Immune checkpoint inhibitors (ICIs) have revolutionized the oncology field. However, a significant number of patients do not respond, at least partly due to the lack of preexisting anti-tumor T-cell immunity. Therefore, it is emergent to add an immune-priming step to improve efficacy. Here, we report a combined approach consisting of intratumoral administration of pro-inflammatory allogeneic dendritic cells (AlloDCs) and systemic treatment with αCTLA-4 that can drastically improve the anti-tumor efficacy compared to αCTLA-4 monotherapy. When evaluated in mice with large established CT-26 tumors, monotherapy with αCTLA-4 neither delayed tumor progression nor improved mice survival. However, combination treatment of AlloDCs and αCTLA-4 drastically improved the effectiveness, with 70% of mice being cured. This effect was T cell-dependent, and all survived mice rejected a subsequent tumor re-challenge. Further investigation revealed an immune-inflamed tumor microenvironment (TME) in the combination treatment group characterized by enhanced infiltration of activated antigen-presenting endogenous DCs and CD8 + T cells with a tissue-resident memory (T RM ) phenotype (CD49a + CD103 + ). This correlated with elevated levels of tumor-specific CD39 + CD103 + CD8 + T cells in the tumor and “tumor-matching” NKG2D + CD39 + CX3CR1 + CD8 + T cells in peripheral blood. Moreover, splenocytes from mice in the combination treatment group secreted significantly higher IFN-γ upon stimulation with the peptide from the endogenous CT-26 retroviral gp70 (model neoantigen), confirming the induction of a tumor-specific CD8 + T-cell response. Taken together, these data indicate a strong anti-tumor synergy between AlloDCs and αCTLA-4 that warrant further clinical investigation with the corresponding human AlloDC product (ilixadencel) for patients receiving αCTLA-4 therapy.

AUC 0-N ) was taken as measure of exposure for DAB and trough plasma concentration (C min ) for TRAM. Efficacy endpoint was progression free survival (PFS). Univariable and multivariable exposure-response analyses were performed, taking into account WHO status, prior treatment lines and brain metastases.Results: In total, 140 pts were included, of whom 468 PK samples were collected.Median DAB AUC per pt was 4608 mg/L*h (IQR 4214 e 5156 mg/L*h) and median TRAM C min 13.2 mg/L (IQR 10.0 e 18.1 mg/L). For DAB, median PFS was 7.1 vs. 7.7 months (mo) for pts with median AUC < 4608 mg/L*h and 4608 mg/L*h, respectively (log rank test, p¼0.5). Multivariable analysis yielded similar results. For TRAM, the previously proposed threshold of 10.6 mg/L did not discriminate in median PFS (7.1 vs. 8.3 mo, p¼0.8). However, when using C min thresholds of 13.0 e 15.5 mg/L significant and relevant differences in PFS were found. Median PFS in patients with C min above 15.5 mg/L (n¼51) was 12.1 vs. 6.2 mo for those with C min below this threshold (n¼89, p¼0.03). Multivariable analysis resulted in a HR of 1.84 (95% CI 1.20 e 2.82, p¼0.005). Of the pts with median TRAM C min < 15.5 mg/L, 9 pts (10%) received a prior dose reduction or interruption due to toxicity (i.e. 90% would be potentially eligible for TRAM dose escalation).Conclusions: PFS is significantly prolonged in pts with TRAM C min 15.5 mg/L, while an exposure-response relationship could not be demonstrated for DAB. Therefore, therapeutic drug monitoring of TRAM could be used to individualize treatment and improve treatment outcomes.Legal entity responsible for the study: Netherlands Cancer Institute.