trial extends well beyond glioblastoma (search). The approach—exploiting blood stem cells as a renewable source of tumor-infiltrating macrophages and co-opting them as guided vehicles to deliver immune signals precisely where needed—is in principle applicable to any solid tumor. Prof. Gentner's laboratory at CHUV-LICR in Lausanne is already developing optimized versions of this strategy targeting other cancers, including ovarian cancer, with independent financial support from the Oak Foundation and the Ludwig Institute for Cancer Research.
The study also reframes the therapeutic potential of interferon-α (search), one of the first molecules ever used in cancer therapy whose clinical development stalled due to systemic toxicity. By delivering it exclusively inside the tumor through the patient's own cells acting as guided vehicles, this work gives a classic molecule a radical new future.
A Model for Translational Medicine
For funding bodies and research institutions, this trial marks a scientific milestone for Swiss translational medicine. The clinical development was driven by years of basic and translational research supported by academic funding, followed by engagement of a start-up company that took over the costs for late-stage development and the clinical trial—a model that could be replicated in Switzerland. The current results provide the clinical proof-of-concept that validates this investment and opens the door to the next generation of myeloid-targeted immunotherapies.
The detailed study of different tumor microenvironments observed in this trial may allow rational adaptation of the therapeutic strategy to reduce the risk of tumor escape in the future, the researchers note.