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Intratumoral Plasmid IL12 Electroporation Therapy in Patients with Advanced Melanoma Induces Systemic and Intratumoral T-cell Responses - PubMed

Clinical Trial

doi: 10.1158/2326-6066.CIR-19-0359. Epub 2019 Dec 18.

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Clinical Trial

Intratumoral Plasmid IL12 Electroporation Therapy in Patients with Advanced Melanoma Induces Systemic and Intratumoral T-cell Responses

Samantha K Greaney et al. Cancer Immunol Res. 2020 Feb.

Abstract

Whereas systemic IL12 is associated with potentially life-threatening toxicity, intratumoral delivery of IL12 through tavokinogene telseplasmid electroporation (tavo) is safe and can induce tumor regression at distant sites. The mechanism by which these responses are mediated is unknown but is presumed to result from a cellular immune response. In a phase II clinical trial of tavo (NCT01502293), samples from 29 patients with cutaneous melanoma with in-transit disease were assessed for immune responses induced with this treatment. Within the blood circulating immune cell population, we found that the frequencies of circulating PD-1+ CD4+ and CD8+ T cells declined with treatment. Circulating immune responses to gp100 were also detected following treatment as measured by IFNγ ELISpot. Patients with a greater antigen-specific circulating immune response also had higher numbers of CD8+ T cells within the tumor. Clinical response was also associated with increased intratumoral CD3+ T cells. Finally, intratumoral T-cell clonality and convergence were increased after treatment, indicating a focusing of the T-cell receptor repertoire. These results indicated that local treatment with tavo can induce a systemic T-cell response and recruit T cells to the tumor microenvironment.

©2019 American Association for Cancer Research.

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Figures

Figure 1.
Figure 1.. Modulation of circulating T cells with tavo treatment.

Frequencies of circulating immune cell subsets were assessed on serial peripheral blood mononuclear cells by flow cytometry. (A) CD4 Teff, (B) Tregs, (C) PD-1+ CD4 Teff, (D) PD-1+Ki67+ CD4 Teff cells, (E) CD8 T cells, (F) PD-1+ CD8 T cells, (G) PD-1+Ki67+ CD8 T cells were gated and expressed as a percentage of total lymphocytes (n = 20). (Wilcoxon matched pairs test.)

Figure 2.
Figure 2.. Antigen-specific T cells responses following tavo therapy in melanoma patients.

IFN-γ response of circulating peripheral blood mononuclear cells (PBMCs) were measured by enzyme linked immunospot (ELISpot). Specificity to (A) gp100, (B) NY-ESO, (C) MAGE-A3, and (D) Melan-A/MART-1 were tested pre- and post-treatment in response to the respective peptide pools. Each line represents a single subject (n = 24). (Wilcoxon matched pairs test.) Antigen-specific T cells responses following tavo therapy between clinical responders and non-responders, with specificity to (E) gp100, (F) NY-ESO, (G) MAGE-A3, and (H) Melan-A/MART-1 (n = 24). Lines indicate median ± interquartile range. (Significance measured by Mann-Whitney U test.)

Figure 3.
Figure 3.. T cell infiltration post-treatment.

Comparison of (A) CD3+ and (B) CD3+CD8+ tumor infiltrating lymphocytes between clinical responders (R) and non-responders (NR) pre-treatment, 11 days after treatment, and 39 days after treatment. Each dot represents a single subject (n = 19). Treated lesions are denoted with filled circles while untreated lesions are denoted with open circles. Lines indicate median ± interquartile range. (Significance measured by Mann-Whitney U test.)

Figure 4.
Figure 4.. Association between intratumoral T cell infiltration and circulating immune responses.

Correlation of CD3+CD8+ tumor infiltrating lymphocytes with antigen specific IFN-γ T cell responses before treatment with plasmid IL-12 electroporation (A, C, E, G), and 39 days after treatment (B, D, F, H) for all patients. Responders are denoted by filled circles while non-responders are denoted by open circles (n = 12). Best-fit lines are overlaid on the graphs. (P- and r-values were determined by Spearman’s rank correlation).

Figure 5.
Figure 5.. Diversity and dynamics of TCR repertoire in tumors.

T cell receptor sequencing was performed on tumor biopsies prior to or following treatment (n = 9). (A) Clonality of biopsy samples obtained pre- and post-treatment samples was assessed (p=0.088). (B) Convergent frequency of pre- and post-treatment samples were also assessed (p=0.019). (C) Morisita’s distance was calculated between baseline and post-treatment timepoints. Boxplots indicate median ± interquartile range, lines represent standard error. (Signficance measured by Wilcoxon matched pairs test) (D) The correlation between convergent frequency and clonality was assessed (r=0.80, p<0.001) (line fitted by a linear regression model).

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