Beyond Target Occupancy in Triple-Negative Breast Cancer: A Medicinal Chemistry Perspective on Modality-Guided Design for Durable Network Control.

Triple-negative breast cancer (TNBC) remains difficult to treat because durable response is rarely achieved with conventional occupancy-driven inhibition. The central challenge is not simply a lack of actionable targets but a mismatch between TNBC's adaptive network biology and the limited depth of reversible node-by-node intervention. In this Perspective, we argue that the key medicinal chemistry question is not only which protein to engage, but which chemical modality best matches a given biological liability. We focus on metabolic coupling, epigenetic scaffold dependence, immune-stromal exclusion, and DNA damage response plasticity and discuss how these vulnerabilities motivate targeted degradation, molecular glues, covalent inhibition, rational polypharmacology, or prodrug design. Across these modalities, ternary-complex productivity, linker topology, warhead presentation, isoform selectivity, exposure control, and postwashout persistence often matter more than potency alone. Biological vulnerability defines the design problem, chemical modality defines the intervention logic, and durable network control defines success.