Preclinical studies show that locoregional CTLA-4 blockade is equally effective in inducing tumor eradication as systemic delivery, without the added risk of immune-related side effects. This efficacy is related to access of the CTLA-4 blocking antibodies to tumor-draining lymph nodes (TDLNs). Local delivery of anti–CTLA-4 after surgical removal of primary melanoma, before sentinel lymph node biopsy (SLNB), provides a unique setting to clinically assess the role of TDLN in the biological efficacy of locoregional CTLA-4 blockade. Here, we have evaluated the safety, tolerability, and immunomodulatory effects in the SLN and peripheral blood of a single dose of tremelimumab [a fully human immunoglobulin gamma-2 (IgG2) mAb directed against CTLA-4] in a dose range of 2 to 20 mg, injected intradermally at the tumor excision site 1 week before SLNB in 13 patients with early-stage melanoma (phase 1 trial; NCT04274816). Intradermal delivery was safe and well tolerated and induced activation of migratory dendritic cell (DC) subsets in the SLN. It also induced profound and durable decreases in regulatory T cell (T reg ) frequencies and activation of effector T cells in both SLN and peripheral blood. Moreover, systemic T cell responses against NY-ESO-1 or MART-1 were primed or boosted ( N = 7), in association with T cell activation and central memory T cell differentiation. These findings indicate that local administration of anti–CTLA-4 may offer a safe and promising adjuvant treatment strategy for patients with early-stage melanoma. Moreover, our data demonstrate a central role for TDLN in the biological efficacy of CTLA-4 blockade and support TDLN-targeted delivery methods.

BackgroundThe sentinel lymph node (SLN) is the first node to receive lymphatic drainage from the primary tumor and the site where naïve T cells are first primed. As such it is of great importance in initiating an effective anti-tumor immune response and an attractive target for immunomodulatory agents. Pre-clinical studies have reported that i.t. administration of anti-CTLA-4 is as effective in inducing tumor eradication as systemic delivery, without the risk of treatment related side effects. However, it remains unclear whether this is due primarily to modulation of the tumor microenvironment or of tumor-draining lymph nodes (TDLN). Here, we have evaluated the safety, tolerability and immunomodulatory effects in the SLN and peripheral blood mononuclear cells (PBMC) of anti-CTLA-4/tremelimumab, delivered locally at the tumor excision site in patients with early-stage melanoma. This unique setting (post tumor excision but prior to SLN biopsy) allowed us to clinically assess the role of TDLN in the biological efficacy of CTLA-4 blockade.MethodsIn this phase I dose-escalation trial, patients with clinical stage I-II melanoma received one intradermal injection of tremelimumab at four dose levels (2, 5, 10 [n=3 each] or 20 mg [n=4]) around the primary excision site of the tumor, seven days prior to re-excision and SLN biopsy. Flow cytometry was performed to study viable cells from melanoma SLN and PBMC (prior to tremelimumab administration [day 0], and at 7 days, 3 weeks and 3 months after tremelimumab injection). Systemic melanoma antigen (MART-1/NY-ESO-1)-specific T cells responses were assessed by IFN-γ ELISPOT assay.ResultsIntradermal delivery of tremelimumab was safe and well tolerated. In terms of biological efficacy it selectively induced profound and durable decreases in Treg frequencies in both SLN and PBMC, decreased systemic MDSC rates, activated migratory dendritic cell subsets in the SLN, and induced T cell activation (by HLA-DR and ICOS up-regulation), both in SLN and PBMC. Moreover, systemic anti-melanoma T cell responses were induced (n=5) or boosted (n=2), in association with T cell activation and central-memory T cell differentiation. Of note, tumor recurrences so far were only observed in two patients who did not develop a systemic anti-tumor T cell response.ConclusionsThese findings indicate that i.d. administration of anti-CTLA-4 may offer a safe and promising adjuvant treatment strategy for patients with early-stage melanoma. Moreover, they demonstrate a central role for TDLN in the biological efficacy of CTLA-4 blockade and warrant the development of TDLN-targeted delivery methods for anti-CTLA-4.AcknowledgementsThis study received funding from the Harry J. Lloyd Charitable Trust; tremelimumab was provided by Pfizer Inc.Trial RegistrationNCT04274816Ethics ApprovalThe study was approved by the Medical Ethics Committee of the VU University Medical Center and Spaarne Gasthuis.