Vaccination and topical imiquimod treatment promote immune signatures in melanoma

Introduction: Infiltration of cancers by T-cells is associated with improved patient survival and response to immune therapies; however, optimal approaches to induce T-cell infiltration of tumors are not known. This study tests the hypothesis that topical treatment of melanoma metastases with the TLR7 agonist imiquimod treatment plus administration of a multipeptide cancer vaccine will improve immune cell infiltration of melanoma metastases. Patients and Methods: Eligible patients were immunized with a vaccine comprised of 12 melanoma peptides and a tetanus toxoid-derived helper peptide, and imiquimod was applied topically to tumors daily. Adverse events (AE; CTCAE v4.03) were recorded and effects on the tumor microenvironment (TME) were evaluated from sequential tumor biopsies. T-cell responses were assessed by IFNgamma ELIspot assay, and T-cell tetramer staining. Patient tumors were evaluated for immune cell infiltration, cytokine and chemokine production, and gene expression. Results and Conclusions: Four eligible patients were enrolled, and administration of imiquimod and vaccination was well tolerated in these patients. Circulating T-cell responses to the vaccine were detected by ex vivo ELIspot assay in 3 of 4 patients. Treatment of metastases with imiquimod induced immune cell infiltration and favorable gene signatures in the patients with circulating T-cell responses. This study supports further study of topical imiquimod combined with vaccines or other immune therapies for the treatment of melanoma. Precis: This clinical trial tested topical application of imiquimod to melanoma metastases combined with a melanoma vaccine. The regimen dramatically upregulated immune rejection gene signatures in melanoma metastases and increased T-cell infiltrate.

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Mauldin IS, Wages NA, Stowman AM, Wang E, Olson WC, Deacon DH, Smith KT, Galeassi N, Teague JE, Smolkin ME, Chianese-Bullock KA, Clark RA, Petroni GR, Marincola FM, Mullins DW, Slingluff CL Jr