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. Biopsies (incisional, core or excisional biopsies) of cutaneous or subcutaneous metastatic melanoma were obtained on day 1 (baseline, pre-treatment) (n=3), day 22 (after 3 weeks of imiquimod treatment, and 1 week after the third vaccine) (n=5) and day 43 (after 6 weeks of imiquimod, and 1 week after the 4th vaccine) (n=3).