TF and cancer: The NP developed (CALAA-01, produced by Calando Pharmaceuticals) was composed of: (1) a linear cyclodextrin-based polymer (CDP), (2) a human transferrin protein (TF) to engage TF receptors (TFR) on the surface of the cancer cells, (3) external PEG chains to promote nanoparticle stability in biological fluids, and (4) an siRNA targeting the M2 subunit of the ribonucleotide reductase protein (RRM2).