Phase I trial of interleukin-12 plasmid electroporation in patients with metastatic melanoma

Abstract

Purpose: Gene-based immunotherapy for cancer is limited by the lack of safe, efficient, reproducible, and titratable delivery methods. Direct injection of DNA into tissue, although safer than viral vectors, suffers from low gene transfer efficiency. In vivo electroporation, in preclinical models, significantly enhances gene transfer efficiency while retaining the safety advantages of plasmid DNA.

Patients and methods: A phase I dose escalation trial of plasmid interleukin (IL)-12 electroporation was carried out in patients with metastatic melanoma. Patients received electroporation on days 1, 5, and 8 during a single 39-day cycle, into metastatic melanoma lesions with six 100-mus pulses at a 1,300-V/cm electric field through a penetrating six-electrode array immediately after DNA injection. Pre- and post-treatment biopsies were obtained at defined time points for detailed histologic evaluation and determination of IL-12 protein levels.

Results: Twenty-four patients were treated at seven dose levels, with minimal systemic toxicity. Transient pain after electroporation was the major adverse effect. Post-treatment biopsies showed plasmid dose proportional increases in IL-12 protein levels as well as marked tumor necrosis and lymphocytic infiltrate. Two (10%) of 19 patients with nonelectroporated distant lesions and no other systemic therapy showed complete regression of all metastases, whereas eight additional patients (42%) showed disease stabilization or partial response.

Conclusion: This report describes the first human trial, to our knowledge, of gene transfer utilizing in vivo DNA electroporation. The results indicated this modality to be safe, effective, reproducible, and titratable.

Figures

Fig A1.

Interferon gamma (IFN-γ) expression measured by enzyme-linked immunosorbent assay in samples obtained from electroporated tumors pre- and postelectroporation. Each panel represents a single cohort with samples from an individual patient depicted with individual bars. The time and type of biopsy specimen is as described in the x axis labels and the quantity of IFN-γ is depicted in a logarithmic scale on the y axis. (A) Cohort 1, (B) cohort 2, (C) cohort 3, (D) cohort 4, (E) cohort 5, (F) cohort 6, (G) cohort 7, and (H) mean and standard deviation of IFN-γ levels for each cohort. Note that cohort 7 (the maximally administered dose) has six patients whereas all other cohorts have three patients.

Fig 1.

Interleukin (IL)-12 expression measured by enzyme-linked immunosorbent assay in samples obtained from electroporated tumors pre- and postelectroporation. Each panel represents a single cohort with samples from an individual patient depicted with individual bars. The time and type of biopsy specimen is as described in the x-axis labels and the quantity of IL-12 is depicted in a logarithmic scale on the y-axis. (A) Cohort 1, (B) cohort 2, (C) cohort 3, (D) cohort 4, (E) cohort 5, (F) cohort 6, (G) cohort 7, and (H) mean and standard deviation of IL-12 levels for each cohort. Note that cohort 7 (the maximally administered dose) has six patients whereas all other cohorts have three patients.

Fig 2.

Histologic appearance of electroporated lesions. (A-C) Hematoxylin and eosin–stained tumor samples on patient 9 (cohort 3). (A) Melanoma lesion immediately pre-electroporation (magnification = 200×), (B) on day 22 (magnification = 200×), (C) on day 39 (magnification = 200×), and (D) pigmented nodule with residual melanosis without viable melanoma excised from the chest 18 months after the electroporation procedure was performed (magnification = 200×). (E-H) Patient 10 (cohort 4). (E) A 50× magnification with hematoxylin and eosin staining with a central viable melanoma tumor surrounded by necrotic tumor removed on day 22, Panel F shows a section from the same tumor at a higher magnification (magnification = 200×) showing inflammatory infiltrates. (G, H) Sections from the same patient with CD4 and CD8 immunoperoxidase staining respectively on day (magnification = 200×).

Fig 3.

Cutaneous lesions in (A-F) patient 9 from cohort 3 and (G-J) patient 14 from cohort 5. (A-C) Right front chest wall. (D-F) Right upper back. A and D were photographed on day 1 (pretreatment), B and E on day 256, and C and F on day 637. Note that the electroporated lesions (2, 3, 4 in panel A) were resected and the sites are shown by white arrows. The nonelectroporated lesions gradually flatten and fade away. (D-F) The seborrheic keratosis (shown by the black arrows) persists whereas the metastatic melanoma lesions flatten and fade with time.

Fig 4.

Cutaneous lesions in patient 14 from cohort 5. A and B were photographed on day 5 after the first electroporation treatment, and C and D on day 513. (A, C) The left lower leg posterior surface. (B, D) The medial surface. Note the depigmentation seen around lesions in C and D.