Immunization of Malignant Melanoma Patients with Full-Length NY-ESO-1 Protein Using TLR7 Agonist Imiquimod as Vaccine Adjuvant

Abstract

T cell-mediated immunity to microbes and to cancer can be enhanced by the activation of dendritic cells (DCs) via TLRs. In this study, we evaluated the safety and feasibility of topical imiquimod, a TLR7 agonist, in a series of vaccinations against the cancer/testis Ag NY-ESO-1 in patients with malignant melanoma. Recombinant, full-length NY-ESO-1 protein was administered intradermally into imiquimod preconditioned sites followed by additional topical applications of imiquimod. The regimen was very well tolerated with only mild and transient local reactions and constitutional symptoms. Secondarily, we examined the systemic immune response induced by the imiquimod/NY-ESO-1 combination, and show that it elicited both humoral and cellular responses in a significant fraction of patients. Skin biopsies were assessed for imiquimod’s in situ immunomodulatory effects. Compared with untreated skin, topical imiquimod induced dermal mononuclear cell infiltrates in all patients composed primarily of T cells, monocytes, macrophages, myeloid DCs, NK cells, and, to a lesser extent, plasmacytoid DCs. DC activation was evident. This study demonstrates the feasibility and excellent safety profile of a topically applied TLR7 agonist used as a vaccine adjuvant in cancer patients. Imiquimod’s adjuvant effects require further evaluation and likely need optimization of parameters such as formulation, dose, and timing relative to Ag exposure for maximal immunogenicity.

Intradermal Delivery of TLR Agonists in a Human Explant Skin Model: Preferential Activation of Migratory Dendritic Cells by Polyribosinic-Polyribocytidylic Acid and Peptidoglycans

“…Conceivably, topical application more effectively addresses lowlevel TLR7/8 expressed in LCs (8). Moreover, topical application of imiquimod has previously been described to lead to the recruitment of both myeloid and plasmacytoid DCs (30). Coadministration of systemic FLT3-ligand further mobilized DC precursors and enhanced the DC-stimulatory effects of imiquimod (31).…”

Toll-like receptor-5 agonist, entolimod, suppresses metastasis and induces immunity by stimulating an NK-dendritic-CD8 + T-cell axis

“…Although at least nine distinct TLRs have been discovered in mammals (62), drug development efforts have focused on targeting TLRs 3, 7, and 9, because they are thought to effectively integrate innate and adaptive immune responses (63). However, the promise of such TLR agonist-based therapies has not been borne out in the clinic, not only because little attention has been paid to identifying the most suitable target tumor types, but also because systemic administration of the pharmacologics used to engage these particular TLR pathways have led to "cytokine storm"-related dose-limiting toxicities (10)(11)(12). This led us to consider that the therapeutic value of the "TLR agonist concept" might be markedly improved by exploiting a TLR system intrinsic to the tumor microenvironment.…”

“…Although proof-ofprinciple for this concept has been demonstrated with agonists of several TLRs (TLR3, -7, and -9) (8), only one, the TLR7 agonist Imiquimod, has been approved for clinical use [however, this is limited to topical treatment of basal cell carcinoma (9)]. The major clinical limitations of many TLR agonists are the risk of dose-limiting toxicities associated with their systemic delivery (10)(11)(12) and metastasis stimulation (13)(14)(15). Furthermore, some previously investigated TLR agonists are restricted to injection directly into tumor tissue (3,(16)(17)(18), an approach that will likely have limited therapeutic value in cancer patients with metastatic disease.…”

CTLA-4 blockade enhances polyfunctional NY-ESO-1 specific T cell responses in metastatic melanoma patients with clinical benefit

“…NY-ESO-1-specific antibodies were measured in serum by ELISA before therapy (week 1) and after therapy at week 12, 20 or later time points as previously described (32).…”