A review.Azurin, a 128-amino acid member of the cupredoxin family of copper-containing redox proteins, demonstrates preferential entry into malignant cells vs. their normal counterparts.It also exhibits significant anti-cancer activity in xenograft models of human cancer.One 28 amino acid fragment of azurin, named 'p28', is essentially responsible for the preferential entry of azurin into cancer cells and the anti-cancer activity.Rapid and efficient solid state cGMP synthesis of p28 formed the basis for a recently completed accelerated dose, Phase 1 clin. trial in late-stage patients with solid tumors that had failed multiple, post-surgical systemic chemo-and immunotherapies.P28 could represent the first of a new generation of cell-penetrating peptides with broad therapeutic and diagnostic imaging potential.This article summarizes the results of the completed Phase 1 trial.