Advanced electrotransfer for IL-12 gene immunotherapy in melanoma: Challenges and possibilities

Main text

The treatment landscape for advanced melanoma has been transformed in the past decade by immune checkpoint inhibitors and targeted therapies, but many patients continue to experience relapse or resistance. Gene-based immunotherapies have emerged¹ as promising complementary strategies, with interleukin-12 (IL-12) standing out as a potent cytokine capable of orchestrating both innate and adaptive immune responses. Heller and colleagues report the development² and preclinical validation of an advanced in vivo electrotransfer platform—termed heat-and-impedance gene electrotransfer (HIGET)—that enables effective intratumoral delivery of an IL-12 plasmid with markedly reduced pulse intensity compared to conventional methods. The work demonstrates that therapeutic antitumor responses can be achieved with lower voltage regimens, thereby potentially minimizing procedure-related pain and tissue damage. While these findings represent an important advance in the modification of gene delivery technologies, their practical application remains subject to further developments, including issues regarding stability of response, applicability to multiple tumor types, and integration with existing immunotherapies.

Introduction: Non-viral gene delivery in immunotherapy

The field of gene and cell therapy has long sought efficient, safe, and clinically practical³ methods for delivering therapeutic nucleic acids. Viral vectors remain powerful, but their complexity, cost, and safety concerns have fueled interest in non-viral strategies. Under Good Manufacturing Practice among physical delivery platforms, electroporation—or gene electrotransfer⁴ (GET)—is particularly attractive for its ability to transiently permeabilize cell membranes and achieve high local transfection efficiency. Over 130 clinical trials have explored GET, primarily in oncology and infectious disease vaccines, establishing its feasibility but also underscoring its limitations. The risks of high-voltage pulses include pain and tissue damage and the absence of real-time monitoring mechanisms to guide delivery.

IL-12 has been a central focus⁵ in gene-based immunotherapy because of its dual ability to activate natural killer cells and cytotoxic T lymphocytes while promoting interferon-γ production. Early clinical trials with recombinant IL-12^5,6,7 protein showed antitumor activity but were plagued by systemic toxicities. The reliance on standard GET protocols with high field strengths (≥1,300 V/cm) limited broader clinical adoption.

Main findings of the current study

Heller and colleagues introduce HIGET, an advanced electrotransfer system that integrates three key innovations: (1) the application of mild heat (∼43°C)⁸ to enhance membrane fluidity and lower the electrical threshold for plasmid uptake, (2) a refined electrode design that allows sectored, independently addressable pulsing, and (3) real-time tissue impedance monitoring⁹ to tailor pulse number to tissue heterogeneity. Together, these modifications permit a substantial reduction in applied voltage—down to 150 V with a 2.5 mm electrode gap (600 V/cm)—an ∼87% decrease from standard protocols. Using the malignant B16-f10 murine melanoma model, the authors show that intratumoral delivery of an IL-12 plasmid via HIGET at 150 V significantly delayed tumor growth and produced complete regression in many mice, with long-term survival comparable to that seen with conventional GET at 325 V. Importantly, no systemic toxicity or weight loss was observed, consistent with previous reports of the safety of IL-12 plasmid GET.¹⁰ Tumor impedance measurements revealed that therapeutic benefit correlated with a threshold reduction in impedance (∼71%–77% of baseline), underscoring the utility of real-time monitoring. In contrast, HIGET at 100 V reduced impedance but did not produce antitumor effects, establishing threshold below which efficacy is lost (Figure 1 and Table 1).

Figure 1.

Schematic representation of standard GET and HIGET

Table 1.

Comparison of key parameters between standard GET and HIGET

	Pulse voltage	Tissue impedance change	Therapeutic outcome	Toxicity profile
GET	≧1,300 V/cm	fixed	robust antitumor activity	no: weight loss yes: tissue damage yes: discomfort
HIGET	600 V/cm	excellent flexibility	robust antitumor activity	no: weight loss no: tissue damage no: discomfort

Significance of the findings

This work provides evidence that advanced engineering of electroporation platforms can meaningfully improve the therapeutic index of gene-based immunotherapy. By lowering voltage requirements while preserving efficacy, HIGET addresses two of the most persistent barriers to clinical translation: patient discomfort and tissue damage. The incorporation of impedance-based feedback transforms GET from a fixed-parameter procedure into a responsive, adaptive technology, potentially enhancing reproducibility across tumors of differing size, vascularity, and stromal composition. Moreover, the demonstration of robust antitumor activity with HIGET opens the possibility of extending IL-12 plasmid therapy not only to cutaneous melanoma but also to other solid tumors accessible to HIGET.

Caveats and critical issues

Several important questions remain before the translational potential of HIGET can be fully established. First, the relevance of HIGET beyond the murine melanoma model needs to be examined. Testing in other preclinical systems, including human melanoma xenografts, would clarify its broader applicability. It is also important to distinguish whether the antitumor effects arise mainly from IL-12 expression or from electroporation-induced membrane changes. Second, the optimal gene constructs for use with HIGET have not yet been defined. The study did not report IL-12 expression levels, leaving open the question of how much mRNA or protein is needed for therapeutic benefit. Exploring additional immunostimulatory genes may further extend the platform’s utility. Third, the long-term durability of immune protection remains unclear. While earlier IL-12 electrotransfer studies suggested vaccine-like effects, it is not yet known whether HIGET can generate similar lasting immunity.

Broader context and future directions

Further research should test HIGET in more clinically relevant melanoma models and compare it directly with standard GET. Studies exploring combinations with checkpoint inhibitors, oncolytic viruses, or adoptive cell therapies may also reveal synergistic effects. Such work will help determine whether HIGET can progress toward clinical use.

Conclusion

HIGET combines heat-assisted membrane modulation and impedance-guided delivery to enable IL-12-based immunotherapy at lower voltages, reducing discomfort and tissue damage. This study provides a valuable foundation for more adaptable and patient-friendly gene delivery methods. Several key questions remain. First, technical improvements are needed to target all tumor types, including melanoma. Second, optimizing the gene construct and delivery system is crucial to enhance and maintain the antitumor activity of therapeutic genes. Third, a comprehensive analysis of human-tumor-implanted mice and cancer organoids is required to understand how to sustain anti-tumor immune responses. Answering these questions will be essential to guide future clinical translation.

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.