Chemokines (CK) play critical roles in the recruitment of immune cells into cancer tissues. Progressing tumors are commonly characterized by local production of regulatory chemokines (CKs) and suppressor cells, while production of pro-inflammatory CKs recruits protective CTLs and Th1 cells, dendritic cells (DC) and NK cells into the tumor microenvironment (TME) in association with effective (immuno)therapeutic intervention. We have recently shown that a combination vaccine targeting tumor vascular antigens (TVA) promotes specific CD8+ T cell responses and the coordinate upregulation of stromal CCL5/CXCL9-11 production and therapeutic T cell infiltration, and reduction in CCL22/CXCL12 production and MDSC/Treg content in the TME. Treatment also promotes de novo production of CCR7-ligand CKs CCL19/CCL21 in the TME, and the development of tertiary lymphoid-like structures (TLS). Remarkably, an autologous ?DC1/TVA peptide-based vaccine administered with dasatinib to immune checkpoint blockade (ICB)-refractory patients with advanced-stage melanoma (NCT01876212) resulted in objective clinical benefit in 6 of 13 (46%) evaluable patients overall, including 4 of 7 (57%) patients exhibiting primary resistance to anti-PD1 blockade therapy. TCRBseq analyses revealed increased TCR convergence (i.e. immune focus) in the therapy-induced TIL repertoire in advance of objective clinical response. Furthermore, clinical responders exhibited unique TIL clonotypes post-treatment that were not detectable in blood, supporting the TME as a relevant site for treatment-dependent T cell cross-priming and ?epitope spreading?. Since new preliminary data in murine B16 melanoma models suggests that therapeutic efficacy of ?DC1/TBVA-based vaccines is superior when combined with the Project 1-developed CK modulation (CKM) regimen vs. dasatinib, Project 3, we will test the hypothesis that therapeutic benefits resulting from ?DC1/vascular peptide-based immunotherapy in immune checkpoint inhibitor (ICI)-refractory, advanced-stage melanoma patients will be increased when combined with chemokine-modulating regimens (including CKM), Specifically, we will perform a Phase I/II trial of Type-1-polarized dendritic cell (?DC1)/TVA peptide vaccination in combination with tumor-selective chemokine modulation (CKM: Interferon-?2b, Rintatolimod and Celecoxib) in advanced-stage HLA-A2+ melanoma patients with primary PD-1/PD-L1 resistance (Aim 1) and analyze the on-treatment changes in TME and blood of patients to determine clinically-relevant changes in immunological analytes (Aim 2). Animal modeling will then be performed to determine the role of vaccine format in the therapeutic efficacy of combination CKM-based immunotherapy +/- immune regulatory antagonists (Aim 3).
In a recently completed pilot clinical trial administering a dendritic cell-based vaccine targeting tumor vascular antigens (?DC1/TBVA) + dasatinib, we observed a high rate of responses (4 of 7 patients; 57% ORR) in melanoma patients who had previously exhibited primary resistance to anti-PD1 checkpoint blockade and objective clinical benefit overall in 6 of 13 patients (46% DCR) on that trial. Treatment benefit was associated with changes in the balance of pro-inflammatory vs. regulatory chemokines and with immune infiltration (including the formation of tertiary lymphoid structures and evidence for T cell repertoire diversification) within patients? tumors. These striking clinical data and our mouse studies showing much stronger therapeutic synergy between ?DC1/TBVA and the chemokine-modulating regimen (CKM) developed within Project 1, compared to dasatinib, prompted us to perform a larger phase II study to evaluate the ability of ?DC1/TBVA+CKM to induce objective clinical responses in patients with primary PD1-refractory, advanced-stage melanoma, identify the underlying mechanisms, and develop tools for prospective studies of survival benefit.
