Synthesis of self-immolative NO donor-aurovertin B conjugate as potent anti-triple negative breast cancer agents

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with a poor prognosis and limited response to existing therapies, posing a serious challenge to global women's health. Aurovertin B (AurB), a microbial-derived ATP synthase inhibitor, has demonstrated selective inhibition against TNBC proliferation and metastasis, emerging as a promising lead compound. However, the therapeutic potential is hampered by its high toxicity. To reduce toxicity and enhance antitumor efficacy, AurB was conjugated with a NO donor, yielding a series of AurB-S-S-NOD derivatives synthesized via disulfide-based self-immolative linkers. These linkers can be selectively cleaved in the reductive environment of tumor cells due to the high intracellular glutathione levels. This cleavage initiates a self-immolation process, ultimately resulting in the controlled release of AurB. In vitro studies revealed that the anti-TNBC activity of the derivatives was closely related to the rapid release of AurB, and the derivative 7g, which exhibited a fast release rate, demonstrated the most potent antitumor effects, with IC₅₀ values of 1.41 μM in MDA-MB-231 cells and 3.10 μM in 4 T1 cells. Mechanistic studies revealed that 7g induces ferroptosis via inhibition of GPX4 activity, leading to tumor cell death. In a BALB/c mouse subcutaneous model, intraperitoneal administration of 7g (10 mg/kg) significantly suppressed tumor growth with a tumor growth inhibition rate of 43.5%. These results suggest that 7g represents a promising therapeutic candidate for TNBC, potentially acting through the induction of ferroptosis.