TTK inhibition activates STING signal and promotes anti-PD1 immunotherapy in breast cancer.

Despite progress in the application of checkpoint immunotherapy against various tumors, attempts to utilize immune checkpoint blockade (ICB) agents in triple negative breast cancer (TNBC) have yielded limited clinical benefits. The low overall response rate of checkpoint immunotherapy in TNBC may be attributed to the immunosuppressive tumor microenvironment (TME). In this study, we investigated the role of mitogen-associated kinase TTK in reprogramming immune microenvironment in TNBC. Notably, TTK inhibition by BAY-1217389 induced DNA damage and the formation of micronuclei containing dsDNA in the cytosol, resulting in elicition of STING signal pathway and promoted antitumor immunity via the infiltration and activation of CD8+ T cells. Moreover, TTK inhibition also upregulated the expression of PD-L1, demonstrating a synergistic effect with anti-PD1 therapy in 4T1 tumor-bearing mice. Taken together, TTK inhibition facilitated anti-tumor immunity mediated by T cells and enhanced sensitivity to PD-1 blockade, providing a rationale for the combining TTK inhibitors with immune checkpoint blockade in clinical trials.

Design, synthesis and biological evaluation of a new class of 7H-pyrrolo[2,3-d]pyrimidine derivatives as Mps1 inhibitors for the treatment of breast cancer.

Monopolar spindle kinase 1 (Mps1), a core component of the spindle assembly checkpoint (SAC), plays a crucial role in the transition of cells from mid-to late mitosis. As an attractive therapeutic target, inhibition of Mps1 induces cell cycle arrest and apoptosis in a variety of tumors, including breast cancer. However, early clinical development of Mps1 inhibitors remains unsatisfactory. Here, we designed and synthesized a new class of Mps1 inhibitors with 7H-pyrrolo[2,3-d]pyrimidine structure using a scaffold hopping approach. Structure-activity relationship (SAR) revealed that 12 is a potent Mps1 inhibitor (IC50 = 29 nM), which inhibited phosphorylation of Mps1 in vitro and in vivo. Treatment with 12 not only impeded proliferation of breast cancer cell lines, but also induced cell cycle arrest and apoptosis of MCF-7 and 4T1 cells. 12 suppressed tumor growth in vivo, and no obvious toxicities were observed. These results demonstrated the potential of Mps1 inhibitor 12 for the treatment of breast cancer.