CSF1R inhibition plus chemotherapy induces systemic anti-tumor immune responses in triple negative breast cancer and sensitizes tumors to anti-PD-1 therapy by relieving resident memory T cell dysfunction [tumor]

ABSTRACT: Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive disease where limited therapeutic options are available. A significant correlation exists between presence of intratumoral macrophages, tumor progression, and poor outcomes in TNBC. Preclinical in vivo studies revealed that inhibition of myelomonocytic colony stimulating factor 1 (CSF1) or its receptor (CSF1R), plus cytotoxic therapy decreases primary tumor growth kinetics and pulmonary metastases by CD8+ T cell-dependent mechanisms. To evaluate safety and tolerability of this immune-based therapeutic strategy, we conducted a phase Ib/II clinical trial evaluating Pexidartinib (PLX3397), a small molecule CSF1R inhibitor plus Eribulin chemotherapy in patients with heavily pretreated metastatic TNBC. Correlate analyses from baseline revealed increased leukocyte activation biomarkers, increased presence of CD8+ and CD4+ T central memory cells, and increased PD-1 expression on CD4+ T cells in patients experiencing a partial response or stable disease, together providing evidence of enhanced anti-tumor immunity. We hypothesized that addition of either PD-1 and PD-L1-blockade following CSF1R inhibition and chemotherapy would lead to a further enhanced anti-tumor T cell response. To test this, we evaluated tumor-bearing MMTV-PyMT transgenic mice comparing addition of PD-1- or PD-L1-blockade to Pexidartinib/Paclitaxel therapy. This revealed tumor regression in ~60% of transgenic mice with combined PD-1, but not PD-L1-blockade. Analysis of mammary tumors from mice treated with the PD-1 combination revealed activation and expansion of short-lived effector and memory T cells, and unique clonally-expanded T cells not observed with the PD-L1-blockade combination. These clinical and preclinical findings together provide rationale for addition of CSF1/CSF1R inhibitors to chemotherapy and PD-1-blocakde to further improve outcomes for patients with BC.

ORGANISM(S): Mus musculus

PROVIDER: GSE267167 | GEO | 2026/02/23

REPOSITORIES: GEO