Conclusion
This work supports neoadjuvant TLR agonist-based immunotherapeutics as realistic options for immune activation in the TME and long-term metastatic protection in TNBC.
Methods
In this study, the local and systemic impact of the intratumoral Toll-like receptor (TLR) 7/8 agonist 3M-052 alone or in combination with anti-PD1 was evaluated in metastatic TNBC models. The IFN-α receptor (IFNAR1) blocking antibody, MAR1-5A3, along with immune-deficient mice and ex vivo assays are utilised to examine the key targets of this agent that are critical for an antimetastatic response.
Results
Single intratumoral administration of 3M-052 reduced mammary tumor growth, induced a T-cell-inflamed tumor microenvironment (TME) and reduced metastatic spread to lung. Metastasis suppression was reliant on IFN signalling and an antitumor immune response, in contrast to primary tumor growth inhibition, which was retained in NSG and CD8+ T-cell-depleted mice. 3M-052 action was demonstrated via dendritic cell activation and production of type I IFN and other pro-inflammatory cytokines to initiate a T-cell-inflamed TME and promote tumor cell antigen presentation.