Metastatic triple negative breast cancer (TNBC) still carries a dismal prognosis with the current treatment paradigms. The effectiveness of drug treatment for many solid tumors such as TNBC is limited by tumor heterogeneity, lack of tumor specificity, off-target toxicities, and transient therapeutic action(s). Strategies that provide tumor-specific, sustained concentrations of drugs to the tumors and tumor receptor-specific binding, while reducing off-target effects are needed to ensure sufficient tumor cell uptake within the primary and metastatic tumor microenvironment. The decreased non-specific adhesivity, receptor-targeted nanoparticle formulations (“DART” nanoparticles) of the invention were assessed for clinical potential in directing biological agents to the cell surface receptor Fn14, which is expressed in many solid cancer types, including TNBC primary tumors and metastatic lesions. They are contemplated for use against solid tumors, particularly brain tumors such as glioblastoma and breast cancer, including metastatic breast cancer.