Emerging Protein Targets in Triple-Negative Breast Cancer: Beyond Conventional Therapy

Triple-negative breast cancer (TNBC) remains one of the most aggressive and therapeutically challenging breast cancer subtypes, lacking expression of estrogen receptor, progesterone receptor, and HER2. Conventional chemotherapy and immune checkpoint inhibitors provide some benefit, but resistance and relapse are frequent. The search for novel targets has therefore become central to developing more effective and durable therapies. Recent advances in proteomics, structural biology, and targeted protein degradation are rapidly expanding the repertoire of actionable molecules in TNBC. This review summarizes current and emerging therapeutic strategies for TNBC, with a focus on targeted approaches designed to address tumor heterogeneity and resistance mechanisms. To this end, recent advances in targeted therapies are examined, including immune checkpoint inhibitors, PARP inhibitors, Trop-2-directed antibody-drug conjugates, anti-angiogenic agents, PI3K/Akt/mTOR pathway inhibitors, androgen receptor antagonists, and CDK4/6 inhibitors, highlighting results from completed and ongoing clinical trials. In addition, we explore novel targets identified through integrative omics approaches, as well as the role of the tumor metabolism and microenvironment in modulating therapeutic efficacy. Finally, we outline innovative radiotherapy strategies based on targeted radiation delivery and biological integration with systemic therapies. Collectively, this review provides an updated and novel overview of the evolving TNBC therapeutic landscape and highlights promising directions for the development of next-generation, biomarker-driven treatment strategies aimed at improving patient outcomes, maintaining a broad perspective on a very large class of targets.