Depletion of mitochondrial copper, which shifts metabolism from respiration to glycolysis and reduces energy production, is known to be effective against cancer types that depend on oxidative phosphorylation. However, existing copper chelators are too toxic or ineffective for clinical application. Here we develop a safe, mitochondria-targeted, copper-depleting nanoparticle (CDN) and test it against triple-negative breast cancer (TNBC). We show that CDNs decrease oxygen consumption and oxidative phosphorylation, cause a metabolic switch to glycolysis, and reduce ATP production in TNBC cells. This energy deficiency, together with compromised mitochondrial membrane potential and elevated oxidative stress, results in apoptosis. CDNs should be less toxic than existing copper chelators because they favourably deprive copper in the mitochondria in cancer cells instead of systemic depletion. Indeed, we demonstrate low toxicity of CDNs in healthy mice. In three mouse models of TNBC, CDN administration inhibits tumor growth and substantially improves survival. The efficacy and safety of CDNs suggest the potential clinical relevance of this approach.

The catalytic properties of proteolysis targeting chimeras (PROTACs) may lead to uncontrolled off-tissue target degradation that causes potential toxicity, limiting their clinical applications. The precise control of this technology in a tissue-selective manner can minimize the potential toxicity. Hypoxia is a hallmark of most solid tumors, accompanied by elevated levels of nitroreductase (NTR). Based on this character, we presented a type of NTR-responsive PROTACs to selectively degrade proteins of interest (POI) in tumor tissues. Compound 17-1 was the first NTR-responsive PROTAC synthesized by incorporating the caging group on the Von Hippel–Lindau (VHL) E3 ubiquitin ligase ligand. It could be activated by NTR to release the active PROTAC 17 to efficiently degrade the EGFR protein and subsequently exert antitumor efficacy. Thus, a general strategy for the precise control of PROTAC to induce POI degradation in tumor tissues by NTR was established, which provided a generalizable platform for the development of NTR-controlled PROTACs to achieve selective degradation.

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A novel and facile process for direct fluorination of unactivated C(sp3)-H bonds at the β position of carboxylic acids was accomplished by a palladium(II)-catalyzed C-H activation. The addition of Ag2O and pivalic acid was found to be crucial for the success of this transformation. This reaction provides a versatile strategy for the synthesis of β-fluorinated carboxylic acids.