Elena Shklovskaya

Immune checkpoint inhibitors (ICIs) have transformed the treatment of advanced melanoma, yet their efficacy is limited by high-grade immune-related adverse events that often require treatment with systemic corticosteroids. Although corticosteroids are widely used, their impact on anti-tumor immunity remains poorly defined. Using an ICI-responsive murine melanoma model, we show that tapered systemic prednisolone administered after three cycles of combined anti-CTLA4 and anti-PD1 therapy compromises ICI-mediated tumor control, leading to delayed progression in one-third of initially responding animals. Mechanistically, prednisolone selectively suppressed CD8⁺ effector T-cell activation in tumor-draining lymph nodes and in the circulation, while expanding activated regulatory T-cells. These changes increased the Treg:CD8⁺ effector ratio, reduced cytotoxic T-cell function and blocked the early ICI-mediated induction of cytokines, including IL-2, IFNγ, VEGF, CCL3/4, IL-13, IL-3, and GM-CSF. Importantly, despite these early immunosuppressive effects, long-term tumor-specific memory responses were preserved. Autologous melanoma:T-cell cocultures validated these findings. Overall, systemic prednisolone disrupts early CD8⁺ T-cell-mediated anti-tumor activity but spares durable immunity, highlighting the critical importance of timing and context in the introduction of corticosteroids during ICI therapy.

C1Q and PD-1 expression on CD16+ macrophages in on treatment biopsies of melanoma patients treated with PD-1 or PD-1+CTLA-4 ICB. Dynamics between pretreatment and early-during treatment biopsies on (a) CD16+ macrophages as a proportion of all macrophages (b) CD16+ C1q+ macrophages as a proportion of all C1q+ macrophages (c) PD-1+ CD16+ macrophages as a proportion of PD-1+ macrophages (d) PD-1+ CD16+ C1q+ macrophages as a proportion of all macrophages (e) C1q+ CD16+ macrophages as a proportion of CD16+ macrophages (f) PD-1+ CD16+ macrophages as a proportion of CD16+ macrophages. (g) Log2 RNA expression of C1qa-c in pretreatment (PRE) and early during treatment (EDT) biopsies of responding and non-responding patients treated with PD-1 or PD-1+CTLA-4 ICB. (h) Flow cytometry analysis of ipilimumab (IgG1) and/or secondary anti-IgG1 binding to CD16+ and CD16- macrophages in a melanoma patient's tumor dissociate. FMO, a no-secondary control.

Representativeness of study participants

Multiplex immunohistochemical staining protocols.

Clinical and mIHC data generated within the study.

Differential expression analysis gene list of FACS sorted CD16+ compared to CD16- macrophages from human melanoma dissociates.

Purpose:This study characterizes intratumoral macrophage populations within baseline melanoma biopsies from patients with advanced melanoma who received either anti-PD-1 monotherapy or a combination with anti-CTLA-4. Particularly, FcγRIIIa (CD16)-expressing macrophage densities were investigated for associations with response and progression-free survival.Experimental Design:Patients with advanced melanoma who received either anti-PD-1 monotherapy or combination anti-PD-1 and anti-CTLA-4 were retrospectively identified. Macrophage populations were analyzed within baseline melanoma biopsies via multiplex IHC in relation to treatment outcomes.Results:Patients who responded to combination immune checkpoint inhibitor contained higher CD16+ macrophage densities than those who did not respond (196 vs. 7 cells/mm2; P = 0.0041). There was no diffidence in CD16+ macrophage densities in the PD-1 monotherapy-treated patients based on response (118 vs. 89 cells/mm2; P = 0.29). A significantly longer 3-year progression-free survival was observed in combination-treated patients with high intratumoral densities of CD16+ macrophages compared with those with low densities (87% vs. 42%, P = 0.0056, n = 40). No association was observed in anti-PD-1 monotherapy-treated patients (50% vs. 47%, P = 0.4636, n = 50). Melanoma biopsies with high densities of CD16+ macrophages contained upregulated gene expression of critical T-cell recruiting chemokines (CXCL9, CXCL10, and CXCL11).Conclusions:Our data demonstrate that tumor microenvironments enriched with CD16+ macrophages are favorable for response to combination anti-PD-1 and anti-CTLA-4 therapy but not anti-PD-1 monotherapy. These data provides a potential biomarker of response for combination immunotherapies in patients with metastatic melanoma.See related commentary by Smithy and Luke, p. 2345

Glioblastoma (GBM) is an aggressive primary adult brain tumor that rapidly recurs after standard-of-care treatments, including surgery, chemotherapy and radiotherapy. While immune checkpoint inhibitor therapies have transformed outcomes in many tumor types, particularly when used neoadjuvantly or as a first-line treatment, including in melanoma brain metastases, they have shown limited efficacy in patients with resected or recurrent GBM. The lack of efficacy has been attributed to the scarcity of tumor-infiltrating lymphocytes (TILs), an immunosuppressive tumor microenvironment and low tumor mutation burden typical of GBM tumors, plus exclusion of large molecules from the brain parenchyma. We hypothesized that upfront neoadjuvant combination immunotherapy, administered with disease in situ, could induce a stronger immune response than treatment given after resection or after recurrence. Here, we present a case of newly diagnosed IDH-wild-type, MGMT promoter unmethylated GBM, treated with a single dose of neoadjuvant triplet immunotherapy (anti-programmed cell death protein 1 plus anti-cytotoxic T-lymphocyte protein 4 plus anti-lymphocyte-activation gene 3) followed by maximal safe resection 12 days later. The anti-programmed cell death protein 1 drug was bound to TILs in the resected GBM and there was marked TIL infiltration and activation compared with the baseline biopsy. After 17 months, there is no definitive sign of recurrence. If used first line, before safe maximal resection, checkpoint inhibitors are capable of immune activation in GBM and may induce a response. A clinical trial of first-line neoadjuvant combination checkpoint inhibitor therapy in newly diagnosed GBM is planned (GIANT; trial registration no. NCT06816927).

Multiplex immunohistochemical staining protocols.